The Trend of Groundwater Variations and Drought in the Karkheh Watershed

Water resources management is essential in countries, such as Iran, with arid and semi-arid climates due to global climate change and population growth. Knowledge of hydrogeological droughts and effective factors on groundwater drawdown is essential in providing management solutions for these vital resources. Therefore, the purpose of this study was to analyze the trend of groundwater variations and assessment of groundwater shortage in the Karkheh Watershed using the SPEI, SDI and GRI drought indices in an eleven -year statistical period (2006-2017). The results indicated that in most of the study areas, there was a correlation between the SPEI and SDI indices. The mean values of the GRI index in the study area of Karkheh watershed area show weak drought for the Sanghar, Nahavand, Sahneh, Hersam, Khorramabad, Tuyserkan, Asadabad, Malayer, Biston-Dinavar, Mian Rahan and Hassanabad-Qala-e-Shian areas. A more severe drought with the drought indices of -1.08, -1.13, -1.21, -1.23, -1.25, -1.31 and -1.35 was determined for Chaghloundi, Kuhdasht, Kangavar, Islamabad Gharb, Ravansar-Sanjabi, Kermanshah and Mahidasht respectively. These indicates a decrease in the water level elevation and an increase in the depth to the groundwater in these areas. The GRI drought index is more visible during the ten-year statistical period in the east, west and center of the Karkheh Catchment Area; while in the last years of this period, the central areas of the catchment had been affected by more severe droughts, which may be confirmed by the SPI zoning map. Although in most cases climatic drought, and consequently hydrological drought had caused the depletion of groundwater level in the basin, the results of comparison between the two types of drought indicated the effectiveness of other factors such as exploitation of the groundwater resources. Therefore, it is necessary to establish an integrated management for the sustainability of groundwater resources, especially in the agricultural sector, as well as reforming the management of traditional groundwater abstraction systems, before meteorological droughts and subsequent surface water shortages affect groundwater levels.