Combining analytical solutions of Boussinesq equation with the modified Kozeny–Carman equation for estimation of catchment-scale hydrogeological parameters

Abstract. Saturated hydraulic conductivity (K), drainable porosity (f), and effective aquifer thickness (D) are essential hydrogeological parameters for hydrologic modelling and predicting. Streamflow recession analysis using analytical solutions of Boussinesq equation can yield estimated values for two of these three hydrogeological parameters when one is known a priori. In this study, we improved the inverse method for parameters estimation by combining the modified Kozeny–Carman equation with analytical solutions of Boussinesq equation to express the three hydrogeological parameters (K, f, and D) in relation to catchment characteristics and recession constants in a sloping aquifer. Here, the three parameters can be estimated simultaneously from streamflow recession analysis. Results of the estimated parameters are compared with the field measurements and the soil-texture based estimations in four small experimental catchments. It shows that our estimated values of these catchment-scale parameters can represent equivalent values in the measured aquifer profiles/sites. In hilly areas, the slope aquifer takes a vital effect on the estimates of K and f. Neglecting the sloping effect can lead to overestimation of K and underestimation of f in 1 ~ 2 orders of magnitude in the study catchments. However, even in the hilly catchments, the estimated aquifer thickness D is much greater than that from measurements on hillslopes while it approaches riparian thickness, indicating that the riparian zone takes a vital role on flow recession and the parameter estimations.