Water Table Rising Consecutive to Surface Irrigation in Alluvial Aquifers: Predective Use of Numerical Modelling

Due to lack of integrated management of agricultural water worsened because of the application of incorrect irrigation methods with respect to local conditions, over-irrigation often occurs and may result in groundwater flooding. Instances for this default of sustainable development are observed in West-Azerbaijan province in Iran. The Mahabad plain has been selected to evaluate the effects of infiltration on the water table fluctuations. A finite difference model of the Mahabad plain silty / sandy aquifer has been developed by processing external constraints as the recharge input (R) due to IDN. The results show that the calibrated unsteady-state model has the ability to simulate the observed piezometric levels. The model is used to evaluate the recharge of the groundwater system from irrigation losses by using the recharge factor R as a tuner so as to honor the observed variations of the water table level within the aquifer. Results of two executed scenarios suggest that by continuing the current method of surface irrigation and crop pattern, in case of network development, the recharge of groundwater by irrigation will cause to change the farms to logged lands in central and eastern parts of the network. Numerical modelling of water table variations in alluvial aquifers and testing of some IDN management scenarios appears to be a cost-efficient approach to assess flooding hazard, suggest a modified and/or new method of irrigation, and design spatial extension of existing network.