Baseflow refers to streamflow sustained between precipitation and snowmelt events, contributed from subsurface reservoirs such as bedrock, saprolite, alluvium, or soil. Because baseflow is extremely important in the context of stream ecology and freshwater supply, a critical need exists to understand the relationships between basin physical properties and baseflow, as well as the ways in which human land use affects these physical properties. Topography and land use, separately, have been demonstrated to exert strong influence on baseflow, but their relative influences and interaction remain unclear. Previous studies have demonstrated inconsistent results as to whether watershed forest cover increases or decreases baseflow discharge, and how such issues relate to watershed scale remains a major unresolved problem in the hydrologic sciences. This project will assess the roles of topography and land use on baseflow in the southern Blue Ridge Mountains, emphasizing the following objectives: 1) assessment of the relationship between basin forest cover and baseflow, 2) determination of the relative influences of topography and land use on baseflow, and 3) prediction of streamflow response to future land-use change using GIS modeling. Sub-basins of the Little Tennessee River basin in North Carolina and Georgia will be characterized using GIS analysis of digital terrain and land-cover data. At least 35 streams will be instrumented with continuous stage recorders, from which baseflow discharge values will be derived and related to land-use and topographic characteristics. Subsequent GIS modeling will allow prediction of baseflow response to further land-use change in the region and will guide development planning to encourage growth scenarios imparting minimal impact on baseflow water quantity.
Adequate freshwater protection has been at the forefront of global issues for decades, and its urgency continues to increase, as water resource demands grow with population and industry. Contaminants entering stream systems via subsurface pathways are most highly concentrated during baseflow, and a firmer understanding of controls on water quantity is imperative to sustaining public health, aquatic biotic integrity, and economic growth. Results from this project will be significant in many realms, from advancement of hydrologic and geomorphic theory to protection of adequate water supply for sensitive aquatic species. The development and testing of modeling capabilities to estimate streamflow response to land use change will assist further research and ongoing monitoring and management agendas. The identification of key topographic and land-use characteristics exerting control on water quantity will benefit sustainable development planning, wildlife protection, water resources management, public health, and industry, and will facilitate and improve future environmental research.
