Effect of vegetation and soil erosion on the hydro-geochemical quality of surface waters Case study: Qolyan River catchment area, Qalikuh region, Lorestan

 The goal of this study was to investigate the relationship between vegetation and soil erosion and changes to the hydro-geochemical properties of water. Soil erosion is closely related to the type of vegetation and land use, and can change water quality in a region. For this, the present study collected and analyzed 15 water samples from the permanent waterways of Pirbadush and Gashun of the Qolyan River in the Qalikuh region of Lorestan, Iran. According to studies, from higher parts of the highlands of the region down towards downstream areas, water quality is reduced with the reduction of vegetation and increase of soil erosion and progressive Quaternary sediments, and with the entry of more cations and anions from sediments to water, and increased electrical conductivity, the total dissolved solids and turbidity. Thus, greater levels of vegetation in the highlands of this region increase soil permeability and reduce soil erosion. In this region, the reduced vegetation depends on the type of bedrock, and in some areas excessive grazing, in addition to altitude changes, thus increasing pollutants such as nitrates. Increased nitrates in the regional water depend on anthropogenic (livestock grazing) and geo-genic (expanded oil shales and the erosion of Quaternary deposits) factors. As a consequence, the regional water quality is more influenced by environmental and geo-genic factors, with anthropogenic factors less contributing to it.