Effect of Model Selection on Computed Water Balance Components

Soil water flow modelling approaches as used in four selected on-farm water management models, namely CROPWAT. FAIDS, CERES and SWAP, are compared through numerical experiments. The soil water simulation approaches used in the first three models are reformulated to incorporate ail evapotranspiration process similar to that used in SWAP. Computations are carried out for three soil types, representing sandy loam. loam and sandy clay loam The reformulated models are calibrated against simulation results obtained with SWAP. All the modelling approaches predict nearly equal estimates of cumulative actual evapotranspiration for a wheat crop. When compared with SWAP Simulation results, the CERES type approach outperformed the other two approaches in respect of estimated cumulative deep percolation losses. A new criterion is proposed to interpret simulation results under deep water table conditions to suggest appropriate depth of water application. The resulting recommendations for irrigation planning suggest that any of the modelling approaches may be used to suggest practical Irrigation considered in the present study.