Effect of drought on groundwater resources in order to optimize utilization management, case study: Plain Alashtar

Drought is the most hazardous natural phenomenon. Although not preventable, its negative effects can be reduced through taking some measures. One of the systems severely affected by drought while less considered is the groundwater. In this study, drought status and its impact on groundwater resources was investigated in Alashtar Plain using Standardized Precipitation Index (SPI) at monthly, quarterly, and annual scales and the Groundwater Resource Index (GRI) during the statistical period of 1991-2010. After data collection, statistical errors were corrected by subtraction and ratios method. Then, to determine the status, SPI and GRI were calculated with DIP software on an annual, seasonal, and three, six, nine, 12, 18, 24, and 48-month time scales for Alashtar Plain. Then, according to SPI and GRI value, the moisture status were determined for each period. Results indicated that the trend of plain meteorological and groundwater drought is negative. Correlation between SPI at different time scales with and without the time delay and with average groundwater level and GRI was analyzed. Statistical analysis showed that SPI was significant at the level of 0.01, in the 24-month time scale without any time delay with mean groundwater level and GRI and had the highest correlation coefficient, suggesting the impact of drought on Alashtar plain groundwater. Regression relation between the mean level of the water table and SPI_24 showed that 64.4% of the variance at the mean level of water table was affected by SPI_24 and 35.6% was affected by other factors. Drought magnitude (DM) analysis showed that meteorological and groundwater droughts are consistent with winter and autumn, respectively. Undoubtedly, optimized utilization management, especially in spring and summer, may have a critical impact on preventing damages to the groundwater resources of the region.