Hydrologic Variability across Climatically, Geologically, and Morphologically Similar Watersheds: Implications for stream ecosystems and ecological thresholds for anthropogenic change.

The “reference” stream or watershed concept is the basis for the design of many ecological studies and water quality assessments as well as paired watershed studies.  For such studies, it is simplistically assumed that if nearby basins drain comparable areas with similar geology, topography, soils, and native vegetation, then the basins will feature similar hydrologic behavior and water quality conditions.  However, significant variation in the hydrologic behavior and water quality conditions of apparently similar watersheds seems to be the norm, not the exception, even when basin vegetation is native and mature.  In this brainstorming session, we will share examples of the hydrologic variability of apparently similar watersheds, consider ways of using the long term hydrologic datasets from nearby streams to quantify the variability in stream and water quality behavior, and consider the implications of this variability for stream ecosystems, ecological study design, and regulatory monitoring programs.  We will also evaluate whether streamflow , water chemistry, or biological datasets from the LTER network can support cross-site assessments of the hydrologic and water quality variability of apparently similar reference streams.