Hydrology of fish culture ponds in Gualaca, Panama

During 1985, rainfall, evaporation and seepage were measured in 12 experimental fish culture ponds at the Gualaca Freshwater Aquaculture Research Station, Gualaca, Panama, to provide baseline pond hydrology data for the area and a water budget for the station. Mean monthly rainfall ranged from 0 to 27 mm day −1, while pond evaporation ranged from 1·4 to 8·4 mm day −1. An equation was developed to predict pond evaporation from solar radiation measured by photometry. Among the 12 ponds, mean seepage ranged from 19 to 58 mm day −1 and averaged 31. Seepage accounted for 87% of water lost from the ponds. A regression equation was developed to predict the quantity of water gained by runoff into ponds during rainfall. Monthly water balances (mm day −1) for the station ranged from −39 to 14 and averaged −13. Water deficits occurred during 9 of 12 months. The annual water deficit could be reduced to zero should seepage be reduced by 66%. Particular attention needs to be given to pond construction on kaolinitic soils, which although high in clay, may be very porous.