TNC gives history of San Pedro river, measures to help it

This is a great article by Shar Porier of the Sierra Vista Herald Tribune about a recent history lesson from The Nature Conservancy (TNC) about the San Pedro River and the measures put into place to protect it. If you have not read any of our previous blog posts, the San Pedro River is the last free flowing (undammed) river in the Southwest. It is home to over 400 species of birds, many threatened and endangered, as well as numerous other animals. It is a beautiful place and worth saving. The article is repeated below in it's entirety and a link to the original piece is at the end.

BISBEE — “Actually, it’s more than a river. It’s an entire ecosystem within this lush forest, the wetlands and different habitats around the river itself,” said Holly Richter, The Nature Conservancy Arizona water projects director and hydrologist, in an online meeting Thursday that drew 244 viewers.

TNC hosted the meeting “As the River Flows: the San Pedro River Story” and provided an overview of the various measures taken to study and learn about the river and its interaction with the San Pedro aquifer in order to preserve the vital ecosystem of the San Pedro Riparian National Conservation Area and those who rely on the groundwater to sustain them.

Richter said she was “amazed at the sheer power of the river’s persistence to continue to survive through extended droughts. It gives me hope for the future.”

The San Pedro River runs for about 110 miles from its source near Cananea, Sonora, in the south to the Gila River in the north, she explained. It is the soul of the SPRNCA and the first national conservation area established by Congress. It provides a permanent home for many mammalian and aquatic species and a migratory path for millions of birds, some of which are protected, threatened or rare. It is a one of a kind, desert mini–world and TNC has been an essential partner in bringing about positive changes to preserve the Southwest’s last free flowing river and the verdant sliver of land these animals call home.

Agriculture and development hindered the river’s health and to restore it many studies were done and monitoring tools installed over the past 20 years to gauge the river’s and aquifer’s decline, said Holly. The river and the San Pedro aquifer are intrinsically linked and the drawdown of water from the aquifer created river reaches in decline, as wells pulled water from it to make up for the drop in the water table.

“There is a groundwater problem throughout the West,” she noted. “We need to ensure there is water for communities as well as the river. And, since we rely on groundwater, we needed the tools to monitor levels in the aquifer and water flowing in the river. It was an exciting time to bring together all the tools for research.”

Through a partnership with the Upper San Pedro Partnership, U.S. Geological Survey, Arizona Department of Environmental Quality, Bureau of Land Management, Fort Huachuca, U.S. Forest Service, cities of Sierra Vista and Bisbee, the Cochise Conservation and Recharge Network and many other state and federal government agencies, a number of monitoring sites for data retrieval were established to provide a view of the health of the San Pedro, she stated.

Sharon Flasser, Sierra Vista Public Works director and a Tucson native, gave a history of the city’s wastewater treatment plants that began in 1957 as a three-acre site and in 2002 led to the establishment of a 640-acre site system in 2003 called the Environmental Operations Park. It allows treated effluent to form wetlands, which provide a 50-acre habitat for many bird species, and below surface water mounds which help the river.

“Since the EOP was built in 2002, the city has put over two billion gallons of water back into the aquifer,” she said. “That’s 2,700 acre feet a year. Think of a football field filled with one foot of water. Then multiply that by 2,700. That’s a lot of water.”

Due to the EOP, researchers could determine which soils worked the best for percolation down into the aquifer, she continued. Bisbee’s wastewater is also being considered for recharge near the river on the east side to help the declining flow in the first reach between the border and State Route 92.

While treated effluent is beneficial, it is not the silver bullet and more needs to be done to offset pumpage from the aquifer. And that is where recharge projects come in to play.

Through data provided, TNC and Fort Huachuca determined the surprising amount of water runoff from impervious surfaces of a new subdivision upgrade on post, reported Holly. It led to the search for land around Sierra Vista’s populated area that could collect urban runoff during rain events. After some testing of possible sites, one of the best locations was found at Coyote Wash southeast of the city.

“It had more parking lots and roads and produced a lot of runoff we could capture,” she continued. “It is under design work and could be constructed in two years.”

The Coyote Wash site will join other projects in the county, like Horseshoe Draw and the Palominas Recharge Project, in getting water slowed enough to allow some percolation into the ground and help prevent massive flood flows to the river and stop erosion. This will be from downward gravity flow or through means of injection wells that would put water directly into the aquifer.

“If additional recharge projects are built, the river could be flowing through 2075. But it’s hard to know the future with population growth and climate change. It’s encouraging, though,” she noted.

In determining the consistence of the flow, she said they factored in global climate changes, but added they needed to “improve predictions on climate change” and refine the estimates. “We recognize the science isn’t perfect on that. Frankly, there’s a lot of uncertainty. We are using the best available science now.”

She also said while some calculation on expected population growth is included in the data to get that date, if growth flourishes, like from a massive subdivision, “Our calculations would not hold true. This is where forecasting gets dependent on assumptions. But all indoor use goes back in the ground. It’s outdoor use that is lost.”

While the USPP was very active, annual reports as required by Congress were completed and submitted until funding ran out and the mandate expired. The annual report acknowledged the drawdown of the aquifer. Since then, there have been no reports done, said Holly. However, the USPP will be putting rain and water data on an accessible website which will have all the information from the monitoring stations.

“It will allow real time sharing of the information of the monitoring that continues,” she continued.


In response to a question about the impact of the border wall, Holly replied, “That’s a question a lot of people are asking these days. One of the most important aspects of the river is that remain free flowing. It’s important to the health of the river. Trying to build any structure along the border that can keep people from moving across the border, but still allow a river that floods at huge volumes to pass through and not only just the water, but these huge rafts of logs and debris, is an impossible engineering assignment.

“Also, we are very concerned it’s ability to withstand or accommodate the flood flows of this free flowing river. It’s a very important aspect of the river system and we want to see those flood flows move freely through the river.”

She went on to say TNC has sent comments to the federal government also about concerns of the construction of the wall in its blockage of wildlife movements in the region.

Rep. Ann Kirkpatrick was online and presented Holly and TNC with a Special Congressional Recognition plaque for the “vital” work being done along with all the volunteers who map the river during the hottest time of the year.

TNC has been doing the wet/dry mapping for 22 years and Kirkpatrick wanted to recognize the hard work they all put in on the project.

“Over 80 people went out to map the river and that’s just an amazing volunteer effort. I can’t even imagine coordinating all that,” Kirkpatrick said. “It’s no small matter. It has wide impact on our ability to care for the San Pedro river. We have to continue to be vigilant and protect our water resources. Your efforts are more needed than ever.”

Holly replied, “It is an honor to receive this recognition on behalf of the hundreds of volunteers who have mapped the flow of the river for 22 consecutive years.”

https://www.myheraldreview.com/news/tnc-gives-history-of-san-pedro-river-measures-to-help-it/article_7b1d8324-e8ae-11ea-854e-7b190588b976.html?utm_source=second-street&utm_medium=email&utm_campaign=Morning+Blend+8-31-20

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