Groundwater Pumping Affects the River
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Effects of pumping on the Verde River
A 1993 study by the Bureau of Reclamation (BOR) concluded: “The findings of the study do not support a location in the Big Chino Valley where a large diversion of groundwater out of the valley would not result in a depletion of flows in the upper Verde River.”
There is no valid scientific basis to question the conclusion that unmitigated groundwater mining in the Big Chino Valley will eventually dewater the first 25 miles of the upper Verde River.
Updated December 19, 2018Groundwater models
The Yavapai County Water Advisory Committee (WAC) retained the US Geological Survey to develop the Northern Arizona Regional Groundwater Flow Model (NARGFM), a computerized simulation tool designed to project changes to groundwater levels and stream flow resulting from different water management scenarios. A scenario describes the location, time, and quantity of all water inputs and withdrawals from the aquifer. The model was published in 2011, generating controversy even in advance of publication. The BCWR partners have vigorously disputed and questioned the geologic data incorporated into the model and the scenarios.
As dissension grew the WAC became dysfunctional, causing the Yavapai County Board of Supervisors to dissolve the Committee.The resulting controversy prevented the WAC from using NARGFM to analyze several future scenarios for the Big Chino.
Updated December 19, 2018Effect on Environment
This graph interprets CWAG’s modeling results. Moving downriver from the USGS Paulden stream gauge at mile 10, the flow from Verde Springs gradually declines until mile 25 at Perkinsville. The yellow line is an estimate of the river flow in 1940 prior to groundwater pumping. The grey-blue line represents the river flow on June 1, 2013 measured by Sierra Club Water Sentinel volunteers at intervals along the river. Note that the base flow at Verde Springs has already declined from the predevelopment flow of 29 cfs to 21 cfs due to historical groundwater pumping.
CWAG modeling results are the purple line, representing the flow in 2110 assuming: a) The BCWR begins pumping 12,000 afy in 2020 with no mitigation, b) population growth of 18% to 12,600 by 2050 (an extremely conservative estimate), c) recharge at 2005 levels, and d) flow conditions along the river as observed in 2013. This scenario projects that by 2110, six miles of river will be dewatered between mile 19 and 25. Also note that six miles of the upper River between Del Rio Springs and Verde Springs were dewatered decades ago.
We project that human groundwater pumping may dewater 6 additional miles of the upper Verde by 2110. One day without water is a very bad day for a fish.
Updated December 19, 2018Summary of Expert Opinion
CWAG member John Zambrano has collated many studies by government agencies, experts, and scientists reporting on the connection between groundwater withdrawals and the base flow of the Verde. His whitepaper is 6 pages, non-technical, and can be viewed online.
Updated December 19, 2018