webheader_Lopez-Hoffman lab


Research Projects

About Ecosystem Services


For Prospective Students



The Colorado River Delta and Estuary – restoration, governance and ecosystem services

The Colorado River Delta – all dried up?

When neighboring countries share watersheds, species and ecological processes, they also share ecosystem services. Because the well-being of humans depends on the services provided by ecosystems, when countries share such services, the welfare of their citizens is linked.  In the southwestern US and northwestern Mexico, shared ecosystem services is nowhere more obvious than in the Colorado River Delta.

The Colorado River Delta, located in Mexico, is an internationally recognized site of ecological importance.  Historically, the Delta supported rich riparian areas and freshwater, brackish, and tidal wetlands and estuaries. The Delta’s estuaries provided nutrients and protection for juvenile fish, including endemic totoba, and others such as Delta clams, corvina (brown shrimp), and vaquitas, the world’s most critically endangered porpoise. The Delta’s nutrients, small fishes, and shellfish in turn provided food for larger fishes, marine mammals (4 pinnipeds, 31 cetaceans and 1 bat), five species of marine turtles, and more than 350 species of birds.

The Delta’s fisheries, carbon sequestration, migratory bird and animal habitat, and cultural and recreational opportunities benefitted people locally in Mexico as well as across the border in the US.

Unfortunately, a century of dams in the US reach of the Colorado River, combined with increasing agricultural and municipal water demands in both the U.S. and Mexico, have decreased freshwater flows to the Delta by 99%, reducing the Delta to 10% of its former size.

Intermittent flooding and restoration efforts by various NGO’s in both Mexico and the US have demonstrated that portions of the Delta may be able to recover with only relatively small, well-timed deliveries of water.

Meanwhile, the largest remaining wetland in the Delta (> 40,000 acres), the Ciénega de Santa Clara, located in Mexico, receives brackish wastewater from the Wellton-Mohawk irrigation district in southwestern Arizona. The Ciénega supports fisheries in the Gulf of California, is an important stopover feature along the Pacific Migratory Flyway, and provides habitat for resident birds including 70% of the population of the endangered Yuma Clapper Rail.

Despite its ecological significance, the Ciénega will be eliminated if the Yuma Desalting Plant (YDP) is activated as ordered by the US Congress in the Energy and Water Appropriations bill of 2004. Reduced flows and increased salinity will very likely decrease the extent of the wetland and degrade ecosystem services provided by this wetland. In May 2010, the YDP started operating at 30% capacity. 

Vegetation and ecological processes: The operation of the YDP is expected to alter decrease water quantity and increase salinity levels in the wetland, impacting vegetation. Through on-site and greenhouse experiments, we are quantifying biomass accumulation rates, evapotranspiration, and plant survival rates under a range of salinities. These experiments will enable predictions about vegetation changes, evapotranspiration rates, and ecosystem services in the Cienega as a result of changing salinity.

Modeling changes in ecosystem services in the Cienega: Changes in the quantity and salinity of water inflows to the Ciénega de Santa Clara wetland have the potential to cause changes in vegetation cover that may negatively affect habitat and resource availability for birds  such as the endangered Yuma clapper rail (Rallus longirostris yumanensis) and other animal species that provide key ecosystem services. Our lab is working with collaborators to develop an integrated ecological modeling approach to assessing the the impact of changes in water availability on ecosystem services.

Breakthroughs in transboundary governance: Long-term drought in the Colorado River basin has led to the current crisis, which is surprisingly creating opportunities to protect the Delta’s natural habitats and services. As stakeholders in the US and Mexico develop strategies for adapting to climate change, they are also discussing ways to dedicate water to the delta and estuary. Environmental NGOs are joining water users and managers from Mexico and the U.S. to develop cross-border projects for meeting municipal, agricultural, and environmental needs.

Ecosystem services are a powerful tool for framing transboundary water and ecosystem governance in terms of mutual interest because the notion of interest—importance to society and human well-being—is inherent in the ecosystem services concept.

Our lab, in conjunction with our research partners and Delta stakeholders, is working to generate breakthroughs in transboundary water governance based on ecosystem services and economic incentives.





photo of delta

delta photo satellite view
delta photo of fishing


Key landscape ecology metrics for assessing climate change adaptation options: rate of change and patchiness of impacts. López-Hoffman, L, DD Breshears, CD Allen, and ML Miller. 2013. Ecosphere 4(8): 101. http://dx.doi.org/10.1890/ES13-00118.1

From Accident to Management: The Cienega de Santa Clara Ecosystem.  Carrillo-Guerrero, Y, KW Flessa, O Hinojosa-Huerta & L López-Hoffman.  2013. Ecological Engineering. 10.1016/j.ecoleng.2013.03.003.

Monitoring Program for the Cienega de Santa Clara. Flessa, K, J Campoy Favela, F Zamora, J García, E Glenn, O Hinojosa, J Ramírez, L Lopez-Hoffman, and others.  2012.  124 pages. Now available online at http://bit.ly/1av0y5u.

From accident to management: The Cienega de Santa Clara Ecosystem
Y Carrillo-Guerrero, KW Flessa, O Hinojosa-Huerta & L López-Hoffman. 2013.  Ecological Engineering. 10.1016/j.ecoleng.2013.03.003. Special issue on the Colorado River delta.

Salinity limits of vegetation in the Cienega de Santa Clara, an oligotrophic marsh in the delta of the Colorado River, Mexico: Implications for a salinity increase. Baeza, K, L López-Hoffman, EP Glenn, KW Flessa & J Garcia-Hernandez. 2012. Ecological Engineeringhttp://dx.doi.org/10.1016/j.ecoleng.2012.08.019.  Special issue on the Colorado River delta.

The Colorado River Delta: An Invaluable Resource for People and Wildlife . Prepared for the Sonoran Institute by L López-Hoffman, CK Presnall, and R Merideth. 2013. English/Spanish, 8 p.

Finding mutual interest in shared ecosystem services: new approaches to transboundary conservation. López-Hoffman L, RG Varady, P Balvanera. 2009.In Conservation of Shared Environments: Learning from the United States and Mexico; L López-Hoffman, E McGovern, RG Varady, & KW Flessa (eds); pp 137-153. University of Arizona Press, Tucson.

Energizing transboundary conservation – Three easy steps. López-Hoffman L, E McGovern, RG Varady, & KW Flessa. 2009. In Conservation of Shared Environments: Learning from the United States and Mexico, L López-Hoffman, E McGovern, RG Varady, & KW Flessa (eds); pp 299-301. University of Arizona Press, Tucson.

  delta photo aerial view of canal
Research Partners

Bonnie Colby

Karl Flessa

Ed Glenn

Francisco Zamora

Osvel Hinojosa-Huerta

Margaret Wilder

Marcela Vásquez-León

Related Links

Jennifer Pitt. Yuma Desalinization Plant and the Ciénega de Santa Clara [download pdf]

Sonoran Institute


Environmental Research Laboratory (ERL)

Yuma Desalting Plant (YDP)

Kate Hucklebridge, et al. 2010. Model of salinity and volume constraints on the vegetation of Cienega de Santa Clara, an anthropogenic wetlands in the delta of the Colorado River, Mexico. Ecological Engineering Volume 36, Issue 7, July 2010, Pages 850-861



phone (520) 626-9868 | e-mail lauralh@email.arizona.edu

logo for Lopez-Hoffman lab

Udall Center building sketch

logo for SNR

Lopez-Hoffman lab Udall Center for Studies
in Public Policy
School of Natural Resources
and the Environment


link to U of A homepage