Elasticity curves describe streamflow sensitivity to precipitation across the entire flow distribution

The rainfall-runoff relationship is often simplistically represented through “elasticity”, defined most frequently as the proportional change expected in average streamflow associated with a 1% change in precipitation over a given time period. Elasticity is typically estimated from the average annual streamflow, but may differ along the flow duration curve, indicating, for instance, that precipitation change has less of an effect on low flows as compared to high flows when particular catchment characteristics are present. We estimate elasticity at multiple points across the annual and seasonal streamflow distributions of 805 river gauging locations in the United States to create elasticity curves which graphically represent the responsiveness of low to high streamflow to precipitation. We show that elasticity curve type (the overall shape of the curve) corresponds closely with water storage and catchment flashiness; curve shape varies independently of the magnitude of response; and that the elasticity curves exhibit a regional pattern. We are further investigating whether elasticity curve shape and elasticity magnitude change over time. This assessment suggests that historical changes in water storage, and groundwater-surface water interaction may have led to substantial shifts in elasticity curves over time. This implies probable underestimation of future streamflow under climate change, unless relevant catchment characteristics are adequately considered