Designing a monitoring network for detecting groundwater pollution based on intrinsic vulnerability, pollution sources and groundwater value: a case study in Khash plain, Sistan and Balouchestan province, Iran

Groundwater quality degradation due to geogenic and anthropogenic factors can endanger the human health. Therefore, designing a groundwater pollution monitoring network can provide the information needed for achieving water resources management goals and improving water and food security. The main objective of this study was to introduce an integrated approach for designing a groundwater pollution monitoring network based on index-based groundwater “protection-monitoring priority” maps created with GIS. The raster layer of “protection-priority index” was prepared by combining aquifer intrinsic vulnerability maps, produced based on the DRASTIC model, and estimated groundwater value based on the quantity and quality of groundwater. Moreover, by overlying pollution-sources risk maps and capture zone maps for wells, qanats and springs, the “monitoring-priority index” was obtained. By overlying the "protection-priority index" and "monitoring-priority index" layers as well as considering the direction of groundwater flow, sampling points were determined. By applying the proposed method, 15 wells were selected for groundwater sampling in Khash-Poshtkuh study area. Water samples collected from these wells revealed that, the concentration of toxic elements such as Arsenic is higher than the permissible limit for drinking in some wells in the southeast and north of Khash aquifer and the north of Poshtkuh aquifer which have geogenic origin.