Download - Canal Maintenance & Operation

8/2/2019 Canal Maintenance & Operation

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INDEX

SR. NO. TOPIC PAGE NO.

1. INTRODUCTION 42. CANAL SYSTEM 5

3. CANAL BRIDGES & AQUEDUCTS 6

4. CONDITIONS & CRITERIA 8

5. MAIN CONSIDERATIONS 11

6. PLANS & SPECIFICATIONS 11

7. CANAL MAINTENANCE & OPERATION 12

8. MANAGEMENT OF CANALS 13

9. ANTICIPATED EFFECTS & BENEFITS 1610. POTENTIAL OF ADVERSE EFFECTS 19

11. CONCLUSION 21

12. REFERENCES 23


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INTRODUCTION :

A permanent irrigation canal or laterals can be defined as constructed

structure to convey water from the source of supply to one or more farms.

The purpose to construct to efficiently convey irrigation water from asource of supply to one or more farms.

Canals are man-made channels for water. There are two types of canal:

1.) Waterways: navigabletransportation

2.) Aqueducts: water supply canal

1.) Waterways: navigabletransportation canals used for carrying ships andboats

shipping goods and conveying people, further subdivided into two kinds:

a.)Those connected to existing lakes, rivers, or oceans. Included are inter-basin

canals, such as the Suez Canal, Erie Canal, and the Panama Canal.

b.)Those connected in a city network: such as the Canal Grandeand others of

VeniceItaly; thegrachtofAmsterdam, and the waterways ofBangkok.

2.)Aqueducts: water supply canals that are used for the conveyance and delivery of

potable water for human consumption, municipal uses, and agricultureirrigation.

Rills and acquits are small versions.

An acquit is a community-operated waterway used in Spain and former Spanish

colonies in the Americas for irrigation. Particularly in Spain, the Andes, northern

Mexico, and the modern-day American Southwest, acquits are usually historically

engineered canals that carry snow runoff or river water to distant fields.In the

middle ages, water transport was cheaper and faster than transport overland.

This was because roads were unpaved and in poor condition and greater amounts

could be transported by ship. The first artificial canal inChristian Europe was the

Fossa Carolina built at the end of the 8th Century under personal supervision of

Charlemagne. More lasting and of more economic impact were canals like the

Naviglio Grande built between 1127 and 1257, the most important of the

Lombard navigli. Later, canals were built in the Netherlands and Flanders to

drain the polders and assist the transportation of goods.
http://en.wikipedia.org/wiki/Waterwayhttp://en.wikipedia.org/wiki/Navigablehttp://en.wikipedia.org/wiki/Aqueducthttp://en.wikipedia.org/wiki/Water_supplyhttp://en.wikipedia.org/wiki/Waterwayhttp://en.wikipedia.org/wiki/Navigablehttp://en.wikipedia.org/wiki/Lakehttp://en.wikipedia.org/wiki/Riverhttp://en.wikipedia.org/wiki/Oceanhttp://en.wikipedia.org/wiki/Suez_Canalhttp://en.wikipedia.org/wiki/Erie_Canalhttp://en.wikipedia.org/wiki/Panama_Canalhttp://en.wikipedia.org/wiki/Grand_Canal_%28Venice%29http://en.wikipedia.org/wiki/Venicehttp://en.wikipedia.org/wiki/Grachthttp://en.wikipedia.org/wiki/Grachthttp://en.wikipedia.org/wiki/Amsterdamhttp://en.wikipedia.org/wiki/Bangkokhttp://en.wikipedia.org/wiki/Aqueducthttp://en.wikipedia.org/wiki/Water_supplyhttp://en.wikipedia.org/wiki/Potablehttp://en.wikipedia.org/wiki/Municipalhttp://en.wikipedia.org/wiki/Agriculturehttp://en.wikipedia.org/wiki/Rillhttp://en.wikipedia.org/wiki/Acequiahttp://en.wikipedia.org/wiki/Waterwayhttp://en.wikipedia.org/wiki/Spainhttp://en.wikipedia.org/wiki/Spanish_colonization_of_the_Americashttp://en.wikipedia.org/wiki/Spanish_colonization_of_the_Americashttp://en.wikipedia.org/wiki/Irrigationhttp://en.wikipedia.org/wiki/Andeshttp://en.wikipedia.org/wiki/Mexicohttp://en.wikipedia.org/wiki/American_Southwesthttp://en.wikipedia.org/wiki/Canalhttp://en.wikipedia.org/wiki/Middle_Ageshttp://en.wikipedia.org/wiki/Christendomhttp://en.wikipedia.org/wiki/Fossa_Carolinahttp://en.wikipedia.org/wiki/Charlemagnehttp://en.wikipedia.org/wiki/Naviglio_Grandehttp://en.wikipedia.org/wiki/Lombardyhttp://en.wikipedia.org/wiki/Naviglihttp://en.wikipedia.org/wiki/Netherlandshttp://en.wikipedia.org/wiki/Flandershttp://en.wikipedia.org/wiki/Polderhttp://en.wikipedia.org/wiki/Polderhttp://en.wikipedia.org/wiki/Flandershttp://en.wikipedia.org/wiki/Netherlandshttp://en.wikipedia.org/wiki/Naviglihttp://en.wikipedia.org/wiki/Lombardyhttp://en.wikipedia.org/wiki/Naviglio_Grandehttp://en.wikipedia.org/wiki/Charlemagnehttp://en.wikipedia.org/wiki/Fossa_Carolinahttp://en.wikipedia.org/wiki/Christendomhttp://en.wikipedia.org/wiki/Middle_Ageshttp://en.wikipedia.org/wiki/Canalhttp://en.wikipedia.org/wiki/American_Southwesthttp://en.wikipedia.org/wiki/Mexicohttp://en.wikipedia.org/wiki/Andeshttp://en.wikipedia.org/wiki/Irrigationhttp://en.wikipedia.org/wiki/Spanish_colonization_of_the_Americashttp://en.wikipedia.org/wiki/Spanish_colonization_of_the_Americashttp://en.wikipedia.org/wiki/Spainhttp://en.wikipedia.org/wiki/Waterwayhttp://en.wikipedia.org/wiki/Acequiahttp://en.wikipedia.org/wiki/Rillhttp://en.wikipedia.org/wiki/Agriculturehttp://en.wikipedia.org/wiki/Agriculturehttp://en.wikipedia.org/wiki/Municipalhttp://en.wikipedia.org/wiki/Potablehttp://en.wikipedia.org/wiki/Water_supplyhttp://en.wikipedia.org/wiki/Aqueducthttp://en.wikipedia.org/wiki/Bangkokhttp://en.wikipedia.org/wiki/Amsterdamhttp://en.wikipedia.org/wiki/Grachthttp://en.wikipedia.org/wiki/Venicehttp://en.wikipedia.org/wiki/Venicehttp://en.wikipedia.org/wiki/Grand_Canal_%28Venice%29http://en.wikipedia.org/wiki/Panama_Canalhttp://en.wikipedia.org/wiki/Erie_Canalhttp://en.wikipedia.org/wiki/Suez_Canalhttp://en.wikipedia.org/wiki/Oceanhttp://en.wikipedia.org/wiki/Riverhttp://en.wikipedia.org/wiki/Lakehttp://en.wikipedia.org/wiki/Navigablehttp://en.wikipedia.org/wiki/Navigablehttp://en.wikipedia.org/wiki/Waterwayhttp://en.wikipedia.org/wiki/Water_supplyhttp://en.wikipedia.org/wiki/Aqueducthttp://en.wikipedia.org/wiki/Navigablehttp://en.wikipedia.org/wiki/Navigablehttp://en.wikipedia.org/wiki/Waterway


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CANAL SYSTEM

The canal system consists of the following:

a.) Main Canal:

Main Canal takes off directly from the upstream side of weir head works or dam.

Usually no direct cultivation is proposed. Most of the main canals are aligned as

contour canals to derive benefit.

b.) Branch Canal:

All offtakes from main canal with head discharge of 14-15 cumec and above are

termed as branch canals.

c.) Major Distributary:

All offtakes from main canal or branch canal with head discharge from 0.028 to 15

cumec are termed as major distributaries.

d.) Minor Distributary:

All offtakes taking off from a major distributary serving more than 40.47 hectares

are termed as minor distributaries. They are named after a prominent place near

about their tail ends.

e.) Field Channel:

All pipe offtakes serving less than 40.47 hectares of ayacut are calledfield

channels and are denoted by numbering as left or right side pipes.


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Canal Bridges & Canal Aqueducts:

1.)Canal Masonry and brick bridges:When canals were built they cut

across estates, farmlands and existing roads. The canal company was

required in the Acts of Parliament that authorized the canal to ensurethat no one was inconvenienced. Hence large numbers of bridges

were required, often doing no more than linking two fields, as in the

simple brick accommodation bridge on the Llangollen Canal on the

left. Much grander structures were erected when country estates

were crossed and the permission of the landowners had to be

courted, as with the high masonry bridge on the Shropshire Union

Canal on the right.

2).CANAL TIMBER AND CAST IRON BRIDGES:

Wooden bridges were cheaper to build than masonry or brick bridges. They were

used for footbridges at locks and sometimes for accommodation bridges like this

ladder bridge on the Oxford Canal, left. The walkway is a single timber beamwhich has sagged considerably over the years. Cast iron bridges were used,

especially around Birmingham. These bridges were built to a common


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elegantdesign. They were also used to take thetowpath over the old loop. (Tony

Lewery)

3.) Canal Turnover or Roving bridges and split footbridges.

Sometimes the towpath had to move from one side of the canal to the other.

Turnover or roving bridges allowed the towing horse to cross the canal without

the tow line getting caught up in the bridge. The smooth curves of these bridges

often make them most attractive structures, as the bridge on the Shropshire

Union Canal on the left. Split bridges were used around locks to enable the towing

line to pass through the bridge when the towpath did not go under the bridge, ason the right on the Staffordshire & Worcestershire Canal. (Photos Tony Lewery)


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4.) Canal Aqueducts

The Aqueducts were not much liked by the early canal builders because the

weight of the water and the clay Stratford Canal on the right which has a cast iron

trough supported on tall slim masonry needed to keep the canal troughwatertight required a very substantial structure to support it. Masonry aqueducts

like the one on the Lancaster Canal on the left bear witness to this stature.

Compare this with the Bearsley Aqueduct on pillars.The cast iron contains the

water and has sufficient rigidity without the great bulk of the masonry aqueduct.

CONDITIONS WHERE PRACTICE APPLIES

A canal or lateral and related structures are needed as an integral part of

an irrigation water conveyance system.

Water supplies and irrigation deliveries for the area served are sufficient tomake irrigation practical for the crops to be grown and the irrigation waterapplication methods to be used.

CRITERIA

All planned work shall comply with all Federal, State, and local laws and

regulations.

Capacity requirements. The capacity of canals or laterals serving a

farm or group of farms shall be determined by considering

1. The delivery demands of all the farm irrigation systems served and theamount of water needed to cover the estimated conveyance losses in the

canal or lateral.

2. In water short areas, where water is not normally available to meet thefarm irrigation demands, the canal or lateral will be sized to convey the

available water supply.

3. Capacity must be enough to handle any surface runoff that is to enter thecanal.

Velocities:

Canals and laterals shall be designed to develop velocities that are nonerosive

for the soil materials through which the canal or lateral passes. Local

information on the velocity limits for specific soils shall be used if available. If


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such information is not available, the maximum design velocities shall not

exceed those shown in Figure 6-2, Chapter 6, TR-25. A Mannings n no

greater than 0.025 shall be used to check that velocities do not exceed

permissible values.

Canals and laterals shall be designed to convey the required flows with themaximum probable retardance conditions. For capacity design, the value of

n shall be selected according to the material in which the canal or lateral is

constructed, the alignment, the hydraulic radius, the expected vegetative

growth and planned maintenance.

Freeboard:

The required freeboard above the maximum design water level shall be at

least one-third of the design flow depth (0.33d) and shall not be less than 0.5feet.

Side slope:.Canals and laterals shall be designed to have stable side slopes. Local

information on side slope limits for specific soils and/or geologic materials

shall be used if available. If such information is not available, the design side

slopes in the canal or lateral shall not be steeper than those shown in Table.

TableMaterial Side

slope

Solid rock, cut section :1

Loose rock or cemented

gravel, cut

Section

:1

Heavy clay, cut section 1:1

Heavy clay, fill section 2:1Sand or silt with clay

binder, cut or fill

Section

1-1/2:1


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Water surface elevations:

Water surface elevations shall be designed to provide enough hydraulic head

for successful operation of all ditches or other water conveyance structures

diverting from the canal or lateral.

Canal or lateral banks:

The top width of canal or lateral banks shall be enough to insure stability,

prevent excessive seepage, and facilitate maintenance. They shall not be less

than 2 feet and shall equal or exceed the flow depth.

Protection from surface waters:

Runoff from adjacent areas shall be conveyed over or under the canal

wherever practical. If runoff is permitted to enter the canal or lateral, the sideslopes shall be protected from erosion, and provisions shall be made for its

disposal. Where sediment-laden water is allowed to enter the canal or lateral,

the design shall include provisions to transport the sediment through the

canal or lateral or measures shall be installed to trap and remove the

sediment.

Related structures.

Plans for canal or lateral installations shall provide for adequate turnouts,

checks, crossings, and other related structures needed for successfuloperation as a conservation irrigation facility. All related structures shall be

designed and installed to meet NRCS standards. Structures needed for the

prevention or control of erosion shall be installed before the canal or lateral is

put into operation.

Linings.

Unlined canals and laterals shall not be constructed on sites where

permeability of the soils is rapid or very rapid. If an excessively permeablesoil site must be crossed, the canals and laterals shall be lined according to the

appropriate standards for ditches and canal linings or shall be piped.

Maintenance access.


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Provisions shall be provided, as required, for maintenance operations. If the

top of the bank or berm is to be used for a roadway, the width shall be enough

to allow equipment travel/operation.

MAIN CONSIDERATIONS:

Consider the effects on downstream flows or aquifers that would affect other

water uses or users.

Consider the effects on the volume and rate of runoff, infiltration, evaporation,

transpiration, deep percolation, and ground water recharge.

Consider the effects of erosion of banks and beds and the movement of

sediment, and the soluble and sediment-attached substances carried by runoffand the movement of dissolved substances to groundwater.

Consider the effects on wetlands or water-related wildlife habitats.

Consider the effects on the visual quality of the soil water and plant resources.

Consider designing storage capacity into the canal to allow for management

flexibility.

Plans and specifications

Plans and specifications for constructing irrigation canals or laterals shall

describe the requirements for applying the practice to achieve its intended

purposes. Site specifics typically include cross-section details, embankment/bank

requirements, channel grades and appurtenant structural details.

This training course on canal operations and control methods is taught by the

Bureau of Reclamation's Hydraulic Investigations and Laboratory Services Group

in Denver, and has been offered each year since 1996. The course covers modern

methods to upgrade the operations of existing canals, including canal automationtechniques and equipment.


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CANAL MAINTENANCE & OPERATION

A properly operated and maintained irrigation canal or lateral system is and

asset to the farm. This practice was designed and installed to safely convey

irrigation water. The estimated life span of this installation is at least 15years. The life of this installation can be assured and usually increased by

developing and carrying out a good operation and maintenance program.

Failure to operate and maintain this system could result in actions to reclaim

cost share and/or loss of any future financial or technical assistance.

This practice will require performance of periodic maintenance and may also

require operational items to maintain satisfactory performance. As well as

stoppages for planned maintenance or emergency repairs, we list temporary

restrictions (when navigations remain open with restrictions in place),

towpath closures and local navigation advice. Also, for manned structures and

facilities, we show opening times and booking details.

Modern Methods in Canal Operation and Controlis designed for watermasters,

canal operators, managers, and engineers who are interested in improved canal

operations. The instruction is geared towards people who want to learn through

active participation and "first hand" experience with canal operations and

instrumentation.

A qualitative assessment has been made of the contribution that the canal

improvements alone would make to these goals. The exact extent of benefits

cannot be accurately known or guaranteed.

However, engineering judgment coupled with review of existingfacilities and

some historic daily flow and stage trends has been used to identify potential

benefits.

A more rigorous analysis will be possible once the sub-regional model has been

constructed and calibrated. This analysis will include both historic rainfall

distributions in the EAA and theoretical peak design events.


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A good operation and maintenance program includes:

Maintain cross-section and gradient by controlling channel erosion and bank

sloughing.

Immediately remove any debris, sediment, foreign material, obstructions orblockage from the channel and from structures, trash racks, head gates, inlets,

or outlets.

Maintain growth of vegetative coverings on outside canal banks. This includes

reseeding, fertilization, and application of herbicides when necessary. Periodic

mowing may also be needed to control excessive growth.

Install and maintain fences as needed to prevent excessive livestock trampling

of banks when adjacent fields are used for pasture.

Eradicate or otherwise remove all rodents or burrowing animals. Immediately

repair any damage caused by their activity.

Immediately repair any vandalism, vehicular, or livestock damage.

Canal Automation is becoming widely used to improve the operation of canal

systems and to conserve water. Automatic control systems are installed on

most new canals, and many older canals are being modernized with datacollection, telemetry, and control equipment to help canal operators better

manage their water.

Management of the Canal:

From late autumn to early spring the main emphasis is on tree and hedge

management. Tree works include restoring a coppice regime in many

woodland areas beside the Canal and cutting back branches that

overhang the Canal.

In addition to these major tasks is a huge variety of other work undertaken by the

Rangers, such as running events, leading volunteers and guiding educational visits

by local primary schools and managing a range of contractors who undertake

tasks such as dredging, towpath resurfacing, tree surgery and hedgecutting.


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DREDGING:Over time the Canal tends to fill up with silt from

decomposing plant matter and soil washed in from adjacent roads and

farmland. Unless the Canal is periodically dredged, it would eventually silt-up, preventing boating and angling and leading to a deterioration in wildlife

habitats. The work has been phased over several years in order to reduce

the immediate impact on wildlife, and current monitoring has shown an

increase in the variety of water plants (on which the rest of the Canal food

chain relies) as a result of the work. The future of boating and angling on

the canal has also been secured for many years to come.

The Ranger Service has also been

working with adjacent landowners to promote sustainable land use, in an

effort to reduce soil eroding into the Canal in the future. Most of the offside

boundary of the Country Park has been fenced to protect the banks fromerosion by livestock and to create wildflower rich buffer strips that provide

excellent habitats for a range of wildlife.

HEDGELAYING: After several decades of being annually trimmed with a

tractor-mounted flail, the hedge has become quite gap and sparse in many

areas. As part of the Country Parks Countryside Stewardship Scheme

agreement, over three miles of hedgerow are being restored through a

combination of hedgelaying and hedge planting.

Hedgelying is a traditional form of hedge management which promotes thick

regrowth from the base of the hedge and creates a bushy hedge which acts well

as a stockproof barrier and provides great habitat for wildlife. Hedgelaying is

particularly popular with the Canals Volunteer Ranger Service who spend many

days on this rewarding activity each winter.


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TOWPATH RESURFACING: Towpath has been resurfaced using crushed

stone from the quarry at West Leigh. This work has been focused on

previously muddy or uneven sections of footpath with the aim of improving

conditions for wheelchair and mobility buggy users in particular.

OFFSIDE BUFFER STRIPS:These strips on the offside protect thecanal from silt and nutrient pollution and provide excellent habitats for

wildlife.

CULVERTS:The culverts allow water from streams and ditches to flowunder the canal but over time they tend to fill up with silt and debris.Specialist enclosed-access teams will undertake this important work.


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ANTICIPATED EFFECTS OF CANAL IMPROVEMENTS:

The independent canal improvements were evaluated with regard to potential

sub regional and regional benefits in the following areas:

Sub-Regional Benefits- Support of the Interim Action Plan

- Operational flexibility

- Flood damage reduction during extreme events

- Control of canal sediments

- Construction scheduling

Regional Benefits

- Reduced backpumping to Lake Okeechobee

- Stormwater Treatment Area optimization

- Releases to estuaries- Water supply to the Lower East Coast

Sub-Regional Benefits

Support of the Interim Action Plan:The original design of the primary canalsystem recognized the extremely flat topography

of the EAA. Drainage pump stations were provided around the perimeter of the

basinwith a system of interconnected canals. The basic canal design concept

considered thatdrainage flows were pumped radially outward from the center ofthe EAA. When water quality concerns for Lake Okeechobee led to the

operational changes of the Interim Action Plan the preferred direction for

drainage flows was south. This flow reversal in the northern reaches of the North

New River, Hillsboro, and Miami canals was not entirely supported by the canal

capacity.

Prior conveyance studies of these canals (Burns & McDonnell) concluded that the

existing cross-sections were inadequate to convey Lake Okeechobee releases

equal to the full capacity of the basin stations. Although farm drainage flows

aredistributed along the primary canal, and are not released at a single point, thecumulative permitted drainage pumping capacities exceed the Lake release rate

and each canaldesign capacity by a factor of 2 to 4 times.


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Operational flexibility:

Water management within the EAA is a daily necessity due to the flat terrain,

minimal surface storage, and need for water table control. Individual farm

operations require drainage or irrigation in response to rainfall, seepage, cropneeds, land preparation operations, harvesting operations, and maintenance

activities.

The size of the EAA and local patterns of rainfall mean that frequently the

distribution of rainfall is non-uniform across the EAA. Frequently farms that

are too wet from rainfall and seepage are pumped for drainage on the same

day that other farms are irrigating. Improvements to the conveyance capacity

of the Bolles, Cross, North New River, and Miami canals will improve the

interconnection between the primary basins of the EAA. This will facilitate

the distribution of excess surface water between basins. The benefits will

include a reduction in drainage pumping from EAA basins that have received

localized rainfall and a reduction in irrigation pumping to EAA basins that lack

sufficient rainfall.

This benefits been demonstrated at the subbasin level as part of the success

of the pumping Best Management Practices (BMP) implemented by EAA

farmers. Recorded daily flows and canal stages, from October, 1992, to

October, 2002, were reviewed to estimate an order of magnitude for

anticipated benefits that canal improvements will have on operational

flexibility.Control of Canal Sediments:

Enlarging the cross-section of the primary canals is likely to have an

immediate benefit to water quality. Excavation will remove the existing

bottom sediments that haveaccumulated over the last 25 years. The increased

cross-section will allow flow at a lower velocity, thus future sediments,

deposited during times of low flow, will be less likely to become suspended

again and carried downstream.

This will improve the water quality of inflows to the STAs and backflows to

Lake Okeechobee, and may also improve the water quality of irrigation flowsto the farms. Precautions will be taken to prevent turbid waters or sediments

from traveling downstream of the canal widening excavation.

Excavated sediments are typically disposed of adjacent to the canal. Future

monitoring and canal maintenance may be needed as new sediments are

deposited. Precautions will be taken to prevent mobilization of contaminants

and nutrients.


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Consideration should be given to the effect on dissolved oxygen of deepening the

canal.

Construction Scheduling:

The independent canal improvements project could also provide somebenefits duringconstruction of the EAA Storage Reservoirs. Because of the

spatial separation between the canal improvements and the proposed

reservoirs, the two elements can easily be separated from a construction

standpoint. Allowing the canal improvements to proceedindependent of the

reservoirs would show early progress on a critical CERP project.

It would also support the goals of the ECP to optimize the performance of the

STAs and reduce nutrient loading to the EPA. Improving the interconnection

of the primary basins would support the construction of the initial reservoir

components.

Regional Benefits

Reduced Backpumping to Lake Okeechobee:

However, given the current constraints on canal conveyance capacity, a

discontinuation of backpumping would cause unacceptable increases in canal

stages during moderate to heavy regional rain eventsIn thefuture.

Stormwater Treatment Area Optimization:Independent canal improvements can provide significant ability to optimize STA

performance through overall increased operational flexibility within the system.

The canal improvements will improve the Districts ability to balance flows

through the STAs to achieve more uniform operating conditions, as well as

providing a major benefit to the areas biological systems.


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BENEFITS OF CANAL MAINTENANCE

An on-going program performed by the Maintenance & Construction Division,

canal maintenance consists of erosion control, repair or replacement of drainage

pipes, and mowing/clearing of lot line ditches and drainage rights-of-way. Canalsare on a mowing schedule of twice per year for the areas that can be reached

with a mowing tractor. The bottoms of the canals are sprayed with herbicide as

needed to keep the flow lines free of vegetation. As the need arises, the bottoms

of the canals are dredged to help keep the flow of water at the right grade.

In the past year, all accessible canals and ditches have had the slopes mowed and

stabilized as well as the bottoms sprayed with herbicide. The Maintenance &

Construction Division is working on a canal rehabilitation program to improve the

Citys overall drainage, and to provide access for routine maintenance. As aresident/property owner, we greatly appreciate your cooperation in not storing

trailers, boats, etc., or erecting fences or sheds, or using the right-of-way as a

planting area. This enables the Public Works crews to operate safely and

effectively to maintain the drainage system.

POTENTIAL ADVERSE IMPACTS

While examining the regional and sub-regional impacts of the proposed canal

improvements, no significant adverse impacts were identified associated with

the timing of the canal improvements. Economic impacts, total projects costs

and land acquisition issues are relatively unaffected by implementing the

canal improvements independent of reservoir construction. The proposed

canal improvements, regardless of when they are constructed, may potentially

impact

1) rateof inflow to the STAs, 2) canalseepage losses,

3) canal evaporative losses, 4) irrigation supply to the farms.

Canal seepage losses are a function of the canal depth, soil properties, proximity to

secondary canals and the difference in water levels. Increasing the canal depth

could increase the seepage depending on the porosity of the underlying soil layers.


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This could be evaluated during the design phase by analysis of representative soil

borings along the canal alignment.

These loses can be partially mitigated by increasing the canal width rather than

increasing the depth. Seepage losses from the primary canal to an adjacent farm

during the wet season would be returned to the canal by increased secondary

pumping. Seepage losses during the dry season may not be returned by secondary

pumping. These dry season losses may in some cases reduce the farm irrigation

demands on the primary canal system.

Canal evaporative losses may be estimated as the product of measured pan

evaporation and the surface area of the exposed open water. Increasing the

canal width will increase the evaporative losses. This will be partially offset by

a reduction in the evapotranspiration losses of the adjacent uplands.

Doubling the canal top width would increase by approximately 8% the net

evaporative losses from the canal and vicinity. At many locations gated

culverts or flash board structures can be operated by the farmers to irrigatethe agricultural lands by gravity. This is dependent on the stage in the primary

canal being at a suitable level. Improvements to the canal cross-section could

lower the canal water surface significantly. This would vary with location and

antecedent conditions. While lowering the canal stages would generally be

beneficial during drainage events, because of non-uniform rainfall patterns.

It could be detrimental to farms trying to irrigate by gravity under

certain conditions. Any proposed changes to the control and operating water

levels in the primary canals would need to be carefully evaluated.

An additional consideration would be the opportunity to use a portion of thesoil excavated from the canals in the construction of the proposed reservoir

levees. Due to the cost of handling and hauling, the borrowed material closest

to the levees would be themost cost effective. If the canal and reservoir levee

construction where implemented at the same time, some needs for land

acquisition may be reduced.


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CONCLUSION:

Improved water management and water conservation is believed to be

ultimately an organization issue. This means that the path to improving water

management in irrigated agriculture may well be through these irrigationenterprises, in terms of assisting them in financial and water delivery record

keeping, managing canal flows and water accounts, staff training, etc. Simple

marginal pricing of water does not appear to be the answer. As a concept,

marginal pricing tends to grossly over-simplify the organizational and economic

condition and practices of these irrigation enterprises. It is an example of a policy

that would generally treat all irrigation enterprises uniformly, as if to say they

were all cut from the same "cookie cutter." Nothing would seem to be further

from the truth, even if these enterprises are known to share many management

practices in common.

a) Reducing hydraulic losses within the primary canal system andsupporting the objectives of the Lake.

b)Improving operational flexibility within the EAA to distribute excesssurface waterand reduce the necessity for minor drainage discharges

from the EAA and minorirrigation releases from Lake.

c) Reducing the risk of flood damage to agricultural and urban lands byimproving thelevee freeboard.

d)Improving water quality by removing existing canal organic sedimentsand reduce thetransport of future canal sediments by lowering

velocities in the primary canals.

e) The intermountain region is characterized primarily by earthen canalsystems. These systems often have important ecological benefits, and

should not be summarily dismissed on the grounds that they are

inefficient. The issue here appears to be more of enterprise staffing and

canal management than simple delivery efficiency based on seepage

losses.

f) The number of employees hired by irrigation enterprises tends to

increase proportionally with the size and complexity of the irrigationsystem. This might be intuitively expected anyway, although other

factors certainly come into play. Irrigation districts tend to hire more

employees than canal companies do. It is not clear why this is so.

g) The continuous flow regime of managing an enterprise's main canal isstill preferred in the intermountain region. Also, the use of "call

systems," involving the ordering of water by farmers 24 to 48 hours in


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advance, and then having ditch riders re-adjust this continuous stream

daily, is still the preferred method of managing the main canal

throughout the irrigation season.


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REFRENCES:

Burns and McDonnell. Everglades Protection Project: Conceptual Design. February

15,1994. SFWMD. West Palm Beach, Florida. SFWMD. Feb. 1994

Burns and McDonnell. Storm water Treatment Area No. 3 & 4, AlternativesAnalysis,Chapter 4 Miami and North New River Canals Conveyance Capacity.

SFWMD. West Palm Beach, Florida. SFWMD.

South Florida Water Management District. S-7 and S-8 Pump Station Statistics.

SFWMD. n. d.

South Florida Water Management District. DBHYDRO (selected records)

South Florida Water Management District. Structure Books. Operations Control

Center, SFWMD South Florida Water Management District Water Resource

Division. Resource Planning Department. Technical Memorandum, An Atlas of the

Everglades Agricultural Area Surface Water Management Basins. September1989.

Water Measurement Manual (third edition)and the Canal Systems Automation

Manual, Volumes 1 and 2.

http://waterlab.colostate.edu/Management/conclusion.htm

http://www.fao.org/docrep/W4367E/w4367e0y.htm#TopOfPage

http://www.palmbayflorida.org/publicworks/services/canal.html

http://www.springerlink.com/content/g8m1546rh407w812/

http://www.canalmanagement.net/
http://www.usbr.gov/pmts/hydraulics_lab/pubs/wmm/index.htmhttp://waterlab.colostate.edu/Management/conclusion.htmhttp://www.fao.org/docrep/W4367E/w4367e0y.htm#TopOfPagehttp://www.palmbayflorida.org/publicworks/services/canal.htmlhttp://www.springerlink.com/content/g8m1546rh407w812/http://www.canalmanagement.net/http://www.canalmanagement.net/http://www.canalmanagement.net/http://www.springerlink.com/content/g8m1546rh407w812/http://www.palmbayflorida.org/publicworks/services/canal.htmlhttp://www.fao.org/docrep/W4367E/w4367e0y.htm#TopOfPagehttp://waterlab.colostate.edu/Management/conclusion.htmhttp://www.usbr.gov/pmts/hydraulics_lab/pubs/wmm/index.htm


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