LEAKAGE OF CLOGGED CHANNELS THAT PARTIALLY PENETRATE SURFICIAL AQUIFERS

A theoretical formulation describing leakage from clogged channels that partially penetrate surficial aquifers is reported in this paper. Leakage characteristics are parameterized by a reach transmissivity, which is defined as the volume flow rate out of the channel per unit length of the channel per unit drawdown. An expression is developed to relate the reach transmissivity to the transmissivity of the formation, mean channel width, distance of drawdown measurement from the channel centerline, ratio of drawdowns on both sides of the channel, and local reach transmissivity associated with clogging. This theoretical expression, and associated limitations, are verified using a fine-scale numerical model. The proposed formulation was field tested at two channels. The measurements of reach transmissivity were found to vary linearly with the drawdown ratio, as predicted by the theory. Furthermore, the aquifer transmissivity obtained by fitting the theoretical formulation to the measurements is in close agreement with independently estimated values.