+ In this section you'll explore the human threats to water quality.

Quality not quantityNot only do we need enoughwater for everyday use, butthe quality of our water is justas important as the quantity.People can suffer from waterstress if their water isn't safe,or is contaminated.

The diagram below showsa wide range of sources ofpollution - the worst can beclassified as:• Industrial pollution• Sewage disposal• Intensive agriculture

• Other

... Sources of water pollution

Disposal ofhazardous

Deforestation

Chemical applicationto parks and lawnsand golf

Excessivefertiliserapplication

Industrial PollutionThe highest levels of water pollution are often found in countrieswith rapid rates of economic growth, such as India and China (seegraph) - which tend to put economic growth before environmentalprotection. Three main types of water pollution from industrial activityare:• Chemicals (e.g. from the manufacture of plastics, oil, pesticides,

and PCBs) and inorganic solid compounds (such as toxicmaterials and cyanide from mines) - these can poison stretchesof river completely, killing all life.

• Radioactive substances (e.g. from nuclear waste treatment) -these can lead to cancers such as leukaemia.

• Thermal (heat) pollution (e.g. from power stations pumping hot wastewater into rivers) - increasing the rate of decomposition of bio-degradable waste, which reduces the river's ability to retain oxygen.

However, as countries develop, they often control pollution by law. Inthe late 1960s, Japan's lakes, rivers and seas were all badly pollutedcausing major health problems and damage to ecosystems. As aresult of recent pollution laws, the rivers entering Tokyo and Osaka Bay- two of Japan's industrial areas - are now almost free of pollutants .

Salt runofffrom roads

Sewage treatmentI

Siltation in

p-mining

Landfill

Septic systemFreshwater aquifer

Undergroundwater storage

Municipalsewage

waste (slurry) discharge

Storm-waterrunoff

disposaldischarge in deep wells

I Water world

Attempts to counterpollution, clean upsMonitoring levelsSustainable strategies

co~"00-

!••'0•] Widespread sewage!

litter/waste pollutionSome farm pollutione.g. Bangladesh

Huge industrial!energy pollutionWidespread agriculturalpollution e.g. China and Indiaor Japan in 1970s and 80s

Improving waterquality e.g. Japantoday

Developing Emerging economiesEconomic development

Developed

Intensive agricultureThere are two main types of water pollutioncaused by intensive agriculture:

• Chemical - Modern commercial agriculturerelies on pesticides and fertilisers to increasecrop yields. The run-off of those chemicalsincreases water pollution as plant nutrientsfrom fertilisers (e.g. nitrates and phosphates)seep into rivers, causing eutrophication.In this case, river water is polluted by richnutrients, leading to the rapid growth of algae.These starve the river water of oxygen.

• Solid - While chemical pollution existswidely, it tends to be less concentrated.Sometimes, animal manure escapes intostreams as slurry, polluting streams with rawsewage. Like eutrophication, slurry dumpingdeprives river water of oxygen, killing manyorganisms.

your questions

1 a Draw a table to classify all of the pollutants fromthe diagram on the opposite page. Use theheadings industrial pollution, sewage disposal,intensive agriculture, and others.

b Which category has the worst impacts? Explainyour answer.

Sewage disposalMany of the world's mega-cities such asMumbai are experiencing rapid urban growth,faster than piped water and waste disposalsystems can be installed. As a result, streamsflowing through the slums and shanty townsof megacities are badly affected by pollution(see the photo). People use the rivers forwashing clothes, boiling water for cooking,or swimming. For people living there, contactwith this water presents three potentialimpacts:

• Diseases - such as cholera, typhoid,dysentery, or hepatitis - caused byharmful organisms (e.g. bacteria, viruses,river worm, rats).

• Domestic sewage consumes oxygen in thewater and kills many organisms throughoxygen depletion.

• Suspended solids affect the colour of thewater and kills fish / shellfish.

2 Draw a spider diagram to show why industries andfarmers may resist laws to control and reduce pollution.

3 Why do you think countries such as India and Chinado not have standards for water quality, as Japan nowdoes?

4 Exam-style question Using examples, explain howpollution threatens water quality. (6 marks)

+ In this section you'll look at some of the impacts of humaninterference in the hydrological (water) cycle.

Human interferenceWater isn't just for drinking and washing.It is used for industry, farming (irrigation),hydro-electric power generation (HEP), andalso for waste disposal - plus we use it forrecreation. Water creates wetland habitatswhich are important environmentally fortheir biodiversity. Many wetlands areprotected as Ramsar Sites.

The wide range of uses reflects theprocesses and links within the watercycle. The diagram on the right showshow people intervene in the water cycle.While some of these have positiveimpacts, others have negative impacts onwater supplies. And the downside of thelinks within the cycle means that over-use for one purpose, or disruption of thecycle, can have serious knock-on effectselsewhere in the system.

OverabstractionIn recent years, overabstraction ofwater in the Thames Valley in SouthernEngland has led to a dramatic drop inriver flow. Some tributary streams have

. dried up completely - damaging the riverecosystem, home to many plants andanimals. Droughts in Southern England,and rising demand from increasingnumbers of homes, has led to increaseduse of groundwater supplies. This haslowered the water table across the ThamesBasin so the aquifer (underground waterstore) is not being used sustainably.

Sea

InterventionsCD Cloud seeding to make rain® Deforestation and changes in land use, leads to loss of

interception capability and possible flooding (Himalayas)® Widespread urbanisation (cuts evapotranspiration)

@ Overabstraction of groundwater leads to fallingwater table

@ Overabstraction from rivers and lakes leads to conflictbetween users and loss of evaporation

® Building qf dams and larger reservoirs

(j) Impacts of global warming melts glaciers

+ Overabstraction meanstoo muchwater is beingtakenfromthe river,lakeor otherwatersource.

i Water world

Most water companies now have strictpolicies called CAMS (Catchment AbstractionManagement Strategies) for managing local waterresources. Water levels are managed to keepthe competing demands of the area in balance -sufficiently high for all the users, but not so highthat there is an increased flood risk.

... Water abstraction in the Test-Itchen CAMS area in Hampshire,

Other agriculture <1

Augmentation --,4._-'2%

Public watersupply 23%

Other <1 %

Watercress12%

ILTII Sustainableuse

Fish farming61%

Reservoir building

In some parts of the world, natural lakes aredrying up, such as Lake Chad in Africa, but inother areas artificial reservoirs can add new storesto the water cycle.

There are several types of reservoir, includingthose that are used for HEP generation (whichusually have high dams in order to get sufficientwater to generate power) and those that are usedfor water storage (which usually have a much lessspectacular earth dam). Reservoirs can be veryuseful, but they can also bring problems:• Loss of land. In the UK, nearly 275 km2 are

covered by reservoirs, some of which havedrowned whole villages and large areas ofvaluable farmland.

.; In some countries they can be a source ofdisease, because they are home to insectssuch as mosquitoes.

• Vegetation drowned by the lakes decaysand releases methane and carbon dioxide(greenhouse gases).

Reservoirs are not all bad news. Sometimes theyare designed to be multi-purpose - like GrafhamWater in the diagram on the right.

DeforestationDeforestation affects the water cycle:• Removing the trees reduces evapotranspiration,

so less green water is recycled. This can leadto a reduction in rainfall and the possibility ofdesertification.

• It exposes the soil surface to intense heat, whichhardens the ground - making it impermeable andincreasing runoff.

• It leads to a loss of soil nutrients (because of a lossof biomass). Nutrients are quickly flushed out of thesystem.

• Raindrop splash washes out the finer soil particles,leaving behind a coarser, heavier sand surface.

• It cuts out the process of interception. If trees areremoved from watershed areas, this can increasethe siltation in rivers and lead to increased flood risk.

Key Cwoodland~ nature reserve

® bird hidesR picnic sites

- cycle route......... bridleways and footpaths......... bank fishing prohibited. bank fishing restricted

refreshments

Grafham Water is a water supply reservoir covering 600 hectares near Huntingdon in theUK. It has been zoned to allow wildlife conservation and different leisure activities, suchas windsurfing, sailing, fly-fishing, cycling and birdwatching .

1 Draw a flow diagram for each of the following, to show theknock-on effects: deforestation, urbanisation, dam building,over-abstraction.

2 Which of these has the worst effects? Explain your reasons.3 Exam-style question Using named examples, examine

how human activities can disrupt water quantity and quality.(6 marks)