Coalition for Sonoran Desert Protection

By Janine Spencer-Glasson, Friends of El Rio Preserve

The Santa Cruz River serves as an important resource for migrating birds in the southwestern United States. Migrating birds depend upon riparian habitat more than any other type of habitat in Arizona. There are several links along the chain of stopovers for migrating birds on the Santa Cruz River. One of them is the El Rio Preserve in Marana. To date, over 240 species of birds have been identified at the Preserve (go to ebird.org and search in Hotspots for El Rio Open Space Preserve to view the complete list of birds).

El Rio Preserve is a 104-acre property located along the western bank of the Santa Cruz River. The site has a long history of human use; it is located at the northern end of the Los Morteros Archaeological site and was occupied from approximately 850-1,300 AD. In the 1960’s, a gravel pit was created there to provide material to build Interstate-10. Later, it was used as a disc golf course. In addition to the Preserve’s role in providing bird habitat, the Preserve also serves as a link between the Tortolita Mountains and the Tucson Mountains, allowing wildlife to access water and move about.

West Lake of the El Rio Preserve in May 2019. Photo By Janine Spencer-Glasson.

This site has flooded periodically over the years, and water tends to remain ponded for six months or more, with periods where it is completely dry. This has created intermittent habitat for birds that need a site with surface water. Throughout this time, birders knew the spot as the “Coachline Gravel Pit.” Occasionally some interesting avian species would appear, including blue grosbeak, grey hawk, peregrine falcon, white-faced ibis, osprey, belted kingfisher, Bell’s vireo, Inca dove, and hooded orioles, to name a few.

An Indigo Bunting at the El Rio Preserve. Photo by Andrew Core.

During a major rainstorm in 2014, the soil berm was breached between the gravel pit and the Santa Cruz River, and water filled the property almost completely, creating a beautiful lake and much buzz among people familiar with the area. Rare birds showed up, like the white-fronted goose, a white pelican, and plenty of ducks. Birders flocked to see the new lake’s avian inhabitants, and the parking area often hosted out-of-state vehicles. This prompted the Town of Marana to take a new look at what was now called the El Rio Preserve.

There were many problems at the Preserve, however. During storm events, invasive weed seeds and huge patches of trash would flow in and settle in the basin. Mosquitoes would breed where water remained under spots of dense vegetation. Much planning and work was needed to create a riparian site that would be an amenity to the neighborhood, while maintaining a natural state for birds, wildlife, and nature-lovers.

Improvements at El Rio Preserve have been a collaborative effort. The Town of Marana dedicated funding for design and implementation of riparian restoration. The Arizona State Forestry Department researched the area and wrote a comprehensive Forestry Management Plan that focuses on invasive species. Pima County and Marana extended the Loop Trail and constructed a parking lot with a ramada. Marana worked with a University of Arizona student, Alex Stoicof, to create a community survey, which identified riparian restoration as the top priority for the Preserve. She then designed a preliminary landscape plan. Marana has constructed a viewing deck, a water fountain, toilet, and interpretive signs, and planted native landscaping

Environmental education is an important element of the El Rio Preserve. Michael Bogan, Professor at the University of Arizona, has led a damselfly and dragonfly viewing and provided information and photos for an interpretive sign at the Preserve. The Town is coordinating with the Marana Unified School District and classes of students have toured the site and focused on science relevant to their studies. Boy Scouts have volunteered, putting up bee boards and bird boxes for kestrels and brown-crested flycatchers.

Birders at the El Rio Preserve. Photo by Andrew Core.

Tucson Audubon Society supplied plants and members helped plant a pollinator garden at the entrance to the Preserve. Bat Conservation International provided agaves and helped volunteers plant them. This spring, the pollinator garden was in full bloom, with butterflies, hummingbirds, and bees enjoying the gaillardia, penstemon, native salvias, desert marigolds, and other flowers.

The pollinator garden at the El Rio Preserve in Spring 2020. Photo by Janine Spencer-Glasson.

The Friends of El Rio Preserve group has been formed to include neighbors and a diverse group of members from other environmental organizations. Friends of El Rio Preserve’s mission is “to promote wildlife habitat and connectivity in this beautiful, diverse natural area, so residents of all ages and interests can enjoy this urban oasis,” and we have planted pollinators, helped with weeding, and provided input on design elements and on interpretive signs. If you would like to learn more about Friends of El Rio Preserve, you can find us on Facebook or Instagram. You can become a Friend if you are willing to roll up your sleeves, join the team, and make a vital contribution to enhancing and protecting El Rio Preserve; contact Kathy at matproject@msn.com or Janine at janines07@comcast.net.

It has been wonderful to see so many organizations and volunteers work to create a beautiful spot for people and birds!

Currently, more improvements are underway. Pima County Flood Control is in the early stages of constructing bank protection which will cost nearly $1.9 M (nesting bird and archaeological surveys have been completed prior to ground disturbance).  The bank protection is designed to allow overflow connectivity with the Santa Cruz River during large rain events. Bank protection should be completed by this fall. There is currently no water flowing into the Preserve while bank protection is being constructed.

This fall, Marana will construct a connection to purchase water from the Cortaro-Marana Irrigation District and create a permanent pond approximately 5 acres in size. The Town is currently in the process of building an island to provide a safe place for birds to wade and rest once the pond is filled. The Friends of El Rio Preserve looks forward to assisting with pole planting native trees such as cottonwoods and willows and seeding other native annuals and perennials on the island.

Come visit El Rio Preserve once construction work is completed – you will be surprised at this lush natural site in the heart of the Sonoran Desert.

Raccoon tracks at the El Rio Preserve. Photo by Janine Spencer-Glasson.