The project is primarily designed to have a continuous circulation of pond water which is necessary for the culture of Macrobrachium rosenbergii, but such is not necessary for other freshwater fishes. Since the water required for pond operation might be limited, the recirculated pond water system might be more economically viable for the project. For freshwater fishes, the stagnant pond water management could be adopted. The stagnant water ponds could also be used for culturing Macrobrachium, if the water could be changed from time to time.
During operation, the nursery and culturing ponds need to be conditioned by filling and drying of ponds. The regular circulation of water is, however, totally dependent on pumped supply.
Water from the inner channel intake after passing through the biological filter is pumped into the retention pond wherein it is allowed to sattle. The top layer of the settled water is made to flow over a spillweir into a rapid sand filter. From here, it is distributed through a network of supply channels into individual ponds. The inlet control board for any particular pond to be completely filled will be fully open. For allowing normal regular flow of water, the lower board at the bottom is left partially open to allow the lower layer of water from individual ponds to flow into the drainage system. The water eventually are let out of the perimeter dykes. When any particular pond is to be drained, the wooden planks at the outlet control structure is fully opened and the water in the pond is released into the drainage channel. Fine screens are permanently provided in the overflow area of the outlet control structure whereas a set of fine screens would have to be introduced while completely draining the ponds. Drainage, however, is difficult during these times of high water level conditions.
There will be a regular backwashing operation of the filter bed and the frequency and duration of backwashing will depend on the bed silt load. Mud (sludge) removal is another item of work and the work is timed when no water is needed for the ponds.
