Research papersEstimation of spatial distribution of groundwater recharge from stream baseflow and groundwater chloride

- A method for estimating spatially variable recharge is proposed.
- Groundwater model can be improved by estimation of recharge variability.
- A sand fraction-hydraulic conductivity transfer function is introduced.

In this study groundwater chloride concentration and baseflow are used to estimate the spatial variability of recharge. Total recharge over the entire watershed is estimated using the baseflow method, and then the spatial variability of recharge is approximated using groundwater chloride concentration. The efficacy of the method is demonstrated using data from a rural watershed in Alberta, Canada. By using the combination of two well established methods of estimating recharge, baseflow and chloride mass balance, there is no need to estimate wet and dry deposition rate of chloride. The presented method is tested by using a steady-state groundwater flow model. The groundwater model showed higher agreement between modeled vs observed heads when spatially variable recharge forced the upper boundary of the model (root mean square error reduced from 13.5 m to 8 m). In addition, we demonstrate a unique method for parameterizing hydraulic conductivity of a fluvial aquifer using a sand fraction transfer function. This new method reduces the dimensionality of the parameter estimation problem and provides a consistency check on the spatially varying recharge estimates.