A novel GIS-based modified multivariate drought index for modeling and management of the hydrogeological drought...

The importance of a comprehensive drought evaluation due to the influence of various parameters has led to an expansion of the use of multivariate indicators in drought assessment. On the other hand, the lack of a specific index for the hydrogeological conditions of the aquifer has led to the presentation of a novel index based on these characteristics within the Geographic Information Systems (GIS) environment in this study. Accordingly, the Modified Standardized Electrical Conductivity Index (MSECI), which is based on the Electrical Conductivity (EC) data of groundwater in quality wells, was used as an indicator of the qualitative status of the aquifer. In addition, the Groundwater Resource Index (GRI), Standardized Well Discharge Index (SWDI), and Standardized Transmissivity Index (STI), which are based on the fluctuations of groundwater level in piezometric wells, the flow rate of pumping wells, and the transmissivity of the aquifer, respectively, were used as indicators of the quantitative condition of the aquifer to construct the novel hydrogeological drought index called Modified Hydrogeological Drought Management Index (MHDMI). Results showed that, when taking into account the impacts of drought, 78% of the study area is in the "Moderate" class, 4.53% in the "Very" class, 0.07% in the "Extreme" class, 17% in the "Low" class, and 0.05% in the "No effect" class, according to the descriptive maps of the MHDMI. Concerning management, the assessed area is divided into four classes: "Exploitation with limited constraints" (53.4%), "Limited exploitation" (24.8%), "Exploitation without limitation" (17%), and "No exploitation" (4.6%). The findings of the descriptive maps of MHDMI indicate that management scenarios must be applied to the most vulnerable area, the southwest boundary of the Hashtgerd Aquifer. According to the results, the method developed in this research can identify and manage areas sensitive to hydrogeological drought stress.