Evaluation of the effect of land use change in Mehran plain on surface water quality parameters in wet and drought periods

In recent years, with the increase in population, the quantity and quality of surface water resources due to human activity have changed. By studying the effects of land-use change on surface water resources, we will be able to understand the interactions between land use and water quality. Therefore, the purpose of this study is to evaluate the surface water quality in the Mehran plain watershed affected by land use. In this study, after extracting land use, the percentage of each land use area in the region for four time periods of 2000, 2007, 2016, and 2020 was determined, then the effects of land-use changes in both wet and dry periods on water quality parameters including anions, cations, SDR, TDS, EC were examined. Finally, Schuler and Wilcox's diagrams were used to determine the drinking water quality parameter. The results showed an increase in barren and urban lands compared to agricultural, rangeland, and forest lands. So barren and urban lands have increased by 13.2% over 20 years and the number of anions compared to the long-term average of 10 years is 14.82% and cations are 21.23% and soluble salts of SDR, TDS, EC is 36.9%, respectively, Increased by 18.35 and 18.30 percent. In most of the studied applications, the trend of changes based on the Mann-Kendall test showed an increase, and based on Pearson correlation between river flow and quality parameters with all parameters has a negative and inverse relationship, which with decreasing river flow, the trend of quality parameters increased. Is. According to Schuler and Wilcox's diagrams, water is in the salinity range for the study area. The results showed that the increase in human activities and climate fluctuations are factors affecting the water quality of the Gavi River, therefore, there is a need to manage programs to control land-use change.