Simulation of soil moisture content of a prairie field with SWAP93

A simulation study of the soil moisture content under a prairie field, in G embloux Belgium, by the use of the one-dimensional model SWAP93, was carrie d out. In order to determine the optimum relationship that S-max is followi ng, two concepts of maximum water extraction rate were examined. The first one assumed a linear variation of S-max with depth z and the second assumed a homogeneous distribution of S-max with depth z. Five statistical criteri a were used to compare the quality of simulation results, such as average e rror (AE), root mean square error (RMSE), root mean square (RMS), modeling efficiency (EF) and coefficient of residual mass (CRM). The differences bet ween the criteria, showed that the assumption of the homogeneous distributi on of S-max throughout the soil profile resulted in a more accurate predict ion of soil moisture content. The agreement between measured and simulated water content profiles, throughout the regarded period, was satisfactory fo r depths >30 cm. The deviation between simulated and experimental values fo r depth <30 cm could be explained by the influence from the cracks in the s oil surface and wormholes that cause water losses and, consequently, undere stimation of the experimental values. (C) 2000 Elsevier Science B.V. All ri ghts reserved.