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13B Gallons of Water Replenish Overpumped San Pedro River Groundwater Supplies

Arizona, USA

At a Glance

The groundwater supplies of the San Pedro River, named one of America’s Last Great Places, were drying up due to the overpumping of its aquifer. Through water replenishment projects that captured water combined with preventing groundwater pumping, 13 billion gallons have been saved since 2015.

Problem Addressed

The San Pedro River, which runs for 143 miles through Mexico and Arizona, is the last undammed desert river in the Southwest United States. Named one of “America’s Last Great Places” by Life Magazine in 1993, the river hosts two-thirds of the avian diversity in the United States, including almost 300 species of migratory birds.

However, hydrological modeling shows that the San Pedro River is drying up, and its base flow will cease within the next 100 years. The primary cause of the change is the pumping of groundwater that supports the river, with billions of gallons more than is recharged by rainwater being pumped each year. Groundwater is the source of drinking water for about half of the US population and nearly all of its rural population. However, in the Southwest, the supply of groundwater has continued to diminish as reliance on it increases during periods of drought.

One of the major users of the San Pedro River’s water is a nearby army base whose pumping started damaging the river in 2003.

To sustain the river’s base flow, and prevent this natural wonder from drying out, innovative steps needed to be taken.

The Nature Conservancy used/is using water replenishment projects to address this/these challenge(s).

Solution(s) Used

The Nature Conservancy and other environmental organization partners have found a way to raise groundwater levels along the river by using an innovative series of water replenishment projects titled the Cochise Conservation and Recharge Network.

Because the loss of river flows has significant consequences, The Nature Conservancy maps the river annually, providing a low-cost, holistic snapshot of the river’s surface flow. These mapping efforts led to identifying areas where replenishment or recharging projects would be best suited.

Next, the Conservancy acquired 6,344 acres of land along the upper river, with funding from the U.S. Army’s Compatible Use Buffer Program. The first several projects were recharge facilities that store runoff or treated wastewater in the ground that otherwise would have been lost, “recharging” it into the aquifer. The projects were supported by neighboring Cochise County, the Hereford Natural Resource Conservation District, and Cochise County’s most populous city, the City of Sierra Vista.

The Network has now expanded to include 8 conservation sites and its impact, preventing groundwater pumping combined with capturing water that previously would have been lost, has measured almost 13 billion gallons since 2015.

The Cochise Conservation and Recharge Network is next looking to expand its efforts into organizing funding for recharge infrastructure projects.

Outcomes

  1. 13 billion gallons of water have been saved or used to replenish groundwater supplies
  2. 8 Replenishment projects have been installed along the upper San Pedro River
  3. Replenishment of groundwater ensures the river can continue to support the drinking water needs of the surrounding population
  4. New flows to the aquifer enable the area to remain a sanctuary for migrating birds

Something Unique

The San Pedro River projects are unique in that they are the first to be designed specifically to sustain the flows of a river system and to help rural communities.

Who Should Consider?

Cities or towns looking to bolster sources of groundwater to avoid depleting natural resources.

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