Surface Hydrology and Its Influence on River Basin Ecosystems and Ecosystem Services

Abstract

River basins serve as important socio-ecological systems in which surface hydrology acts as an underlying regulator of ecological integrity and the supply of critical ecosystem services. Anthropogenic influences and climatic shifts resulting in an increase in extreme flood and drought conditions and changes in land use are impacting the sustainability of these essential systems. This paper examines the Bhavani River Basin (a biodiversity hotspot) to characterize the influence of hydrological variation on ecological processes over 30 years. Changes to water purification, flood mitigation, and habitat suitability were examined using the Soil and Water Assessment Tool (SWAT) and Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) models. It observed a decrease in mean annual discharge and an increase in seasonal variability, resulting in a 14% reduction in water purification service and a 450 km² increase in high-risk flood areas. Corresponding declines in riparian health and fish spawning habitats are correlated with increased hydrological variations. The analyses demonstrate that existing hydrological regimes are severely compromising ecosystem health and human well-being at the regional scale. Thus, an integrated management approach considering environmental flows and watershed-level reforestation efforts are needed to improve resilience in the basin. By locating "hotspots" for mitigation, the results offer targeted approaches to reconcile human well-being with water service provision through the implementation of sound hydrological management practices.