Hydrological modelling of a small watershed using MIKE SHE for irrigation planning

The physically based distributed modelling system, MIKE SHE, is used to sim ulate the hydrological water balance of a small watershed with the objectiv e of developing the irrigation plan. Simulation is first conducted over 109 days, concentrating the attention on the main cropping season, i.e., khari f (Jul-Oct), and the average water balance is calculated. It is observed th at in spite of the frequent rainfall in the season, there are phases when t he water content in the root zone goes below the allowable deficit. In case irrigation is not supplied during these periods, the yield of the paddy wi ll only be about 70% of the potential yield. To attain the potential yield, the irrigation requirement is calculated as 490 and 340 mm for the upstrea m and downstream ends of the watershed respectively. Irrigation schedule fo r the purpose is suggested. Hydrological water balance simulation is furthe r extended to the second cropping season, i.e., rabi (Nov-Feb), over 100-da y period. Here, the water stored in the existing tank at the outlet is used for the supplemental irrigation in the season. It is seen that the actual yields obtained are very close to the potential yields of the selected crop s. The results overall illustrate the applicability of a comprehensive hydr ological modelling system for the management of water resources for agricul tural purposes in a watershed. (C) 1999 Elsevier Science B.V. All rights re served.