Groundwater withdrawal adjustment based on changes in groundwater balance components (a case study: an arid region in central Iran)

The aim of this study was to investigate how to adjust groundwater withdrawal in the Zayandeh-Rud River Basin in the arid region of central Iran due to changes in groundwater balance components. Two time periods (2006–2012 and 2013–2019) were considered to evaluate changes in groundwater level and different components affecting these changes. Groundwater level unit hydrographs in 6 important aquifers (in terms of groundwater abstraction) located in this study area were prepared using the Thiessen method. Also, the changes in precipitation and evapotranspiration in the study area were determined in both time periods. Groundwater balance equation was revised based on changes in precipitation, evapotranspiration, and surface flow variations between these two time periods. Results showed that the groundwater level has a negative trend since 2013. By 2012, the annual groundwater level increased about the 0.42 m, but from 2013 to 2019, the annual groundwater level declined about the 1.2 m, approximately. The surface flow had the more adjustment coefficient and contribution with groundwater recharge. Due to the decrease in precipitation and surface flow, increase in evapotranspiration, and adjustment of groundwater overdraft, in total, the groundwater withdrawal should be reduced from 2228.9 to 1929.1 MCM (13.1% decrease) in the study area. © 2021, Saudi Society for Geosciences.