Flood Control District to receive additional effluent to improve aquatic habitats in Santa Cruz

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PIMA COUNTY, April 14, 2021 – The Pima County Regional Flood Control District (District) will receive additional effluent to support habitat for the endangered Gila topminnow living downstream of the Agua Nueva Water Reclamation plant. The topminnow was once considered gone from its native areas like the Santa Cruz River. Though, it was again discovered here in 2017, with populations steadily increasing since.

With the additional supply of effluent guaranteed, the Flood Control District is developing concepts to improve aquatic habitat conditions. These include the removal of invasive vegetation and the reintroduction of native trees to help protect the diversity within the river environment.

“With increasing water scarcity, it is an accomplishment that our community has committed water to the environment, which will have long-term positive effects for the watershed and surrounding areas,” said District Director as well as Chief Engineer Suzanne Shields.

Flood Control District and Regional Wastewater Reclamation Department Treatment Facility Upgrades

Regional Wastewater Reclamation Department treatment facility upgrades were completed in 2014. These greatly improved the quality of water discharged into the Santa Cruz. Furthermore, it prompted a steady improvement in the diversity of aquatic and flora habitats within the river.

The Santa Cruz River is the longest effluent-dependent reach in Arizona. Upstream and downstream of the effluent-dependent reach, the Santa Cruz River is an ephemeral river. It flows mainly during the summer monsoon-dominated months or in response to winter frontal storms.

Except for a few isolated large winter events, the river is dry 70 percent of the time. The sporadic occurrence of natural flows is insufficient to support the habitat for fish in addition to aquatic invertebrates. This makes effluent flows north of the wastewater reclamation facilities crucial for the ecosystem health of the river.

A Supplemental Agreement between Pima County and the City of Tucson allocated additional effluent. They authorize and designate 10,000 acre-feet of effluent per year. This is to provide a dependable water source for the establishment of riparian habitat projects within the Santa Cruz River.

This agreement created the Conservation Effluent Pool (CEP) to manage allocations of reclaimed water generated at the County’s Agua Nueva and Tres Rios wastewater facilities for riparian habitat projects. However, in the more than 20 years that this agreement has been in place, there has never been a successful application to use this pool. The District requested and received a portion of the CEP to support wildlife habitat in the Santa Cruz River. Subsequently, obtaining the CEP is another step in the District’s plan. This should help make this portion of the river a thriving habitat for flora and fauna and gives the community a place to enjoy.

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