Comparison Between WAVE, SWAP and DRAINMOD Models in Respect to Lateral Subsurface Drainage

The WAVE model describes the transport and transformations of matter and energy in the soil, crop and vadose environment. A lateral field drainage subprogram was added to the WAVE model to simulate the lateral subsurface drainage flow. The subsurface drainage is considered as the drainage provided by evenly spaced parallel drains with a free outlet, either drain tubing or ditch. The rate of subsurface water movement into drain tubes or ditches depends on the hydraulic conductivity of the soil, the drain or ditch spacing, the hydraulic head in the drains, the profile depth and the water table elevation. Hooghoudt's steady state equation, as used by Hooghoudt (1940), was selected for incorporation in the WAVE model. The subsurface drainage subprogram was calibrated and validated by comparison with SWAP model (The Netherlands) and DRAINMOD (USA) using seven years of field data in The Netherlands, under fallow and cropped condition. It is concluded that the WAVE model, in comparison to the SWAP and DRAINMOD model, provides as good a prediction of the lateral subsurface drainage flow to drains.