Application of the Convolution Relation to Estimating Recharge from an Ephemeral Stream

Abstract

A linear model that permits calculation of recharge to the water table from a source of finite width and infinite length uses water level measurements made in an observation well near the source and independently estimated aquifer constants. The method requires determination of the input given the output (water level measurements) and the impulse response as a function of space and time. The latter is derived from the linear equations of groundwater motion for the particular geometry of this study. The input is obtained from the discrete form of the convolution integral by using the synthetic division method and is then summed over the appropriate time period to obtain total recharge. For the particular recharge event studies, results agree satisfactorily with an independent estimate of recharge and demonstrate that the convolution relation has practical application to groundwater flow problems.