Evaluating Stream Discharge-Concentration Relationships for a Range of Hydro-climatic Regimes

Complex interactions between hydrological and biogeochemical processes have served as a constant challenge in ecosystem studies. These inter-related processes are highly affected by watershed characteristics and regional atmospheric deposition rates. Deposition of pollutants has been linked to the degradation of ecosystems by altering both stream water and soil chemistry. The current study focuses on establishing relationships between discharge-concentration trends, watershed characteristics and regional atmospheric deposition. We evaluate data from a number of watersheds located across a range of hydro- climatic regimes and varying physical characteristics. Water quality data for each stream system was obtained from the United States Geological Survey (USGS), with a focused analysis on calcium, magnesium, and nitrate concentrations. Atmospheric deposition data for the same constituents was also gathered from regional National Atmospheric Deposition Program (NADP) sites. Discharge-concentration hyperbolic dilution models were fitted for each selected watershed system. Trends in hyperbolic model parameters were related to differing watershed characteristics and regional deposition rates, i.e. higher parameter values were observed for highly disturbed watersheds and lower parameter values were observed for undisturbed watersheds. Developing relationships between model parameters and atmospheric and watershed characteristics can be used to establish pollutant loads and outputs from similar systems where chemical data may not be readily available.