Abstract
Abstract. Streamflow hydrograph analysis has long been used for separating streamflow into baseflow and surface runoff components, providing critical information for studies in hydrology, climate and water resources. Issues with established methods include the lack of physics and arbitrary choice of separation parameters, problems in identifying snowmelt runoff, and limitations on watershed size and hydrogeological conditions. In this study, a Gravity Recovery and Climate Experiment (GRACE)-based model was developed to address these weaknesses and improve hydrograph separation. The model is physically based and requires no arbitrary choice of parameters. The new model was compared with six hydrograph separation methods provided with the U.S. Geological Survey Groundwater Toolbox. The results demonstrated improved estimates by the new model particularly in filtering out the bias of snowmelt runoff in baseflow estimate. This new model is specifically suitable for applications over large watersheds which is complementary to the traditional methods that are limited by watershed size. The output from the model also includes estimates for watershed hydraulic conductivity and drainable water storage, which are useful parameters in evaluating aquifer properties, calibrating and validating hydrological and climate models, and assessing regional water resources.
Highlights
A streamflow hydrograph is the time-series record of streamflow at a gauging site
A Gravity Recovery and Climate Experiment (GRACE)-based hydrograph separation model is developed in this study to address the weaknesses of traditional methods in baseflow estimate, such as the lack of physics and arbitrary choice of separation parameters, problems in identifying snowmelt runoff, and limitations on watershed size and other conditions
The model first constructs a baseflow model using winter data and uses streamflow observations to solve the baseflow in all seasons
Summary
A streamflow hydrograph is the time-series record of streamflow at a gauging site. Streamflow includes baseflow (the longer-term delayed flow from natural water storage such as groundwater discharge from aquifers) and quick flow (or surface runoff, the short-term response to a rainfall event or snow melt). Separating streamflow observed at a gauging site into baseflow and surface runoff helps characterize watershed hydrogeology and understand the water dynamics such as rainfall–runoff relationships and climate change impact on groundwater discharge (van Dijk, 2010; Gao et al, 2015; Rudra et al, 2015; Foks et al, 2019). The approaches started with manual separation of the streamflow hydrograph into surface runoff and baseflow.
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