The SPAW (soil plant air water) model simulates the daily hydrological and water budget of agricultural landscapes. There are two connected modules, one for farmland and the other for reservoirs such as wetland ponds, lagoons or reservoirs. The model was established to understand and predict agrohydrology and its interaction with soil and crop production. It can be applied to a variety of hydrological analyses, including: estimation of farmland runoff and leakage of agricultural farms, as well as the design and performance evaluation of water supply, waste management and water management of agricultural ponds, lagoons and reservoirs. The simulation results estimate daily vertical water budget depths for all major hydrological processes, including runoff, infiltration, evapotranspiration, soil moisture profile and seepage.