Impact of intensive groundwater exploitation on an unprotected covered karst aquifer: a case study in Kermanshah Province, western Iran

Abstract

Islam Abad region, located in the southwestern of Kermanshah Province, is a karst region where over-exploitation from the deep karst water resources has directly affected the water balance of the whole area. Using a combination of geophysical investigations and analysis of well log data and other relevant hydrogeological studies, we looked for the actual relationship between over-exploitation from deep-water wells, penetrated into the covered karst aquifer, and the drying out of some of the main karst springs throughout the study area. In total, 20 piezometric wells and 4 main karst springs have been chosen for groundwater monitoring network. By integrating GIS processing system and a classical water balance method together with hydrogeology and hydrogeochemical spatial maps, critical zones of human impacts on groundwater resources, made by water extraction for agricultural demand, were identified. Results show that water balance in the Islam Abad basin is in clear disequilibrium, since 2.15 mcm of water depletes from the main aquifers of the study area, annually. This volume of water shortage has resulted in a 7 m groundwater level decline in the last decade, which caused both drying out and reduction in discharge rate of some of the main karst springs throughout the study area. Depths of penetration of deep-water wells into the covered karst aquifer vary from 1 to 93 m. Hydrogeochemical evaluations, including ion relations and hydrogeochemical diagrams, show interactions between karst and alluvium aquifers. Results showed a broad connection between these two resources and, therefore any pressure on alluvium aquifer will affect the karst aquifer, especially by excessive deep-water wells drilling in mutual alluvial and covered karst aquifers.