THE ANTHROPOGENIC AND CLIMATIC EFFECTS ON THE SCALING OF DISCHARGE AND DRAINAGE FOR MULTIPLE WATERSHEDS FROM USGS DISCHARGE RECORDS

River discharge is the fundamental process operating in a fluvial system, with the surrounding drainage area contributing this discharge. The increase in discharge and drainage area downstream is intuitive but datasets describing this increase within individual watersheds are not common. The scaling of discharge and drainage area can be described as: Q = kA^c, where “Q” is river discharge, ”A” is drainage area, and ”k” and ”c” are scaling constants. While ”k” is not often illustrative of watershed processes, the constant ”c” represents the rate at which discharge (Q) increases downstream when compared to drainage area (A). This study compiles the annual peak and mean discharge records of rivers from USGS gauges to analyze the rate at which discharge and drainage increase downstream. Peak discharges are effective geomorphic agents and can pose flooding hazards, while mean discharges can be critical for supporting aquatic biota and for water resource management issues. The peak and mean annual discharge records from over 40 rivers were selected to represent a variety of watersheds across multiple climatic and geographic settings as well as to illustrate the effects of anthropogenic land-use change and water management changes over the length of the records. Peak and mean annual discharges were plotted versus drainage area at the gauging station and averaged by decade to illustrate any secular trends. It is often assumed that the scaling between discharge and drainage area is linear, and the majority of these watersheds exhibit this behavior over the length of their record. However, multiple rivers also show nonlinear behavior, as the discharge scaling values (c) are less than linear with the amount of discharge generated per unit drainage area decreasing in the downstream areas of the watershed. Variables such as slope, evapotranspiration, runoff generation, and winter snowpack contribution to peak annual discharges may be spatially inconsistent in a watershed, creating the nonlinear behavior in the scaling of discharge.