A new study shows water quality and fish activity improving in the Santa Cruz River near Rio Rico in the last three years, and suggests that the upgrade of the Nogales Waste Water Treatment Plant in 2009 has played a key role.
The study by the Tucson-based Sonoran Institute, called "A Living River: Charting the Health of the Upper Santa Cruz River," tracks the 2010 water year and compares current findings with those from prior years. The nonprofit organization said it joined five years ago with other groups, including Friends of the Santa Cruz River and the National Park Service, to monitor the health of the river in an effort to anticipate and help prevent future problems.
"We had a wake-up call in 2005 when there was a massive die-off of native cottonwoods and willows along eight miles of the Santa Cruz near Rio Rico," said Emily Brott of the Sonoran Institute in a news release. "No one knew why hundreds of trees were dying and fish had all but disappeared from the area. We knew we had to act."
Among the changes was the upgrade to the water treatment plant, which the study shows has helped improve water quality by lowering nitrogen levels and increasing levels of oxygen.
The study also shows that fish are returning to the river. In 2008, only two indigenous Longfin Dace were found in the Santa Cruz, while in 2010, more than 1,800 fish were found, including 600 Dace.
"We hope that with such improved water quality, other native fish like the endangered Gila Topminnow might be washed down with the rains from where they live upstream and find themselves able to survive in this habitat," Brott said.
Continuing challenges include heavy metals and E. coli levels, the study says, and scientists are still studying the impact of treated wastewater, or effluent, on the ecosystem.
"The Santa Cruz River is central to our history and culture, providing drinking water for millennia of inhabitants and support for vegetation that cools our region and cleans our air," said Jen Parks, president of Friends of the Santa Cruz River.
"It has a major impact on our quality of life every day, providing habitat, wildlife corridors, and exceptional recreation opportunities."