Development of a New Drought Index for Groundwater and Its Application in Sustainable Groundwater Extraction

The main aim of this study was to develop an index to determine groundwater drought. Then, as a case study, for the sustainable use of groundwater, the optimum cropping pattern was determined in full compliance with the drought conditions in a plain. The newly presented index, known as the groundwater recharge drought index (GRDI), was determined based on the values of recharge in different zones in the plain. The GRDI for different zones within the region was calculated using the data covering 30years (1980-2010). Based on this index, groundwater drought was found to occur frequently in these regions since 1981. According to the obtained results, the developed index, as compared with other indices, had several basic features including the ability to predict drought in groundwater, consideration of the possible effects of basin characteristics on groundwater drought, the capability of using different methods and models to calculate the GRDI, and separation of the human effects on the hydrological system from natural drought. Therefore, the index could be used in the forecasting and warning systems for management and planning purposes. According to the optimization results, the selected cropping patterns for three scenarios, including normal, dry, and wet years, were in such a way that the exploitation of groundwater resources remained in safe yield range and groundwater-level decline was reduced, contributing to sustainable groundwater management.