A survey of water quality of Gharasou River, Kermanshah, Iran

Water quality is essential for drinking, agricultural and industrial purposes, and sustainable water management. The Gharasou sub-basin is the primary water supply resource for the Karkheh River Basin (KRB), the third-largest and most productive river basin of Iran. This paper addressed the published papers about the water quality assessment of the Gharasou River. For this purpose, natural or anthropogenic pollution sources, land cover/land use, and soil erosion/runoff were considered. Water pollution indices, such as water quality index (WQI) and trophic diatom index (TDI), were also investigated. The suitability of the Gharasou River water for irrigation purposes was also studied. The results indicated that drought, weathering of bed sediments, and cation-exchange processes in the soil–water interface are natural sources of water pollution of the Gharasou River. A large-scale release of raw sewage and industrial chemicals, the geological texture, agricultural activities, and vehicles are anthropogenic sources of water pollution. WQI ranges from 33 ± 3 to 76 ± 6, and TDI ranges from 39.2 ± 5 to 71.3 ± 15, reflecting a significant level of pollution in the Gharasou River. USSL and FAO methods classified water as C 2 S 1 (medium-salinity and low-sodium hazards). However, water quality indices indicated that there is a regional sodicity problem evidenced by a high risk for permeability index (PI) > 75%, Ca 2+ /Mg 2+ ratio 50 as well as nutritional and irrigation problems. Converting rangelands to rain-fed lands, overgrazing, and deforesting hilly land are the main factors affecting soil erosion/runoff, which consequently impacted the water quality of the Gharasou River.