River discharge is a primary influence on stream ecosystems, and discharge has been substantially modified by humans via irrigation, dam operation, and climate change. These changes are known to affect the physical properties of rivers, but their ecological impacts are poorly understood. Our goal is to systematically analyze how stream ecosystem processes vary with differences in discharge, and to synthesize this information into a single metric that we call the "Ecological Dominant Discharge," which is that discharge responsible for controlling the majority of stream ecosystem processes for a given site. We will investigate this concept by studying four rivers in the Adirondack Park of upstate New York (2 dam-modified rivers, one of which has regular releases of water and 2 natural, unmodified rivers). These rivers possess a range of both physical parameters (e.g., variations in discharge) and ecological parameters (e.g., transport of particulates, etc.). The information derived from this research will be highly relevant to the management of rivers impacted by flow regulation, and for guiding potential river restoration efforts. The physical and ecological impacts of flow regulation are becoming better understood, but unifying these impacts into a single concept has been difficult in the past, and the concept of ecological dominant discharge will potentially alleviate these problems.
