Research papersA modified simple dynamic model: Derived from the information embedded in observed streamflows

•Normalized relation for rate of change of recession flow versus recession flow.•Regression model relating minimum recession flow and antecedent flow.•Propose simple streamflow generation component proportional to net infiltration.

A zero-dimension hydrological model has been developed to simulate the discharge (Q) from watershed groundwater storage(S). The model is a modified version of the original model developed by Kirchner in 2009 which uses a unique sensitivity function, g(Q) to represent the relation between rate of flow recession and the instantaneous flow rate. The modified dynamic model instead uses a normalized sensitivity function g(Qnorm) which provides the model the flexibility to encompass the hysteretic effect of initial water storage on flow during recession periods. The sensitivity function is normalized based on a correlation function F(Q) which implicitly quantifies the influence of initial storage conditions on recession flow dynamics. For periods of either positive or negative net recharge to groundwater the model applies a term similar in form to an analytical solution based on solution to the linearized Boussinesq equation. The combination of these two streamflow components, the recession component and the net recharge response, provides the model with the flexibility to realistically mimic the hysteresis in the Q vs. S relations for a watershed. The model is applied to the Sagehen Creek watershed, a hilly watershed located in the Sierra Mountains of California. The results show that the modified model has an improved performance to simulate the discharge dynamic encompassing a wide range of water storage (degree of wetness) representing an almost ten-fold variation in annual streamflow.