Investigating the effects of incoming floods from Afghanistan on the quantitative and qualitative changes of groundwater resources in Sistan plain

The aim of this study was investigating the effects of incoming floods from Afghanistan on the quantitative and qualitative changes of groundwater resources in Sistan plain. For this purpose, first by determining the direction of flood flow in Sistan plain, 16 wells drilled near the flood flow were selected. Estimates of reservoir volume changes as well as comparison of rainfall in the region in the same period. In the following, Using groundwater balance equations and single hydrograph equations before and after flood entry, quantitative changes in groundwater resources in Sistan region over a period of 4 years (1394-1398) were investigated. The qualitative changes in aquifer with sampling of observation wells during the balance and investigation of time changes in water quality parameters such as electrical conductivity (EC) and acidity (pH) was analyzed. The data shows that the floods increased the water level in the wells by an average of 0.39 meters the process of change has a high correlation (R² = 0.85) with the volume of floods in the region. Also, the hydrographic survey of the plain unit indicates significant changes in groundwater level before and after the flood in the area. As, during the 4-year period, the average water level is 2.16 meters higher than before Floods have increased. With the flooding amount of 20.66202 million cubic meters during the balance period, the reservoir volume has been naturally increased. Due to the low rainfall in the region, the nutrition of groundwater aquifers is affected by low rainfall.