Evaluation of On-Farm Pond Water Budget in Khon Kaen Province, Thailand

Abstract

An on-farm pond is an essential technique for water resources management in northeast Thailand. It can be used for many purposes e.g. farm water supply, supplementary irrigation, livestock, aquaculture, and flood mitigation. The purpose of this research is to evaluate the suitability of two calculation methods for on-farm pond water budget. Two on-farm ponds in Ban Wangwa were selected to be the study sites and the water balance of the ponds including water inflow and water outflow components were calculated. Water inflow was determined by two methods, namely watershed routing and synthetic unit hydrograph. The results show that the synthetic unit hydrograph method gives the better agreement to the observed data than the watershed routing method in both of peak discharge and runoff volume. The main causes of water losses are evaporation, water usage, and seepage. Evaporation from the ponds was determined by two methods, namely the Penman method using Priestley-Taylor evaporation equation and the Evaporation pan method. Subsequently coefficient of the Priestley-Taylor evaporation (α) and coefficient of the evaporation pans (K_p) are 1.66 and 0.88, respectively. The evaporation by pan evaporation is fast, simple and easier than Priestley-Taylor evaporation.