Analysis of well losses pertaining to artificial recharge.

Abstract

An experimental recharge well at the Water Resources Research Center Field Laboratory, University of Arizona, was used to compare the head losses for discharging conditions with the head losses during recharging conditions. For discharging conditions the formation loss coefficient, B, increased from an initial value of 14.0 sec/ft^2 to an almost constant value of 16.4 sec/ft^2 after 200 minutes of pumping. The initial value o B 1or recharging conditions was 16.8 sec/ft^2, increasing to a maximum of 18.3 sec/ft^2 after 90 minutes of recharge. After 90 minutes 13 began to decrease, reaching a value of 16.4 sec/ft^2 after 200 minutes of recharge. The decline in the rate of growth of B during pumping and the decrease in the value of B during recharge probably reflected a decrease in the convergence and the divergence losses, respectively, as the cone of influence and the groundwater mound increased to a size such that the aquifer began to act more homogeneously. The well loss coefficient, C, had an average value of 6.9 for discharging conditions. The initial value of C during recharge was 1.4 which increased to a value of 4.8 after 200 minutes. It is speculated that the increase was caused by plugging of the aquifer by entrained air and fine suspended particles in the recharge water. The results indicate that step drawdown pumping tests on a particular well with conditions similar to those at R#1 can be used to estimate the magnitude of B and C in that well tor recharging condition0