guidance on pond construction 2

8/10/2019 Guidance on Pond Construction 2

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TRAINING MATERIAL ON SIMPLE METHODS OF POND

CONSTRUCTION

FAO Project Support to Fishery and Aquaculture Management in the Kyrgyz Republic

GCP/KYR/003/FIN

Training Material Series 2


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TRAINING MATERIAL ON SIMPLE METHODS OF POND

CONSTRUCTION

Prepared by

Sunil N. Siriwardena

International Team Leader

Training Material Series 2

(Distribution free of charge)

FAO Project Support to Fishery and Aquaculture Management in the Kyrgyz Republic

(GCP/KYR/003/FIN)

Funded by the Government of Finland

Bishkek, Kyrgyz Republic 2011


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I NFORMATION TO THE USERS

A) For whom?

This training material is primarily intended for farmers, extension workers and technicians to

help farmers to use it by themselves or extension workers and technicians to use in theirextension work to train farmers. The training material can be used by a farmer as self guide or

by a trainer as a trainers guide to train farmers.

B) In what form it is prepared and how it can be used?

The training material is prepared to answer many questions that may farmers need answers.

Therefore, this training material can be used as a whole or as selected parts to address farmers

need in a training programme.

C)

What farmers, extension workers and technicians will learn from this training

material?

This training material is aiming at providing information to develop skills of farmers,

extension workers and technicians in selection of a suitable site, design criteria and

construction methods as they are vital for good pond construction. Often farmers seek

information and advice to solve problems related to pond designing and construction.

Therefore, the training material includes following aspects of site selection, designing and

pond construction.

1. How to select a suitable site to construct a pond for fish culture

Why site selection is so important?

What are the important factors a farmer should consider in selection of a suitable site for

pond construction?

a)

Space availability and topography

b)

Water supply and water quality

i) Water source

ii) How to estimate the amount of water needed to operate your fish pond?

iii) Water quality:

c) Soil quality

i) Physical quality:

How do you determine the adequacy of clay in soil for construction of ponds?

How do you determine the ability of soil to hold water in your pond?

ii) Chemical quality:

How do you measure acidity?

What is acid sulphate soil?

What is potential acid sulphate soil?

How do you identify potential acid sulphate soils?

2. What are the important factors a farmer should consider during designing of ponds?


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a)

How to select and prepare the pond layout design?

b) How to align the pond direction

c)

How to protect your ponds from flood

d) How to design the pond bottom

e)

How to position inlets and outlets?f) What are the types of dikes?

g) What is the suitable shape of the dike?

h) How to determine the dike dimensions?

How to determine the dike height?

How to select side slope, base and crown width of a dike?

How to determine the base width of the dike?

How to determine the top width or the crown width of the dike?

How to use the trapezoidal equation to determine the dike height, top width,

dike base and side slopes?

3. How to do the actual construction of ponds?

a) Preparation of the site

What are the factors should be considered before excavation?

How to prepare the site before construction?

b) How to mark the boundaries of the pond and construct the clay core (cut-off trench)?

c)

How to excavate the soil?

d) How to Pile up soil to construct dikes?

How to maintain a uniform dike height along entire dike length?

How to stabilise the dike slopes?

e)

How to plan fish pond construction

4. What are the material and structures you can use as supply and drainage canals, inlets and

outlets?

i) Pipes

-

Simple pipe outlet

- Stand pipe outlet

ii) Open gutters

iii) Earthen canals

iv) Gates

Components of a sluice monk outlet:

What are the important points to know when designing outlets?

5. How to supply water to ponds from the water source?


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D) Some calculations based on formula are given in this material for the understanding of

the Extension workers/trainers and technicians and such formula should be used in the

training only if the target group is able to grasp such information.

E) Where calculations are given, rules-of-thumb are also included for the easy

application by some farmer groups instead of using calculations.

F)

The users of this training material is recommended to read the following training

material which are also use for some information in preparation of this training

material.

Handbook on small-scale freshwater fish farming. Training Series 24, Food and

Agriculture Organisation of the United Nations, Rome 1994.

FAO training series on pond construction for freshwater fish culture (FAO 1995)


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ACKNOWLEDGEMENTS

The author is indebted to the Government of Finland who provided the financial support for

the FAO project Support to Fishery and Aquaculture Management in the Kyrgyz Republic

(GCP/KYR/003/FIN) which enabled printing of this training material to distribute among

farmers and trainers. Specific thanks are due to Ms. Aijan Kydyralieva, the project translator,for translating the original English version into Russian Language, Mr. Kuvanych Satybekov

and Mr. Mamytbek Omursakov for assisting the translator with technical terms for translation

and Mr. Bakyt Kulov, the project web Designer for art work of the cover page and drawings

in the training material.

The author further gratefully acknowledge the support and encouragement given by a number

of staff of FAO, including Mr. Mustapha Sinaceur and Mr. Raymon Van Anrooy, FAO

Aquaculture and Fishery Officer, who was the Lead Technical Officer of the project, (FAO

Sub-regional Office for Central Asia, Ms. Dinara Rakhmanova (Assistant FAO

Representative in Kyrgyz Republic and Ms. Mairam Sarieva and Ms Olimpia Adambaeva

(FAO project GCP/KYR/003/FIN staff).


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1. HOW TO SELECT A SUITABLE SITE TO CONSTRUCT A POND

FOR FISH CULTURE

Why site selection is so important?

The first step or the most important preconstruction activity is to select a correct site ascareful site selection is a pre-requisite in pond construction. Improper site selection may lead

to:

difficulties in holding water in the pond,

high seepage,

dike erosion,

low productivity of the pond, resulting low yields and economic loss

inability to drain water completely, and

difficulties in harvesting.

What are the important factors a farmer should consider inselection of a suitable site

for pond construction?

There are several factors a farmer should consider in selection of a suitable site. The most

important are:

a) space availability and topography of the site,

b)

water supply and quality, and

c) soil quality.

a) Space availabil i ty and topography

The site should at least have a space of 200 m2to construct a pond.

It is better to select flat land or lands with a slight gradient.

Sites with slight gradients (0.5 to 3 percent is better. Avoid sites with gradients more

than 5 percent) have the advantage of obtaining water into the pond and drain water

out from the pond by gravity.

Try to avoid areas with large undulations and rocks and with large trees. This type of

areas will increase the construction cost and also prevent good sunlight into the pond.

b) Water supply and water quali ty

i) Water source

The site should be adjacent to or in close proximity to a suitable water source in order to fill

the pond easily.

The source of water should have adequate amount of water with required quality to

supply water into the pond throughout the year or at least throughout grater part of the

year.

The water should not be acidic and should be free from pollutants such as waste and

pesticides. Streams, large rivers, small rivers, lakes and reservoirs can be used as water sources.


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Stream and river water is generally rich in dissolved oxygen than lakes and reservoirs.

With respect to state of pollution all these water sources can have same pollution

problems, but reservoirs and lakes are relatively slow than streams and rivers in

recovering from the pollution state.

ii) How to estimate the amount of water needed to operate your fish pond?

You need an idea about the following aspects to estimate the required quantity ofwater to operate your fish pond.

Pond volume:

If your pond is 20m in length and 15m in width, your pond has an area of 300m2(20m

x 15m).

If you need an average 1.2m depth of water in your pond to culture fish, you need a

360m3 (300m x 1.2m) of volume of water in your pond

You need to maintain this depth of water in your pond to culture your fish. Then you

need to know roughly how much water is seeping through your soil and how much

water evaporates from your pond. If you construct your bunds properly compacted

there will be very little water loss through bunds. Then you need to calculate only the

amount loss through your pond bottom. The water loss through pond bottom seepage

is dependent on the type of soil.

20m

15m

Average depth

of water 1.2m


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Natural soil type Seepage losses (mm/day)

Sand 25.0250.0Sandy loam 13.076.0

Loam 8.020.0

Clayey loam 2.515.0

Loamy clay 0.255.0

Clay 1.2510.0

Source: FAO 1981

Example to calculate water loss through bottom seepage:

If you have a pond of 1000 m2surface area and your pond bottom soil is clayey loam, the

seepage loss from clayey loam is between 2.515.0 mm/day. If you take the average, it is

8.75 mm/day or 0.00875 m/day. Therefore through a 1000 m2area the bottom seepage will be

0.00875 x 1500 = 13.125 m3/day

Water loss through bottom

seepage

Water loss through evaporation


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iii) Water quality:

The most important water quality parameters in freshwater ponds are temperature, pH

value, dissolved oxygen

Temperature influences almost all the physiological activities of fish/shrimp such asrespiration, growth, feeding, moulting, disease resistance.

- In general the suitable range for tropical fish is 25 to 300 C.

The Dissolved oxygen in water is one of the most important water quality parameter

to maintain a healthy pond environment.

- The dissolved oxygen level of 5.0 to 6.0 mg/litre is better for many fish.

pH value will tell you whether water is acidic or otherwise (basic). The pH of pond

water is a good indication of health of fish and pond environment.

- For most of fish a pH value between 6-8.5 is better.

c) Soil quality

Soil quality should be considered in two ways

i). Physical quality, and

ii). Chemical quality

i) Physical quality:

Soil has particles of various sizes, namely, sand, silt and clay. Among these three

types sand is the largest and clay is the finest. The relative amount (percentages) of

these three sizes is known as soil texture.

- Pond soil should have enough clay to hold water and prevent erosion of ponddike.

- 100% clay is not suitable for pond construction, since the pond dikes crack

when expose to sunlight.- Once the dikes are cracked, they get weak and water may leak out.

How do you determine the adequacy of clay in soil for construction of ponds?

Test 1:

Take a handful of soil and wet it, so that it begins to stick together without sticking to

your hand.

Squeeze it hard, then open your hand.

If the soil retains the shape of your hand, there is probably enough clay in it to build a

pond.

If the soil does not retain the shape of your hand, there is too much sand in it.


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Test 2:

Take a handful of moist soil and squeeze it into a ball

Throw the ball into the air about 50 cm and then catch it

If the ball falls apart, it is poor soil with too much of sand

If the ball sticks together, it is good soil with enough clay in it

Test 3:

Take a handful of moist soil and roll it between your palms and fingers to make like athread

Try to bend it and make it to a circle

If the thread breaks into parts before without form into a circle, it is poor soil with too

much of sand

It it forms circle, it is good soil with enough clay in it

How do you determine the ability of soil to hold water in your pond?

Dig a hole/pit as deep as your waist

Early in the morning fill it with water to the top of the hole/pit

In the evening you will notice some of the water have absorbed into the soil and thewater level has gone down

Then fill the hole/pit with water again to the top and cover the hole/pit opening withsome leafy branches or some boards

Next day examine the water level in the morning. If most of the water is still in the

hole/pit, the soil is good to hold water in your pond

ii) Chemical quality:

Your pond soil should not be acidic

Acidic-soils reduce the pond productivity. For example growth of algae, which is

natural food for many fish and essential for a good pond environment, may be greatlyreduced.

Acidic-soils make the pond water acidic

Acidic-water retards growth of fish and causes stress situation favouring infections

and diseases.

How do you measure acidity?

Soils may have acidic or opposite of acidic condition

This opposite of acid condition is termed as alkaline or basic condition.

Some soils are neither acidic nor alkaline. Such soil condition is called neutral

condition.


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The measure of this soil condition is expressed by pH value. The pH value varies

from 0 to 14

pH value 7 indicates neutral condition.

Values smaller than 7 indicate acidic condition and values grater than 7 indicate

alkaline condition.

Smaller the value below 7 greater the acidity Higher the value above 7 greater the alkalinity.

Testing soil pH with beetle leave juice:

Make a soil suspension by mixing one part of soil with two parts of distilled water orpure rainwater directly collected in a clean container or battery water, which can be

purchased from a fuel filling station.

Extract beetle juice by chewing or grinding beetle leaves

Add juice into the soil suspension

If the water in soil suspension turns remains red indicates non-acidic.

If the water in soil suspension turns black indicates acidic.

Testing soil with litmus paper:

What is litmus paper: Paper strips to determine the pH of a water or watersolution/suspension

Make a soil suspension by mixing one part of soil with two parts of distilled water or

pure rainwater directly collected in a clean container or battery water, which can be

purchased from a fuel filling station.

Partly dip the litmus paper in soil suspension.

Turns red in acidic condition, blue in alkaline condition and no colour change inneutral condition.

Testing soil with pH paper:

Make a soil suspension as above.

Partly dip a pH paper in soil suspension.

Match the changed colour of the pH paper with the given colour chart.

Read the number given in the colour chart.

If the given number is less than 7, it is acidic and above 7, it is basic or alkaline.

If the given number is 7, it is neutral.

Testing soil with a pH meter:

The most accurate method of determining soil pH is by means of an electrical pHmeter, which gives a direct reading of the pH value.

Acidity increases Basisity increasespH

140


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Make a solution with one part of the soil and two parts of distilled water.

Insert the electrode of the pH meter in the solution.

Stir the solution with the electrode.

Allow the electrode to stand still for a while in the solution.

Read the value shown in the meter once it stabilizes.

What is acid sulphate soil?

Acid sulphate soils are not good for pond construction.

Their pH value is equal to or less than 4.

Pale yellow mottles are usually abundant in the acid sulphate soil.

What is potential acid sulphate soil?

They are waterlogged, unconsolidated soil, which will become acid sulphate upondrainage and exposure to air.

Their pH varies around 5 to 6.

If kept submerged or unexposed to air potential acid sulphate soil will never become

acid sulphate soil and will not give negative effects

If any of the sub soil layers are proved to be potential acid sulphates you should notexposed such layers. If exposed they become too acidic and cause problems

How do you identify potential acid sulphate soils?

i)

Take a dry soil ball and break it. Examine the inside areas of the broken soil

ball. If you see yellow colour mottles and/or streaks, the soil may containpotential acid sulphate.

ii) Take a handful of the soil to be tested.

If the sample is dry, moisten it.

Make the soil sample into a cake of one cm thick.

Put the moist cake into a thin polythene bag and sealed it.

After one month, measure the pH of the soil in the cake.

If the pH has dropped below 4, the soil is a potential acid sulphate soil.

(If you need to identify potential acid sulphate soils quickly soil samples has to taken to a

laboratory)

Soil sample

Sealed thin polythene bag

I t is very important that you should not expose potenti al acid sulphate soil

layers dur ing pond construction!


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2. WHAT ARE THE IMPORTANT FACTORS A FARMER SHOULD

CONSIDER DURING DESIGNING OF PONDS?

a) How to select and prepare the pond layout design?

Pond layout can be done either in a series or parallel.

The advantage of arranging the ponds in a series is it is cost effective when compared

to arranging in parallel.

However, it has the disadvantage of difficulties in maintaining a healthy pond

environment as it has a greater risk of spreading disease and contaminations from one

pond to the other. Therefore, it is not a good option.

From water supply To drainage

From water supplyTo drainage

From water supplyTo drainage


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b) How to align the pond direction?

Wind plays a role in fishpond design. Strong wind generates waves and the waves

break on the dikes, it will to erode the sides of the dikes.

To minimize this, position the longer pond dimensions (longer pond axis) parallel to

the direction of the main prevailing wind direction so that the wave action would beon shorter length of dikes and erosion would be less.

c) How to protect your ponds from flood?

If the fish pond site is prone to flooding, construct a diversion canal along the

perimeter dike to divert runoff water during heavy rains. Construct a larger and higher perimeter dike to prevent inflow of water.

d) How to design the pond bottom?

Pond bottom should be flat and sloping towards the outlet or drainage gate with a gentle

gradient.

For small ponds keep a gentle slope of the pond bottom of about 0.5% to 1.0% from the

water inlet to water outlet or drainage gate to ensure easy and complete drainage of the

pond.

N

E

S

W

Main wind

direction

Long pond axis is parallel

to the wind direction


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If you have problems to excavate the bottom of the pond to hold water up to the required

depth, you may construct peripheral and/or central ditches or canals in the pond bottom to

provide deep areas for fish.

These canals or ditches should be 0.25 - 0.5 m X 0.250.5 m.

(Include a sketch with a cross section to show the peripheral and central canals)

e) How to position inlets and outlets?

It is better to position inlet and outlet diagonally.

If a pipe is used as an inlet, it should be projected enough into the pond so that water will

fall into the pond at 900directly into the pond and prevent dike erosion by falling along

the dike.

If earthen canals along the dike crown are used as inlets, it is better to allow the water to

fall into the pond along several steps (weir) constructed along the side slope into the pond

at the inlet point. This will not only prevent erosion of the dike but also oxygenate the

supply water.

Outlet should be placed at a level below the lowest level of pond bottom.

Inlet

OutletBottom slope towardsoutlet

Peripheral canal

Central canal


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If peripheral and central bottom ditches or canals are constructed, they should be slope

towards the outlet.

f) What are the types of dikes?

Types of dikes in a single pond:It has only the surrounding dike, which is called the

perimeter dike.

Types of dikes in multiple ponds:The dike running around all ponds is the perimeter dike.

The dikes that separate two ponds are secondary dikes.

Inlet

Outlet

Weir


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Secondary dike usually has a dike base and top width less than those of the perimeter

dike.

The perimeter dike and secondary dikes should maintain at least a height of 50 cm

above the pond water level. This area of the dike is called free board.

Tertiary dikes are usually smaller than secondary and tertiary dikes and less in height

as nursery ponds usually hold less water depths than main ponds.

g) What is the suitable shape of the dike?

Construct dikes with trapezoidal cross section with the top width, the side slopes and

the height proportionally designed according to the soil material used.

h) How to determine the dike dimensions?

Dike dimensions are dike height, top width or crown, dike base and side slope

How to determine the dike height?

Dike height will be determined by the depth of water that you need to retain in the pond,

height of the free board of the dike (dike height above the pond water level) and your

experience in the flood levels of the area or site.

Pond depth water and free board should be around 1.0 and 0.5 meter, respectively. Hence,the pond dike height should be at least 1.5 meters.

Trapezoidal cross section of a dike

Top width or crown

Dike

height

Side slope

Dike base


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If you have experience of frequent flooding in the area, the perimeter dike height of your

ponds should be above the flood level to prevent escape fish from your pond during

floods.

How to select side slope, base and crown width of a dike?

What is side slope?

The side slope or steepness of the dike is the ratio of the horizontal length to the

vertical rise

In other words how much a side of the dike should move horizontally from the edgeof the top width of the dike for each vertical meter of the height of the dike

For example:If a pond has a dike height of 2 meters and top width of 1 meter and a side

slope of 1:1, for each meter of the vertical height, the bottom edge of the side should move

one meter horizontally from the edge of top width. Therefore, for the total two meter height

of the dike, the side should move two meters away from the edge of the top width.

Water depth

Free board

Centre line

First one meter of vertical height

Second one meter of vertical height

1m.5m.5m 1m1m

3m

5m


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How to determine the base width of the dike?

The base width is determined by the side slope of the dike. In above example the base

width is five meters.

How to determine the top width or the crown width of the dike?

The crown width is determined by what equipment you want to move along the dike. Crown width should be wide enough for the farmer to walk or push a wheelbarrow along

the dike.

Berm

You may use thi s rule-of-thumb to select the side slope based on

soil type and dike heights:

If the soil contains good clay the side slopes can be 1:1.

If the soil containsloose soil, silt, silty sand, sandy loam theside slope can be 2:1

If the soil contains soft clay, clay loam the side slopes can be

be 1.5:1

If the soil contains sand or wet clay the side slopes can be be

3:1

Dikes lower than 3 m may have a slope of 1:1. Dikes above 3

m should adopt a 2:1 slope.

You may use the following rule-of-thumb to

determine the top width of the dike.

The minimum top width or crown is 1.0

m for dikes less than 3 m high

The top width of dikes used as access

road is 4.0 m.

Construct a 0.5-0.6 m wide berm or

shoulder on each side of a roadway dike

to prevent rolling of soil.


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How to use the trapezoidal equation to determine the dike height, top width, dike base and

side slopes?

It is better to use the following equation to calculate the side slope, crown or the topwidth, dike base width and dike height. This equation is known as the trapezoidal

equation

b = T+ 2 (Zd)

Where,

T = Crown width

Z = Horizontal side of the side slope

d = Hieght of the dike

b = Base width of the dike

Example:If you want to know the base width of your dike that you want to construct with a

dike height of 1.5m and a crown with of 1.0m. The soil has enough clay to have a side slopeof 1:1.

Crown width (T) = 1.0 m

Side slope = 1:1

Horizontal side of slope (Z) = 1

Height of the dike (d) = 1.5 m

Therefore the base width (b) = Crown width + 2(horizontal value of side slope x dike height)

b = 1.0 + 2(1.0 x 1.5)

= 4.0 m

How to calculate the volume of earth that you need to construct your dike?

First calculate the area of the cross section of the dike by using the following equation and

using the same figures given in above example.

d

b

T

Z


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A = {(b + T)/2} x d

Where,

A = Cross section of the dike

b = Base width of the dikeT = Top width

A ={(4.0 + 1.0)/2} x 1.5

A = 3.75 m2

Once the cross-sectional area of the dike is known the required volume of earth to construct

the dike can be calculated by multiplying the cross-sectional area by total length of the dike.

If the pond has dimensions of 11 x 28m, then the total length of the dikes of the pond is 78m.

Therefore, volume of earth required to construct the perimeter dike

= A x total length of the perimeter dike

= 3.75 x 78

= 292.5 m3

You need to add the 10 to 20% of the volume of earth as settlement or shrinkage allowance.

This additional soil is important to maintain the required dike height as after dike

construction with time soil tend to settle and reduce the dike height

If the soil is too sandy or contains lot of organic matter the shrinkage allowance may be as

high as 40%. This will increase cost. Therefore, selecting the site with good clay soil is

important

If shrinkage allowance = 10%

= 29.25 m3

Therefore, the total volume of earth = 292.5 + 29.5= 322 m3

You can calculate the dike dimesions and earth volumes needed to construct the secobdary

and tertiary dikes using the same methods.

Alternatively you may use this rule of thumb of the relationship between top width, bottom

width or base length, height of the dike and side slope


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3. HOW TO DO THE ACTUAL CONSTRUCTION OF THE POND?

a)

Preparation of the site

What are the factors should be considered before excavation?

Pond need to hold water to a depth of 1.0 meter.

Potential acid sulphate layers should not be exposed.

Should not excavate to a depth so that the pond can not be drained completely by

gravitational flow.

How to prepare the site before construction?

Clear the trees, scrubs and bushes in the site before excavation. Top soil has to be removed and taken away from the pond construction area of the site

Do not use the top soil to construct your pond dikes as it may contain roots and

decaying organic material which are unsuitable for pond dike construction.

You may store this surface soil in a suitable location, close to the site to use this fertilesoil for the following purposes.

- To cover the top width and inner sides of the dikes above water mark

- Spread a layer of this soil on top of pond bottom to increase pond fertility

- To prepare compost piles

Level the site. If the site is with the suitable slope to receive water into and discharge

water from the pond, level the site along the slope.

You may use thi s relationship to determine the dike height, top

width and dike base at dif ferent side slopes

Relationship among the top width, bottom width and height of dike

with a given side slope

Height

Top width

of crown

(m)

Dike base (m) at a given side slope

1:1 ratio 1.5:1 ratio 2:1 ratio

1.5

2

3

4

1

1

2

3

4

5

8

11

5

7

11

15

7

9

14

19


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b) How to mark the boundaries of the pond and construct the clay core (cut-off

trench)?

Mark the boundaries of the base of the pond using pegs and string

If the top soil layer does not have enough clay you need to build a clay core (cut-offtrench) to reduce water seepage under the dike.

To build the clay core, you need to cut a trench along the centre of the dike.

For small dikes (small ponds) the width of the trench should be 0.5 m and for large

dikes (large ponds) 1.0m. The depth of the trench should be 0.5m to 1.0m and for

large ponds the depth should reach at least 30 cm into the soil layer with enough clay

under the top layer without adequate clay.

To cut the trench, first mark the centre line of the dike base with pegs and string. On

each side of the centre line clearly mark the width of the trench that you want to cut.

Dig the trench to a desired depth and fill the trench to the ground level with good

quality clay. Wet it if necessary (if it is too dry) and compact well the soil in the trench with a

concrete tamper or metal tamper

You need to be careful if you bring clay soil outside the site to test it for acidy orpotential acidity

Pond dike baseboundaries

String

Pegs

Width of cut-off

trench

Concrete tamper Metal tamper


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c) How to excavate the soil?

Excavate to the predetermined desired depth (taking the conditions given in factors to

be considered before excavation).

Excavated soil can be used to build the dikes (after removing top soil).

If the excavated soil is not enough due to the limitations given above, you can pushearth from the sides of the pond to supplement the excavated soil to make dikes.

Excavated area of the sides of the pond can be used as drainage canals.

If the site can not be excavated due to its topography and status of elevation which

prevent gravity discharge of water, push earth from the sides to construct the dikes.

If this pushed soil is not adequate transport soil from a suitable site.

If soil has to be transported check the soil for its physical and chemical qualities forits suitability for pond construction.

d)

How to pile up soil to construct dikes?

When you are piling up of soil to make the dike, it is important you maintain the side slope of

the dike. In order to maintain the side slope during piling up of soil follow the procedure

given below.

Use pegs an a string as shown below to mark a line along all four sides of the pond20cm above the bottom parallel to inner and outer boundaries of the pond dike base.

Fill the first layer of soil along all four sides of the pond up to the 20 cm mark and

compress and compact the soil using either a concrete, metal or thick wooden tramper

(thick wooden board with a large surface area fixed to a vertical pole) or using avibration plate or a roller.

20cm

String

Pegs

Inner boundary

of dike base

Outer boundary

of dike base


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For each dike move the inside boundary and outside boundary of the dike base

towards the centre line of the dike by a distance equal to 20cm x side slope.

Then use pegs along this distance to mark the new inner and outer boundaries of the

dike base and raise the string to mark 20cm height above and parallel to the new

boundaries

For example:If the inside pond side slope and outside pond side slopes are 1.5:1, then the

distance is 20 cm x 1.5 = 30cm

Fill the second layer of soil along all four sides of the pond up to the new 20 cm markand compress and compact the soil using either a concrete, metal or thick wooden

tramper (thick wooden board with a large surface area fixed to a vertical pole) or

using a vibration plate or a roller.

For each dike, move the inside and outside dike base boundaries towards the dike

centre line by the same distance as previously (30cm) and raise the string another

20cm along and parallel to the boundaries

Fill the third layer of soil along all four sides of the pond up to the new 20 cm markand compress and compact the soil using either a concrete, metal or thick wooden

tramper (thick wooden board with a large surface area fixed to a vertical pole) or

using a vibration plate or a roller.

Repeat these steps until you reach the level of the top of the dikes. If the last soil layer

is less than 20cm thick, adjust the level of the string with the level of the top of the

dike, instead of 20 cm height.

Once you repeat this steps the sides of the dikes will look like staircases

In order to obtain a smooth side slope follow the following steps

- On the top of each dike, set out the planned dike top width, measuring half of itsvalue on either side of the centre line and mark the limits with pegs and a string

20cm20cm

30cm30cm

Outline of finished dike

20cm20cm


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- Starting from the top of the dike, obliquely cut the end of each soil layer on thesides of the dikes following a slope that joins the limits of the dike top width to

the bottom limit of the layers, until reaching the dike base

- Remove all the cut soil, pegs and strings

It is better to pile up soil 10%-20% more than the required dike height at the final

stage, i.e., when piling up the final layer. This 10% -20% additional soil layer is called

shrinkage allowance and it is for settlement or for shrinkage of dike height with time

after construction.

How to maintain a uniform dike height along entire dike length?

It is very important to have a uniform dike height when constructing the dike. You

can use the following simple technique to ensure the uniformity of dike height along

the dike length.

Get a 50 m long transparent plastic tube/hose. Fill the hose with water. Hold one end

of the hose at one end of the dike and the other end at the next 40 m away.

If the water levels at both ends are the same, the dike is level. Repeat this process

along the whole length of the dike

How to stabilise the dike slopes?

After levelling the pond, plant creeping grasses on the dikes to prevent erosion. Plant

bananas at the outside slope of the perimeter dike to serve as wind breakers.

Do not plant trees along the dikes because the roots will cause leakage and seepage.

The program of work is the basis of implementation of the project. Evaluate and

calculate each item realistically so that each job is properly developed andeconomically done.

Top width

Outline of dike

Shaped side of the dike


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e) How to plan fish pond construction

Planning of fishpond construction must be done carefully and systematically.

The system of pond construction is based on a prepared program and schedule ofdevelopment.

Below are examples of how to prepare the schedule of development and programme.

The charts given below are only to show how to prepare a schedule and a programme. The

timing (months, days), labour requir ements and support facil i ties can be vary according to

the locali ty and situation

Schedule of Development:

Months

Jan. Feb. Mar. April May June

1. Clearing/marking path & Levelling2. Earthwork:

a. Construction of dikes

b. Construction of canals

c. Levelling

3. Construction and installation of gates and pipes

a. Construction

b. Installation

4. Finishing touches

Proposed program of work:

ActivitiesNature of

work

Daily Labour

requirement

(8 hr/day)

No. Of

days to

complete

the work(days)

Support facilities &

equipment

Clearing/marking &

levelling of dikesDaily

Earthwork

a. construction of dikes

Contract

labour or own

labour

Contract

labour or own

labour


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b. construction of

canals

c. Levelling

Contract

labour or own

labour

Contract

labour or ownlabour

Construction &

installation of gates &

pipes

a. construction

b. Installation

Daily

Daily

Finishing touches Daily

4. WHAT ARE THE MATERIAL AND STRUCTURES YOU CAN

USE AS SUPPLY AND DRAINAGE CANALS, INLETS AND

OUTLETS?

Supply canals are the structures you deliver water from the water source to the pond.

Drainage canals are the structure you drain water away from the pond.

Inlets are the structures you let water into the pond from supply canal.

Outlets are the structures you drain water from the pond into the drainage canal.

The following can be used as inlets and outlets.

i) Pipes

Bamboo, PVC pipes, Coconut trunks with a hollow centre, galvanized pipes, orreinforced concrete pipes can be used as simple inlets and outlets.

Pipes can be used to supply water as the supply canal as well as inlets. Pipes can also be used as outlets to drain water from the pond into the drainage

canal.

Simple pipe outlet:

Outlet secured with a cap


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If simple pipes are used to drain pond water, the following can be used as a guide in

determining the proper pipe diameter to be installed.

Guide in determining pipe diameterSize of drain pipe in

inchesCondition

4

6

12

Can drain 1 ha. pond with average depth of 1 m

in 6 days

Can drain the same in three days

Can drain the same in one day

With proper scheduling of draining time, it is adequate to use 4 to 6 inch pipe for one hectare

pond and 6 to 11 inch pipe for larger ponds.

Stand pipe outlet:

If you use a plastic pipe you can make a better outlet pipe than a simple pipe outlet.

Two plasti pipe pieces canbe joint together using L shaped plastic joint as shown

below.

This type of outlet pipes is called stand pipes.

Stand pipe outlet

Move the verticle arm 900to

complete drain. Control the

angle of move ment to drain

water partially

Horizontalarm

Vertical arm

L joint


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It is important to protect the vertical arm of the outlet by accidental movements. Tiethe vertical pipe to pole fixed firmly into the ground so that it will not move or slip

down accidentally and let the water out of the pond before you want to drain the pond.

The top of the vertical arm of the stand pipe should be about 5 cm above the water

level of the pond. If pond water level rises above this level, it will overflow from thevertical pipe.

ii) Open gutters

PVC open gutters, split bamboo can be use as inlets.

iii)Earthen canals

It is better to construct earthen canals with a trapezoidal cross section foreffectiveness and efficiency of water delivery or drainage.

Earthen canals can be used to supply water as well as inlets (if the earthen

canal is constructed along the dike crown).

Shape of the trapezoidalcross section

Earthen canal running along the

dike to serve as the supply canal

as well as the inlet

Supply canal

Inlet


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Outlet pipeline should be placed at the very bottom of the monk.Sluice monk type gates can be made out of concrete or wood

Place three pairs of grooves on each side of wooden or concrete gates extending from bottom

to the top of the dike where they are installed. The middle pair of grooves allows the

removable slabs to regulate the flow of water. The first and third pairs enable the screens to

prevent the escape of cultured fish. These screens may either be of bamboo splits or nylon

attached to a wooden frame.

What are the important points to know when designing outlets?

You will need the outlet to let water out of pond when you want to empty the pond

Outlet should be large enough to drain the pond within a reasonable amount of time Place the outlet at the bottom of the dike at the lower end of your pond bottom and

select the deepest part so that the outlet will be low enough to ensure complete

drainage of the pond

On the pond side of the outlet, it should be at least 10 cm lower than the lowest point

of the pond bottom

Outlet should slope away from the pond, preferably with a slope equal to or greater

than 1%

At its other end (end outside the pond), it is at least 20 cm higher than the bottom of

the drainage canal

5. HOW TO SUPPLY WATER TO PONDS FROM THE WATER

SOURCE

If your water source is a borehole you have to pump water from the borehole and

directly deliver water through a pipe into the pond.

If your water source is a reservoir you can supply water from the reservoir through a

supply canal or a pipe using gravitational flow into the pond.

If your water source is a river or a stream, often rivers and streams are not muchhigher than your ponds, it may be difficult to get water to run down into your ponds.

By building a barrage as shown below, you can raise the level of the stream so that

water will run down more easily into your fish ponds.


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You can build a simple barrage using a woven mesh of tree branches or closelystacked stones or rocks or closely arranged set of logs into the stream.

A barrage does not hold back all of water that runs down the stream. Depending onhow the barrage is built, some of the water will be held back and some of the water

will flow through or over the barrage.

If the tree branches or stones or logs are placed tightly together, the water level behind

the barrage will be higher.

After you have built a barrage and the water behind it has reached its highest level,

you will need to dig a supply canal or a ditch to take the water to your ponds.

Construct the supply canal/ditch just behind the barrage where the water is deepest.

Dig it in a way that the water in the stream will not flow into the canal/ditch. To do

this start the supply canal/ditch about one meter away from the edge of the water.

When you want to supply water into your pond, remove this one meter strip and

connect the water into the canal/ditch. After supplying the water in to your pond, you

can fill again this strip and stop water flowing into the supply canal/ditch

Barrage

Stream

Stream


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A supply canal/ditch with above dimensions can supply water to a small pond of 400

m2

Alternatively build a wooden or concrete sluice gate at the top of the supplycanal/ditch just behind the one meter strip that you left at the edge of the water when

you began digging the canal/ditch. This is a better option to control the water flow

into your ponds.

The sluice gate will have three slots in each wall. Two sets of slots are for wooden

boards (wooden planks) and the third set is for a screen to keep out wild fish that may

enter through the sluice gate.

Fill the space between the two sets of boards with good clay soil to prevent any waterleaking through the sluice gate.

Stream

Stream

1m

A

A1

AA1

30 cm

30 cm

30 cm


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Remove the one meter strip of soil you left at the edge of the stream and allow the

water to fill up to the wooden planks in the sluice.

Later when you are ready to fill water into the ponds, you can control how much

water will reach your ponds by removing some of the wooden planks from the sluice

The figure below illustrate how you can build wooden a sluice gate

Construct the supply canal/ditch to supply water in a way that it will supply water to

all your ponds (first to last pond). The supply canal/ditch will branch into each pond

as inlet canals/ditches to supply water to each pond.

Construct the supply canal/ditch beyond the last pond for about 10 meters and thenbring the canal/ditch slowly to the surface so that when you fill the ponds, any

additional water will flow out at ground level.

BoardsScreen

Floor of the opening of

sluice gate

Foundation


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guidance on pond construction 2

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