Operation schedule
The operation schedule of ponds is prepared for a pond complex having the production target of 1 million fingerling annually, which corresponds to that of the Hub complex.
In case of Tarbela the number of ponds is increased proportionally to its production target, and the size of ponds is also enlarged.
The annual water demand is computed on the basis of the following assumptions:
Brood fish and donor ponds are filled once a year.
Two nursery and two rearing ponds are prepared for stocking each week. 28 weeks of spawning means 28 stockings, and the number of pond fillings is 56. Therefore the average number of pond fillings in case of nursery ponds is:
and in the case of rearing ponds it is:
Pond filling
| Pond | No. | Water depth m | Average area ha | Total volume m3 | Number of filling | Total demand m3 |
| Brood fish pond | 4 | 1.7 | 0.27 | 27 600 | 1 | 27 600 |
| Nursery pond | 10 | 1.0 | 0.14 | 14 000 | 5.6 | 78 400 |
| Rearing pond | 16 | 1.5 | 0.44 | 105 600 | 3.5 | 369 600 |
| Donor pond | 4 | 1.7 | 0.48 | 32 800 | 1 | 32 800 |
| Total | 44 | 508 400 |
Replacement of evaporation losses
The ponds operate all year round the year and evaporation losses are computed in due course.
| Brood fish pond | January – December | Evaporation = 2 529 mm |
| Nursery ponds | February – August | Evaporation = 1 821 mm |
| Rearing ponds | March – October | Evaporation = 2 166 mm |
| Donor ponds | January – December | Evaporation = 2 529 mm |
| Brood fish pond | 2 529 mm × 1.63 ha = | 41 200 m3 | (rounded) |
| Nursery ponds | 1 821 mm × 1.40 ha = | 25 500 m3 | (rounded) |
| Rearing pond | 2 166 mm × 7.04 ha = | 152 500 m3 | (rounded) |
| Donor pond | 2 529 mm × 1.95 ha = | 48 800 m3 | (rounded) |
| Total evaporation loss | 268 000 m3 |
Replacement of seepage losses
In the absence of soil tests the seepage is estimated to be 10 mm/day. The length of operation of ponds is also taken into account.
| Brood fish pond | 10 mm/day × 365 days × 1.63 ha = | 59 500 m3 | (rounded) |
| Nursery pond | 10 mm/day × 28 weeks × 1.40 ha = | 27 400 m3 | (rounded) |
| Rearing pond | 10 mm/day × 34 weeks × 7.04 ha = | 167 000 m3 | (rounded) |
| Donor pond | 10 mm/day × 365 days × 1.93 ha = | 70 400 m3 | (rounded) |
| Total seepage loss | 324 900 m3 |
Inflow due to rainfall
The water for pond filling is from tube wells. Therefore the rainfall is only considered on the pond surface.
| Brood fish pond | 856 mm × 1.63 ha = | 14 100 m3 | (rounded) |
| Nursery pond | 663 mm × 1.40 ha = | 9 300 m3 | (rounded) |
| Rearing pond | 700 mm × 7.04 ha = | 49 300 m3 | (rounded) |
| Donor pond | 856 mm × 1.93 ha = | 16 500 m3 | (rounded) |
| Total inflow from rainfall | 89 200 m3 | ||
Summary
The annual water demand is the sum of the above amounts with the appropriate sign.
Pond filling | + 508 400 m3 |
Evaporation loss | + 268 000 m3 |
Seepage loss | + 324 900 m3 |
Rainfall | - 89 200 m3 |
Annual water demand | 1 012 100 m3 |
rounded to | 1 012 000 m3 |
