Investigating the effect of drought on the quantitative changes of groundwater resources of Bijar-Divandere Aquifer using geographic information system and groundwater resource index.

Due to the occurrence of periods of drought and increased exploitation of the aquifer, the expansion of agriculture and the increase in groundwater harvesting, the level of the underground water level has decreased in the Bijar-Divandere Aquifer, which is the result of the decrease in the level of the underground water level and the decrease the efficiency of the wells has increased. The aim of this research is to investigate the effect of drought on the quantitative changes of underground water resources using geographic information system and groundwater resource index of Bijar-Divandere Aquifer based on representative hydrograph. In order to carry out this research, the statistics of 25 observation wells during the period of 2017-2018 were examined. At first, statistical data was collected and after entering the data into the geographic information system (GIS) with interpolation method, maps of parallel lines and zoning of changes in the level of underground water, as well as from the water source index. The underground GRI was used to monitor the time of drought of underground water sources in Bijar-Divandere Aquifer. The results of the changes in the reservoir volume of Bijar-Divandere Aquifer showed that the deficit of the reservoir volume is equal to 11.5 million cubic meters. Also, the time monitoring of the drought of the groundwater resources of the plain with the GRI index has a downward trend towards drought during the twenty-year period, and the most severe groundwater drought in the year 2018 has occurred with an index of -1.97. The obtained results indicate that if the current management process continues, we will witness a sharp drop in the aquifer and irreparable damage in the next few years.