Understanding the Spatio-Temporal Variability of Stream Temperature Across Pennsylvania

Stream temperature is an important characteristic of both water quality and ecosystem health. It directly affects the geographic distribution of aquatic species, and controls many vital biotic and abiotic processes. Climate and land use changes threaten to alter stream temperatures, thereby endangering habitat for aquatic organisms dependent on particular temperature regimes. This effect is especially pronounced in Pennsylvania, where the combined effect of high water temperatures and low flows may render many once cold-water streams uninhabitable for cold and cool water aquatic species. In order to determine how aquatic ecosystems will be affected by environmental change and how water temperature varies across a region, we need to understand influences on water temperature sensitivity. We define ‘thermal elasticity’ to quantify the sensitivity of a given stream to environmental change. Our work focuses on the nature of the relationship between air and water temperature in Pennsylvania, the regionalization of the factors that control the strength of this relationship, and on how stream temperature characteristics have changed over the last decades.