An appraisal of pumping effects on the Edgeley Aquifer, La Moure County, North Dakota, as determined by a digital model

A finite-difference digital model simulated hydrologic conditions in the Edgeley aquifer, which is an unconfined glacial-drift aquifer. The calibrated model supported the hypothesis that under natural steady-state conditions, recharge is from precipitation and discharge is through evapotranspiration. This hypothesis was further supported by comparing simulated water levels to observed water levels collected during a 3-year period of irrigation withdrawal.

Predictions of the effects of continued withdrawal of currently allocated water were made. One prediction using recharge equal to 25 percent of the average annual precipitati on showed that an equilibrium between pumping and recharge would be established within 10 years and water levels would be 2 to 4 feet below 1977 levels . A second prediction included a 2-year drought of one -half the average recharge from precipitation. This prediction also showed equilibrium within 10 years, but water level s would be 3 to 5 feet below 1977 levels . Predictions using additional withdrawals based on allocation requests were inde terminate.