Numerical ground-water change model of the C aquifer and effects of ground-water withdrawals on stream depletion in selected reaches of Clear Creek, Chevelon Creek, and the Little Colorado River, northeastern Arizona

Abstract

The base flow in parts of Chevelon and Clear Creeks and of the Little Colorado River near Blue Spring in northeastern Arizona is sustained by discharge from the C aquifer, and in some reaches supports threatened and endangered fish species. C aquifer water is proposed as a replacement supply to relieve pumping from the N aquifer-the current source of water for a coal slurry pipeline used to transport coal mined from Black Mesa to Laughlin, Nevada. Locations of the proposed withdrawals are in the area of Leupp, Arizona, about 25 miles from a perennial reach of lower Clear Creek. A simulation tool was needed to determine possible effects of the proposed withdrawals from the C aquifer, particularly the effects of depletion of streamflow in Clear Creek, Chevelon Creek, and the Little Colorado River in the area of Blue Spring. A numerical groundwater change model was developed for this purpose. The model uses the U.S. Geological Survey finite-difference model code MODFLOW-2000 and data sets representing key features of the C aquifer to simulate change in the system that would result from withdrawing water at proposed locations. Aquifer thickness was estimated from a hydrogeologic framework model, and values of aquifer properties such as hydraulic conductivity and specific yield were estimated from aquifer-test data. Two scenarios with differing withdrawal rates were run for a 101-year period that included 51 years of withdrawals followed by 50 years of no withdrawals. About 6 percent of the ultimate volume of depletion occurs in the 101-year period for either scenario. The maximum streamflow depletion rate for all reaches in the scenario with the greatest withdrawal rates was computed to be about 0.6 cubic foot per second. The depletion rate was highest in lower Clear Creek, the reach that is closest to the well field. A model that simulates historical conditions was used to help select the most reasonable parameter sets for a Monte Carlo analysis of computed stream depletions.

Dissolved Uranium and Arsenic in Unregulated Groundwater Sources – Western Navajo Nation

“…The main source of water for the western portion of the NN comes from the N aquifer; however, increased withdrawals from the C aquifer have been proposed to supply the Navajo people with an alternative water resource (Leake et al 2005). Seepage of contaminated mine groundwater to surface water introduces a pathway of exposure.…”

Adjoint modeling of stream depletion in groundwater‐surface water systems

“…This assumption is consistent with commonly used groundwater flow models such as the Stream package [ Prudic , ] in MODFLOW‐2000 [ Harbaugh et al ., ]. MODFLOW, along with its associated river and stream packages, has been used in numerous case studies that calculate stream depletion [e.g., Myers et al ., ; Leake et al ., ; Peterson et al ., ; Leake and Pool , ; Stanton et al ., ; Lambert et al ., ]. Thus, an adjoint approach based on the assumptions used in MODFLOW has potential for widespread use.…”

A Bayesian approach to improved calibration and prediction of groundwater models with structural error

“…There have been many documented cases where pumping induced groundwater piezometric head decline and stream depletion lead to water right conflicts and/or threaten ecosystem services [ Barlow and Leake , ; Scanlon et al ., ]. Numerical models are increasingly being used to support conjunctive regulation of groundwater and surface water resources [ Leake et al ., ; McKusick , ; Wagner and Gannett , ].…”