ective - portugal - european commissioncontents 1 introduction 1 1.1 background 1 1.2 scope 5 2...

CONTENTS

1 INTRODUCTION 1

1.1 BACKGROUND 11.2 SCOPE 5

2 COUNTRY REPORT - PORTUGAL 7

2.1 PORTUGAL - THE CONTEXT 72.2 THE DESIGNATION PROCESS - THE URBAN WASTE WATER TREATMENT

DIRECTIVE 92.3 THE DESIGNATION PROCESS - THE NITRATES DIRECTIVE 20

3 MARINE/COASTAL WATER AND ESTUARIES 23

3.1 INTRODUCTION 233.2 EUTROPHICATION - OVERVIEW 233.3 THE NORTH COAST - VULNERABILITY 253.4 THE TAGUS ESTUARY 263.5 THE SADO ESTUARY 293.6 THE MONDEGO ESTUARY 33

4 REVIEW OF FRESHWATERS DESIGNATED AS SENSITIVE AREASUNDER THE URBAN WASTE WATER TREATMENT DIRECTIVE 36

4.1 SURFACE FRESHWATER 364.2 THE PORTUGUESE CLASSIFICATION SYSTEM 364.3 SURFACE FRESHWATER QUALITY - AN OVERVIEW 374.4 NITRATE CONTAMINATION 414.5 WATERS USED FOR THE ABSTRACTION OF DRINKING WATER 484.6 GROUNDWATERS 54

5 REVIEW OF THE WATERS DESIGNATED AS VULNERABLEZONES UNDER THE NITRATES DIRECTIVE 57

5.1 INTRODUCTION 575.2 SURFACE FRESHWATER 575.3 GROUNDWATERS 60

6 CONCLUSIONS 78

7 REFERENCES 80

ANNEX A NITRATE CONCENTRATIONS IN GROUNDWATERANNEX B SURFACE FRESHWATER QUALITY MAPSANNEX C NITRATE CONCENTRATIONS IN SURFACE FRESHWATERANNEX D MAPS

ENVIRONMENTAL RESOURCES MANAGEMENT EUROPEAN COMMISSION - DGXI

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1 INTRODUCTION

1.1 BACKGROUND

The objectives of the Urban Waste Water Treatment Directive (UWWTD)1 andthe Nitrates Directive2 are to reduce and prevent “pollution”, from urbanwaste water treatment plants and from agricultural nitrates respectively.Some aspects of the Directives are closely defined, others are – to some degree– left open to interpretation by Member States, individually or collectively.The waters that must be studied and identified under both the Urban WasteWater Treatment Directive (91/271/EEC) and the Nitrates Directive(91/676/EEC) are similar. Consequently, the examination of the identificationof these waters has taken place concurrently during this study.

1.1.1 Nitrates Directive

The Nitrates Directive deals explicitly and exclusively with pollution resultingfrom agricultural activities. The Directive defines pollution as direct orindirect discharges of “nitrogen compounds from an agricultural source into theaquatic environment” which, (among possibilities irrelevant to estuarine andcoastal waters) causes “harm to living resources and to aquatic ecosystems.”The definition of eutrophication is identical to that of the UWWTD except thatit is restricted to nitrogen compounds from agriculture. The Directive has asimilar dual objective – the reduction of water “pollution caused or induced bynitrates from agricultural sources”, and “preventing further such pollution”.Article 3.1 requires the identification of polluted waters, and those which“could” be affected if action is not taken, according to the criteria set out inAnnex I. This Annex simply states that “Waters referred to in Article 3 (1) shallbe identified making use, inter alia, of the following criteria.” Three criteria are setout:

1. Whether surface freshwaters, in particular those used for the abstraction ofdrinking water, contain or could contain, if action pursuant to Article 5 isnot taken, more than the concentration of nitrate laid down in accordancewith Directive 75/440/EEC;

2. Whether groundwaters contain more than 50 mg/l nitrate or could containmore than 50 mg/l nitrate if action pursuant to Article 5 is not taken;

3. Whether natural freshwater lakes, other freshwater bodies, estuaries,coastal waters and marine waters are to be eutrophic or in the near futuremay become eutrophic if action pursuant to Article 5 is not taken.

1Council Directive of 21 May 1991 concerning urban waste water treatment (91/271/EEC).

2 Council Directive of 12 December 1991 concerning the protection of waters against pollution caused by nitrates from agriculturalsources (91/6765/EEC)


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1.1.2 Urban Waste Water Treatment Directive

There are a number objectives and requirements of the UWWTD that relate tothe estuarine and coastal environment. The main elements are:

• First, the stated objective, “to protect the environment from the adverse effects” ofwaste water discharges and “pollution” arising from waste water (Article 1);

• In order to achieve this secondary treatment shall generally be required

(Article 4); • However within ‘Sensitive Areas’ additional action is required, throughout

the catchment area, for those treatment plants that contribute to “pollution”(Article 5.5). For estuaries and coastal waters the current or future potentialfor eutrophication is a criteria that results in their prescription as aSensitive Area (Annex II). While Annex II allows some flexibility for “smallagglomerations”, the requirement for “large agglomerations” is absolute:phosphorus and/or nitrogen should be removed unless it can bedemonstrated that removal will have “no effect” on the “level” ofeutrophication – a claim that a contribution will be ‘insignificant’ does notprovide a defence for failure to implement.

• In addition an estuarine or coastal water “must be identified” as a Sensitive

Area where further treatment than that set out in the UWWT Directive is“necessary to fulfil [other] Council Directives”.

• The Directive also allows for the creation of ‘Less Sensitive Areas’, LSAs,

providing “comprehensive studies” demonstrate that discharges “will notadversely affect the environment” (Article 6.2). Such discharges must receiveat least primary treatment. In estuaries this stipulation applies todischarges from “agglomerations” of between 2,000 and a maximum of10,000 person equivalents, p.e.. Above this size LSA status is not allowedand the provisions of Article 4 regarding secondary treatment apply. Incoastal waters the equivalent limit is 150,000 p.e.

• Estuarine discharges under 2,000 in estuaries or under 10,000 p.e. in coastal

waters must, by 2005, receive “appropriate” treatment – that necessary tomeet the “relevant” aspects of this and other Directives.

• Other Directives relevant to estuaries and coastal waters included thoserelating to hazardous substances, bathing water, shellfish, and habitats andspecies protection.

Article 5: For the purposes of paragraph 2 in the Directive, Member Statesshall by 31 December 1993 identify sensitive areas according to criteria laiddown in Annex II.


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Criteria for identification of sensitive and less sensitive areas

(a) Sensitive areas

A water body must be identified as a sensitive area if it falls into one of thefollowing groups:

• natural freshwater lakes, other freshwater bodies, estuaries and coastalwaters which are found to be eutrophic or which in the near future maybecome eutrophic if protective action is not taken.

The following elements might be taken into account when consideringwhich nutrient should be reduced by further treatment:

• lakes and streams reaching lakes/reservoirs/closed bays which are

found to have a poor water exchange, whereby accumulation may takeplace. In these areas, the removal of phosphorus should be includedunless it can be demonstrated that the removal will have no effect on thelevel of eutrophication. Where discharges from large agglomerations aremade, the removal of nitrogen may also be considered;

• estuaries, bays and other coastal waters which are found to have a poor

water exchange, or which receive large quantities of nutrients.Discharges from small agglomerations are usually of minor importancein those areas, but for large agglomerations, the removal of phosphorusand/or nitrogen should be included unless it can be demonstrated thatthe removal will have no effect on the level of eutrophication;

• surface freshwaters intended for the abstraction of drinking water

which could contain more than the concentration of nitrate laid downunder the relevant provisions of Council Directive 75/440/EEC of 16June 1975 concerning the quality required of surface water intended forthe abstraction of drinking water in the Member States if action is nottaken;

Areas where further treatment than that prescribed in Article 4 of thisDirective is necessary to fulfil Council Directives.

(b) Less sensitive areas

A marine water body or area can be identified as a less sensitive area if thedischarge of waste water does not adversely affect the environment as a resultof morphology, hydrology or specific hydraulic conditions which exist in thatarea.

When identifying less sensitive areas, Member States shall take into accountthe risk that the discharged load may be transferred to adjacent areas where itcan cause detrimental environmental effects. Member States shall recognizethe presence of sensitive areas outside their national jurisdiction.


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The following elements shall be taken into consideration when identifyingless sensitive areas: open bays, estuaries and other coastal waters with a goodwater exchange and not subject to eutrophication or oxygen depletion orwhich are considered unlikely to become eutrophic or develop oxygendepletion due to the discharge of urban waste water.

UWWTD: Biochemical oxygen demand and eutrophication

Having allowed for the requirements of other Directives, two aspects ofpollution specifically deal with by the UWWTD are the biochemical oxygendemand (BOD) of the decomposing sewage effluent, and eutrophication.BOD, with quantitative criteria set out in the Directive’s annex, is relativelystraight-forward, at least in its definition. However that for eutrophication ismore complex.

The Directive states (2.11) that “‘eutrophication’ means the enrichment of water bynutrients, especially compounds of nitrogen and/or phosphorus, causing anaccelerated growth of algae and higher forms of plant life to produce an undesirabledisturbance to the balance of organisms present in the water and to the quality of thewater concerned.”

With the exception of the insertion of the value judgement “undesirable” this isfairly close to the standard scientific definition of eutrophication. Onesignificant difference is that, in scientific terms, the organic (carbon) burdencan also result in eutrophication, entering the food chain via bacteria andcertain facultative or obligate heterotrophic microplankton, rather than via‘plants’, although in taxonomic and functional terms the distinction canbecome rather indistinct. Although allowed for in the Directive definition, theemphasis is on nitrogen and phosphorus. Another distinction is that‘eutrophication’, as a process, might be said to have ceased – scientificallyspeaking – once the situation has stabilised at a new, higher level, althoughthat state would be more eutrophic. Of course, the site would be still beaffected by ‘pollution’.

In practice eutrophication has come to be interpreted in a narrower sense thanthat allowed for in the Directive. Water bodies (particularly estuaries in thecontext of this report) vary significantly in their natural, background, nutrientconcentrations. Anthropogenic nutrient inputs result in a shift along thiscontinuum. Relatively speaking a small input into a nutrient poor(oligotrophic) estuary may have a greater impact on its biodiversity than alarger input to a naturally rich (eutrophic or, in extreme cases, hypertrophic)site. Yet the policy concern, (including other fora such as PARCOM, itssuccessor, OSPAR, and the North Sea Ministerial Conferences) has beenalmost exclusively at the (more visible) extreme hypertrophic end of the scale– massive algal blooms, algal weed mats and deoxygenationi.


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While understandable politically, this represents a major flaw in theimplementation of this Directive. Arguably, as sites shift ‘up’ the scale, it is theoligotrophic sites that are at greatest risk of elimination. Certainly the impactupon them should not be ignored, and indeed the Directive does not allowthis.

For an estuarine or coastal site, if the Directive definition of eutrophication ismet, or it has “poor water exchange” (undefined), then it automatically qualifiesas a Sensitive Area. ‘Standard’ Article 4 or LSA sites must not, by definition,be eutrophic, or under threat of eutrophication if preventative action is nottaken. On this the Directive is absolutely clear. The wording in the annex isthat, for those estuaries, bays and other coastal waters “which are found to havea poor water exchange, or which receive large quantities of nutrients, then theremoval of phosphorus and/or nitrogen should be included unless it can bedemonstrated that the removal will have no effect on the level of eutrophication”.

Thus a high standard of proof is required for lack of action. It is also astringent requirement – especially so once it is appreciated that eutrophicationis a continuum, not just gross effects such as algal mats or exceptional blooms.It also applies to areas which in the “near future” may become eutrophic ifprotective action is not taken.

1.2 SCOPE

‘Verification of Vulnerable Zones identified under the Nitrate Directive andSensitive Areas under the Urban Waste Water Treatment Directive inPortugal’.

The analysis of the parameters/criteria enables the identification of thewaters, which should have been identified under either or both Directives andhave not been identified. As required by the Commission, the followinginformation has been provided for all these areas:

• location of waters concerned;• detailed assessment of relevant parameters and criteria indicating that the

area in question should be identified under either or both Directives;• assessment, identification (agricultural area, agglomeration or others),

description (qualitative and quantitative) and characterisation(significance) of all nutrient sources for all relevant areas;

• assessment of the transboundary coherence of identified waters; and• information regarding any methodological inconsistencies.

Regarding the Nitrates Directive, where it is considered that areas should bedesignated as vulnerable zones and have not been, the following informationis provided:

• nature of catchment;• nature of land-use;


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• assessment of potential nitrate sources other than agriculture – e.g. urbanwaste water treatment, industrial sources, atmospheric deposition – andtheir relative significance; and

• identification and assessment of the justification for transboundaryincoherence between designations.

During this study, the differences between both Directives (e.g. definition ofeutrophication), as well as the possible links between the Directives, havebeen taken account of.


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2 COUNTRY REPORT - PORTUGAL

2.1 PORTUGAL - THE CONTEXT

2.1.1 Background

Portugal is located in the extreme South of Europe and has about 800 km ofAtlantic coastline. This coastline is characterised by strong currents andupwelling.

Four major rivers cross the boundary with Spain: the Douro, Tagus, Guadianaand Minho. The other main rivers in Portugal are shorter and more irregular.These are the Vouga, Mondego and Sado.

Figure 2.1 Portugal’s main hydrological Basins

Source: INAG


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In 1990, agricultural areas occupied about 45% of the total mainland area. Thetrend during the 1980’s was a decrease in arable land (about 2%) and anincrease in areas devoted to permanent plantings (11%). Forests and otherwoodland cover about 36% of the total area.

The most important demographic phenomenon in Portugal is theurbanisation and migration from the inteRior of the country to the coast.About half of the population is concentrated in the Lisbon and Porto areasand the Northern districts of Braga, Aveiro and Coimbra. It is reported ii thatover 75% of the population lives within 50 km of he coast.

Due to the irregularity of the pluviometric regime, and hence a necessity forregulating rivers, over 80 reservoirs/lagoons have been constructed.However, the trophic status of these reservoirs is not well known, and littlestudied, with the exception of the largest ones. This is reviewed in Section 3.2.3of this report.

2.1.2 Overview of water quality

The state of surface waters with regards to nitrogen compounds is relativelywell known in Portugal (as opposed to heavy metals and pesticides). Thereare several water quality monitoring networks in place in Portugal, one ofwhich is managed by INAG (Instituto da Agua - see figure 2.2). About 25% ofthe total length of rivers in Portugal are moderately to very polluted,according to the EU classification (Suspended matter, dissolved oxygen (DO),O2 and ammonia). However, on the whole it appears that nitrogencompounds in waters have been decreasing. The critical problems are foundaround the main agglomerations but also in rural areas where intensive pigfarming, for example, is tacking place.

The quality of coastal waters is, on the whole, satisfactory. The bathing waterquality standard, as prescribed by the EC Directive, is generally reached. Theworst polluted areas are the Tagus and Sado estuaries where nutrients andlarge quantities of heavy metals from industry are present. Other estuaries ofconcern are those of Minho and Mondego, as well as the reservoirs ofAlbufeira and Obidos. The reservoirs of Aveiro and Formosa are severelypolluted, especially by agricultural wastes, causing eutrophication. However,it has been reported (1) that the pollution burden from nutrients is generallylower than in other European countries as the use of fertilisers is generallyless intensive in Portuguese agriculture.

(1) OECD (1993), Environmental Performance Review - Portugal, OECD


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Figure 2.2 Water Monitoring Network (INAG)

Source: INAG

2.2 THE DESIGNATION PROCESS - THE URBAN WASTE WATER TREATMENTDIRECTIVE

2.2.1 Introduction

It seems that the main strategy used by the authorities was, in the firstinstance, only to designate waters which presented an unequivocal case (ie.where sufficient information could support a designation, where there weresignificant urban waste water discharges, traditionally sensitive areas such asria Formosa, etc.).

Water QualityMonitoring Network

stations main rivers secondary rivers hydrological basins


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Such a strategy appears to have been adopted primarily for economical/financial reasons. The 4-year review required by the Directive would enablethe authorities to obtain further information/ studies on other areas andrevise the designations if necessary. The authorities consider, however, thatmore areas that should have been have been classified 1. This is the case inparticular for the Nitrates Directive for which it appears that there aredetailed discussions between INAG and the Ministry of Agriculture withregards to the designation of Vulnerable Zones.

2.2.2 Sensitive Areas

Sensitive Areas in Portugal were designated according to three criteria:

• natural freshwater lakes, other freshwater bodies, estuaries and coastalwaters which are found to be eutrophic or which in the near future maybecome eutrophic if protective action is not taken (Criteria 1).

• surface freshwaters intended for the abstraction of drinking water which

could contain more than the concentration of nitrate laid down under therelevant provisions of Council Directive 75/440/EEC of 16 June 1975concerning the quality required of surface water intended for theabstraction of drinking water in the Member States if action is not taken(Criteria 2);

• Areas where further treatment than that prescribed in Article 4 of thisDirective is necessary to fulfil Council Directives (Criteria 3).

The water bodies identified as Sensitive Areas are listed in Table 2.1 and areshown on Figure 2.3. In 1994, a report iii on the designation of Sensitive Areasand criteria used to designated such areas was prepared by INAG. Itprovides a list of 93 Sensitive Areas in surface freshwaters, estuaries andcoastal waters. The official designation in 1997 listed a total of 41 SensitiveAreas. The 52 areas which where not designated are listed in Table 2.2. Ascan be seen, most areas which where not designated are reservoirs, part of anational/natural park or are on the border with Spain.

(A) Surface Freshwaters - Reservoirs

Partly due to the irregularity of the pluviometric regime in Portugal and theneed for regulating rivers, over 80 reservoirs have been constructed inPortugal. In such reservoirs, the main eutrophication factor has beenconsidered to be the presence of nutrients which enables the growth ofmacrophyte algae, the limiting factor being phosphorus (as opposed tonitrates). Other factors such as temperatures, depth, turbulence, etc. areconsidered to play a major role. The eutrophication status of such waterbodies was not identified according to numerical chemical factors.

1 Mrs Mira da Silva (INAG), person. Comm.


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Table 2.1 Designated Sensitive Areas - Surface Freshwaters and Estuaries

No. Name Basin Type Criteria Treatment

1 Canicada Rio Cávado Reservoirs 1 No discharge withe.p.>10,000

2 Alto Cavado Rio Cávado Reservoir 1 secondary(p.e.<10,000)

3 Alto Rabago Rio Cávado Reservoir 1 No discharge withe.p.>10,000

4 Venda Nova Rio Cávado Reservoir 1 No discharge withe.p.>10,000

5 Paradela Rio Cávado Reservoir 1 No discharge withe.p.>10,000

6 Guilhofrei Rio Ave Reservoir 1 No discharge withe.p.>10,000

7 Andorinhas Rio Ave Reservoir 1 No discharge withe.p.>10,000

8 Alfandega daFé

Rio Douro Reservoir 1 No discharge

9 Burga Rio Douro Reservoir 1 No discharge withe.p.>10,000

10 Salgueiro Rio Douro Reservoir 1 No discharge withe.p.>10,000

11 Torrao/Tamega

Rio Douro Reservoir 1/2 No discharge withe.p.>10,000

12 Vilar Rio Douro Reservoir 1 No discharge withe.p.>10,000

13 Varosa Rio Douro Reservoir 1/2 No discharge withe.p.>10,000

14 Azibo Rio Douro Reservoir 2/3 No discharge withe.p.>10,000

15 Barrinha deEzmoriz

Rio Douro Reservoir 3 No discharge withe.p.>10,000

16 Ria de Aveiro Rio Vouga whole area 1/3 No discharge withe.p.>10,000

17 Frossos Rio Vouga Pateira 1 No discharge withe.p.>10,000

18 Fermentelos Rio Vouga Pateira 1 No discharge withe.p.>10,000

19 Quiaios coastal streambetweenMondego andVouga

Lake of Braças e Vela 1 N/P removal

20 Agueira Rio Mondego Parts of the reservoiroriginating fromriver Dão and riverMondego

½ Secondary

21 Mira Rio Vouga Lagoon of Mira eBarrinha

1/3 No discharge

22 Febres Rio Vouga Reservoirs of Bunho,Hortas, Coudiçais

1 No discharge

23 S. Tomé Rio Vouga Reservoir 1 No discharge


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No. Name Basin Type Criteria Treatment

24 Ervideira coastal streambetweenMondego e Lis

Reservoir 1 No discharge

25 Tagus Rio Tagus Estuaries of Seixal,Coina and Moitaand Montijo of theTagus astuary

1/3 N/P removal

26 Óbidos Oeste stream Reservoir 3 No discharge

27 Divor Rio Tagus Reservoir 2 No discharge

28 Lagoa dealbufeira

Apostiça stream Stretch of RioGuadiana from itsconfluence with RioCaia up to itsconfluence with RioChança

3 No discharge

29 Guadiana Rio Guadiana Reservoir 2/3 More than secondary

30 Vigia Rio Guadiana Reservoir 2 No discharge

31 Monte Novo Rio Guadiana reservoir 2 No discharge

32 Murtega Rio Guadiana Murtega stream 2 Secondary

33 Caia Rio Guadiana Reservoir 2/3 No discharge

34 Roxo Rio Sado reservoir 2 More than secondary

35 Monte daRocha

Rio Sado reservoir 2 No discharge

36 Costa da Galé Coastal streamof Galé

reservoir of Melides,Santo Andre andSancha

3 No discharge

37 Santa Clara Rio Mira reservoir 2 No discharge

38 Sapal deCastro Marim

Rio Guadiana Entire area of Sapaldo Castro Marim

3 No discharge

39 Ria Formosa Algarvestreams

Entire area of the RioFormosa with theexception of theRamahete estuary,Faro canal, Marimcanal and Taviracanal

3 More than secondary

40 Salagos Algarvestreams

reservoir 1 no discharge

41 Ria de Alvor Alvor stream Entire area 3 Secondary


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Table 2.2 Waters Considered But Not Designated under Directive 91/271/EEC

No. Basin Name Identification

1 Minho river Minho Stretch of the river bordering Spain

2 Lima/Cavado rivers Peneda-Gerès All parts of the river included in the GerèsNatural Park

3 Rio Douro Montesinho Allparts included in the MontesinhosNational Park, including the Montesinhoreservoir, and the border stretch of the Maçasriver

4 Douro river Douro Border section of the Douro river

5 Douro river Pocinho Reservoir

6 Douro river Valeira Reservoir

7 Douro river Réga Reservoir

8 Douro river Carapatelo Reservoir

9 Douro river Crestuma-lever Reservoir

10 Douro river Alvão All section included in the Alvão NationalPark

11 Tagus/MondegoRivers

Estrela All sections included in the Estrella NationalPark

12 Mondego river Raiva Reservoir

13 Mondego river Fronhas Reservoir

14 Mondego river Açude de Coimba Reservoir

15 Tagus river Cabril Reservoir

16 Tagus river Campinha Reservoir

17 Tagus river Malcata All section included in the Serra a MalcataNatural Park, including the Meimoa reservoir

18 Tagus river Corgas Reservoir

19 Tagus river Pisco Reservoir

20 Tagus river Santa Agueda(Marateca)

Reservoir

21 Tagus river Idanha Reservoir

22 Tagus river Penha Garcia Reservoir

23 Tagus river Toulica Reservoir


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24 Tagus river Castelo do Bode Reservoir

25 Tagus/Guadianariver

S. Mamede All sections included in the Serra de S.Mamede including the Apartadura reservoir

26 Tagus river andRibeira de Oeste

Aire eCandeeRios

All sections included in the Serras de Aire eCandeeiros Natural Park

27 Tagus River Boquilobos All sections included in the Natural Reserveof Paul de Bolquilobo

28 Tagus river Maranhão Reservoir

29 Sado river Alvito Reservoir

30 Sado river Monte da Rocha Reservoir

31 Ribeira de Morgavel Morgavel Reservoir

32 Guadiana river Tapada Grande Reservoir

33 Ribeira de Odeaxere Bravura Reservoir

34 Arade river Arade Reservoir

35 Arade river Funcho Reservoir

36 Ave river Andorinhas Reservoir

37 Douro river Torrao Reservoir

38 Douro river Azibo Reservoir

39 Douro river Ranhados Reservoir

40 Douro river Penereiro Reservoir

41 Mondego river Fagilde Reservoir

42 Tagus river Pracana Reservoir

43 Ribeiras de Oeste Sintra/Cascais All sections included in the Sintra/CascaisNatural Park, including the Rio de MulaReservoir

44 Douro river Santa Maria deAguiar

Reservoir

45 Sado river Sado Natural Reserve of the Sado Estuary

46 Vouga river Qunita dasCainhas

Reservoir

47 Ribeiras CostaSudoeste andVicentina

Protected Areas All protected areas


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48 Algarve rivers Formosa NationalPark

The whole park

49 Douro river Águeda Border sections of Águeda river and Tourõesriver

50 Tagus river Erges Border section of Erges river and Torto river

51 Tagus river Tagus Fronteira Border setion

52 Tagus river Sever Border section

53 Guadiana river Ardila Border section

54 Guadiana river Chança Border section

55 Mondego river Paul de Arzila Paul de Arzila Natural Reserve

56 Mondego river Quinta de Taipal Classified sites of Mounts of Santa Olaia andFerrestelo

57 Mondego river Paul de Madriz all protected areas

58 Vouga river Açude de Maeira Reservoir

A reservoir is considered to be eutrophic if it fulfils the following criteria:

Table 2.3 Eutrophication factors for reservoirs

Parameter Limit value Methodology

Total phosphorus (µg/l) >35 As referenced in “Water analysis forAquaculturalists “ (1983)

Chlorophyll a (µg/l) >9 Calculated with the Lorenzen equation(1967)

Light (Secchi) (m) <3 20cm diameter discNote: These limit values correspond to annual medianSource: OECD 1982

Reservoirs will only have been identified as Sensitive Areas if they are usedfor abstraction of drinking water or recreation by the general public or if theirtrophic status has a negative impact on its use or the quality defined for itsuse or by other Directives. Protected reservoirs/lagoons presentingsymptoms of eutrophication must also be designated as Sensitive Areas.


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(B) Surface Freshwater - Rivers and Estuaries

With regards to rivers and estuaries, no limit values were established toestimate the level of eutrophication. However a series of criteria were used toidentify eutrophication in rivers and estuaries:

• occurrence of algal blooms;• alterations in the growth of macrophytes;• oxygen levels;• nutrient concentration;• alterations to flora and fauna;• alterations to benthic communities;• water subject to discharges of significant quantities of nutrient, except

where it can be shown that the removal of phosphorus or nitrogen does notinfluence the level of eutrophication.

It must be mentioned that, due to the lack of long term studies andinformation, estuaries with strong currents and water exchange and openbays have not been designated and are considered as “Normal Areas”. Thiswill be revised once more comprehensive studies are be available (1) .

(C) Surface Freshwaters Used for the Abstraction of Drinking Water

For application of criteria 2, historic data obtained from the national waterquality network were used. This data is analysed in Section 3 of this report.water bodies were identified as Sensitive Area according to criteria 2.

(D) Areas of Ecological Importance

Several water bodies located in areas of high ecological importance wereidentified as Sensitive Areas.

2.2.3 Less Sensitive Areas

The Directive allows for the creation of ‘Less Sensitive Areas’, LSAs,providing “comprehensive studies” demonstrate that discharges “will notadversely affect the environment” (Article 6.2). Such discharges must receive atleast primary treatment. In estuaries this stipulation applies to dischargesfrom “agglomerations” of between 2,000 and a maximum of 10,000 personequivalents (p.e.). Above this size LSA status is not allowed and theprovisions of Article 4 regarding secondary treatment apply. In coastal watersthe equivalent limit is 150,000 p.e.

(1) DGA & IHRH (1996), Estudo de Avaliacao Da Vulnerabilidade Da Capacidade de Recepcao Das Aguas E ZonasCosteiras Em Portugal.


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The Directive also requires Member States to take into account themorphology, hydrology, oxygen depletion and/or specific hydraulicconditions of the receiving water. In Portugal, the entire coast, with theexception of the Algarve coast, has been designated as a Less Sensitive Area.

This decision was based on the characteristics of the West coast of Portugalwhich is characterised by a straight continental platform with strong currentsall along its length. In addition, during the summer, the orientation of thecoastline in relation to the dominant winds provoke an upwelling of the deepand cold ocean waters of the Atlantic ocean towards the surface of the coastand back towards the interior of the ocean (upwelling occurs along the westcoast from spring to early autumn under fairly strong and steady northernwinds, while on the South coast of Portugal, upwelling only takes place whenthere are suitable (temporary) wind conditions. This phenomenon has astrong influence on the coastal climate. Indeed the climate on the West cost ofPortugal is significantly different to the South coast. During the winter, thereare strong currents from South to North which are stronger at the oceansurface. This phenomenon results in a water mass transport parallel to thecoastline.

With regards to eutrophication, the information used by the authorities tendsto show that, in general, the waters of the west coast of Portugal benefit fromgood levels of water exchange, high tides and strong currents. It is thereforeconsidered that eutrophication resulting from urban waste water dischargesto coastal waters is highly improbable. Although several studies claim thatno clear signs of eutrophication have been found along the west coast ofPortugal, it is known that localised signs of eutrophication have beenobserved near waste water discharges or near urban areas.

In order to control the effects of discharges of urban waste water into coastalwaters and hence designation of Less Sensitive Areas, the following limitvalues have been established:


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Table 2.4 Parameters for Designating Less Sensitive Areas

Parameters Limit Value at theSurface

Observations Analytical Method

Dissolved Oxygen >90% saturationduring summer

At least 90% of theresults must comply

Winkler method orelectrochemical

method

Dissolved nitrates 15 µmole/l duringwinter

as above molecular absorption

Chlorofill a <10 mg/m3 duringsummer

as above Fluorescence

Light (Secchi disk) >2 m during winter as above visual observation

As mentioned above, the waters complying with the above-limit values weredesignated as Less Sensitive. Indeed, such waters are considered not to harmthe environment. This resulted in the entire coast, with the exception of thecoast of Algarve, being designated as Less Sensitive Areas. When applyingsecondary treatment to the receiving waters a reduction of no more than 10%is observed. It was thus considered that a more advanced level of treatmentthan primary treatment did not present any advantages for the environment.

The water bodies having the characteristics described in Table 2.5 areconsidered as ‘Normal Areas’ (marine waters).

Table 2.5 Parameters for Designating Normal Areas

Parameters Limit Value at theSurface

Observations Analytical Method

Dissolved Oxygen >70% saturationduring summer

At least 90% of theresults must comply

Winkler method orelectrochemical

method

Dissolved nitrates <20 µmole/l duringwinter

as above molecular absorption

Chlorophyll -a <15 mg/m3 duringsummer

as above Fluorescence

Light (Secchi disk) >2 m during winter as above visual observation


19

Figure 2.3 Designated Sensitive Areas

Source: INAG


20

2.3 THE DESIGNATION PROCESS - THE NITRATES DIRECTIVE

2.3.1 Introduction

Member States must identify “Vulnerable Zones”- usually referred to as“Nitrate Vulnerable Zones”- covering areas of land which form the catchmentsof waters which are polluted or could be polluted by nitrate from agriculture.Polluted waters are identified either because of eutrophication (defined asenrichment, which is leading to undesirable ecological disturbance), or becauseof problems with the drinking water parameter of 25-50 mg NO3-/l.

Article 3.1: Waters affected by pollution and waters which could be affectedby pollution if action pursuant to Article 5 is not taken shall be identified bythe Member States in accordance with the criteria set out in Annex 1 of theDirective.

Annex 1: A. Waters referred to in Article 3 (1) shall be identified making use,inter alia, of the following criteria:

1. Whether surface freshwaters, in particular those used for the abstraction ofdrinking water, contain or could contain, if action pursuant to Article 5 isnot taken, more than the concentration of nitrate laid down in accordancewith Directive 75/440/EEC;

2. Whether groundwaters contain more than 50 mg/l nitrate or could containmore than 50 mg/l nitrate if action pursuant to Article 5 is not taken;

3. Whether natural freshwater lakes, other freshwater bodies, estuaries,

coastal waters and marine waters are to be eutrophic or in the near futuremay become eutrophic if action pursuant to Article 5 is not taken.

2.3.2 The Designation Process

It was indicated by the Portuguese authorities that there were severalproblems in identifying Vulnerable Zones such as :

• “There has been insufficient monitoring, or no monitoring at all of thenitrate content of surface freshwaters to determine the state ofeutrophication ”. (mainly due to the fact the P is the limiting factor andtherefore nitrates were not considered to be an issue);

• “ Lack of data on Nitrate levels in the waters concerned obtained over a

peRiod of several years, which would allow reliable predictions to be madeas to how the situation will evolve and enable us to identify water whichwill be polluted by a certain date “.

Therefore, the data obtained since 1992 were used to:


21

• assess the nitrate levels of waters used for the abstraction of drinkingwater, identifying waters with nitrate levels >50 mg/l;

• assess the eutrophication status of all waters with regards to nitrates andidentify those which are eutrophic.

Vulnerable Zones were identified according to the following procedure:

1. “ Surface Freshwaters: first the polluted section of the water course must bedelimited. The corresponding VZ will be the part of the drainage areawhich drains into this part of the water course. The natural contours ofthis part of the drainage area must also be delimited and any man-madedrainage structure taken into account. Examination of the QualityNetwork data available shows compliance with Article 5 of Directive75/440/EEC with regards to nitrate levels: this being the case, the criterionwill not be applied in the designation of Vulnerable Zones at this stage.

2. Groundwater: In places where groundwater is collected for the abstraction

of drinking water, where nitrate levels are more than 50 mg/l, thecorresponding VZs are the areas of land which drain into the water tablesor aquifers from which the water is abstracted and are polluted mainlyfrom agricultural sources. In cases where the areas in question are adjacentto one another, they may be regarded as a single VZ for the purpose of theDirective.

3. With regards to eutrophication, the following is considered: water,

lagoons, reservoirs, rivers and other water courses which is not being usedfor drinking water production or intended for such use. The limiting factorin these waters is usually a low phosphorous level, not nitrogen. … ThiscriteRion will not be applied in the designation of VZ at this stage.

4. Estuary, coastal and marine waters. Due to the lack of data concerning the

state of eutrophication (in relation to nitrates) of such waters, there is nopoint attempting to designate VZs. If some of these waters are eutrophic,as is likely, the origin of the nitrates will have to be identified. In practicethis would be extremely complicated, if not impossible. Therefore, at thisstage such waters will not be considered “.

This clearly shows that the procedures applied by the Portuguese authoritiesto designate Vulnerable Zones, although justifiable, do not entirely fulfil therequirements of Directive 91.676/EEC.

The designated Vulnerable Zones are listed in Table 2.6.


22

Table 2.6 Designated Vulnerable Zones

Name Type1 Vila do Conde Unconfined aquifer between Esposende and Vila

do Conde2 Aveiro Aveiro quaternary aquifer3 Vagos Vagos quaternary aquifer4 Mira Mira quaternary aquifer5 Campina de Faro Campina de Faro miocene, jurassic aquifer


23

3 MARINE/COASTAL WATER AND ESTUARIES

3.1 INTRODUCTION

This chapter presents an assessment of eutrophication and nutrientenrichment along the coast of Portugal. The first section presents an overviewof the eutrophication status of the Portuguese coast. The following sections,all sites which may require designation are assessed and reviewed.

3.2 EUTROPHICATION - OVERVIEW

The Portuguese coast is part of the Iberian Upwelling system. Thisphenomenon occurs along the western Atlantic coast from spring to earlyautumn under relatively strong and steady winds coming from the north. Onthe South coast, upwelling only takes place when westerly winds occur andthese will usually be temporary.

A paper presented by Portugal iv at an OSPAR ad hoc working group oneutrophication looks at the trend of phytoplankton biomass (Chlorophyll -amg/m3) during the 80’s and 90’s. The results are summarised below.

Results of the study

Surface values from 12 sampling stations located along a transept 1 (coastal-coast), 15 (shelve edge) and 60 (oceanic-offshore) miles from the coast wereanalysed. The results show that the surface values are low and similar with aminimum of 0.04 mg/m3 and a maximum of 1.74 mg/m3. The spatialdistribution shows that Chlorophyll -a concentrations attain a maximum valueof 1.74 mg/m3 at the coastal stations and 1.46 mg/m3 at the shelf edge stationsand 0.47 mg/m3 at the oceanic stations.

Figure 3.1 Spatial maximum chlorophyll a (mg/m3)

Transept 00 Transept 01 Transept 02 Transept 030

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

Chl

a

Transept 00 Transept 01 Transept 02 Transept 03

CSO

Source: IPIMAR


24

When looking at yearly trends, the maximum reached is 5 mg/m3 at thecoastal station, which is still well below the maximum of 50 mg/l. Also, it isvery low when compared to the values found in northern Member States suchas Germany (10 µg/l) and Holland (90-100 µg/l).

It is reported that all waters studied are well oxygenated with values ofsaturation greater than 80%. It must, however, be mentioned that episodes ofalgal blooms have occurred off the Portuguese coast and have had harmfulconsequences. It is though that the appearance of flagellate blooms is aconsequence of oceanographic conditions such as winds and currents whichsustain the development of flagellatesv.

The report also indicates that the phytoplanktonic biomass of the coastalstations during the peRiods 1985-1987 and 1994-1996 were similar.“Nevertheless, in winter the chlorophyll decreased strongly at coastal stations andexhibited an opposite trend at the oceanic stations, which is the result of the currentsystems corresponding to the climatological wind systems. Of the west coast ofPortugal and Spain, the wind stress is directed southwards during the summer, andupwelling develops as a result of the associated offshore Ekman transport. Duringwinter, a reversal of the meridional component of the wind northwards induces anonshore Ekman transport north to about 40ºN, which is accompanied by the polewardsurface current”.

The results tend to show that there is no increasing trend, no differencebetween the different regions along the coast, and no clear signs ofeutrophication (or its symptoms) in Portuguese coastal waters. However, theauthor mentions that “we should keep in mind that the relationship betweenphytoplankton biomass and eutrophication is not clearly understood and can berelated to abiotic conditions”.

A report by Oliveira & Cabecadas (1996)vi mentions that certain lagoons andestuaries along the Portuguese coast have very complex topographies(enclosed arms, etc) and show seasonal signs of eutrophication (pooroxygenation, increasing nutrient levels and development of microalgae). Themain ones are:

• Ria de Aveiro reservoir (designated as a Sensitive Area in 1997);• Sado Estuary;• Ria Formosa Reservoir (designated as a Sensitive Area in 1997);

Symptoms of Eutrophication

In general it can be said that the exposure of the open west coast to strongwave action and tidal currents rapidly disperses polluted waters dischargedfrom rivers or coastal towns. Therefore, changes in the natural flora onaccount of pollution have not been noticed, with the exception of occasionalevents near harbours or sewage discharges. It must, however, be mentionedthat due to a lack of long-term studies, there is limited information on changesor modifications. Indeed, very limited reliable information is available on


25

coastal algal vegetation. Nevertheless, in spring and summer, occasionalgreen tides of Ulva rigida, Ulactua and Enteromorpha spp (free floating species)have occurred on the south coast. The settlement of dense communities of theinvasive Sargassum muticum in large semi-open basins of sand and mudbottoms on the Minho coast (North of Porto) has also been observed.

However, in the most important estuaries/reservoirs (Douro, Ria de Aveiro,Tagus and Sado), there is a strong tidal current which prevents or reduce therisk of eutrophication IV. However, investigations by J.C. Marques (CoimbraUniversity) have shown eutrophication in the Mira and Mondego estuariesand a progressive increase in Enteromorpha spp. populations and biomasstogether with reduction in Zostera beds in the southern arm of the Mondegoestuary.

Signs of red tides have already been observed in Portuguese coastal waters. Itis assumed that the development of such red tides is associated with certainspecific nutrient and physical conditions.

Generally, the morphology of the main estuaries and reservoirs, together withthe tidal regime, favours good water exchange and hence limitseutrophication to localised areas. On the open coast, strong wave action andtidal currents rapidly disperse urban and industrial effluents. No algalproliferation or significant changes in benthic population have been observed,except occasionally near coastal towns. The invasions of sargassum muticum(in the North), green tides of Ulva in the South, as well as the red tide bloomsin several coastal areas, are generally thought to be un-related toeutrophication (Olivera & Cabeçadas).

It is therefore reasonable to assume that, due to natural conditions, the marinewaters of the west coast of Portugal are not affected by eutrophication and amore advanced treatment than primary treatment would not significantlyimprove the quality of marine waters. There are, however, several areasalong the coast (in harbours and estuaries) which show clear signs ofeutrophication (very localised and often temporary) and which do not qualifyfor designation as Less Sensitive Areas.

3.3 THE NORTH COAST - VULNERABILITY

It was reported (1) that the Portuguese littoral is facing degradation caused byurbanisation, industrial and agricultural activities and tourism and that waterpollution caused by the use of agro-chemicals and discharge of waste water(urban and industrial) are the main causes of degradation of the ecosystem.Although the major urban centre along the coast have more or less efficientwaste water treatment plants (1), most of them still discharge directly to sea.

(1) DGA & IHRH (1996), Estudo de Avaliacao Da Vulnerabilidade Da Capacidade de Recepcao Das Aguas E ZonasCosteiras Em Portugal.


26

Although it is clear that this creates an impact on the local environment, therecurrently are no reports which enable a thorough scientific assessment of thesituation (eg. the macroinvertebrate community is almost unknown, the fishpopulations need to be studied in more detail from the point of view ofconservation (as opposed to economic concerns), etc).

It has been widely agreed that it is urgent for systematic scientific studies tobe initiated (according to inter-regional plans) and which would allow ascientific data base on these ecosystems to be established.

3.4 THE TAGUS ESTUARY

The estuary can be clearly divided into three zones:

• the upper zone: relatively shallow zone which consists of delta;• the central zone which is the largest one with an average depth of 7 m;• the terminal zone which made up of a straight and deep canal (46 m).

The estuary is roughly pear-shaped, approximately 30 km long and varies inwidth from about 15 km at the northern upstream section to 2 km at themouth (south of Lisbon). The circulation in the estuary is mainly driven bytides which have a 2-4 m amplitude. However, the circulation in the mouth ofthe estuary is also influenced by the wave field.

To the south of its central part, the estuary extends into the Setubal Peninsulain four different parts:

• Seixal estuary;• Coina estuary;

• Moita estuary;• Montijo estuary.

Although these are directly linked to the Tagus estuary and are, as such,integral parts of it, they are considered to be estuaries on their own as theircharacteristics are very different to any other part of the Tagus estuary. Asinlets in the Peninsula, these water bodies are characterised by poorcirculation and water exchange and hence are subject to higher risks ofeutrophication. These four estuaries have been designated as Sensitive Areasby the Portuguese authorities.

The Tagus river is the main input of freshwater into the estuary and theaverage flow rate is about 200 m3/s. Outside the estuary, in the zone where asea outfall is located, the wind and currents also play an important role indriving the flow. The upstream section of the estuary is very shallow withextensive inter-tidal flats. Downstream, the depth reaches 40 m in theentrance channel which is 14 km long.


27

Figure 3.2 The Tagus Basin and Tagus Estuary

Source: INAG

The presence of elevated concentrations of bacteria of faecal origin, especiallyin front of urban areas such as Lisbon, have been reported in several studiesvii. In the Zone cala do Norte , in the proximity of the mouth of the RiverTrancão, there are seasonal problems caused by organic pollution (causingoxygen depletion) and toxic metals from industries located in Sacavém andVila Franca de Xira.

Several studies have assessed the behaviour of nitrates in the estuary, which isconsidered to be stable. Indeed, the main sources of nitrates in the Tagusestuary are rivers. This means that average concentrations increase with theflow. Nevertheless, values above the dilution limit have been observed andcorrespond to the “problematic” zones of Cala do Norte and area of dischargeof the Lisboa stream.

Figure 3.3 shows the distribution of Chlorophyll -a in the Tagus estuary.Although the data originates from a monitoring campaign carried out in 1983and is therefore very old, it shows that the highest concentrations occur in thenorthern part of the estuary, which corresponds to the above-mentioned zoneof Cala do Norte.

Tejo Estuary

Punto Canas

Patudos Reservoir

Valada

Stations Principal rivers Secondary rivers


28

Figure 3.3 Distribution of Chlorophyll -a in the Tagus estuary

Source: IMAR


29

CONCLUSION

Although the estuary, as a whole, does not show clear signs of eutrophication(mainly due to tidal currents), there are localised signs of nutrient enrichment.The main areas where such conditions occur are:

• in the central part of the estuary in and around Lisbon and the Lisboa river;• Cala do Norte at the northern end of the estuary.• in the estuaries of Seixal, Coina, Moita and Montijo which have been

designated as Sensitive Areas.

The more detailed studies carried out on the quality of the Tagus estuary werenot available at the time of writing and therefore, a more detailed assessmentcould not be carried out. However, there is little doubt that enrichment isoccurring in these areas and it is most likely that they do qualify fordesignation as Sensitive Areas.

3.5 THE SADO ESTUARY

The drainage basin of the Sado estuary covers 7,640 km2 and is characterisedby a central bay and a 35 km long, narrow channel. The Sado estuary isdominated by a wide tidal flat bay and narrow channel and has two mainfreshwater sources, namely the Sado river which contributes up to 90% of thefreshwater inflow (wet/dry regime and significant interannual variation) andthe Marateca river (see Figure 3.4). The tidal regime in the estuary is semi-diurnal with amplitudes ranging from 1-4 m. The upper limit for saltintrusion is near the town of Alcacer do Sal and the tidal influence extends 25km upstream (IV). Some parts of the estuary are characterised by salt marshes,especially around Marateca Bay. Industrial and urban activities are wellestablished along the northern shore and agriculture dominates the entirebasin. Agriculture is known to be the main source of diffuse pollution in theestuary (mainly tomatoes and rice covering about 10,000 Ha). However, thestrong tidal currents in the estuary appear to reduce or prevent seriouseutrophication.

It has been established that the nitrates and phosphorus in the estuaryoriginate mainly from the Sado river and, to a lesser extent, from the Maratecariver. Studies on the phytoplankton biomass of the estuary were carried outin 1993 by L. Cabeçadas. A monitoring programme has also been carried outby the Instituto Hidrografico in the upper and lower estuary since 1986.


30

Figure 3.4 The Sado Basin and Sado Estuary

Source: INAG

The above mentioned studies, as well as studies carried out by Cabeçadas andBrogueira (1991) and Oliveira (1992) seem to show that the estuary’s system ismoderately productive and that clear symptoms of eutrophication and/orblooms have not been detected. In addition, Oliveira and Cabeçadas conclude:“Although there is evidence that nitrogen is the limiting nutrient tophytoplankton productivity along the estuary, the Alcace zone presentshigher nutrient levels in winter (NO3 - N up tp 96 µM, NH4+ - N up to 70 µM,SiO2 up to 160 µM) compared to the main body of the Marateca Bay (NO3 - Nup tp 21 µM, NH4+ - N up to 76.5 µM, SiO2 up to 52 µM and Chlorophyll a upto 14.3 mg/m3). “. It has also been shown that toxic algae only appearsporadically and always at very low densities.

It is accepted that the phytoplankton community in the estuary is controlledby several factors which result in different temporal and spatial scales for theresponse to environmental changes. Cabeçadas viii observed thatcomparatively high cell numbers of nanoplanktonic flagellates and relativelyhigh spring and summer concentrations of Chlorophyll -a seem to be a generalfeature in the upper estuarine region (despite inadequate light conditions).However, the study concludes that there are no obvious signs ofeutrophication in the upper zone in the Sado estuary (either in terms of thequantitative level of phytoplankton or in terms of species compositionchanges).

However it has been shown that, from the month of February, there is arelative stabilisation of the water column in the estuary which is associated

The Sado Estuary

Marateca BayAlcacer Channel

Comporta estuary


31

with an increase in solar radiation and higher nutrient concentrations whichinitiate the “spring blooms”. Similarly, Chlorophyll -a concentrations undergoa clear seasonal variation. However, there is a slight spatial variation as well(from South to North) which indicates the riverine origin of Chlorophyll -a inthe Sado estuary.

Some studies have studied the influence of nitrogen and phosphorous fromaquaculture units. Indeed some areas of the estuary (Marateca Bay andAlcacer Channel) have, since the beginning of the 90’s, been utilised foraquacultural activities and the establishment of fish farms. In the MaratecaBay, NO3 and Si patterns show different behaviour than NH4. During winter,concentrations show an increase at flood. Pointing to a transport of nutrientsfrom the estuary into the Bay and during summer, the lower values observedtowards the estuary suggest instead an export of these nutrients to theestuary. In the Alcacer channel, peak concentration of NO3 occurred at lowtide and minimum concentrations at flood tide, and near the bottom. Thisindicates an export of nitrates to the estuary through the Sado river. Theconclusions were that these have no influence on the quality of the estuary.

Nitrates values vary seasonally with values between 1-8 mmol/L. Duringwinter nitrate concentrations vary between 7-18 mmol/L. During spring,concentrations range between 4-5 mmol/L. The hydrodynamics of theestuary indicate that incoming water is mainly of coastal oceanic origin.Water from the central estuary shows much lower concentrations of nutrientsand Chlorophyll -a. throughout the year than around the vaRious inlets.

With regards to phosphorus (P), adsorption/desorption of P andprecipitation/flocculation of humic material occurring at the freshwater/seawater interface at different tide stages and states lead to an equilibrium of Pforms and almost constant level of phosphate in the lower estuary (Babeçadas,1993)ix. Considering that the estuary is subjected to considerable freshwaterinputs, it is assumed that ‘buffer mechanisms’ must operate systematicallyand, to a large extent, control phosphate levels in the system.

It can be concluded that nutrients reach relatively high levels in winter andthat phytoplankton biomass reaches relatively high levels in spring, bottomwaters never became anoxic, even by late summer. This indicates that thesenutrients are being efficiently utilised and that the system can handlerelatively large amounts of nutrients. The results collected between 1979 and1993 do not show any sign of increase/decrease.

Figure 3.5 illustrates land use around the Sado estuary. From this map it isclear that both the Sado and Marateca rivers are bordered by arable land(annual culture) which are probably a major source of nutrients in the riverand which adds to the inputs from aquaculture.


32

Figure 3.5 Soil Use Around the Sado Estuary

Land cover(CORINE)

Source: INAG

The dark green areas indicate the presence of forests and the light green areasindicate the presence of permanent vegetation. The red area shows the townof Setúbal which is surrounded by heterogeneous agricultural areas (northernshore of the estuary). It also indicates that the land alongside the Maratecaand Sado rivers is essentially agricultural (arable) land. Agricultural land alsodominates around the Comporta estuary. This must undoubtedly contributeto the nutrient loading in both rivers and the estuary.

Conclusion

Although there no clear signs of eutrophication in the estuary and the averagevalue for the chemical parameters (nutrients, Chlorophyll -a, dissolved oxygen,etc) are currently not causing extreme oxygen depletion and excessive growthof phytoplankton, the Marateca Bay is an enclosed embayment which ispoorly flushed and presents seasonal signs of high nutrient enrichment(although no signs of eutrophication). It may, however, be considered asvulnerable to an increase in anthropogenic nutrient loads. Any futuredevelopments (eg. aquaculture, etc) in its drainage basin must be carefullycontrolled. This also applies to the Alcacer channel where “spring blooms”occur and where there is a general nutrient increase during the summerperiod.

It is therefore considered that both the Marateca Bay and the Alcacer channelshould be designated as Nitrate Vulnerable Zones, together with theirrespective drainage basins.

Artificial space

Arable land: Annual crops

Permanent Cultures

Heterogeneous agricultural

areas

Forests

Area of dense vegetation

Open spaces

Maritime zones

Continental waters


33

3.6 THE MONDEGO ESTUARY

The Mondego estuary is located on the Atlantic coast of Portugal near thetown of Figueira de Foz, a commercial harbour of vital regional importance.The estuary is composed of two arms (north and south) with very differenthydrographic characteristics. The north arm, where the harbour is located, isdeeper and it is through this arm that most of the freshwater flows. The southarm, on the other hand, is almost silted up in its upstream section. In otherwords, the water circulation in the south arm is mainly tidal. Very little watercomes from the Pranto river.

Human activities around the Mondego estuaries have been developing/diversifying considerably in the last few years. The main pressures whichincrease the estuary’s vulnerability are:

• the lack of a waste water treatment plant in the region of Figueira da Foz.There is a 100% seasonal increase in population during the summer in thatregion.;

• the direct discharge of urban waste water into the estuary in four `different

locations: Ponte de Gala, Camara Municipal, Trapiche and Marina. • Rio Pranto discharges directly into the estuary. The waters of the Pranto

river contain high levels of nutrients and other chemicals which areresponsible for the occasional eutrophication of the south arm of theestuary (which is a known source of tensions with the owners ofaquaculture units);

• High discharges of organic pollutants and nutrients from the estuary of

Armazéns

Figure 3.6 The Mondego Estuary

Source: IMAR


34

As mentioned above, besides the harbour facilities and dredging activities, theMondego river supports industrial activities, salt works and aquacultureunits. The discharges from agricultural areas in the river valley may also besignificant during certain periods.

Therefore the organic enrichment of the estuary from agricultural activitiesand other sources leads to the estuary’s eutrophication and the presence ofthick layers of macroalgae (mainly enteromorpha spp. and Ulva spp.). Theseblooms are periodic and occur from March to September/October (1) .According to IMAR, “depending on the species affected, the abundance can increaseor decrease. Vertical migrations upward of many species can occur. This affects thepredation of macroinvertebrates by wading birds “.

Figure 3.7 Land use in the Mondego Basin

(1) IMAR (1999), the Mondego Estuary

Land cover(CORINE)

Mondegoestuary Artificial space


Permanent Cultures


areas

Forests


Open spaces

Maritime zones

Continental waters


35

CONCLUSIONS

Although the results of more detailed analysis were not available at the timeof writing, it has be shown that periodic blooms occur on the Mondegoestuary and result in a thick layer of macroalgae. The estuary is thereforehighly eutrophic from March to September.

The organic enrichment has been show to originate from agricultural activitiesaround the estuary. This is confirmed in Figure 3.7 which clearly shows thatboth the estuary and Mondego river are surrounded by arable land andpermanent heterogeneous agricultural land.


36

4 REVIEW OF FRESHWATERS DESIGNATED AS SENSITIVE AREAS UNDERTHE URBAN WASTE WATER TREATMENT DIRECTIVE

4.1 SURFACE FRESHWATER

The quality of surface freshwaters is reviewed in this section of the report.The first section provides an overview of water quality in 1998 for eachregion. This will be followed by an assessment of nitrate pollution,eutrophication in reservoirs, waters used for the abstraction of drinking waterand groundwaters.

4.2 THE PORTUGUESE CLASSIFICATION SYSTEM

Water quality monitoring is carried out by the five regional environmentalauthorities (DRA Norte, DRA Alentejo, DRA Centro, DRA Lisboa e Tejo Valeand DRA Algarve). The monitoring network consists of a total of 276 stations.This corresponds to a density of approximately 3.1 station/1000 km2.

Surface freshwaters intended for the abstraction of drinking water areclassified according to the criteria defined in the Decreto-Lei nº 236/98(Chapter II - Section 1), transposing Directive 75/440/EEC which definesthree classes of water: A1, A2 and A3. Different treatment levels areprescribed for each category.

Surface water courses (for multiple uses) are classified according to 27 criteria,the main ones being summarised in Table 4.1.

Table 4.1 Surface freshwater classification criteria

Parameter A B C D E

pH 7-7.9 <7 - >8 <6 - ≥9Temperature (ºC) <= 20 21-25 26-28 29-30 >30Conductivity (uS/cm) <= 750 751 - 1000 1000 - 1500 1500 - 1300 >3000SST (mg/l) <= 25 25.1 - 30 30.1 - 40 40.1 - 80 > 80DO (% Sat) >= 90 89 - 70 69 - 50 49-30 < 30BOD5 (mg/l O2) <= 3 3.1 - 5 5.1 - 8 8.1 - 20 > 20COD (mg/l O2) <= 10 10.1 - 20 20.1 - 40 40.1 - 80 >= 80.1Ox. (mg/l O2) <= 3 3.1 - 5 5.1 - 10 10.1 - 25N-NH4 (mg/l) <= 0.1 0.11 - 1 1.1 - 2 2.01 - 5 > 25N-NH3 (mg/l) 0-0.5 5.1 - 25 25 - 50 50.1 - 80 > 80P2O5 (mg/l) <0.54 <= 0.94 > 0.94 >= 80.1Total Coliforms (N/100ml) <= 50 50-5000 5000 - 50000 > 50000Faecal coliforms (N/100 ml) <= 20 21-2000 2001 - 20000 >20000Key: A=not polluted, B=temporarily polluted, C=polluted, D=very polluted, E= extremelypolluted


37

Other surface freshwater bodies (for multiple use) are classified according tothe following criteria:

Table 4.2 Classification of surface freshwater for multiple use

PARAMETERS Q1 Q2 Q3 Q4

Dissolved Oxygen (mg O2/l) 8 7 5 4NH4 (mg/l) 0.04 0.2 1 2BOD5 (mg O2/l) 3 5 7 9Orthophosphate (mg P2O5/l) 0.1 0.2 0.7 1Nitrates (mg NO3/l) 25 30 50 70Faecal coliform (/100 ml) 20 2000 20 000 30 000

Compatible use aquaculturebathing waterhuman supply

(A1)irrigation

aquaculturebathing waterhuman supply

(A2)

human supply(A3)

Human supply(>A3)

The three classification systems will be referred to in several sections of thischapter.

4.3 SURFACE FRESHWATER QUALITY - AN OVERVIEW

4.3.1 Introduction

As mentioned at the beginning of the report, there has been a shift ofpopulation from inland areas to the coast. This has been accompanied by asimilar trend in industrial settlements and therefore pollution burden ofsurface freshwater. The mainland rivers are said to present less problems hasthey drain areas of low(er) population densityx. Eutrophication is also knownto be a common problem in reservoirs in Portugal. Another important factoris the seasonality. Indeed, pollution shows a distinct seasonality which isrelated to river run-off. Reservoir management doesn’t provide either for aguaranteed minimum flow for the preservation of ecological processes.

As reported by WWF, ”industrial effluents are disposed untreated in rivers. Veryfew industries have effluent treatment installations, and even those which dispose ofsuch systems do not operate them. […]. The worst pollution incidences occur in theriver AVE, north of the city of Porto, which drains an area with several textileindustries, in the river Alviela which receives the effluents of the numerous pig-farmsand tanneries located in its catchment […]. Furthermore, due to the inappropriateuse of pesticides and fertilisers, diffuse pollution is becoming a serious environmentalproblem especially in the Ave basin and in Alentejo.”


38

4.3.2 Regional Environmental Directorates (DRA) - Surface FreshwaterMonitoring

A number of monitoring station from the national monitoring network havebeen selected in all Regional Environmental Directorates (DRA) in order to carryout a monthly assessment of the evolution of surface freshwater qualitythroughout the country. This started in July 1998 and, at the time of writing,data are available up to March 1999. The accompanying colour-coded mapsare presented in Annex B of this report.

The results, as made available by INAG, are summarised in Table 4. 3

Table 4.3 National Overview of Surface Freshwater Quality

Date DRA Basin Section Quality / Criteria

July 1998 North

Alentejo

Ave

Guadiana,Sado

Overall Overall bad quality due tolow dissolved oxygen andhigh faecal coliforms

August 1998 North Minho, Lima,Cávado, Douro

Overall Decrease in quality due to aclear increase in organicmatter related to urban/industrial waste waterdischarges and a decrease inriver flows.

September 1998 North Minho, Limaand Douro

Overall Improvement in quality

Douro Pocinhoreservoir

Low oxygen levels

LVT Tagus Overall

Divorreservoir

High levels of organicmatter

High levels of totalcoliforms resulting in ClassD-E designation

Alentejo Guadiana, overall

Azenhas dosCerieiros


High levels of totalcoliforms resulting in ClassD-E designation

Sado Overall

Alvitoreservoir


High levels of total coliformresulting in Class D-Edesignation


39

Date DRA Basin Section Quality / Criteria

Mira Overall High levels of organicmatter

October 1998 North Cavado, Ave Overall Worsening of the overallsituation due to highphosphate levels

Alentejo Guadiana Monte daVinha,Azenha dosCerieiros,Ardila andTapa Grande

High levels of coliformresulting in designation inClass E

November 1998 North Cavado, Ave Overall Improvement of the overallquality

Centro Rib. De Oeste Overall “severe” problems due tourban waste water withouttreatment or withinadequate treatment

LVT Tagus As forNovember 98

Alentejo Sado, Mira As forSeptember 98

Guadiana Monte daVinha,Azenha dosCerieiros,Ardila, Pulode Lobo

Bad quality due to totalcoliform

Algarve Ponte Pereiro,Vidigal

Designated in Class E dueto total coliforms

December 1998 North Minho, Douro Overall limited degradation

Centro Rib, Oeste Overall As for November 98

LVT Tagus Overall As for November 98

Alentejo Guadiana Monta deVinha

High level of total coliforms

February 1998 North Minho, Douro,Vouga

Overall improvement

Source: INAG


40

Overall it can be observed that, during summer months, the basins ofnorthern Portugal (Cávado, Ave, Douro, Minho and Lima) are characterisedby high concentrations of faecal coliforms and low dissolved oxygen whichindicates contamination from urban waste waters. Similar situations occur inthe Guadiana basin (and more particularly in Monte de Vinha, Azenha dosCerieiros, Ardila and Tapa Grande), Ribiera de Oeste (Centre region), Tejobasin (especially the Divor reservoir), Sado basin (Alvito reservoir)

4.3.3 Direction Regional do Ambiente - Lisboa and Tagus Valley

(A) Rio Alviela

The basin of the Alviela river covers an area of about 327 km2 and is located inthe same area as the Tagus river (and is part of the Tagus basin itself). Itincludes the districts of Santarém, Alcanena, Golegã and Torres Novas. Dueto the geological characteristics of the region, surface waters andgroundwaters are linked and have high productivity.

Pollution sources in the region include agriculture with the most frequentcrops being tomatoes, maize, wheat, beans and fruits. However, industrialactivities in the region are also very important. Indeed, 85% of the country’sleather production units are in the Alcanena district, which represents 65% ofnational production. This is the main activity in the region and is the mainsource of pollution. However, the majority of industrial facilities in the regionare equipped with pre-treatment units and discharges are treated by theETAR de Alcanena plant.

In 1993, all samples taken in the Alviela, Monsanto and Carvalho rivers whereclassified as Q4 (see section 4.2 for the classification system). In 1997, 4 out of 7for Alviela river, all on Carvalho river still classified as Q4. Although it is notspecified which criteria was responsible for classification in Q4, thecharacteristics of the Q4 waters are those of waters contaminated by urbanwaste waters. However, an exact interpretation is impossible at this stage.

It is, however, known that the Pisão river makes a significant contribution tothe contamination of Alviela river. The worst results where observed in theCarvalho river. After the confluence with the Carvalho river the quality of theAlviela river largely improves. Indeed the levels of orthophosphates andorganic matter decrease but the nitrate concentration appears to increase,especially during the dry season. It seems that only when the Minde andMira d’Aire treatment station will come into operation, will the quality ofCarvalho improve.

(B) Rio Trancão

The Trancão river starts near Alto do Casal (Malveira) and after flowing forabout 30 km, discharges into the Tagus river, in its estuary near Sacavém. Itsbasin covers an area of about 288 km2 which is heavily populated with about400,000 inhabitants distributed between 271 agglomerations.


41

Currently there are 11 monitoring stations where samples are taken on amonthly basis. These are located on three rivers: Loures, Póvoa and theTrancão itself. The stations of Ponte Canas, Ponte Pinhal and Ponte Resingaare part of the OSPAR network which aims at preventing marinecontamination. The waters were also classified according to the criteriadefined in Table 4.2. of this report.

An analysis of the data shows that:

• the Póvoa has the highest concentrations of BOD5 which clearly suggestorganic pollution originating in that area. There are no indications as tothe exact sources of organic pollution.

• In Ponte Sacavém, the sea and strong tidal currents provide good dilutionand hence low values are observed for most parameters.

• The basic treatment provided hasn’t had any practical effects on waterquality in this basin.

4.4 NITRATE CONTAMINATION

The data used by the Portuguese authorities(1) in relation to nitrateconcentrations in surface freshwater are presented in Annex C of this report.It shows that only in a few areas, for the year 1996, have seasonal peaks ofnitrate concentrations occured. These are:

Table 4.4 NO3 - Seasonal Peaks (1996)

DRA Region Name of monitoring station NO3 (mg/l) Month

North MarachaoMonte AzenhasPonte do Porto

Castelo

43.800/48.0044.646.649.2

July/AugustSeptember

AugustSeptember

Centre Amor Milagres 74 November

Lisbon/Vale Tagus reservoir dos PatudosPunto Canas

114.555.58

AprilMay

Amongst the above monitoring stations, the main problems appear to be thePatudos reservoir and Punto Canas which are located on the Tagus (as shownin Figure 3.2) and which have nitrate concentrations well above 50 mg/l..Marachao is located on the Cavado river in the North.

INAG has also made available the results of the surface freshwatermonitoring network which provides monitoring data for at least the last ten

(1) as provided by INAG (March 1999)


42

years or so (1) . This database covers the entire country but the availableinformation varies significantly (quantitatively and qualitatively) both fromone region to another and from year to year. The main parametersconsistently measured which are of interest to us are Chlorophyll -a and NO3.

An assessment of the data available for the years 1994-1998 revealed that nosurface freshwater bodies had nitrate concentrations above 50 mg NO3/l orconcentrations approaching this limit-value. On the other hand, manyshowed high levels of Chlorophyll -a. Table 4.5 lists all monitoring points withhigh Chlorophyll -a values.

Table 4.5 Chlorophyll -a concentrations in surface freshwater

Basin Name Chlorophyll -a (µg/l) Date

Minho/Ancora Monção 13.615.8

08/199605/1997

Canado Alto Cavado reservoir > 10 07-11/1996/7

Douro Lameirão 10.2 - 128.3 06-10/1996Aç. Veiga de Chaves >20 summersRib. De Pena >20 summersAnelhe 30-138 08-11/1996/7Miranda do Douro reservoir 20-54 summersSemealho 10-53 summersPinhão >10 summersPenereiro reservoir 15.4-73.0 year roundBemposta reservoir >20 summers

Vouga Carvoeiro 10-367 summersPonte Requeixo 12-52 year roundPte S. João Loure 10-36 April-October

Mondego Nelas 10-56 summersPonte Faia 155 06/1998

245 07/1998Aguieira reservoir >10 year roundFerreirós >10 April-OctoberPonte Mucelas 198 06/1998Ponte Cabouco 572 06/1998Ponte Penacova 781 07/1998Ac. Raiva 698 06/1998

Lisboa and ribeiracostera

Monte Real 133-782 June-September

Amor >20 summersPonte Mestras 11-65 summersPonte Pedrinha >10 summersAlmeirão >100 June-july

Guadiana Monte Novo reservoir (abstr) 13-150.8 1994

(1) available on INAG's web site: http://set.inag.pt:80/snirh


43

All of the surface water bodies mentioned above have summer chlorophyll-aconcentrations above 10 µg/l. It is not unreasonable to assume that suchconcentrations indicate a degree of eutrophication. According to thePortuguese classification, a reservoir or lake will considered eutrophic ifChlorophyll -a concentrations are above 30 mg/m3.

4.4.1 Eutrophication - reservoirs and lagoons

Introduction

Due to hydrological pressures (spatial and temporal irregularity of wateravailability), numerous reservoirs were built throughout Portugal. There area total of 163 reservoirs located throughout the country. The location of themain reservoirs is shown on Figure 4.1.

Figure 4.1 Reservoirs

Source: DGA

These reservoirs were built for several different purposes, including:

• Energy production• Irrigation• Supply of water for domestic use• Supply of water for industrial use


44

The proportion of use is illustrated in Figure 4.2 and 4.3.

Figure 4.2 Use of reservoirs

Key: Energ=Energy, Raga=irrigation, Ab.con= domestic use, Ab.ind= industrial useSource: INAG

In the main basins (Douro, Tagus, Guadiana), the reservoirs are mainly usedfor supply of water for domestic use. On the other hand, to the North of theTagus river, this water is mainly used for energy production and to the South,for irrigation. Figure 4.3 illustrates the use of these waters in the mainhydrological basins.

The quality of these waters is therefore crucial and it appears that it has oftenbeen the reason for inadequacy for their planned or future use (INAG, 1998).A detailed list of all lakes and reservoirs with their individual use could notbe obtained.

INAG published a report in 1996 on the quality of surface freshwaters inPortugal (peRiod 1994/95). It focused on the biological quality of a series ofwater bodies, most of which were reservoir and dams. In relation toeutrophication, a trophic state index (TSI)1 was derived for all water bodiesinvestigated :

Table 4.6 Indicator of Eutrophic State

TSI STATUSTSI <45 Oligotrophic

45<TSI<52 MesotrophicTSI > 52 Eutrophic

Other eutrophication factors used were light penetration (minimum 3m) andconcentration of Chlorophyll -a (< 10 µg/l).

All water bodies investigated had TSI values > 53 that indicates signs ofeutrophication in all of them. In addition all water bodies had Chlorophyll -aconcentrations and Secchi disc readings that would qualify the water body aseutrophic. The data is summarised in Table 4.7.

1 TSIcla=9.81 Ln{cla} / 30.6 and TSI ds = 60 - 14.41 ln ds


45

Figure 4.3 Reservoir water use by basin


46

The majority of the reservoirs listed show clear signs of eutrophication .However, no detailed assessment of the quality of each individual reservoir,their uses and the sources of nutrients was carried out. It therefore seems thateach of these reservoirs should be considered for designation under bothDirectives. An overview of the quality of each reservoir is provided below.

Table 4.7 Indication of Eutrophication xi

TSI Chlo -a Secchi Comments

Albufeira de Miranda 60 20.7 2.6 showing signs of advancedeutrophication

Albufeira do Pocinho 58 15.7 2.2 considered to be eutrophic

Pinhão (albufeira da Régua) 54 10.6 1.8 considered to be eutrophic

Rio Mosteirô (albufeira doCarrapatelo)

55 11.8 2.7 considered to be eutrophic

Albufeira do Carrapatelo 53 9.4 3.1 considered to be meso-eutrophicwith a trend towards improvement

Entre-os-Rios 53 9.7 2.4 considered to be mesotrophic buttrends seem to show a trend towardseutrophication

Albufeira de Crestuma - Lever 53 9.9 2.1 considered to be mesotrophic buttrends seem to show a trend towardseutrophication

Ponte de Canaveses 60 19.7 1.9 showing signs of advancedeutrophication

Albufeira de Caniçada 53 10.3 4.4 Oligotrophic but with high potentialfor eutrophication to take place

In another study (Gil, 1996) xii, the quality of a series of reservoirs and smallrivers were assessed in order to determine their trophic status. The waterbodies are managed by EPD and therefore the monitoring is also carried outby EPD. With the monitoring results obtained the reservoirs were classifiedaccording to the criteria defined in the National Plan of Environmental Policy(Plano Nacional da Politica de ambiente (PNPA) - MARN, 1994) and theresults compared (see Table 4.8).

On the whole, the EDP data shows that five reservoirs are identified aseutrophic and not classified or classified as mesotrophic under the PNAPscheme. The main reason for this is that, under the PNAP scheme, theretention time, which can differ significantly from one lake to another, wasnot taken into account (ie Fratel reservoir);


47

Table 4.8 Eutrophication in EDP lakes

Name Status - PNPA Status - EDP

Alto Lindoso Eutrophic Mesotrophic

Alto Rabagão - Mesotrophic

Caldeirão Eutrophic Mesotrophic

Castelo Bode Mesotrophic Mesotrophic

Fronhas Eutrophic Eutrophic

Paradela Mesotrophic Oligotrphic

Pracana Eutrophic Eutrophic

Raiva Mesotrophic Mesotrophic

Salamonde Mesotrophic Mesotrophic

Torrão Eutrophic Eutrophic

Touvedo - Mesotrophic

Vilarinho Furnas Oligotrophic Oligotrophic

Bemposta Eutrophic Eutrophic

Bouça - Mesotrophic

Carrapatelo Eutrophic Eutrophic

Crestuma Eutrophic Eutrophic

Fratel Mesotrophioc Eutrophic

Miranda - Eutrophic

Picote - Eutrophic

Pocinho Eutrophic Eutrophic

Régua - Eutrophic

Valeira - Eutrophic

On the other hand, a series of reservoirs classified as eutrophic under thePNAP scheme were classified as mesotrophic under the EDP scheme. Thereason for this is that EDP considers that the time period during which watersare anoxic or have values inferior to 20% saturation must be taken intoaccount as opposed to PNAP which considers only the water depth.


48

Therefore, according to the results of this study, the following water bodiesshould be considered for designation under either or both Directives:

• Fronhas reservoir;• Pracana reservoir;• Bemposta reservoir;• Torrao reservoir;• Carrapatelo reservoir;• Crestuma reservoir;• Miranda reservoir;• Picote reservoir;• Pocinho reservoir;• Régua reservoir;• Valeira reservoir.

However, and as stated above, more information on the use of the these waterbodies as well as nutrient sources is required for their designation asVulnerable Zones. Such studies were not available at the time of writing.

One reservoir which is not mentioned above and which shows clear signs ofeutrophication is the Magos reservoir. This reservoir was constructed near thetown of Salvaterra de Magos, in the hydrographic basin of the Tagus river.Two of the main factors contributing to the lake’s eutrophication areagricultural activities and local climatic conditions (long exposure to sun).Indeed the main source of nutrient is agricultural effluents coming fromupstream of the reservoir which are rich in nitrogen and phosphorous. It ishowever considered that urban waste water should also be taken intoaccount. This reservoir has limited use (as defined in the DecretoRegulamentar 2/88), does not classify as a protected area and is mainly usedfor irrigation of rice fields in the region (about 534 ha). Its secondary uses aresailing, swimming and fishing. In 1987, the Magos reservoir was included inClass C, according to a classification made for all reservoir according to theiruse. Class C means the reservoir is “moderately polluted, sustaining a fishcommunity (the more resistant species), recreation without direct contact andirrigation in general “. It was commented by Almeida et al. xiii that thiseutrophication process is not irreversible and that this reservoir should beincluded in a programme. Obviously the main step is to reduce nutrientinputs into the reservoir.

4.5 WATERS USED FOR THE ABSTRACTION OF DRINKING WATER

As detailed in annex II of the Directive, surface freshwaters intended for theabstraction of drinking water which could contain more than theconcentration of nitrate laid down under the relevant provisions of CouncilDirective 75/440/EEC of 16 June 1975 concerning the quality required ofsurface water intended for the abstraction of drinking water in the MemberStates if action is not taken, should be designated as Sensitive Areas.


49

Figures 4.4 shows the quality and proportion of surface freshwater abstractedfrom 1993-1998. It shows that the quality of the water abstracted has largelyimproved since 1993. However, a non-negligible proportion (>10%) of theabstracted water is still of A3 quality.

Figure 4.5 shows the surface water abstraction points throughout the country.As can be observed, abstraction of surface freshwater is mainly carried out inthe northern part of Portugal and, to a lesser extent in the upper part of theTagus basin and western part of the Mondego basin.

Figure 4.4 Quality of surface water abstracted


50

Figure 4.5 Surface Water Abstraction Points

Source: INAG

Surface FreshwaterAbstraction Points

abstraction Point main rivers secondary rivers hydrological basins


51

4.5.1 Tagus Basin

According to the results obtained during a monitoring programme carried outby DRARN/LTVxiv, several waters are classified in category A3 and are notsuitable for abstraction of drinking water. The parameters responsible forsuch classification suggest contamination from urban waste water thatrenders these waters unsuitable for drinking water:

• Rio da Mula reservoir (Penha Longa river): COD• Valada (Tagus river): Cadmium, faecal streptococci;• Olhos Agua (Alviela river): faecal streptococci;• Mouriscas (Rio FRio river): COD

Although nitrate concentrations in these waters do not appear to be an issue,the COD is high and clearly shows contamination. High concentrations offaecal streptococci in Olhos Agua also seem to show contamination of‘domestic’ origin. It must be noted that during the year 1995/96, Olhos deAgua and Mouriscas were falling in category A1. This clearly shows adegradation of water quality in this region. The situation in the Alviela basinis discussed in the next section.

As mentioned before, the water quality at Valada (where 280,000 m3 areabstracted from the Tagus sub-system every day and released directly into theTagus) is of A3 (according to the criteria of Directive 75/440) and is due toparameters which indicate pollution of urban origin (faecal coliforms, BOD5and phosphates).

4.5.2 Alviela Basin

As stated above, Olhos de Agua is located in the Alviela basin which is partof one of the most important hydrogeological units in the country. In thissystem of aquifers of high productivity, groundwaters and surface waters arehighly inter-linked. The lower part of the basin is a zone of predominantlyagricultural activity (arable). The most frequent crops are tomatoes, wheat,maize, melons and fruit trees. The upper part of the basin lies on less fertilesoils and is therefore characterised by a higher number of industries. Atreatment plant was built in 1988 in Alcanena and treats most industrialeffluents (pre-treated at the industrial plant). This plant has a capacity ofabout 10,000 m3/day with an organic load of 400,000 population equivalent.

In 1997, monitoring at 10 stations (7 on the Alviela , 1 on the Monsanto and 2on the Carvalho) was carried out in order to classify the rivers. Allmonitoring points were in categories 3 and 4 which are characterised bynitrate concentrations > 50 mg/l, orthophosphate concentrations above 0.7mg/l and dissolved oxygen of 5 mg O2/l. It is assumed that the Pisão rivercontributes significantly to the pollution of the Alviela. In general, the qualityof the Monsanto river is not as bad as it may appear. The worst results havebeen obtained for the Carvalho which also contributes to the pollution of theAlviela. After their confluence, a decrease in organic matter and an increase


52

in nitrates can be observed. However treatment stations have been plannedfor Minde and Mira d’Aire. These will treat industrial effluent from theregion and it is thought that it will considerably improve the quality of theCarvalho river.

CONCLUSION

Rio de Mula reservoir, Olhos de Agua and Mouriscas should be consideredfor designation under the Urban Waste Water Treatment Directive. Althoughthere are figures indicating existing problems, more detailed information isrequired in order to confirm whether this water body (or part of it) should bedesignated or not.

4.5.3 The Ave basin

The basin of the Ave is located in the North of Portugal and surrounded bythe Cavado and Douro basins. The source of the Ave is located in the Serra daCabreira (1,200 m) at about 93.5 km from the mouth of the river at Vila doConde. The main tributaries are the Pele, the Pelhe and the Este on the Northbank and the Selho and Vizela on the South bank. The basin is characterisedby high precipitation, amongst the highest in the country.

This basin lies on fertile soils and is characterised by a high populationdensity and industrial plants (textiles mainly). There are nine abstractionpoints in the Ave basin, six of which are located on the Ave, one on the Esteand two on the Vizela.

On the basis of data gathered during successive monitoring campaigns, it iswidely recognised that, generally, the quality of the water in the entire basinis very low and that the water is not suitable for any use (especiallyabstraction of drinking water). Only the monitoring stations locatedupstream of the river show better results. In 1992, all monitoring data showedthat the entire basin requires designation in Class 3 (according to Directive75/440/EEC). The main pollutants appear to be oil, faecal coliform, P2O5 andN-NH4. The main cause for such low quality was the lack of waste watertreatment facilities.

The most polluted areas are those of Guimarães, Santo Tirso and Vila Nova deFamalicão where the majority of industries are located, together with about50% of the bassin’spopulation. The main source of pollution is urban wastewater as well as industrial effluents.


53

Figure 4.6 The Ave Basin

Source: INAG

CONCLUSION

The results from the above-mentioned report clearly indicate that the entireAve basin would have qualified for designation under the Urban WasteWater Treatment Directive. One of the reasons for which it may not havebeen designated is the plans made under the PEDIP programme, involvingtreatment capacity of about 1,220,000 p.e. and providing tertiary treatment.Indeed, it was a greed in 1991 that three waste water treatment plant wouldbe built on the Ave basin and should significantly improve the water qualityon the entire basin:

• Gondar: 0.35 m3/s or 270,000 p.e.• Rabada: 0.70 m3/s or 480,000 p.e.• Trofa: 0.70 m3/s or 390,000 p.e.

4.5.4 Alentejo

In 1997, a monitoring campaign took place in the region of Alentejo. The aimwas to assess the quality of (a) surface freshwater used for the abstraction ofdrinking water and (b) surface freshwater with multiple uses (includingrecreation - direct contact), as required by Directive 77/197/EEC.

With regards to waters used for the abstraction of drinking water, all wereclassified as A1 in relation to nitrate concentrations (See Section 4.2).


54

Nevertheless, several water bodies were classified as A2 or A3 in relation todissolved oxygen and BOD5. These are:

• Apartadura Class A2: Faecal coliforms• Ardila Class > A3: BOD5

• Monte ClerigoClass >A3: Dissolved oxygen• Monte Novo 1 Class >A3: BOD5

• Rocha de Nora Class >A3: BOD5

• Santa Clara 1 Class A3: BOD5

When compared to the 1996 results, no quality improvement can be observedand the classification remains identical.

It must be noted that the samples in Monte Clerigo reservoir were taken indeep waters and, consequently, the DO and BOD results are not considered tobe serious. Indeed this reservoir is almost redundant and is not monitoredanymore, with the exception of peRiodic measurements in relation togroundwater quality in the area.

In Monte de Rocha, it appears that effluents released by a nearby cattle-rearing unit is the cause for high BOD and signs of eutrophication.

With regards to waters intended for multiple uses, the majority of waters areclassified in class C (see Section 2) which means that these are suitable formost uses under the condition that they undergo rigorous treatment.

Two water bodies show a decline in quality between 1996 and 1997. These arethe reservoirs of Monte de Rocha and Monte Novo. Both have beendesignated as Sensitive Areas in 1997. Other water bodies classified in the C-D categories are Ardila (>= C), Bufo (>= C), Caia (C), Moinho da Gamita (D),Monte Clerigo (>=C), Monte da Vinha, (>=C), Povoa e Meadas (>=C), Pulo deLobo, Roxo (>= C), Santa Clara (C), Vigia (C) and Tapa Grande (C).

On the other hand, an improvement of the general situation is seen in theDivor, Ardila, Gafete and Azenha de Cereeiro reservoirs.

4.6 GROUNDWATERS

The regions where occurrence of groundwater contamination (fromanthropogenic sources) is most likely are the regions of Centre, North andAlgarve.

In the North, the main problems arose from:

• Barcelos district: 11.5% of the samples taken between 1987 and 1990 wereconsidered to be chemically unsuitable for use (especially in relation to

1 Designated as Sensitive Area by the Portuguese Authorities


55

nitrate concentrations). Only 28.8% were considered to be chemically andbacteRiologically suitable;

• Esposende district: over 25% of the samples taken between 1987 and 1990

show high nitrate concentrations (> 50 mg/l). Due to the presence ofcoliforms, about 82% of the samples were considered to thebacteRiologically unsuitable;

• Porto district: Nitrate concentrations in the region have been high in the

past (>50 mg/l). A decreasing trend has however been observed in the lastfew years.

In the Centre, the contamination of groundwater is due to both point sources(eg. domestic waste water discharge) and diffuse sources (eg excessive use ofpesticides).

• It is reported that in the region of Estarreja (aquifer system of BaixoVouga), the pollution level in the superficial aquifer has reachedsignificant levels due to discharges from both urban settlements and theChemical Complex of Estarreja.

In the hydrographic region of the Tagus, the following groundwater problemshave been detected:

• Sandro river valley: strong contamination of organic origin has beendetected and nitrate concentrations ranging between 74 and 471 mg/l NO3

have been measured. The main sources of pollution are thought to beagricultural, industrial and domestic.

• Almada/Seixal: this area is contaminated by heavy metals of industrial

origin.

In the region of Alentejo, agricultural activities are believed to be the cause forhigh nitrate concentrations in the aquifer of Odemira.

In Algarve, nitrate concentrations in groundwater are high and mainly causedby intensifying agricultural activities and excessive use of pesticides andfertilisers. In 1991, the average nitrate concentration in the surface aquifer ofCampina de Faro was 195,94 mg/l NO3.

A study (1) assessed the vulnerability of groundwaters in Portugal, the resultsof which showed that the most vulnerable aquifers are those located along thecoast, especially in the region between Espinho and Nazaré (Plio-quartenaryformation of sandy origin). Also of high vulnerability are the calcareousformations of the Jurassic and Cretaceous, which essentially occur in theAlgarve between Cabo de S. Vicente, Almádena and Estômbar, Escarpão

(1) DGA & IHRH (1996), Estudo de Avaliacao Da Vulnerabilidade Da Capacidade de Recepcao Das Aguas E ZonasCosteiras Em Portugal


56

( between S. Bartolomeu and the Southwest of Castro Marim), the west ofLisbon near Serra da Arrábida, to the east of Sesimbra and to the west ofSantiago do Cacém.

In a more general way, studies carried out in the region of the Centre, Lisboa eVale do Tagus and Algarve have shown both positive trends (eg. Porto andAlgarve) and stabilisation (eg. Vale de Tagus and lower Mondego) of thelevels of nitrate in groundwaters.


57

5 REVIEW OF THE WATERS DESIGNATED AS VULNERABLE ZONESUNDER THE NITRATES DIRECTIVE

5.1 INTRODUCTION

The methodology used by the Portuguese authorities to designate VulnerableZones is described in Section 2 of this report. In terms of available data, themain source for surface freshwater was the national monitoring networkwhich included drinking water abstraction points. With regards togroundwaters, the national groundwater monitoring network was being‘upgraded’ at the time of designation in order to ensure that all required dataare available.

5.2 SURFACE FRESHWATER

5.2.1 Introduction

One of the region most affected by nutrients from agricultural sources is theCentre-West region where animals density is very high. In that region, manywater courses are contaminated by nutrient from agriculture. These watercourses are also subject to extreme flow variations (drought during summermonths). Other regions which are know for the vulnerability of theirgroundwaters are the Tagus basin, Algarve, the Setùbal peninsula, as well asthe calcareous plains of Sierra de Aire e Candeeiros. Nitrate measurement inthese regions have shown concentrations up to 300 mg NO3/l.

As reported by WWF x, the worst pollution incidences occur in the riverAlviela which receives the effluents of numerous pig-farms located in itscatchment and the Ave basin and Alentejo where inappropriate use ofpesticides and fertilisers are making diffuse pollution a serious environmentalthreat.

5.2.2 Monitoring

As mentioned above, the national monitoring network, which covers theentire territory, provides nitrate concentrations in surface freshwater. Thesurface freshwater monitoring data used by INAG to designate SensitiveAreas was provided to ERM. The data provides nitrate concentrations infreshwaters for the year 1996. It appears that no surface freshwater bodieshave nitrate concentration strictly above 50 mg NO3/L. Nevertheless, someareas show nitrate concentrations approaching this limit-value, some of whichare areas with well-known problems (eutrophication, agricultural run-off,etc).

The monitoring points showing the highest nitrate concentrations are listed inTable 5.1.


58

Table 5.1 Nitrate Concentrations in Selected Surface Freshwater Monitoring Points

Name Region Basin NO3 (mg/l) Date

Açude Veiga Chaves (abst.) North 41.1 01/1996Arcozelo (abst.) North 40.700 01/1996Castelo (abst.) North 49.2 09/1996D.A. Caniçada (abst.) North 43.40 10/1996Foz do Tamega (abst.) North 41.00 01/1996Marachão (abst.) North 48.00 07/1996Marachão (abst.) North 43.80 08/1996Monte Azenhas (abst.) North 44.60 10/1996Segude (abst.) North 42.70 07/1996Castanheiro North 47.40 06/1996Ponte do Porto North 46.40 07/1996Ribeira de Pontes North 43.50 10/1996Milagres Centro 40.67 01/1996Reservoir dos Patudos LTV 114.95 04/1996Pt Canas LTV 55.58 05/1996

Source: INAG, 1996

Lisboa and Tagus Basin

It is acknowledged that agricultural activities are the main source of nitratesin the surface freshwaters of the Tagus valley. More specifically the districtsmost affected by nutrients are those of xv:

• Alcobaça• Caldas da Rainha• Rio Maior• Lourinhá• Torres Vedras• Moita• Montijo• Palmela

All of these districts are shown on Figure 5.1.


59

Figure 5.1 Districts affected by nutrients from agriculture

The river basins which are most affected are :

• Rio Tornada• Rio Arnoia (Lagoa de Obidos)• Rio Sizandro• Rio Grande

Lagoa de Obidos

This lagoon is a fragile coastal system which possesses both large intrinsic anduse value. This lagoon presently suffers from erosion and pollution of itsinner waters.

Magos Reservoir

As mentioned in Section 3.2, the Magos reservoir was constructed near the townof Salvaterra de Magos, in the hydrographic basin of the Tagus river. A seriesof studies have shown, without reasonable doubt, that this lagoon iseutrophic. Two of the main factors contributing to the lake’s eutrophicationare agricultural activities (by far the main pressure) and local climaticconditions (long exposure to sun). Indeed the main source of nutrients isagricultural effluents coming from upstream of the reservoir and which arerich in nitrogen and phosphorous.

The latest pollution case in the lagoon is related to ‘blue’ algae which posessevere health hazards for both the animal and human communities.According to studies done by Salvaterra’s Health Centre, the level of Bluealgae is about fourteen times above the permissible level. Consequently, anycontact with water must be avoided.

12

345

6 8

7

1. Alcobaça2. Caldas da Rainha3. Rio Maior4. Lourinhá5. Torres Vedras6. Moita7. Montijo8. Palmela


60

The contamination has reached such levels that one proposed solution was toempty the lagoon ,clean it and fill it up again. This clearly is not a long termsolution and only reflects the pressure created by agricultural practices in thearea.

5.3 GROUNDWATERS

5.3.1 Introduction

Williams & Mousco (1992) mentioned that aquifers are affected byagricultural pollution in the Ave basin, north of Lisbon (pig-farming) andAlgarve. The plains of the Tagus basin, Algarve and Serra de Aire eCandeeiros are know to be very vulnerable to groundwater contamination.Some measurements have shown concentrations above 200 mg NO3/l (seeFigure 5.1b).

Figure 5.1b Nitrate Concentrations in the regions of Estremadura, Baixo Tejo and Sado

Sources: Lobo Ferreira et al., 1994


61

5.3.2 Monitoring

Groundwater monitoring has been carried out in Portugal since about 1978 (atNUTS I and II scales) but concentrated on the aquifers of Algarve, lowerTagus, Sado and Aveiro.

The groundwater monitoring data provided by the Portuguese authoritiesconsists of the results in five aquifers, all which have already been designatedas Vulnerable Zones:

• Villa do Conde• Aveiro• Vagos• Mira• Campina de Faro

Comprehensive data is available for the region of Algarve, which isconsidered to be the most problematic area with regards to groundwatercontamination by nitrates from agriculture.A study by J.P. Lobo Ferreira (1995) xvi aimed to characterise the vulnerabilityof Portugal’s groundwaters in relation to nitrate pollution resulting fromurban, agricultural and industrial activities. The most vulnerable acquifersare those of :

• Silves - Querença• Falfosa;• Vale da Rosa;• Chaveca;• Laranjeiro;• Faiana.

However, aquifers which are less vulnerable than those listed above are notprotected from nitrate contamination. For example, the Campina de Faro(designated as Vulnerable Zone) and Campina de Luz de Tavira aquifers aresignificantly contaminated by nitrates.

The situation in the areas of the above-mentioned regions considered to bemost affected by nitrate pollution is summarised below.

5.3.3 Aquifers of Algarve

The Algarve’s main aquifers are shown in Figure 5.2.


62

Figure 5.2 Algarve's main aquifers

Source: INAG

Analytical Results

The results provided by DRA Algarve indicate that several aquifers havehigh nitrate concentrations. These are listed in Table 5.2.

Table 5.2 Groundwater Quality in Algarve

MONITORING STATION MAP REFERENCE NITRATES (MG/L) DATE

Quinta Grande 595/171 92.290 05/96

Cerca do Ouro 596/604 143.880 05/96Cerca do Ouro 596/604 60.700 11/96

Aroal 596/605 64.330 05/96

Alto Hortas JK6 600/62 68.420 05/96Alto Hortas JK3 600/63 84.180 11/96

Nora TD2 600/190 60.940 05/96Nora 600/190 57.260 11/96

Alporchino 604/69 50.060 05/96Alporchino 604/69 48.130 11/96

Maritenda 605/282 90.100 05/96Maritenda 605/282 78.620 11/96

Fabrica do Sumol 606/434 109.300 05/96Fabrica do Sumol 606/434 101.530 11/96


63

Paço Branco 607/134 105.300 05/96Paço Branco 607/134 80.620 11/96

Pé Outeiro 607/329 80.620 05/96

S.Pedro 608/67 108.640 05/96S. Pedro 608/67 65.070 11/96

Campina 608/477 55.520 05/96Campina 608/477 69.120 11/96

Covões 609/9 78.430 05/96

Montenegro 610/20 104.300 05/96Montenegro 610/20 103.290 11/96

Brejo 611/71 54.500 05/96Brejo 611/71 55.800 11/96

Fábrica de Cimento/Subetão 611/92 65.830 05/96Fábrica de Cimento/Subetão 611/92 69.660 11/96

Campina de faro 611/156 209.700 05/96Campina de Faro 611/156 176.620 11/96

Areal Gordo 611/225 93.140 05/96Areal Gordo 611/225 85.210 11/96

In the region of Algarve, only the Campina de Faro miocene jurasic aquifer wasdesignated as Vulnerable Zone by the Portuguese authorities. There arehowever numerous other points showing very high nitrate concentrationswhich would qualify for designation under the Nitrate Directive.

In general, high nitrate concentrations in the Algarve’s groundwaters are dueto the intensification of agricultural activities, and hence use of fertilisers andpesticides.


64

Figure 5.3 Groundwater Monitoring Network in Algarve

Source: INAG

In general it can be said that the calcareous aquifers, such as the Silves-Querença aquifer, are the most vulnerable to nutrient pollution. The upperJurassic formations and Cretaceous formations (eg Falfosa, Vale da Rosa,Chaveca, Laranjeiro, Faina, etc) also are relatively sensitive to pollution.The Miocene aquifer in Campina de Faro has been significantly polluted bynitrates for a time and it is estimated that there will be great difficulty inimproving the quality of the aquifer. The aquifer adjacent to Campina deFaro is also a carbonaceous Miocene aquifer separated by impermeableformations. The pollution in this aquifer is said to progress from top tobottom only.

Other aquifers showing high nitrates concentrations are those of Campina daLuz de Tavira which are located in Miocene and Cretaceous formations. Allof the above-mentioned aquifers are areas of intense agriculture. In the regionof Ribeira da Quarteira-Montenegro, the highest nitrate concentrations varybetween 61 and 221 mg/l. The source of nitrates in this region is estimated tobe solely agriculture. High nitrate concentrations can also be found in thesouth-west of Algarve and North of the agglomerations of Lagos andPortimao (Unida de Alvor-Albufeira), where most measurements are between50 and 100 mg NO3 /l.

A study carried out in 1994 by DRNA Algarve, provided additional data. Themonitoring points with high nitrate concentrations which were not included

Monitoring point principal river secondary river Basin


65

in Table 5.2 are listed in Table 5.3. in some instances it shows extremely highnitrate concentrations (eg Patacão - 248.80 mg nitrate/l).

Table 5.3 Nitrate concentrations in groundwaters (Algarve)

NAME MAP REFERENCE NO3 DATE

Monte Ruivos 026/587 57.60 12/92Monte Ruivos 026/587 79.60 03/93Monte Ruivos 026/587 62.96 01/94

Fonte de Louseiros 206/595 254.50 12/92Fonte de Louseiros 206/595 238.10 03/93Fonte de Louseiros 206/595 236.80 06/93Fonte de Louseiros 206/595 175.58 09/93Fonte de Louseiros 206/595 282.84 01/94

Paço Branco 134/607 131.20 03/93Paço Branco 134/607 183.90 06/93Paço Branco 134/607 81.56 09/93Paço Branco 134/607 162.28 01/94Paço Branco 134/607 52,00 03/94Paço Branco 134/607 56.48 09/94

Vale da Rosa 453/607 61.70 12/92Vale da Rosa 453/607 56.70 03/93Vale da Rosa 453/607 58.30 06/93

Campina da Luz 366/608 55.28 09/93Campina da Luz 366/608 93.50 03/93Campina da Luz 366/608 95.61 06/93Campina da Luz 366/608 89.55 09/93Campina da Luz 366/608 95.29 01/94

Patacão 093/610 248.80 03/93Patacão 093/610 230.60 06/93Patacão 093/610 213.20 09/93Patacão 093/610 216.60 01/94

Marchil 189/610 123.80 06/93Marchil 189/610 123.30 09/93Marchil 189/610 119.19 01.94

Brejo JK3 071/611 53.80 01/93Brejo JK3 071/611 52.20 06/93Brejo JK3 071/611 53.50 09/93Brejo JK3 071/611 57.62 01/94

João D’Ourem 085/611 56.60 12/92João D’Ourem 085/611 61.60 03/93João D’Ourem 085/611 63.20 06/93João D’Ourem 085/611 59.94 09/93

It is recognised that these high nitrate concentrations are correlated withagricultural practices in the region of Algarve. This can also be confirmed bythe soil-use map below which shows that a majority of the land in Algarve isused as mixed agricultural land and arable land.


66

Figure 5.4 Soil Use in the Algarve

Aquifers with high nitrate concentrations

The aquifers with high nitrate concentrations are briefly reviewed in thissection. The graphs illustrate the nitrate trends in these aquifers (includingseveral of the points listed in Table 5.2 and Table 5.3).

(a) Covões aquifer

Due to very high nitrate concentrations which reflect severe contamination ofagricultural origin, the water quality of this aquifer is classified as A3. Thereappears to be a cycle in these concentrations. The highest concentrations aremeasured in November. It must be mentioned that measurements have onlyto be taken at one sample point for the whole aquifer. The graph belowshows nitrate concentration trends.

Source: INAG

Land Use(CORINE)

Artificial space


Permanent Cultures


areas

Forests


Open spaces

Maritime zones

Continental waters


67

(b) Querença-Silves

As a whole, the water quality of this aquifer is very good (A1). However,over the years, occasional degradation of this quality is observed, mainly dueto nitrate contamination.

(c) Albufeira-Ribeira de Quarteira aquifer

The quality of this aquifer is, as a whole, A1. However, in the northern part ofthe aquifer (monitoring point 596/604), very high concentrations of nitrateshave been observed. These are said to be point source events and notrepresentative of this zone. A cycle is also observed in nitrate concentrations.The highest concentrations are observed in April-May.

Source: INAG

(d) Quateira aquifer

Although the global quality of this aquifer is A1, there are clear signs ofsignificant nitrate contamination of agricultural origin in the middle of theaquifer (monitoring point 605/282). This is illustrated in the graph below:

Source: INAG

(e) João de Venda-Quelfes aquifer

In this aquifer there are several points which show high nitrate concentrations(mainly points 607/134 and 607/278). This contamination result fromagricultural activities. This is illustrated in the graphs below.


68

Source: INAG

(f) Luz de Tavira

The overall degradation in the quality of this aquifer is due to an increase innitrate concentrations. The trend shows that even when the nitrate limit-value is not reach, the nitrate concentration remains very near the limit. Theworst situation is encountered at monitoring point 608/67 (as shown below).

(g) São Bartolomeu aquifer

Overall the quality of this aquifer is classified as A3, mainly due to nitrateconcentrations. The highest concentrations are observed in points 600/63 and600/190). The graph below shows that concentrations are on the increase.


69

Source: INAG

Conclusion

The most severely affected parts of the Algarve are those of Campina de Faroand Ria de Alvor, both of which have been designated as Sensitive area. OnlyCampina de Faro was designated as a Vulnerable Zone. Generally, the sourceof nitrates in this region is agriculture and the most recent studies carried outshow an increasing trend of nitrate concentrations in groundwaters. Thezones in SW Algarve may present high nitrate concentration due to highvulnerability caused by sedimentary rocks.

• The high nitrate concentrations in the Alvor reservoir region are mainlydue to an increase in agricultural activities and increased use of fertilisers.This shallow groundwater resources do, therefore, appear to qualify fordesignation under Directive 91/676/EEC.

• The zone of Quarteira Montenegro also presents nitrate concentrations wellabove the limit, the source of which can be assumed to be solelyagriculture. This zone, therefore, appears to qualify for designation underDirective 91/676/EEC.

• SW Algarve: here again, the high nitrate concentrations are related toagricultural activities, which suggests that the groundwaters qualify fordesignation under Directive 91/676/EEC.

As illustrated above, it seems that the following aquifers do qualify fordesignation as Vulnerable Zones:

• Covões;• Querença-Silves;• São Bartolomeu• Albufeira - Ribeira de Quarteira;• São João da Venda - Quelfes;• Luz de Tavira;• Quarteira.


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5.3.4 Central Region

Estarreja

In conjunction with the industrial development in this region, agriculturalactivities in the region of Estarreja have also increased over the last few years.This has also influenced population density which has now reached 200inhabitants/km2. A Sensitive Area was also designated in the region ofEstarreja (Ria de Aveiro). In this region the average annual concentration liesaround 80 mg NO3/l, with values up to 260 mg/l. The high nitrateconcentrations around the chemical complex of Estarreja seem to be a specificcase. In an assessment carried out in 1989 (Mestrado de Silva, 1989), 40 wellsout of 60 showed concentrations above 50 mg/l nitrate.

Cantanhede - Aveiro - Ovar

A study assessing figures collected in 1983-1984 in the quaternary waters ofthe lower Vouga groundwater system available. The distribution of the datacollected shows concentrations above 46 mg NO3/l in several locations (11 intotal) around Ria de Aveiro. According to Cristoxvii, the high values show aclear lack of adequate infrastructure for urban waste water and an increasinguse of fertilisers and pesticides. The Cretaceous and Jurassic systems adjacentto the quaternary system showed lower nitrate concentrations - reaching 30mg NO3/l on only two occasions.

In this region, the Aveiro quaternary aquifer was designated as a VulnerableZone.

5.3.5 Alentejo

Evora

A study by Chambel (1992) showed that nitrate concentrations have reached ahigh levels in the region of Evora where more than 50% of measurementsmade showed concentrations above 50 mg NO3/l.

The statistical distribution of these values, according to soil formations, is asfollows:

Table 5.3 Nitrate concentrations in the Evora region

NO3 (mg/l) Arithmetic mean Average Maximum Minimum

Total 70.6 52.1 285.2 10.5Quartzodiorito 75.7 55.8 285.2 19.8Gnaisse 57.4 42.2 210.8 10.5Corneana 60.0 71.3 124.0 19.2Xisto 114.1 63.2 248 31.0


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It is believed that the waters intended for the abstraction of drinking wateraround Evora are very much prone to contamination by nitrates. Deeperaquifers, however, do not show nitrate contamination. The nitrates are clearlyof agricultural origins.

Elvas - Vila Boim

In a report by Silva (1991) the distribution of NO3 concentrations collectedduring two monitoring campaigns in the region are compared (max: 322 mgNO3/l, min: 22 mg NO3/l and average 81 mg NO3/l). The majority of wellshave concentrations between 50 and 100 mg NO3/l.

Although it shows globally similar values, concentrations are very different(at some places and at some periods) and seem to demonstrate a certaininstability in nitrate concentrations in groundwater. It has been establishedthat the nitrates are of agricultural origin.

Beja District

Another study looked at nitrate concentration in groundwaters used for theabstraction of drinking water in the region of Beja. It appeared that severalmeasurements showed concentrations well above 50 mg/l.

Gouveia (1994) reported that a large number of measurements made in theBeja region are well above 50 mg/l. Their distribution is shown in Annex A ofthis report.It has been established that the nitrates are of agricultural origin.

Verride (lower Mondego valley)

A study carried out in 1989 showed that a large number of wells located Eastof Figueira da Foz have nitrate concentrations well above 50 mg/l (8 wellswith concentration between 50 and 100 mg/l and 3 wells with concentrationsbetween 100 and 200 mg/l).

Figures indicate a declining trend in nitrate concentrations and have nitrateconcentrations below 30 mg/l by the end of the 1980’s. However, a few wellsstill showed concentrations well above 60 mg/l (up to 160 mg/l) by the end of1980’s.

Odemira District

It was reported by Gouveia (1994) that all several areas in the district havehigh nitrate concentrations due to agricultural activities.


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CONCLUSION

Several areas of the Central region also show high nitrate concentration ingroundwaters.

• Aveiro - Ovar region. The Portuguese authorities designated the Aveiroquaternary aquifers as Vulnerable Zone. This zone extends to the south-east of the agglomeration of Aveiro. Although adjacent groundwatersystems have much lower nitrate concentrations, the system around Ovar(north of Aveiro) also shows very high nitrate concentrations ingroundwater. It was shown by Lobo Ferreira (1995) that groundwaters inthis zone are particularly vulnerable due to floods and are affected bysandy formations of generally high permeability. It therefore seems thatthe Vulnerable Zone should be extended northwards along the coast whichis mainly formed of arable land (annual crops).

• High NO3 concentrations were also detected around Estarreja. It seems

however that such nitrate levels are due to industrial activities in theregion and that it therefore does not qualify for designation.

• Aquifers have also been found to have high nitrate concentrations of

agricultural origins in the districts of Beja, Evora and Elvas.

5.3.6 Lisbon and the Tagus Valley

For this region, nitrate measurements in groundwaters have been made since1956 and include a total of 861 water bodies. The spatial distribution ofnitrate concentrations in both water bodies and wells is shown in Figures 4.5and 4.6 respectively. As can be seen in Annex A, the majority of groundwaterswith concentrations above 50 mg/l are shallow groundwaters. The mostsevere conditions are in the alluvial formations of the Tagus and the sandyzones on the peninsula of Setubal. This is related to the high vulnerability ofthe whole area. The situation in deep aquifers is a lot better, althoughconcentrations between 50 and 100 mg/l were recorded in several wells to theSW of Alcobaca. Figure 5.5 show the land use in the region.


73

Figure 5.5 Land Use in the Tagus Basin

Source: INAG

Other data from Novo (1991) show repeatedly high nitrate concentrations (>50 mg NO3/l) in the Torres Vedras zone near the Sizandro river. Nitratevalues there ranged between 74 and 471 mg/l. In this case, the contaminationis of industrial origin.

More generally, high nitrate concentrations have been recorded in severallocations in the region, including several above 200 mg NO3/l: Rio Maior(325,3 mg/l), Seixal (274,5 mg/l), Almeirim (226,1 mg/l) and Torres Vedras(203,5 mg/l).

CONCLUSION

As mentioned above, the are several wells showing high nitrateconcentrations in shallow groundwaters in the region. The most alarmingcases appear to be associated with alluvial formations of the Tagus andSetubal peninsula, which according to Lobo Ferreira (1995) also are highlyvulnerable to nitrate pollution. Figure 5.5 shows that the areas along theTagus river and upstream of the Sado estuary are mainly arable land (annualcrops).

Land Use(CORINE)


74

Golegã District

The aquifer formations of the region are part of the larger hydrogeologicaldivisions of the Tagus and Sado sedimentary basin. According to S.Rodrigues et al. (1989), this basin is formed of Miocene and quaternaryformations linked together. It can therefore be assumed that it forms a singleaquifer. According to DRA, there are about 100 abstraction points varyingfrom a few meters to 270 m depth.

A monitoring campaign carried out in 1996 revealed that, out of 14 stationssurveyed, seven had nitrate concentrations higher than the limit valuerecommended for drinking water. All of these are said to be caused byagricultural activities, urban waste water and industry.

It can be concluded that shallow groundwaters ( < 40m) in this region arecontaminated by nitrates and have, in some areas, concentrations above 70 mgNO3/l. Deeper groundwaters (> 200m) do not appear to be affected.However, there is no detailed information that allows the source of nitrates tobe identified in more detail.

5.3.7 Northern Region

Synthetic data

The majority of data in this part of the country are only available in syntheticform and are presented by district.

• Amares

mg NO3/l %NO3 < 1 34.69

1 ≤ NO3 ≤ 10 36.7310 ≤ NO3 < 25 18.3725 ≤ NO3 ≤ 50 9.69

NO3 ≥ 50 0.51

• Terras de Bouro

mg NO3/l %NO3 < 1 62.35

1 ≤ NO3 ≤ 10 35.4910 ≤ NO3 < 25 1.8525 ≤ NO3 ≤ 50 0.00

NO3 ≥ 50 0.31


75

• Barcelos

mg NO3/l %NO3 < 1 20.43

1 ≤ NO3 ≤ 10 36.0710 ≤ NO3 < 25 25.0825 ≤ NO3 ≤ 50 11.61

NO3 ≥ 50 6.81

11.5 % of the samples collected in the region of Barcelos between 1987 and1990 were considered to be of very bad chemical quality, especially withregards to nitrates.

• Esposende

mg NO3/l %NO3 < 1 16.03

1 ≤ NO3 ≤ 10 29.0110 ≤ NO3 < 25 28.2425 ≤ NO3 ≤ 50 19.08

NO3 ≥ 50 6.87

Just under 30% of the samples collected between 1987 and 1990 showedhigh nitrate concentrations (>50 mg/l). The bacteriological and biologicalquality of the water was also considered to be bad.

• Montalegre

mg NO3/l %NO3 < 1 16.03

1 ≤ NO3 ≤ 10 29.0110 ≤ NO3 < 25 28.24

• Povoa de Lanhoso

mg NO3/l %NO3 < 1 23.02

1 ≤ NO3 ≤ 10 51.1910 ≤ NO3 < 25 18.2525 ≤ NO3 ≤ 50 5.95

NO3 ≥ 50 1.59

• Braga

mg NO3/l %NO3 < 1 20.05

1 ≤ NO3 ≤ 10 33.5210 ≤ NO3 < 25 25.0025 ≤ NO3 ≤ 50 15.11

NO3 ≥ 50 6.32


76

• Veira do Minho

mg NO3/l %NO3 < 0.5 20.80

0.5 ≤ NO3 ≤ 5 56.905 ≤ NO3 < 10 15.9

10 ≤ NO3 ≤ 25 5.325 ≤ NO3 ≤ 45 1.1

• Vila Real

mg NO3/l %NO3 < 1 20.54

1 ≤ NO3 ≤ 10 59.9210 ≤ NO3 < 25 17.4325 ≤ NO3 ≤ 50 2.11

NO3 ≥ 50 0.00

• Resende

mg NO3/l %NO3 < 1 0.00

1 ≤ NO3 ≤ 10 0.00NO3 < 25 51.85

25 ≤ NO3 ≤ 50 46.76NO3 ≥ 50 1.39

Porto District

The results of monitoring where summarised by Alpendurada et al. (1991) byrange of concentration:

Table 5.3 Groundwater concentrations in the Porto District

District % NO3 < 25 (mg/l) 25 ≤≤≤≤ %NO3 ≤≤≤≤ 50 (mg/l) % NO3 > 50 (mg/l)

Amarante 57 14 29Baiao 78 0 22Felgueiras 40 0 60Gondomar 24 13 63Lousada 100 0 0Maia 33 24 43Marco de Canaveses 71 29 0Matosinhos 29 17 54Paços de Ferreira 44 34 22Parades 42 16 42Penafiel 71 0 29Porto 39 23 38Povoa do Varzim 29 42 29Santo Tirso 58 15 27Valongo 35 14 51Vila do Conde 44 26 30V.N. de Gaia 36 21 43


77

The above table shows that several areas have more than 50% of sampleswhich have a nitrate concentrations above 50 mg NO3/l and hence maypresent severe nitrate contamination. These areas are:

• Feilgueiras• Gondomar• Matosinhos• Valongo

But more generally, the percentage of samples with concentrations above 50mg/l is relatively high and shows a more general problem in the Porto districtrather than localised contamination.

Conclusion

Although no detailed data were made available, the synthetic data clearlyshows that a very high percentage of samples taken in the Porto district havenitrate concentrations above 50 mg/l. Particular problem areas includeFeilgueiras, Gondomar, Matosinhos and Valongo.

It therefore appears that there is extensive nitrate contamination in theregion’s groundwaters and that it should be taken into consideration fordesignation under Directive 91/676/EEC.


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6 CONCLUSIONS

The following table summarises the water bodies which were identified asqualifying for identification under either or both Directives. For many areas,however, it was not possible to identify the source of nutrients. It is thereforevery difficult to identify under which Directive they should be designated.

Table 6.1 Water Bodies Qualifying for Designation

Nº BASIN NAME CRITERIA VULNERABLEZONE

SENSITIVE AREA

1 Sado Marateca Bay and AlcacerChannel (Sado estuary)

nutrient enrichment andalgal blooms

��

2 Mondego Mondego estuary eutrophication ��

3 Tagus Mago Reservoir eutrophication ��

4 Algarve Covões aquifer NO3 ��

5 Algarve Querença-Silves aquifer NO3 ��

6 Algarve Albufeira-Ribeira deQuarteira aquifer

NO3 ��

7 Algarve Quarteira aquifer NO3 ��

8 Algarve João de Venda-Quelfesaquifer

NO3 ��

9 Algarve Luz de Tavira aquifer NO3 ��

10 Algarve São Bartolomeu aquifer NO3 ��

11 Algarve Alvor NO3 ��

12 Sado Evora aquifer NO3 ��

13 Guadiana Elvas-Vila Boim aquifer NO3 ��

14 Guadiana Beja aquifer NO3 ��

15 Tagus Cala do Norte (TagusEstuary)

Bacteria of faecal originand organic pollution

��

16 Tagus Rio da Mula reservoir Bacteria of faecal originand organic pollution

��

17 Tagus Tagus (near Valada) Bacteria of faecal originand organic pollution

��

18 Tagus Olhos de Agua (Alvielariver)

Bacteria of faecal originand organic pollution

��


79

Nº BASIN NAME CRITERIA VULNERABLEZONE

SENSITIVE AREA

19 Tagus Mouriscas (Rio Frio) Bacteria of faecal originand organic pollution

��

20 Ave The whole basin Bacteria of faecal originand organic pollution

��

21 Tagus Alviela river Q4 quality ? ?

22 Tagus Carvalho river Q4 qulaity ? ?

23 Tagus Pisão river Q4 quality ? ?

24 Tagus Trancão river organic pollution ? ?

25 Tagus Póvoa organic pollution ? ?

26 Tagus Punto Canas NO3 ? ?

27 Tagus Reservoir dos Patudos NO3 ? ?

28 Cavado Cavado (around Marachao) NO3 ? ?

29 Douro Miranda reservoir eutrophication ? ?

30 Douro Pocinhos reservoir eutrophication ? ?

31 Douro Pinhão (Régua reservoir) eutrophication ? ?

32 Douro Mosteirõ (Carrapateloreservoir)

eutrophication ? ?

33 Douro Entre Rio trend towardseutrophication

? ?

34 Douro Crestuma Lever reservoir trend towardseutrophication

? ?

35 Tagus Ponte de Canaveses eutrophication ? ?

36 Mondego Fronhas reservoir eutrophication ? ?

37 Tagus Pracana reservoir eutrophication ? ?

38 Douro Torrão reservoir eutrophication ? ?

39 Douro Bemposta reservoir eutrophication ? ?

40 Douro Picote reservoir eutrophication ? ?

41 Douro Valeira reservoir eutrophication ? ?


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7 REFERENCES

i Anon. (1993). Eutrophication Symptoms and Problem Areas. Oslo & Paris

Commissions. London. 26 pages plus maps.ii OECD (1993), OECD Environmental Performance Reviews - Portugal, OECD Paris.iii INAG (1994), Identificação de zonas sensíveis e menos sensíveis - Directiva 91/271/CEE

Águas Residuas Urbanas, INAG Direcção de serviços de recursos hídricos.iv IPIMAR, Seasonal and Spatial Aspects in Chlorophyll a in Portuguese Watersv M.H. Cavaco (1998), Seasonal and Spatial Aspects of Chlorophyll a distribution in

Portuguese waters during the peRiod 1985-1996, Bulletin of the Sea Fisheries Institute2(144), 1998.

vi Oliveira and Cabeçadas (1996), Marine Benthic Vegetation, Recentvii IHRH (1996), Estudo de Avaliacao da Vulnerabilidade daCapacidade de Recepcao das

Aguas e Zonas Costeiras em Portugal - RelatoRio de Sintese, Instituto de Hidraulica eRecoursos Hidricos.

viii Cabeçadas (1993), Ecologia do fitoplâncton do estuáRio do Sado: para uma estratégia deconservacão. Estudos de Biologia e Conservacão da Natureza 10. SNPRCN, Lisboa.

ix Cabeçadas and Brogueira (1993), The behaviour of Phosphorus in the Sado Estuary,Portugal, National Institute of Fisheries Research, Lisbon.

x D. Hatzilacou, C. Haynes (1996), Protecting the Freshwater Ecosystems of SouthernEurope - Strategy for an Integrated Approach, WWF 1996

xi INAG (1996), InventaRio do estado de qualidade das aguas doces superficias, Anohidrologico de 1994/95, MinisteRio do Ambiente July 1996

xii Lourenco Gil (1996), Classificação trófica das albufeiras exploradas pela EDP, Labelec-Grupo EDP

xiii Almeida et al., Programma de monitorisacao de cianobacterias- Albufeiras de Coruche ede Salvaterra do magos

xiv DSA-DHR Sector Qualidad de Agua (1999) Qualidad de Aguas Superficiais Destinadasa Producao de Agua Para Consumo Humano

xv J.T. Capucho (DRA Lisboa e Vale do Tagus), Pers. Communication (11/02/99)xvi J.P. Lobo Ferreira (1995), Caracterizacão do Estado das Ãguas Subterrâneas em relação à

poluição causada por Nitratos, LaboratoRio Nacional de Engenharia Civil.xvii Cristo (1985),

Annex B

Surface Freshwater Quality

Classification System

A B C D E

PARAMETERS

pH 6.5 - 8.5* - 6.0 - 9.0 5.5 - 9.5 -Temperature (ºC) <=20 21 - 25 26 - 28 29 - 30 >30Condutivity (uS/cm,20ºC) <=750 751 - 1000 1001 - 1500 1501 - 3000 >3 000SST (mg/l) <=25.0 25.1 - 30.0 30.1 - 40.0 40.1 - 80.0 >80.0Sat OD (%) >=90 89 - 70 69 - 50 49 - 30 <30BOD5 (mg O2/l) <=3.0 3.1 - 5.0 5.1 - 8.0 8.1 - 20.0 >20.0COD (mg O2/l) <=10.0 10.1 - 20.0 20.1 - 40.0 40.1 - 80.0 >80.0Oxygen (mg O2/l) <=3.0 3.1 - 5.0 5.1 - 10.0 10.1 - 25.0 >25.0Ammonia (mg NH4/l) <=0.10 0.11 - 1.00 1.10 - 2.00 2.01 - 5.00 >5.00Nitrates (mg NO3/l) <=5.0 5.0 - 25.0 25.1 - 50.0 50.1 - 80.0 >80.0Phosphates (mg P2O5/l) <0.54 - <0.94 >0.94 -Total coliforms (/100 ml) <=50 51 - 5000 5001 - 50000 >50000 -Faecal coliforms (/100 ml) <=20 21 - 2000 2001 - 20000 >20000 -Iron (mg/l) <=0.50 0.51 - 1.00 1.10 - 1.50 1.50 - 2.00 >2.00Manganese (mg/l) <=0.10 0.11 - 0.25 0.26 - 0.50 0.51 - 1.00 >1.00Zinc (mg/l) <=0.30 0.31 - 1.00 1.10 - 5.00 - >5.00Copper (mg/l) <=0.020 0.021 - 0.05 0.051 - 1.00 - >1.00Chromium (mg/l) <=0.05 - - - >0.05Selénium (mg/l) <=0.01 - - - >0.01Cádmium (mg/l) <=0.0010 - 0.0011 - 0.0050 - >0.0050Mercúry (mg/l) <=0.00050 - 0.00051 - 0.001 - >0.001Arsenic (mg/l) <=0.010 0.011 - 0.050 - 0.051 - 0.100 >0.100

Figure B1 Surface Freshwater Quality in Portugal - July 1998

Figure B2 Surface Freshwater Quality in Portugal - August 1998

Figure B3 Surface Freshwater Quality in Portugal September 1998

Figure B4 Surface Freshwater Quality in Portugal October 1998

Figure B5 Surface Freshwater Quality in Portugal November 1998

Figure B6 Surface Freshwater Quality in Portugal December 1998

Figure B7 Surface Freshwater Quality in Portugal - January 1999

Figure B8 Surface Freshwater Quality in Portugal - February 1999

Figure B9 Surface Freshwater Quality in Portugal - March 1999

Figure B10 Surface Freshwater Quality in Portugal - April 1999

Figure B11 Surface Freshwater Quality in Portugal May 1999

SOIL USE

JULY 1998

AUGUST 1998

SEPTEMBER 1998

OCTOBER 1998

NOVEMBER 1998

DECEMBER 1998

JANUARY 1999

FEBRUARY 1999

MARCH 99

APRIL 1999

MAY 1999

ective - portugal - european commissioncontents 1 introduction 1 1.1 background 1 1.2 scope 5 2...

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