How water storage controls hydrologic extremes among catchments with diverse physiography and climate

Abstract:

River flow can show strong disparity with meteorological conditions; precipitation events do not necessarily lead to streamflow response, while in many cases rivers continue to flow in periods without precipitation. Although water storage is an obvious explanatory factor, it remains difficult to decipher the role of water storage for streamflow conditions across a diverse set of catchments. Here, we use data from several hundred catchments located in different climatic regions and show how water storage strongly controls hydrologic extremes on both ends of the flow spectrum. For high flow conditions the majority of the study catchments depend on antecedent wetness conditions to generate annual maximum flows, leading to distinct regional patterns in the seasonality of annual maximum flow conditions. For low flow conditions, evaporation-dominated storage depletion postpones annual low flow conditions by several weeks to months, and depending on the sensitivity of streamflow to water storage changes, the inter-annual variability of low flow conditions can vary orders of magnitude between places. The resulting process understanding of floods and low flow conditions can improve the prediction of streamflow and identify those regions where hydrologic regimes are most sensitive to short and long-term perturbations of water storage.