Groundwater Key to Verde River Flow

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Verde River Canyon Photo by USFS

Upper Verde River, photo by the USFS

The Verde River flows continuously for nearly 140 river miles from its headwaters near Paulden to Horseshoe Reservoir about 40 miles southwest of Payson. Continuous flow depends upon the discharge of groundwater into the river over most of its course throughout the year.

For more than a decade, concern has existed that pumping of groundwater from the Upper Verde River watershed, consisting of Little and Big Chino Valleys near Prescott, and from the Verde Valley between Clarkdale and Camp Verde, will deplete groundwater discharge to the river and its tributaries to the point that the river will cease to flow over much of its length.

This concern largely results from the population growth that occurred from the late 1950s to the present time and from likely continued growth over the coming decades. The main source of water that has supported this growth and is presently available for future growth is groundwater.

USGS NARGFM Cover

In 2013, the U.S. Geological Survey released “Human Effects on the Hydrologic System of the Verde Valley, Central Arizona, 1910-2005 and 2005-2110, Using a Regional Groundwater Flow Model”. Click here to read a summary.

A 2011 study by the USGS titled “Human Effects on the Hydrologic System of the Verde Valley, Central Arizona, 1910-2005 and 2005-2110, Using a Regional Groundwater Flow Model” clearly indicates that past and present pumpage in Upper and Middle Verde Valleys has reduced groundwater discharge to the river. Ultimately, the reduction will nearly equal the total amount pumped.

Additional pumpage to support an expanded population will expand the effect, further exacerbating the depletion of groundwater discharge to the river.

Saving the Verde River is more than a local issue however. In 2014, the Arizona Department of Water Resources (ADWR) issued a report titled “Arizona’s Next Century: Strategic Vision For Water Supply Sustainability”.

The report concludes that importation of water from outside of Arizona will be required within the next 25 to 100 years in order for the water demand associated with projected growth in the Verde River Watershed to be sustainable.

The potential long-term solution for sustainability in the watershed suggested by ADWR is participation in and exchanging water from a desalination plant located on the Pacific Ocean or the Sea of Cortez with an entity that receives water from the Colorado River.

Implementation of this solution requires overcoming substantial legal, political, and environmental issues. The financial resources for accomplishing this do not exist locally.

A sustainable water supply without importation of water will require restricting demand to the water supply that is locally available. At the same time saving the river will require the establishment of a rate of groundwater withdrawal that is less than the natural discharge of groundwater to the river. These are seemingly contradictory goals.

Throughout much of the state, including the Big Chino and Verde Valleys, Arizona law does not regulate groundwater withdrawal.

Further, for all practical purposes it does not recognize the vital connection between groundwater and surface water, and thus the dependence of year-round flow of streams and rivers on groundwater discharge.

This means that Arizona does not recognize the fact that withdrawal of groundwater has already depleted and will continue to deplete the flow of the Verde River. Arizona’s failure to legally recognize the connection between groundwater and the State’s rivers and streams is almost unique to our state as this relationship is understood and legally enforced in one manner or another throughout the west with the exception of California.

The failure of the State to recognize the connection between groundwater and surface water sanctions the use of groundwater without consideration of this use on the Verde River.

Assuring the existence of a healthy Verde River for future generations requires that steps are taken now to reduce the impact of both existing and future groundwater pumping on the river. Such steps could include: 1) evaluating the feasibility of increasing groundwater recharge from storm waters, 2) maximizing the use of treated wastewater for both potable and non-potable purposes, 3) instituting low-water-use landscaping, 4) land-use management and zoning to reduce the impact of development on water use, 5) rainwater harvesting for landscape irrigation, and 6) purchase of development rights on yet-undeveloped tracts.

These steps will not, in and of themselves, save the Verde River or save a sufficient quantity of water to meet future needs, but together they can be part of the overall solution. Care must be taken, however, that in pursuit of the above short-term goals we are not simply encouraging continued growth that ultimately makes more difficult the overall goals of saving the Verde while at the same time meeting the demand of continual growth.

Article by Bill Meyer, retired hydrologist, Board Member of the Verde River Basin Partnership
April 2016

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