Restoration Efforts in the Colorado River Delta are Working
Sound science is helping us help birds.
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Until recently, a visit to the Colorado River’s delta, below Morelos Dam, would be met with a mostly dry barren desert sprinkled with salt cedar and other undesirable invasive plant species. Today, that arid landscape is broken up with large areas of healthy riparian habitat filled with cottonwood, willow, and mesquite trees. These are restoration sites which are stewarded through binational agreements between the United States and Mexico, and implemented by Raise the River—a coalition of NGOs including Audubon. The restoration efforts are done with support and partnership from the U.S. Bureau of Reclamation, Conagua (Mexico’s national water agency), and both the United States’ and Mexican sections of the International Boundary and Water Commission (IBWC). For almost a decade, water and funding have been flowing to this area under these binational agreements, and we’ve been able to celebrated water flowing to the Delta, and detailed the outsized importance of the Delta for birds and other wildlife. But what does restoration here look like, and what impacts are we seeing from this work?
The binational agreements include a robust monitoring program to help us understand both how our restoration approach is working, and if small changes can be made to achieve even greater results. The data collected through this monitoring program feeds into a collaborative adaptive management process that utilizes the expertise of academics, agency experts, and restoration practitioners, who publish their conclusions in biannual reports. Recently, the IBWC published the first report under the current Minute 323 agreement, documenting the cumulative environmental benefits of these restoration efforts realized up to 2018. The good news is that our restoration efforts are effective in creating and maintaining habitat for birds.
In 2018, bird monitoring teams saw more total birds (74%) and species types (20%) such as Yellow-breasted Chat, Black Phoebe, and Cactus Wren in restored riparian areas than in unrestored lands in the floodplain, highlighting the importance of the habitat provided by these restoration sites. Previously, marsh birds were scarce in the delta outside of the Cienega de Santa Clara and El Doctor wetlands, but in the last decade the Least Bittern and Yuma Ridgway’s Rail have been observed in exponentially increasing numbers in the Hardy River, a small Colorado River tributary that carries flows comprised of agricultural drainage and treated wastewater into the upper Estuary, where the Colorado River meets the sea. These flows have increased in volume and certainty in recent years as Raise the River partners worked with a local wastewater treatment facility increase its’ capacity via nature based solutions in exchange for dedicating a portion of the treated water to the river. The additional flows in the Hardy River and efforts to improve hydrological connectivity in the Estuary have also helped breeding colonies of water birds such as Double-crested Cormorant and Great Blue Heron move into and expand their use of the lower Hardy River and upper Estuary. Since the 2018 monitoring season, Audubon has initiated a project with our partner, Pronatura Noroeste, to conduct surveys of shorebirds by plane to better understand their presence in the largely inaccessible mudflats of the Estuary and the Cienega de Santa Clara. What we learn through these surveys will shape restoration approaches in these areas.
The binational monitoring program also helps us identify challenges and make improvements in our approaches for following years. We learned that the significant increase in vegetation observed throughout the riparian corridor after a large, and widely reported, pulse flow in 2014 was short-lived, returning to pre-pulse flow conditions by 2018. And so during the 2021 and 2022, environmental water deliveries were strategically designed to target the central delta where favorable groundwater conditions persist creating more sustainable ecological benefits.
It is a testament to the hard work of everyone involved that many of the reports’ recommendations are currently being put into action, including: developing monitoring practices to quantify social and recreational benefits, developing a binational database to store data and enable more interdisciplinary analysis, and holding adaptive management workshops to support continued learning and improvement in restoration approaches.
The birds are telling us that binational cooperation to restore habitat in the Colorado River Delta is working. Thanks to the committed efforts of dozens of people in the United States and Mexico, working at federal and state agencies, universities, and nonprofits, we are breathing life back into this ecosystem. Sound science is making a difference.