Lower Santa Cruz River Study Results

Newly Released Living River Report Tracks Changing River Conditions

TUCSON, Ariz. (July 12, 2016) –  Pima County and the Sonoran Institute have finalized the third EPA-funded report in a series entitled A Living River. The new report describes the changing conditions of the Lower Santa Cruz River between October 1, 2014 – September 30, 2015. The Lower Santa Cruz River flows year-round through northwest Tucson and Marana, with most of the water coming from two regional water reclamation facilities. This stretch of the Santa Cruz River provides the longest length of river dominated by effluent in the state.

Pima County began operations of the expanded and upgraded Tres Rios WRF and the new state-of-the-art Agua Nueva WRF in 2013. Since the upgrades went into effect, river conditions have improved substantially:

  • Water quality and clarity have significantly improved in the Santa Cruz River.
  • Four fish species are now living in the river, three more than in previous years.
  • Reports of long-standing odors by users of The Loop have been significantly reduced. RWRD has implemented odor-measuring technology that shows little to no odors leaving the facilities’ properties.
  • Water quality improvements have led to improved infiltration in the river bed which has resulted in the doubling of the aquifer recharge rate.

The Pima County Regional Flood Control District and the Sonoran Institute are hosting an event to present the report findings (report online at link).  Report collaborators will detail notable improvements and changes in the river. The event will take place on Thursday July 21, from 6 p.m. to 7 p.m. at the Ellie Towne Flowing Wells Community Center located at 1660 W. Ruthrauff Rd (register here).

The improvements to river conditions are the result of upgrades to Pima County’s two metropolitan wastewater treatment facilities: the Tres Rios Water Reclamation Facility (WRF) and the Agua Nueva WRF. According to Regional Wastewater Reclamation Department (RWRD) Director Jackson Jenkins, “The improved quality of our effluent enhances the environment along the Santa Cruz River and opens up reuse options in our desert community. The river now supports diverse riparian habitat that was not present in the past; and our high-quality reclaimed water can be put to greater use in the community.”

The improved water quality has resulted in increased recharge of the aquifer. With the increase in recharge rates, effluent in the Santa Cruz River no longer flows as far as it once did. This has resulted in some areas no longer receiving effluent flows. These areas have experienced a reduction in aquatic habitat and appear to be reverting to a more desert-like environment.

While the extent of the river flow has been reduced, the increased quality of the water has significantly improved the remaining aquatic habitat which supports fish, birds and other wildlife living in and along the river. In addition, the amount of water that recharged local aquifers in 2015 has more than doubled the amount that recharged annually prior to facility upgrades – an amount equivalent to about 20% of the water delivered to Tucson Water customers.

The improvements to the community’s wastewater treatment infrastructure have had a positive impact on the environment and the wildlife it supports. These improvements impact the local economy which benefits from tourism and recreational activities related to our desert environment.

According to Sonoran Institute Ecologist Claire Zugmeyer, “The Living River project is helping to connect people to the river. Outreach efforts associated with the project include community presentations and the Living River of Words, a project that introduces area students to the wonders of a desert riparian habitat and teaches them about this unique resource in our community. This project is a main component of Sonoran Institute’s 25 year history of working on the River as we attempt to reconnect Tucson to this important watershed that has nourished and sustained our community for thousands of years.”


Claire Zugmeyer, Sonoran Institute, czugmeyer@sonoraninstitute.org, 520-290-0828 x1143

Evan Canfield, Pima County Regional Flood Control District, evan.canfield@pima.gov 520-724-4636