Description

Abstract: A water budget simulation model that can be used for forecasting water requirements for aquaculture ponds has been developed. Water sources considered in the model include regulated inflow, precipitation and runoff, whereas water losses include evaporation, seepage, effluent discharge, and overflow. The model has been validated for ponds located at the Asian Institute of Technology (AIT), Thailand and at El Carao, Honduras which are, respectively, located in the humid and dry tropics. Simulation results indicate that precipitation accounted for 69.8% of the total water gains for the AIT and 43.2% for El Carao. Regulated inflow provided 27% of the gains for AIT and 52.8% for El Carao. Runoff gains were minimal at both locations due to small watershed areas. Evaporation accounted for 54.9 and 40.1% of the overall water loss predicted for the AIT and El Carao locations, with seepage accounting for the remaining loss. Predicted water requirements at AIT over a 5-month period exceeded actual amounts by 14.9%, apparently because seepage loss was over-estimated. For El Carao, however, predicted water requirements were only 78.2% of the amount actually added, apparently due to poor estimates of evaporative water loss which averaged 0.32 cm day-1 compared to pan evaporative measurements of 0.43 cm day-1. In contrast, the predicted evaporative water loss for the AIT pond (0.47 cm day-1) closely matched pan evaporation measurements (0.45 cm day-1). The availability of relative humidity and cloud cover data for AIT explain the higher accuracy in evaporative water loss estimates, and therefore water requirements, compared to El Carao. If comprehensive weather datasets are available, the water budget model developed herein is a useful tool for estimating pond water requirements at individual facilities located in different geographical regions.