An FAO training course on Aquaculture Engineering was held in Hungary in 1983. The proceedings of this course were subsequently published (ADCP, 1984) and can be consulted for a more detailed account of fish farm planning and construction methods.
Types of pond
Two major factors have an influence on the design of pond fish farms: land topography and sources of water available. Accordingly, ponds can be classified as follows:
| Factor | Types of pond |
| Topography | Barrage pond |
| Contour pond | |
| Paddy pond | |
| Sources of water | Rain fed pond |
| Tide fed pond | |
| Diversion pond | |
| Seepage pond | |
| Ground-water pond |
Barrage ponds are made by constructing a dam/dike across a gently sloping flat valley.
Contour ponds are constructed along the side of a valley; the bottom of the pond lies along the contours of the land.
Paddy ponds are constructed on flat ground by building dikes on all four sides.
1 Based on material provided by Mr I. Tóth, Fish Culture Research Institute (HAKI), Szarvas, Hungary
Rain fed ponds. There are some parts of the world where rainfall is heavy and frequent throughout the year. Thus the water supply of the ponds can depend on the rainfall. In those regions where there is a single rainy season, the rain water has to be stored for the dry season.
Tide fed ponds. On coastal areas with suitable ground elevation, the water supply and drainage of a pond can be ensured by utilization of the natural energy of tidal motion.
Diversion ponds. This type of pond is supplied with water through a supplying canal which diverts the water from a river or some other type of water body.
Seepage ponds. Seepage ponds can be constructed in the depressed areas of ground in the delta of a river. These ponds are usually dug-out ponds without the possibility of gravity drainage. This is a serious limitation of this type of pond.
Ground-water ponds. The ponds are supplied with ground water by pumping from wells.
Major components of a pond fish farm
The land topography and the water source determine the basic physical characteristics of the farm. There is a wide variety of farms within each category, according to the size of the farm, the species of fish cultured, the management level, etc.
Nevertheless some facilities can be found in every pond fish farm. The farm is a complex of three major types of facility: earthen ponds, water control structures, and supporting or auxiliary facilities.
(a) Earthen ponds
A pond fish farm is a complex system comprising a number of ponds with different purposes. Among those ponds used for cultivating or holding fish, three major categories exist: broodstock ponds, nursery ponds and fattening ponds.
Broodstock ponds. The breeders provide the sexual products needed for the propagation of the new generation of fish. The valuable broodstock has to be held in fairly small and deep ponds close to the hatchery, where the conditions for holding and handling are good and where the stock is protected against theft.
Nursery ponds. After hatching, the larvae are reared in tanks or in special facilities inside the hatchery for a few days. When the larvae start to eat external food, they are transferred to nursery ponds where they are nursed for about a month until the early fingerling stage is reached. The nursing period is a very critical stage of life for the fish, which require very precise and careful treatment. The nursery pond should meet the requirements of this careful nursing by providing optimal living conditions.
Fattening ponds. The fingerlings are raised to marketable size in fattening ponds. Their surface area is larger than the others, and the pond must meet the requirements of production work. In certain circumstances the fingerlings are raised to marketable size in two phases in different ponds. However, since there is not much difference between the basic characteristics of these ponds, all of them are referred to as fattening ponds.
There are other types of pond in a fish farm which are closely related to the cultivation of fish. However, these ponds constitute only a small part of the farm and therefore of the design. These ponds are:
Spawning ponds are used for induced spawning of fish by simulating the natural environmental conditions. In some cases transition ponds are used for stocking and starving the fingerlings before they are transferred to the rearing ponds.
Storage ponds serve for temporary storage of fish before transfer to the market.
Wintering ponds. In some climates the fish have to be held in protected ponds during winter.
Harvesting ponds serve as harvesting basins.
There are also ponds in which fish are not cultivated or even held, but the operation of which may be necessary under certain circumstances.
Water storage ponds. In areas where the water supply to the farm is not continuous, water storage ponds can be used to conserve water for periods of shortage.
Feed ponds. In some cases natural supplementary food is produced in separate ponds that are called feed ponds.
Settling ponds. In areas where the water supply is heavily loaded with solid particles, it may be necessary to provide a settling pond for water before it enters the farm.
(b) Water control facilities
Earthworks
Dikes (embankments, bundhs) are made of soil preferably from the same area. The dikes separate the fish ponds from each other. They must be of adequate size and shape to hold the water and prevent seepage under or through the dike.
Canals: There are two major types of canal in the fish pond system: supply canals for carrying water to the fish ponds and drainage canals for draining the ponds. When necessary, small drainage ditches are also constructed inside the pond to ensure complete drainage. In areas where the farm is in danger of flooding by run-off water, a diversion canal is constructed to protect the farm.
Water control structures
Two main types of water control structure are commonly used both for water inlet and drainage, namely the sluice gate and the monk.
Sluice gates are usually preferred as a main control gate, or in situations where a large amount of water or fish must be passed through quickly.
Monks are the most common water control structure in fish farms, because of their easy and fairly cheap construction, effective and convenient operation.
In some barrage pond fish farms, run-off water may cause the ponds to overflow. This can be avoided by constructing a spillway as a water control structure.
The water control structures may have other purposes than water control. The water inlet can be used also for aeration, and outlet structures can be combined with a fish catching structure.
(c) Supporting or auxiliary facilities
Several supporting facilities are needed for the normal operation of the farm. There is no general rule about what kind and what size of supporting facilities have to be taken into account during the design of a farm, because this is determined by many factors, such as the size and location of the farm and the intensity of fish production. The design of these facilities should be based on the specific features and conditions.
The major supporting facilities consist of buildings and services:
Office, which is the headquarters of the farm management and administration.
Laboratory for routine water chemistry, hydrobiology and agrochemistry.
Residences for key personnel, especially for those who must be available at the site continuously.
Workers' amenities providing changing, shower, resting and sometimes canteen facilities for the farm staff.
Stores for storing feed, fertilizer, chemicals, spare parts, tools and minor equipment.
Machinery centre with workshop and garage, for the maintenance and storage of the farm machinery.
Access road (including the necessary culverts and bridges) with a hard surface should connect the farm to the road system.
Drinking-water supply. The laboratory offices, residences and the workers' amenities must be supplied with drinking water.
Electricity supply is convenient for the normal operation of a farm and essential above a certain level of management.
Sewers. Septic tanks meet the requirement for sewage disposal on an average farm.
Fencing is recommended to protect the farm centre and the broodstock. It is advisable to construct a fence all around the farm.
Fish pond maintenance
(a) Earthworks
During their first few years of operation, fish ponds need a greater degree of maintenance, because unforeseen, hidden faults appear at this time, e.g., the unexpected subsidence and settlement of dikes and more serious erosion on the surface of dikes and excavations. Maintenance must be carried out continuously from the first year of operation. The following troubles are commonly encountered with dikes: slope failure, soil slip, notch, slight erosion of the slope.
Slight erosion is in most cases caused by precipitation and its trickling down the slope. The thorough soaking and drying of the surface and negligence of dike maintenance can also cause slipping of the upper surface of the slope. If there is a more serious erosion of the gradient, shoulders must be constructed on the slope and new horizontal layers must be compacted onto the top of the slope. After reconstruction, the dikes must be protected against erosion.
Soil slip is caused most frequently by poor compacting, the drenching of the dike or quick water discharge. In such a case, a large quantity of soil slips down from the slope in some places. The slipped soil must be replaced with well compacted horizontal layers of earth and possibly reinforced with a sustaining wall.
Slope break-through has the same causes as soil slip. In this case a part of the slope slips down in a rounded form. For the reconstruction of such a failure, racking back and a foot wall should first be constructed, then good quality earth material should be filled and compacted in thin layers.
Slumping is generally caused by insufficient compacting of the dike. It can also occur where the layers containing humus or organic matter were not removed from beneath the dike. Reconstruction in this case is carried out by putting a new layer of earth onto the top of the dike.
Not only the base of the dike, but the dike itself can also settle. Settlement of smaller dikes is generally not greater than 2–4% of the height of the dike. Protection can generally be provided by construction of protecting shoulders/footwalls on one or both sides of the dike.
Bigger scale erosion and silting up generally occur in canals of large water current capacity or after a longer operation time. The maintenance must ensure the original water supply capacity of the canals. The erosion occurring at the bottom and on the surface of the slope, the soil slip and notch, must be corrected at least once a year. At the same time the accumulated silt and mud must be removed and the vegetation obstructing free water flow must be mowed.
At the bottom of fish ponds, the mud must be removed from the internal harvesting canals after drainage of the pond. Maintenance of their good condition can be assisted by putting the feeding places in these canals.
(b) Maintenance of the biological slope protection
The biological slope protection needs constant through checking and maintenance, as wave action can cause the erosion of the slopes. In Hungary a strip of the bank is normally planted with reeds for biological slope protection. Until the reeds become strong enough, temporary protection is provided by matting.
Any deficiencies in the reed strip must be made good. The protecting reed strip must be treated continuously. Recently new biological slope protection methods have been elaborated, whereby plastic material (geotextile, plastic net) is put onto the earth slope. The plastic, together with the plants and their roots, forms a protecting layer on the slope.
(c) Maintenance of water control structures
Structures must be checked by a separate inspection of all the elements (concrete parts, steel structures, flash boards). Sediments and mud must be removed from the structures before the inspection begins. Leakages occurring at the joints of structures can cause cavities which must be filled with properly compacted earth or, where necessary, with concrete. The leakage can be eliminated by repairing the joint or by application of bitumen filler.
Where settlement of structures, and sometimes consequential cracking occurs, the method of reconstruction must be determined for each individual case depending on the circumstances.
Steel structures. The components of steel structures must be protected against corrosion. The built-in structures must be cleaned each year with a wire brush, then painted with one layer of rust-preventing paint and two layers of oil paint. The moving elements of structures must be regularly oiled or lubricated.
Stone and concrete linings. If the stones become loose in the linings, or the filling material is damaged, the stones must be replaced. Settlement of the dike can cause damage to the lining. The same damage can occur when waves wash away the bed of the lining or the supporting earth. In such a case the lining must be removed from the damaged areas, the slope must be filled up with bedding material, then a new lining must be made.
The most frequent fault in concrete linings is underwashing. Reconstruction is the same as for stone linings.
Erosion at the ends of the lining must be filled with gravel as soon as possible, as otherwise the lining can be destroyed very easily.
Reconstruction works
After a few years of operation the fish ponds become silted up and their dikes damaged. The length of time this takes depends on the dike material, method of operation and level of dike protection. Ageing is accelerated where duck production is done in the ponds. Ducks are advantageous from the point of view of economics, but necessitate more maintenance of ponds.
The necessity for maintenance and/or reconstruction is shown not only by external visible factors (such as damage to the dikes, the pond bottom and the slope-protecting lining) but also by the decrease of production in the fish ponds. As a consequence of the erosion, the operating water level must be lowered, and thus the useful water volume in the fish pond is reduced.
The following reconstruction work is normally needed:
reconstruction of the crowns of dikes
replacement of eroded slopes
elimination of unevenness of pond bottoms
partial removal of mud in order to ensure harvestability and drainage
removal of water weeds
reconstruction of dike protection
Most reconstruction work can be done only when the fish pond is dried out. However, in some cases it is impossible to attain dry conditions during the time of reconstruction. In such cases maintenance and reconstruction cannot be carried out without special machines.
Dikes. When a large earth dam is reconstructed, specially classified construction material should be applied on the basis of individual testing. Dikes with lower loads can be constructed of material dug out from the pond bottom in dry conditions or by hydromechanical work.
During reconstruction of an old dike, or construction of a new one, the existing biological slope protection must be saved as much as possible.
When dikes are reconstructed, or new dikes are built, some space should be left along the dikes for the free movement of canal cleaner and ditcher machines, and for the deposition of the mud removed from the canal.
When a new dike is designed, its crown width should be wide enough to allow movement of farm vehicles on the top of it if necessary.
Internal drainage canals must be reconstructed with an angle of slope at least 1:4 and 5.0 m bottom width. The extracted earth must be removed from the pond or spread on the surface of the pond bottom. To make harvesting easier, construction of an internal harvesting basin or a central external harvesting basin can be useful.
Reconstruction of water control structures. The purpose of reconstruction is to restore the structures to their original condition. At the joints of elements of structures the water resistance must be renewed (by bitumen fixation, etc.). The cavities occurring along the joint linings must be reconstructed as described in the section on works on the lining.
During the reconstruction, some new structures can also be built where they are necessary for the modernization of the farm.
Reference
ADCP. 1984 Inland aquaculture engineering. Lectures presented at the ADCP Inter-regional Training Course in Aquaculture Engineering. Budapest, Hungary, 6 June-3 September 1983. Rome, UNDP/FAO, ADCP/REP/84/21, 591 p.
