Groundwater resources management of Mian-Ab Plain with emphasis on water requirement of agricultural crops using groundwater modeling

Mian- Ab is one of the most important plains in Khouzestan province and the most water demands in this plain is related to the irrigation for agriculture. In this research, the agricultural water requirement was first calculated using Penman- Monteith FAO method due to the necessity of water resources consumptions revision in agricultural field. Then, the numerical groundwater model of the study area was prepared to know about the water balance and consumed water. The model was calibrated from September 2016 to September 2017 in the unsteady state conditions with the 0.94 m of RMSE error. According to the calculations, the actual crop water requirement is 278.89 MCM per year. The model results show that 334.07 MCM of water is used though irrigation network and wells for agricultural purposes. Therefor, 55.27 MCM of water is used more than the actual water needs. Three scenarios were considered for excess consumed water including the transfer of all surplus water to southern lands through the development of irrigation network, decreasing the rate of well pumping and the integrated management of surface and groundwater resources. Applying the discussed scenarios to the numerical model showed that the fist scenario causes drawdown and water logging in the northern and southern parts of the aquifer, respectively. Applying the second scenario will cause a severe water logging in the northern parts of the study area. In the third scenario, the excess consumed water will be managed by decreasing the 8.5 percent of exploitation wells rate (equal to 25.27 MCM) and transferring the remaining water (30 MCM) to the southern lands of study area. Therefore, considering the hydrodynamic conditions of the aquifer and the model results, the third scenario is more desirable for the management of excess consumed water.