APPENDIX I
TECHNICAL REPORT ON THE HATCHERY-NURSERY POND COMPLEXES AT HUB, TARBELA AND MANGLA RESERVOIRS

1. INTRODUCTION

This report forms part of the Consultant's Final Report. Its content is limited to the technical description and explanation of the drawings. Its basic aim is to give help to technical staff to complete final detailed designs.

At present, while the WAPDA staff includes many civil engineers experienced in construction and maintenance of earthworks and structures, few are familiar with the specific requirements of fish farm construction. Thus, this report attempts to explain what is expected of the facilities, and how they should be developed and operated to achieve the expected results.

The structures of ponds and the hatchery are common in all complexes and therefore the drawings are numbered in the following order:

Note is made where further drawings must be prepared. This is either due to the lack of data, or relates to areas not specific to fish culture (e.g. architecture).

While the present report deals with aquaculture engineering problems, a short description of the production process is essential to make the functions understood for those who are not involved in fisheries, but will participate in finalizing the designs.

2. HATCHERY PRODUCTION/OPERATION

To improve utilization of the reservoirs involved, hatchery-nursery pond units will be established at each site. Their purpose is to produce the required number of quality fish seed for stocking in each reservoir.

The need for mass production of quality fish seed can only be satisfied by artificial propagation methods. These methods permit the incubation and hatching of eggs and the rearing of seed under well protected conditions, independent of local weather. The production process is under human control, and therefore 10–70% of the eggs produced can be raised to viable fingerlings as compared with a survival rate of less than 1% in natural waters.

The hatchery-nursery pond unit provides the facilities to produce quality fish seed in the required amount.

Artificial propagation is a chain of activities. These activities can be summarized as follows:

Steps 2a, 2b, 3 and 4 take place in the hatchery component of the unit, while the others take place in the ponds.

The Hub and Tarbela units are designed to provide capacity for rearing of brood fishes, but capture of brood fishes from wild stock may also be considered.

The specific requirements of the above production steps are discussed in the appropriate chapter where necessary.

3. HUB HATCHERY-NURSERY POND UNIT

3.1 The site

The site is located in front of the WAPDA colony, on the right bank of the main canal of the reservoir, about 500 m downstream of the dam.

The site is accessible on blacktop road and electrical power is available at the colony.

According to the only map which was available at the time of the consultancy, the surface elevation is between 81.50 m and 84.50 m above sea level. Although there are few practical limitations to the available site area, the land utilized is 10.6 ha. In the centre of the site there is a natural depression that may be utilized for drainage.

The water for filling of ponds and for replacement of losses can be supplied from the main canal. Preliminary investigations show that this water is not suitable for hatchery use, and therefore the tube well water is also required.

The general layout is presented on 1:2 500 scale map. This has been enlarged from the above mentioned map which is at 1:10 000 scale. As this displayed contour lines in five feet grades, elevations on the enlarged map are not in rounded metric figures.

3.2 The soil

Satisfactory soil survey has yet to be carried out. The results of the preliminary investigation are presented in figures. These data are of indicative value only.

In general, the samples contain fine sand and silt, with silt content of between 10 and 20%. Soils of this grain size distribution can be used for pond construction, provided the necessary precautions are taken.

Samples Nos. 2 and 3 contain clay. Their plasticity indexes are 16% and 7% respectively.

In the depressions on the site, layered gravel deposits can be observed. Their exact locations must be investigated to determine the allowable maximum depth of excavation. Traces of impervious soil can also be visually observed close to the pervious deposits. These will also have to be defined.

It is possible that the site is on alluvial deposits, and therefore it will be very important to determine the areal pattern and stratification of soils on the site as suitability for ponds may vary considerably within relatively short distances. Efforts must therefore be made to check the layers in the area for uniformity, to detect any singularities such as beds of rivulets, and abandoned streams, which are always potentially present in alluvial areas.

3.3 Production target and operation schedule

The production target of the Hub unit is 1 million fingerlings annually. The fish species selected for propagation are common carp, Chinese carps and Indian major carps. Their spawning seasons are from February to August and therefore semi-continuous operation is planned.

Figure 3 shows the operation schedule of the ponds. In each pond one week preparation and one week pond drying periods is allowed. Thus the operational cycle of the nursery ponds lasts for five weeks and that of the rearing ponds lasts for eight weeks. For additional security one additional nursery pond is provided.

There are also ponds for brood fish rearing and for donor fishes.

3.4 Pond pattern

The following ponds are proposed (for details see Table 1):

The nursery and brood fish ponds are located close to the hatchery building to decrease transport distance.

The water surfaces in the ponds follow the slope of ground surface to reduce where possible the amount of excavation required.

The dikes are designed to be homogeneous. However, it is possible that on certain sections the availability of materials may suggest the use of an impervious core and pervious cover.

As the ponds are small, the effect of waves is likely to be unimportant. However, for safety a 0.50 m freeboard in the brood fish-donor-and in rearing ponds and a 0.40 m freeboard in the nursery ponds is proposed.

The slopes of dikes are 1:2 on both sides. The side slopes of drainage canals are 1:15, but should be modified to 1:2 if soil conditions require it. Alternatively, a simple canal lining may be used to permit steeper gradients. This kind of slope protection is particularly advised if the drainage structures are close to each other, where lining should be constructed to protect the canal bed against erosion of the outflow water.

The drainage structures serve as harvesting places, and therefore should be accessible by small trucks. The contour dikes will have the crest width of 3.00 m. However, where transportation is considered, the crest should be widened to 4.00 m. Partition dikes between nursery ponds will have 2.00 m crest width; all other crests will be 2.50 m wide.

The pond bottoms have 20 cm slope running from the pond inlet to the drainage structure.

There are trenches along the contour dikes to collect seepage water from the ponds.

The hatchery building is located on the higher part of the site, close to the road.

The elevated reservoir is situated outside the farm area, on the top of a nearby hill.

The site is fenced around to protect against unauthorized persons.

With the present information on land survey, elevation data should be considered informatory only and therefore no cross sections of earthworks are prepared. However, the typical cross sections of Mangla pond complex (Drawing C-3 and C-4) may be applied here once the detailed survey is prepared.

3.5 Water supply to the ponds

Water for pond filling and for replacement of losses is from the main canal.

To estimate the total water demand from the main canal, the evaporation loss and inflow due to rain are evaluated:

¹ The available data are incomplete; therefore the number of years to compute the mean values are indicated in the Table.

The computation of annual water demand is summarized below: (for details see Annex 6).

During the weekly operation schedule there are also some ponds to be filled; water requirements should be also ammended accordingly. It is estimated that the weekly water demand in the peak season is 20 400 m³ (Annex 7).

The capacity of the main canal is 7.8 l/s. Considering the dimensions of the outlet structure and the water column in the reservoir, the discharge capacity of the outlet is practically unlimited, and thus the amount of water taken to the farm can easily be replaced from the reservoir.

The operational water level in the canal is defined as 81.52 m.a.s.l. However, the elevations of ground surface presented on the map and the visual observation are inconsistent. According to the map the site area should be higher than the canal, but in fact it appears to be lower. A properly conducted site survey will resolve this question. If the map is indeed accurate, a pump station may be necessary.

The discharge capacity of the pump station is computed in Annex 7. The recommended pumping capacity is 60 l/s. For security reasons it is better to install two units. Further data is required before pump selection and construction can be defined. This should be more clear when the site survey is completed.

If a pump station is not required, the water supply can be obtained by gravity, in which case, the water may be conveyed to the farm via an open canal. The length of the canal is approximately 250 m; the operational water level is 85.50. If soil conditions require, lining should be employed to eliminate seepage loss.

The water enters the gravel filter pool, where undesirable aquatic organisms are removed. The filter material should be regularly changed. The water from the pool is distributed to the ponds through pipes.

At each pond an inlet branch pipe with a gate valve runs from the main. The end of the pipe should be about 25–30 cm over the water level in the pond. For improved aeration a perforated steel plate can be fixed to spread the inflow water. This should be arranged to splash the water as much as possible. Below the pipe outlet the dike slope should be protected against erosion by a 1.5–2.0 m wide strip of lining. The diameter of the inlet pipes is 125 mm; valves should be at least 100 mm.

3.6 Drainage of ponds

The ponds are drained through drainage structures. The nursery ponds are paired, and one structure serves two ponds. In other ponds, the structures are of single monk type.

A double set of wooden control boards is used to allow the farmer to control the pond water level in 25 cm steps (the depth of each board) and allows the release of surface water when draining is needed.

Detailed description and explanation of these structures and their accessories are given in Chapter 6.

The water is collected and evacuated from the site in drainage canals. If soil conditions are unfavourable, lining may be necessary. Its function is only that of protection against erosion, and therefore it is not required to be watertight. The side slope of drainage canal is 1:1.5.

3.7 Service roads

Harvesting takes place at the drainage structures and they must therefore be accessible by transport vehicles (e.g. pick-ups). The dikes where drainage canals are located are widened and the crest width is 4.0 m.

3.8 Hatchery

The hatchery building is located on the higher part of the site, close to the road.

The details of the hatchery are discussed in Chapter 7.

4. TARBELA HATCHERY-NURSERY POND COMPLEX

4.1 The site

The site is located at Khiwa village, Khalabat pocket. It is accessible on blacktop road from Haripur which is about 4.5 km away. Electricity is available at Khiwa.

There is only one map of 1:10 000 scale displaying the site. The contour lines of the map significantly deviate from reality and had to be modified according to visual site observation. It is therefore very important to check the accuracy of the map. (The problem is explained in the report on the second visit to Pakistan - Working Document 8).

The site is above the maximum water level of the reservoir. Thus, the ponds can be drained completely at high reservoir water level.

Water for both pond filling and hatchery use can be provided from tube wells.

The general layout is presented on a 1:2 500 scale map which is enlarged from the only available map of 1:10 000 scale. The original map shows the contour lines in five feet grade, and thus metric elevations on the enlarged map are not rounded off.

4.2 The soil

The soil survey of the site has still not yet been made. The decision that the soil is suitable for pond construction is based only on a site visit and on the log of a nearby tube well.

The soil is clay, sandy clay loam and appears to be good for dike construction. It is known, however, that there is a permeable gravel deposit in the area. Its exact location must be discovered before finalizing the specifications of earthworks.

4.3 Production target and operation schedule

The annual production target is 2.5 million fingerlings of different species.

The operation schedule is similar to that of the Hub station. For each pond one week for pond operation and one week for drying are allowed in defining the size required.

To avoid using ponds which are too large, two of each of nursing and rearing ponds should be prepared for stocking each week.

There are also ponds for brood fish rearing and for donor fishes.

4.4 Pond pattern

The unit occupies 20 ha, but the water surface of ponds is only 12 ha, as listed below:

The nursery and brood fish ponds are located close to the hatchery building to reduce transport distance.

The ground surface slopes toward the reservoir and the water levels in ponds follow this pattern. The difference between water levels in neighbouring ponds is maximum of 0.60 m.

The dominant wind direction is not recorded, but the effect of wind may be considerable. A 0.40 m freeboard in nursery ponds and 0.50 m in other ponds is therefore provided.

The slopes of dikes are 1:2 on both sides. The side slopes of drainage canals are 1:1.5.

The drainage structures also serve as harvesting points and should therefore be accessible by car. The crest width of dikes along the drainage canals is 4.00 m. The contour dikes have a crest width of 3.00 m, while partition dikes have a width of 2.50 m, except between nursery ponds where it is only 2.00 m.

The pond bottoms have a 20 cm drop in the direction of drainage structures. The drainage canals follow the natural slope of the ground surface to minimize excavation.

There are trenches along the contour dikes to collect seepage water from ponds and to evacuate the inflow rainwater from the site.

The hatchery building and the elevated reservoir are located on the higher part of the site.

A 200 m long service road is designed to link the complex to the existing road to Haripur.

At present, elevation data is indicative only as a full survey is required. No cross sections of earthworks are therefore prepared; though more detailed site levels are established, the corresponding drawings of the Mangla complex (Drawings C-3 and C-4) may be used for guidance.

4.5 Water supply of ponds

Water will be supplied from tube wells. There will be separate wells for the ponds and for the hatchery, but these will be interconnected for security purposes.

For computing water requirements, the following hydro-meterological data were evaluated:

The annual water demand of the ponds is summarized below (for details see Annex 8):

The weekly water demand in peak season is 35 320 m³ (see Appendix 9).

The computation of the required pumping capacity is based on the weekly water demand, and for two pumps is 102 l/s.

The water is distributed to the ponds through pressure pipes. Depending on the selected pumps, the diameter of the pipes would be about 10 mm.

These tube wells may also supply water to the hatchery and are therefore interconnected to the aeration tower and elevated reservoir. During maintenance of the hatchery tube well, one of these pond supply pumps should provide the necessary amount of water.

At each pond an inlet branch pipe with a gate valve runs from the main. The end of the pipe should be about 25–30 cm over the water level in the pond. For improved aeration a perforated steel plate can be fixed to spread the inflow water. This should be arranged to splash the water as much as possible. Below the pipe outlet the dike slope should be protected against erosion by a 1.5–2.0 m wide strip of lining. The diameter of the inlet pipes is 125 mm; valves should be at least 100 mm.

4.6 Drainage of ponds

The ponds are drained through drainage structures. The nursery ponds are paired, and one structure serves two ponds. In other ponds, the structures are of single monk type.

A double set of wooden control boards is used to allow the farmer to control the pond water level in 25 cm steps (the depth of each board) and allows the release of surface water when draining is needed.

Detailed description and explanation of these structures and of their accessories are given in Chapter 6.

The water is collected and evacuated from the site in drainage canals. If soil conditions are unfavourable, lining may be necessary. Its function is only that of protection against erosion, and therefore it is not required to be watertight. The side slope of drainage canal is 1:1.5.

4.7 Service roads

Harvesting of fry and fingerlings take place at the drainage structures and they must therefore be accessible by vehicles. The dikes along the drainage canals, where drainage structures are located, are widened and the crest width is 4.0 m.

4.8 Hatchery

The hatchery building is located on the higher part of the site. The details are discussed in Chapter 7.

5. MANGLA HATCHERY-NURSERY POND UNIT

5.1 The site

The site is located about 1.5–2.0 km southwest of the Mangla Dam on the right bank of the Bong irrigation (Upper Jhelum) canal. It adjoins the existing hatchery.

The site area is limited, being bordered by a road, a ghee mill and by electric transmission line respectively on three sides. The available area is 9.2 ha.

The site is accessible by road and electricity is available nearby.

The ground surface slopes in north-south direction. The highest spot on site is 266.0 m.a.s.l. and the lowest 261.0 m.a.s.l.

Water for pond filling will be pumped from the irrigation canal, but its water temperature and sediment and suspended colloid content make it unfavourable for hatchery use.

The general layout is presented on 1:1000 scale map that has been enlarged from a 1:1200 scale map (1 inch = 100 ft) for the purpose of using SI dimensions.

5.2 The soil

A soil survey has been carried out to identify its characteristics. The results are presented in Table 4. Samples are taken from 7 bore-holes in depths of 1.2 and 3 m. According to the records, the soils are good for dike construction except those deposits which contain a large amount of gravel or greater particle sizes. The plasticity index of sandy-loam, silty-loam soils should be checked again. However, these kind of soils, with 8–12% of clay content, usually have some plasticity. The permeability coefficient is presented in terms of cm/s.

During the site visit some puddles were observed on the lower part of the site, which suggests sufficient impermeability of the soil.

In summary, the soil on site is good for fish pond construction, but attention must be paid to those layers and deposits which contain boulder, cobbles and gravel.

5.3 Production target and operation schedule

The annual production target of the unit is 2.6 million fingerlings of different species.

The operation schedule is similar to that of the Hub station. Two nursery and two rearing ponds should be prepared for stocking each week.

5.4 Pond pattern

The hatchery-nursery pond complex occupies 9.2 ha, but the water surface of ponds is only 8.13 ha. The new site is only for ponds, as all other facilities (the hatchery, the elevated reservoir) are accommodated on the site of the existing hatchery-nursery complex.

There are no donor ponds, though some of the brood fish ponds may serve this purpose.

The total pond surface is less than that calculated on the basis of production target, but the site area is limited. The capacity of the existing tanks may increase the production security and potential, if the management improves.

If it is necessary, brood fish pond No.1 may serve as a settling and filtering pool for the nursery ponds. In this case a gravel-sand filter should be constructed in the pond, similar to that of the gravel-filter pool at Hub.

The freeboard in the nursery ponds is 0.40 m and in the other ponds is 0.50 m. The dike slopes are 1:2. The side slope of drainage canals is 1:1.5 and will be protected against erosion by lining.

The drainage structures also serve as harvesting points and therefore should be accessible by road.

The crest widths are as follows:

In some specific areas the above may vary as shown on the relevant cross-sectional drawings.

The pond bottom slopes 20 cm toward the drainage structure in each pond. The drainage canals follow the natural slope of ground surface.

The hatchery building is located on the site of the existing hatchery-nursery station. The two establishments will be integrated into one unit.

5.5 Pond water supply

Water for pond filling and for replacement of losses will be pumped from the Bong irrigation canal.

As the canal water is released from the bottom of the reservoir, its temperature does not exceed 18°C and therefore is not suitable for hatchery use, but may be warmed up in ponds during the preparation period.

For computing the losses and inflow water, the following hydro-meterological data were used.

The annual water demand of the pond component is summarized below (for details see Appendix 10).

Pumping capacity is based on weekly water demand which is 30 734 m³ (see Appendix 11). The designed pumping capacity is 90 l/s, provided by two units.

The water is distributed to the ponds through pressure pipes. Depending on the pumps selected, the diameter of pipes would be about 100 mm.

At each pond, an inlet branch pipe with a gate valve runs from the main. The end of the pipe should be about 25–30 cm over the water level in the pond. For improved aeration a perforated steel plate can be fixed to spread the inflow water. This should be arranged to splash the water as much as possible. Below the pipe outlet the dike slope should be protected against erosion by a 1.5–2.0 m wide strip of lining. The diameter of the inlet pipes is 125 mm; valves should be about 100 mm.

5.6 Drainage of ponds

The ponds are drained through drainage structures. The nursery ponds are paired, and one structure serves two ponds. In other ponds, the structures are of single monk type.

A double set of wooden control boards is used to allow the farmer to control the pond water level in 25 cm steps (the depth of each board), and allows the release of surface water when draining is needed.

Detailed description and explanation of these structures and of their accessories are given in Chapter 6.

The water is collected and evacuated from the site in drainage canals. The side slopes of the canals are 1:1.5, the bottom width is 0.60 m. The canals should be lined as protection against erosion.

5.7 Service roads

Harvesting of fry and fingerlings takes place at the drainage structures which should therefore be accessible by vehicle. The dikes along the drainage canals are 4.0 m wide on the crest.

5.8 Hatchery

The hatchery is located in the already existing hatchery-nursery unit. Its details are discussed in Chapter 7.

6. POND STRUCTURES

6.1 General

The ponds are operated according to defined schedule. They must be filled and drained separately.

The water is distributed to the ponds through pipes; inflow water can be regulated by gate valves. Additional aeration is usually needed; to assist this a perforated steel plate should be fixed on the end of the pipe to spread the inflow water. Under the inflow the dike slope is protected against erosion.

The pond base should have a uniform slope from the intake to the outlet point. The fall of the base is 20 cm.

The drainage structures are constructed on the opposite sides to the inlets to ensure flow through the ponds.

The ponds are deepest at the drainage structures and should be able to be fully dewatered by gravity. The drainage structures ensure rapid dewatering and control of water surface, and allow for release of excess water automatically.

At the drainage structures the pond base drops an additional 20 cm to form a pit or sump which is essential for collecting the fish at harvesting.

Harvesting takes place at the drainage structures. To make harvesting easier a certain area around the structure (as indicated on the drawings) is covered by cement concrete slabs on a sandy-gravel bedding.

The structures are connected to the drainage canals via a pipe. There is a 10 cm fall along the pipe from the structure to the drainage canal. There is thus a 0.50 m difference between the pond base level at the inlet end, and the pipe outlet in the drainage canal.

Around the drain pipe outlet, a lining is used to avoid erosion in the drainage canal. Its length is 2.50 – 3.50 m. At the Hub and Mangla units the drainage canals should be lined all along. Since the water level in the canals will not exceed 60–70 cm in the most unfavourable conditions (e.g. more ponds are drained at once), the height of lining is a maximum 1.00 m (6 rows of 30 × 30 × 8 cm slabs).

The lined sections in the canals as well as those in the ponds should be bordered with a c.c. beam.

The bottom width of the drainage canals is 0.60 m. The bottom slope should be hydraulically dimensioned. Flow of drainage water should be neither too slow nor too rapid.

There are some crossings on the canals, and culverts should therefore be constructed.

The drainage structures operate as follows:

1. There are three grooves on the structures: the outer one is for the steel screens and the two inner ones are for the control boards.

2. the control boards are placed in the grooves in a double row as high as the desired pond water level.

3. The space between the two rows of control boards is filled with some impermeable material (e.g. clay) to minimize seepage.

4. The dimension of control boards allows 25 cm steps in water level. Excess water automatically overflows the top board.

5. When the water level is to be decreased, the upper boards should be removed. After dropping the water level 25 cm, the next pair of boards should again be removed. This procedure ensures gradual draining of ponds and limits erosion of dikes due to rapid dewatering.

6. As the water level decreases the fish move together in front of the drainage structure, where the water is the deepest. This can be helped by using nets to move the fish towards the outlet.

Good and watertight closure of control boards is an important factor in minimizing seepage loss at the structure. The grooves are lined with steel channel of 50 × 50 × 5 mm. They must be made with steel bar fixing pins, set at appropriate distances. These are concreted into the structure. The control boards should be individually fitted and numbered by structure and by groove.

The steel screens are to prevent the escape of fish through the drainage structure. The gap between the bars is too wide for small fish and larvae, and so an additional net of suitable mesh size must be attached.

6.2 Drainage structure of brood fish ponds

The drainage structure of brood fish ponds is the traditional monk.

The monk is a structure which is U shaped in plan, open at the front, facing the pond. Its internal dimensions are 0.40 m wide, 1.00 m deep and 2.50 m high. Three grooves are formed to accommodate the steel screens and control boards.

The water is conveyed to the drainage canal through a prefabricated cement concrete pipe of internal diameter 300 mm.

The slope of the dike is 1:2, but around the structure this is increased to 1:1.5. Thus the crest width is widened by 1.25 m, the cross section of dike is strengthened and the area of lining is reduced. The structure is placed at the toe of the original slope.

A widened foundation slab is provided to avoid overturning. The opening area is spread out to provide better flow towards the drainage part.

The monk outlet is designed specifically to prevent the pipes sliding apart.

The length of the pipe basically depends on the distance between the axis of dike and the axis of drainage canal.

The drainage structures of donor ponds are exactly the same as those discussed above.

6.3 Drainage structures of rearing ponds

The drainage structures of the rearing ponds are identical to those of brood fish ponds, except that the height of the monk tower is only 2.30 m.

6.4 Drainage of nursery ponds

The drainage structure of nursery ponds is different from that of the other ponds, as in addition to providing water level control, it also serves as a harvesting structure for fry.

The structure is that of U shaped sluice between two ponds, serving both ponds at once. This structure is parallel to the axis of the common dike.

Because there is no need for transport along the common dike, a bridge slab over the structure is not required.

As with the other structures, the water level is controlled by boards. Boards are also placed in front of the outlet pipe, which is of ID 200 galvanized iron pipe.

Harvesting is managed as follows:

1. Firstly the overall water level is decreased in the pond, and then the front boards are removed, and one row of boards is placed in the first groove. In the groove behind it a net of appropriate mesh size fixed on a wooden frame is fitted.

2. The first set of boards is removed to allow the fish to move into the net.

3. If the net becomes full, the first set of boards is replaced in the groove and the net is lifted out for emptying.

4. During harvesting, fresh water is syphoned from the neighbouring pond.

5. During harvesting, the water level is adjusted by the boards in front of the pipe.

The internal dimensions of the structure are 1.00 m wide, 1.70 m high and 7.10 m long. The openings of the structure run out to a 1:1.5 slope. The slopes around the structure change to 1:1.5 from 1.2. The cross section of the dike is thus reduced, but as the dike is only a partition dike, it is not endangered. This also helps to reduce the amount of concrete works.

6.5 Culverts

There are some crossings on the drainage canals and culverts should therefore be constructed.

The internal diameter is 0.60 m and is constructed of prefabricated cement concrete pipes. To keep the pipe assembly together, both the inlets and outlets are constructed on site on a blinding concrete bed which has a concrete key deepened into the soil base.

6.7 Pressure pipes

The pressure pipes conveying water to the ponds may be either placed on the crest or on the slope over the water level. They must be fixed to the dike body by buttresses at tees, turnings and at 30–40 m intervals of straight sections.

7. HATCHERY

7.1 Building

The hatchery building is a single storey structure with reinforced concrete flooring and a pitch roof. The skeleton is of r.c.c. columns with steel trusses. The roof is covered with corrugated asbestos sheets. The outer walls and some of the inner walls are of double skinned brick, 23 cm/19“/wide. Partition walls are also made of brick, of 12 cm/4 ½” width. The foundation of the columns depends on the specific conditions on each site. However, single pad foundations will probably be sufficient.

The building has the following rooms:

The hatching - rearing hall accommodates the following equipment:

The Chinese type r.c.c. circular spawning tanks and the two fibre glass rearing tanks are located outdoors. Two multipurpose r.c.c. twin tanks are also constructed outdoors to increase the operational flexibility of the hatchery.

The large space between the incubator - rearing units enables the staff to carry out different operations conveniently at each point.

Free communication between indoor and outdoor facilities is provided through three large double doors. Sufficient ventilation is maintained through windows. Generally, the great amount of water in the hatching-rearing hall gives excellent air temperature. However, in the other rooms a false ceiling is designed for heat insulation purpose.

The outdoor tanks are sheltered to avoid overheating. The shelter is a simple light steel truss with a corrugated a.c. cover mounted on steel columns. This structure is not shown on the drawings.

The elevations in the drawings of the hatchery are given in local system and the ± 0.00 level is to be considered the floor level of the building.

7.2 Hatchery systems

The hatchery accommodates facilities for two methods of propagation:

1. Hormone induced ovulation with artificial fertilization of eggs, hatching and larval rearing in vertical flow-through jars of different size.

2. Chinese method for induced spawning and hatching in circular tanks.

Some facilities serve both methods of propagation. The combination of the two technologies, together with the possible spawning in ponds, may considerably increase the flexibility of the complex.

7.2.1 Incubators and rearing jars

The hatching of eggs and rearing of hatchlings take place in the vertical flow-through fibre glass incubators and rearing jars. The jars are grouped on modular steel stands. The stands are manufactured from round steel bar with welded joints and should be protected against corrosion.

The base frame (Drawing E-3.1) holds the water distributing pipe (Drawing E-4.3) and the fibre glass drain trough (Drawing E-4.2).

Additional elements are welded on the base frame to hold the 20 l and 60 l jars (Drawings E-3.2 and E-3.3). The 200 l jars have individual stands due to their weight (Drawing E-3.4).

The jars are connected to the inflow distribution pipe with flexible, e.g. rubber, pipe of 20 mm. The water current is adjusted by the globe valves. Each unit is equipped with two additional globe valves to supply water for additional units. One valve is for drainage.

The jars are grouped in units as follows:

All jars have a removable filter of fine mesh sieve (0.5–0.6 mm) fixed on plastic or fibre glass frame. The large filtering surface is to avoid overflow due to choking.

The units are connected to the main pipe by flexible pipe of ID 50 (2").

7.2.2 Circular spawning and hatching tanks

The circular spawning and hatching tanks are located outdoor.

The spawning tank is constructed from reinforced concrete. Its inner diameter is 2.50 m, the depth is 1.50 m. The water enters the tank through four nozzles, in the direction of 45° to the axis. This position ensures the continuous circulation of water. The water level is regulated by the plastic (PVC) turn-down pipe (ID 50) that also serves as a drain. The water depth in the tank is 1.35 m. A brick platform is set around the tank to make it easier to operate.

The hatching-rearing tanks are made of fibre glass. The diameter is 1.2 m and the depth is 1.00 m. The water supply is through a pipe of ID 40. Water control and drainage is via a turn-down pipe of ID 50.

Both tanks have conical bases from which the drainage pipes are connected.

7.2.3 Multipurpose r.c.c. twin tanks

Four twin tanks of r.c.c. will be constructed to serve various purposes, such as holding brooders during propagation course, holding larvae before stocking and in case of medical treatment, etc.

Three out of the four have the internal dimensions of 2 × 2.00 × 0.80 × 1.00 m. One set is located outdoors. The fourth one is larger, with dimensions of 2 × 4.00 × 0.80 × 1.00 m. The bottom slopes toward the ID 50 (2") turn-down pipe. The inner surfaces of the smaller tanks are glaze-tiled for easy cleaning and sterilization. The grooves are for holding wooden framed screens to segregate fish (see Drawings E-2.2 and E-2.3).

7.3 Water supply and drainage

Safe operation in a hatchery requires a sufficient amount of water at each phase of the propagation process. The water supply is therefore designed for peak water demand.

Thus the minimum water demand is 3.70 l/s
maximum water demand is 8.30 l/s, and
mean water water demand is 6.00 l/s.

For all units tube wells are used as a source of water. Pumping capacity is 9.05 l/s using two pump units.

The water is pumped to an elevated reservoir, where additional aeration is provided. The elevated reservoir also stores water for emergency purposes. Its storage capacity is 84.0 m³. The emergency reserve is for two hours of operation.

From the elevated reservoir the water is conveyed to the two overhead tanks by gravity through ID 125 galvanized iron (G.I) pipe.

The two overhead tanks serve only to provide balanced static water pressure and do not provide emergency reserves.

The water is distributed to the devices through PVC pipes. In case of any repair works, the system can be sectioned by gate valves. However, maintenance of the system should normally be done out of spawning season.

The water flows through the jars vertically, entering at their bases and leaving them on through an upper outlet point. The shape of the jars produces smooth, vortex-free flow. Used water is collected in a trough and conveyed to floor drains.

In the circular tanks and in the r.c.c. tank the water flows horizontally. The supply valves (ID 40) are about 10 cm over the edge (approx. 30 cm over the water). Drainage is through a turn-down pipe to the floor drain.

The floor drain collects water and evacuates it from the building. It is made of cement concrete with light reinforcement and covered with a steel grate (see detail D on Drawing E-1). At the exit point a syphonic drainage trap is installed. Before disposal, the water can in emergency be repumped to the overhead tank.

There is a washhand basin and laboratory sink in the passage and in the laboratory office respectively.

The sanitary installations and plumbing in the toilets need no detailed drawings. The sewage from the toilets is disposed in septic tanks separately from the drained water of the hatchery system.

7.4 Miscellaneous

Lighting of the building is by fluorescent lamps fixed to the steel trusses. Power lines should only be provided in the passage and in the rooms, but must be leakage-protected according to standards. The building must be protected against lightning.

8. GENERAL RECOMMENDATIONS

In the present chapter some guidelines are given to help finalizing the designs. Some specific requirements for fish pond construction are also given.

8.1 Land and soil survey

The main characteristics of the units are laid down in the previous chapters, but some questions need to be resolved before implementing the projects.

In both Hub and Tarbela land and soil surveys must be completed.

In general the fish ponds should be partly excavated and dikes are partly filled. It is difficult to achieve an exact balance between excavation and filling, but for economy of construction an effort should be made to reach it. A well detailed land and soil survey is therefore essential.

The most important data to be displayed on the layout map are:

• the elevation of ground surface plotted on the map at 20–25 cm contour line intervals;

• the boundary of the site and any natural formations which may influence the pond pattern;

• geodetical identification marks, the north direction;

• structures, existing buildings, etc.;

• connection to transportation facilities (e.g. roads);

• electric and telephone lines;

• source of water and possible receiver of drained water;

• cross and longitudinal sections of natural depressions, or of existing canals.

The soil survey must provide data for soil consistency, soil components and for index properties.

In case of structures in ponds, the safe bearing capacity of soil is usually sufficient if other properties satisfy the requirements. In case of the hatchery building and elevated reservoir, the requirements of soil properties are as in other civil engineering works.

It is necessary to underline that in pond design, the impermeability of the dike is important, but not absolutely essential. As long as the seepage loss does not exceed 20 mm per day (except for the absorption loss of first filling after a long period of drying), it will be acceptable. Applying a clay, clay loam layer on the slopes and on the pond base along the dike may reduce the seepage. Seepage will also be reduced by using manure. It must be emphasized however that the free communication between the soil of the pond base and the pond water is one of the most important factors in the production of fish in ponds. Solid pond lining must therefore be avoided as seepage protection.

If it is possible, the pond location and elevation should be selected to avoid cutting into permeable (gravel) layers.

To avoid unexpected seepage problems, it is recommended to take soil samples along the proposed contour dike area at an interval of 50–75 m.

8.2 Design

8.2.1 Earthworks

In the case of the Mangla unit, the details of the earthwork are designed. The ponds and drainage canals of the others will be similar, and these designs may therefore be used as guidelines.

8.2.2 Structures

The structures of ponds are well detailed but their reinforcement must be designed. It is usually a simple reinforcement of 10 mm diameter steel bars, centre to centre, 200 mm in both direction.

8.2.3 Pump stations - tube wells

The detailed designs and thus the specification of pump stations and tube wells remain to be completed because of the lack of data or the aquifer. The pumps should preferably be remote controlled or at the least the actual water level state in the elevated reservoir should be obvious to the operator.

The loading of pumps during starting should be done gradually (1–2 minutes delay) to avoid rapid suction resulting in unfavourable inflow of small particles from the soil.

8.2.4 Elevated reservoir

The structural design of the elevated reservoir depends on its foundation. It may be earth mounted, but in case of Tarbela the possibility of placing it on r.c.c. columns must not be overlooked. The elevation depends only on the required conveying capacity of the connecting pipe to the hatchery.

8.2.5 Hatchery

The requirements of the hatchery are specified, but some structural designs are still to be completed (foundation and steel trusses of roof).

8.2.6 Energy supply

Electric energy is available at or nearby the site. However, a standby generator must be included in the equipment.

The design of electric energy supply is based primarily on the energy consumption of the pumps. Until these are selected there is no purpose in specifying this.

8.3 Construction

Before commencing excavation in any portion of the site, all vegetation, roots and trees must be cleared. The top soil should also be removed and deposited. If unfit material is found (not being suitable for dike construction) it should be removed from the site. This kind of soil may be used for levelling areas in front of the hatchery component.

Any top soil removed after completing the dike construction should be laid on dike slopes and on the pond bottom.

Excess soil material can be placed at the toes of dikes to form berms.

The dikes should be well compacted by mechanical rollers, rammers, vibrators or other approved means so as to produce a minimum dry density equal to 90% of the maximum dry density determined in accordance with “Standard methods of tests for moisture-density relation of soils using 10 lb hammer and 18 inch drop” ASTM Designation D 1557 - Method A, or equivalent. The compacted fill should consist of approved material spread and compacted in layers approximately horizontal and of uniform thickness not exceeding 25 cm with a slight outward slope.

The terrain correction and land levelling prescribed in the plan should be accomplished with ± 5 cm tolerance and the same should be applied for the pond bed correction.

The surface upon which the dikes are to be placed should be cleared and all depressions backfilled. The area must then be scarified prior to placing the dikes.

The above specifications are the most important ones in pond construction, but the usual recommendations of earthworks must also be considered.

8.4 Protection against predators

This is an important factor in pond operation. Predators may be either aquatic organisms or birds. Filtering the inflow water provides good protection against wild fishes or their eggs, but, for example, against frogs, additional protection must be provided.

Frogs are harmful for the larvae and must therefore be kept away from the nursery ponds. The ponds should be fenced around with a net of small mesh size. Thus netting should be regularly checked. The smallest damage on the fencing can reduce its success in protection.

8.5 Reference books

The following technical papers and books are highly recommended as further reading.

• Inland aquaculture engineering. Lectures presented at the ADCP Inter-Regional Training Course in Inland Aquaculture Engineering. Budapest, 1983, 596 p. ADCP/REP/84/21 (FAO)

• Jhingran, V.G. and R.S.V. Pullin, 1985. A hatchery manual for the common, Chinese and Indian major carps. Manila, ADB/ICLARM Publ., 191 p.

• Bowles, J.E. Foundation analysis and design. McGraw-Hill Book Co., 1968, 659 p.

• Huet, M. 1972. Textbook of fish culture. Breeding and cultivation of fish.

• Woynarovich, E. and L. Horvath, 1980. The artificial propagation of warmwater finfishes: A manual for extension. FAO Fish.Tech.Pap., (201):183 p.

The above books have also chapters of engineering requirements and design criteria for ponds and hatcheries and therefore are useful for everybody dealing with hatchery-nursery pond complex design.