Assessing the impact of land use changes, dams, and water transfers on river sustainability

Abstract

Land use changes (LUC) and river overexploitation present critical challenges to the sustainability of aquatic ecosystems. This study offers a novel and comprehensive assessment of the impacts of human interventions, specifically LUC, dam construction, and water transfer projects, on river water quality and violations of environmental flow requirements (EFR). By employing MODIS images to analyze LUC trends in river basins, this research utilizes advanced raster and vector processing techniques with ENVI 5.0, ArcGIS 10.8, and Google Earth, introducing innovative methodologies for quantifying long-term changes in salinity (EC), acidity (pH), total dissolved solids (TDS), and nitrate concentrations across multiple rivers. The violation of EFR was determined using the average EFR calculated using four hydrological methods: variable monthly flow, Tessmann, Smakhtin, and Tennant. Significant declines in forest and agricultural land, at rates of 1.1% and 1.5% annually, were identified, alongside increases in pasture and residential areas of 1.5% and 1%, respectively. While EC and TDS levels remained relatively stable, notable variations in pH (6.8-8.8) and nitrate concentrations (2.4-19.9 mg L −1 ) were observed, correlating with heightened EFR violations as forest areas decreased and cultivated lands expanded. Importantly, this study revealed that dam construction on the Tajan river and water transfer from the Talar river, significantly exacerbated LUC impacts, increasing EFR violations from 9.7 to 30.1% and 12.2 to 22.2%, respectively. This research not only quantified the relationship between LUC and EFR violations but also provided critical insights into the cumulative effects of anthropogenic interventions on river ecosystems. The findings underscore the urgent need for integrated land and water management strategies that prioritize ecosystem health, highlighting that current development plans jeopardize both river basin ecosystems and human wellbeing.