The Colorado River Delta, one of the largest desert estuaries in the world, has lost more than 80 percent of its wetlands over the last 80 years. Extensive damming and diversion of water for agriculture and development in the river basin have all but eliminated flow to the delta’s wetlands, and the resulting habitat loss poses a serious threat to wildlife populations and human communities dependent upon wetland resources for their livelihoods. The imperative to restore and conserve these imperiled ecosystems has led to increasing bi-national cooperation among Mexican and U.S. agencies and institutions, and has resulted in the formation of community-based restoration initiatives. Three such initiatives are currently underway in the delta, focusing on the restoration of marshlands, riparian stands, and mesquite bosque. Although differing somewhat in scope and scale, these projects all revolve around more efficient use of available water resources, most of which come in the form of agricultural drainage. Project planners view the willingness of local community members to lend their support and guidance to these restoration efforts as a significant stride toward realizing larger conservation goals in the region.
Unnamed Road, Sonora, Mexico, 32.3937514, -115.48507760000001
Country or Territory:
Freshwater Ponds & Lakes
Area being restored:
Approx. 1,546 hectares
Primary Causes of DegradationAgriculture & Livestock, Fragmentation, Urbanization, Transportation & Industry
Wetlands in the Colorado River Delta have been reduced by 80 percent over the last 80 years due to water management practices in the Colorado River basin (Valdés-Casillas et al. 1998). The diversion of water for agriculture has been a major factor in the decline of the river system, but increasing population pressure has also played a role. The Colorado River is the main source of water for northwestern Mexico, the desert region of the southwest United States, and the southern California coastal plain. At present, the river supports more than 23 million people–21.5 million spread over 7 states in the USA and the rest in the states of Baja California and Sonora, Mexico (Carrier, 1991; CNA, 1997; Glenn et al, 1997). In order to meet these anthropogenic demands, some twenty dams have been constructed along the river’s course, and the resulting impoundment and diversion of water has created fundamental changes in hydrology and sediment movement. In fact, except for unusually high flood years, virtually the entire flow of the Colorado is now captured and used before even reaching the river’s mouth. Consequently, wetland habitats in the delta have shrunk, and many of the extant areas only survive due to brackish agricultural drainage. Indeed, “losses” from irrigation systems sustain the remaining 1,500 ha of cottonwood-willow stands (out of “tens of thousands” of original hectares) and the 6,000-hectare Ciénega de Santa Clara, the largest marsh in the Sonoran Desert and a protected natural area.
The loss of habitat has, in turn, led to a decline in avifauna populations in the delta. Ten species of breeding birds and fourteen species that use this area as stopover or wintering grounds have required a status of legal protection under Mexican laws (i.e. Endangered, Threatened, or Special Protection; Diario Oficial de la Federación 2002). Moreover, populations of many species have declined regionally, and some have been extirpated locally, including populations of five breeding species and two wintering species (Hinojosa-Huerta et al. in press). Most affected have been riparian-obligate breeders, waterfowl, and marshbirds. There has also been major concern for the endemic subspecies of Yuma Clapper Rail (Rallus longirostris yumanensis) and Large-billed Savannah Sparrow (Passerculus sandwichensis rostratus; Mellink and Ferreira-Bartrina 2000, Hinojosa-Huerta et al. 2001a).
Reference Ecosystem Description
Prior to the dam era, the cottonwood (Populus fremontii) – willow (Salix gooddingii) forest was very common in the Colorado River Delta, extending over tens of thousands of hectares throughout the Mexicali Valley (Sykes 1937). Thick mesquite (Prosopis spp.) bosque dominated the upland terraces, in association with arroweed (Pluchea sericea) and quail bush (Atriplex lentiformis) (Mearns 1907). Oxbows, backwaters, and seepage were common, and provided for vast extensions of marshlands (Sykes 1937).
One of the largest desert estuaries in the world, the Colorado River Delta provides important habitat for resident and migratory species of both waterbirds and shorebirds. Although anthropogenic impacts have dramatically reduced delta wetlands, it continues to nurture an abundance of avifaunal species. Between 1993 and 2002, 353 bird species were detected in the Colorado River delta in México (Patten et al. 2001, Hinojosa-Huerta et al. in press). The delta provides habitat for 24 protected Mexican species, for migratory and wintering waterbirds along the Pacific Flyway, and for neotropical migrant landbirds (Mellink and Ferreira-Bartrina 2000; García-Hernández et al. 2001; Hinojosa-Huerta et al. 2001a, 2001b; Diario Oficial de la Federación 2002). Nearly 200,000 shorebirds and 60,000 ducks and geese use the delta wetlands as wintering grounds or stopover habitat during migration (Morrison et al. 1992, Mellink et al. 1997), and at least 110 species of neotropical migratory landbirds visit the delta during their migratory movements (Patten et al. 2001).
The goal of these projects is to reestablish the ecological functions of the Colorado River Delta through an efficient use of available water, and to thereby ensure the conservation of biodiversity and the preservation of the social and cultural values in the region.
The project does not have a monitoring plan.
The interest in restoring wetlands in the Colorado River Delta and allotting water for the environment has been increasing on both sides of the border (Valdés-Casillas et al. 1998, Pitt 2001). Opportunities for restoration have been identified (Briggs and Cornelius 1998, Luecke et al. 1999), and these ideas have been discussed in public forums incorporating environmental considerations into the political, social, and economic framework (Varady et al. 2001). An important result of these efforts is a binational consensus among stakeholders, agencies, environmental groups, and academia on the importance of developing and implementing a binational conservation/restoration program, based on robust scientific information that takes into account water requirements for wildlife conservation.
One major stride toward the realization of this goal is the incorporation of local communities in the process, in particular through representation afforded by the Ecological Association of Users of the Hardy and Colorado Rivers (AEURHYC). This organization was formed in 1998 by different sectors of the local communities of the Río Hardy to work together toward the restoration of the Colorado River Delta. The association includes fishermen, farmers, the Cucapá tribe, aquaculturists, and the tourist sector. In particular, members of the AEURHYC call for: 1) a reconsideration of water treaties, which will include considering the environment as another user of river water, 2) the designation of all delta wetlands under a protection status, and 3) the implementation of restoration projects (AEURHYC 2001). Slowly but steadily, government agencies in Mexico are recognizing AEURHYC as a legitimate representative of local interests and are according it a voice in the planning process.
Description of Project Activities:
- Campo Mosqueda The Campo Mosqueda site is in the Río Hardy wetland system, on the western side of the Colorado River Delta, and at the southern portion of the Mexicali Valley. The objective of the Mosqueda restoration effort is to re-establish 10 ha of wetland, mesquite and riparian habitat types on lands that were formerly used for agriculture. A nursery of native plants has been established to provide materials for the Mosqueda project as well as for subsequent riparian revegetation efforts. The Mosqueda restoration effort is establishing three types of plant communities: a 0.5-ha open water zone with intermixed marsh areas dominated by cattails (Typha domengensis), bulrush (Scirpus americanus), and sedges (Juncus spp.); a 0.5-ha hectare riparian woodland dominated by cottonwoods and willows; and a 10-ha mesquite zone dominated by screwbean (Prosopis pubescens) and honey mesquite (Prosopis glandulosa). Approximately 1,000 mesquite trees have been planted on 15 acres at an upland site, and cottonwoods and willows have been planted along the agricultural drain adjacent to the campo. - Laguna del Indio El Indio wetland is located at the lower end of the Mexicali Irrigation District, in the buffer zone of the Upper Gulf of California and Colorado River Delta Biosphere Reserve, within Ejido Indiviso, Baja California. El Indio is a 100-ha subtropical floodplain dominated by saltcedar (a non-native species), but includes other species of smaller stature, including arroweed (Pluchea sericea), seep willow (Baccharis salicifolia), saltbush (Atriplex spp.), and iodine bush (Allenrolfea occidentalis). In addition, pockets of cattail, bulrush, and other hydrophytes persist in areas where soils remain saturated throughout the year. Salt grass (Distichlis palmeri and D. spicata) forms significant patches on the salt-affected wetland fringes at the south end of El Indio. These lagoons are part of an old stream of the Colorado River on the eastern delta; now they are supported by agricultural run-off water from the Mexicali Valley. These wetlands were created when a drain broke in 1993, flooding about 90 hectares as water was retained between a flood control levee and an agricultural drain. The restoration project is focusing on a rectangular portion of El Indio (roughly 1,650 m long and 220 m wide) that occupies about 36 ha. Currently, the activities at El Indio are aimed at securing a source of water for these wetlands, and exploring the opportunities of water re-use for environmental purposes and some economic activities, in particular ecotourism and small-scale aquaculture. Key elements of this project include: 1) management of agricultural drains to enhance water availability in the lagoon; 3) saltcedar (Tamarix) removal in areas that contain significant amounts of native wetland species; and 3) community participation in the restoration design and in the development of local backyard projects that will address both community and environmental issues. - Río Hardy Wetlands The current appearance of the Río Hardy wetlands began to be shaped during the 1930's, when several consecutive flooding events created a natural dam or sandbar 35 km upstream from the Gulf of California that blocked the flow of water from the western delta (Glenn et al. 1996). The sandbar maintained a 20,000 ha marsh in the Río Hardy even during the 50-year period when Lake Mead and Lake Powell were filling and there were few or no flows to the region (Glenn et al. 1996). One of the activities of AEURHYC is the construction of a dike in the lower part of the Río Hardy that will maintain a larger wetland area, increase river depth, and restore habitat for migratory waterbirds and associated wildlife. The general idea of the AEURHYC project is to simulate the functions of the sandbar, evaluate the feasibility and potential environmental benefits of the project, and to generate information on the hydrologic variables of the river in relation to the dike. The 120-m dike will restore approximately 1,500 ha of marsh, extending over 25 river kilometers. The first phase of the dike was built during July and August 2001, using sandbags as the main material. The primary force was the participation of more than 80 volunteers from different communities on the delta, and the continuous involvement of the Indigenous Cucapá Community. A second phase was finished in August 2002, in which the dike was extended to reach higher terraces and increase the area to be restored.
Ecological Outcomes Achieved
Eliminate existing threats to the ecosystem:
Because these projects are ongoing and recovery is gradual, no data has yet been collected to ascertain the extent of recovery to date. Major milestones at this stage have been largely the collaborative and promising relationships that have taken shape between Mexican and U.S. stakeholder agencies and institutions and the willingness of local communities to actively participate in these restoration projects.
Socio-Economic & Community Outcomes Achieved
Economic vitality and local livelihoods:
Delta communities have witnessed environmental changes in the wetlands and negative impacts to their livelihoods over the past decades (Valdés-Casillas et al. 1998). Nevertheless, the natural revegetation and maintenance of wetland areas with agricultural drainage water has maintained community interest and hope for conserving a functional ecosystem. Community support has sparked interest in starting restoration efforts that could function as models to obtain information for management of the delta ecosystem, and that could explore the possibilities of using agricultural drainage water, irrigation water, private and ejido lands, and marginal fields for environmental purposes. A more integrative system of land management will ultimately be of much benefit to local communities, whether dependent upon agriculture, fisheries, eco-tourism, or a combination.
Key Lessons Learned
The community-based projects in the Colorado River Delta show that diverse habitat types can be re-created or improved through restoration work. These restoration efforts should be expanded as part of an overall conservation strategy for the Colorado River Delta. That being said, it is unlikely that bird populations can be sustained through localized restoration actions only. The ecological integrity of the riparian and wetland ecosystems of the delta needs to be maintained as well. An overall bird conservation strategy for the delta should find alternatives to large-scale destruction of wetlands and riparian forests, while creating islands of high-quality habitat at suitable sites through restoration projects. These efforts should be coupled with the support and interest of local communities working toward the long-term recovery and conservation of the desert wetlands of the Colorado River Delta.
A local monitoring program has been developed and implemented, integrating traditional knowledge and support from members of the community. The program focuses on monitoring birds, vegetation, and fluctuations in water levels. Key communities involved in the program are Ejido Luis Encinas Johnson and the Cucapá community. Several community members have provided their expertise on the local geography and ecology and received training to participate in monitoring activities. The program includes marshbird surveys; point counts for riparian birds; banding to monitor productivity, survivorship, and migration of land birds; and surveys for yellow-billed cuckoos and willow flycatchers. Three hundred forty survey stations and two banding stations are operational. Vegetation and habitat surveys are also being performed throughout the year at specified sites.
Although the interest and involvement of local communities in the conservation of the delta has been encouraging, to significantly improve the delta’s wetland, riparian, and inter-tidal areas, the management of the Colorado River must meet the ecological needs of these ecosystems. This means allowing the occasional large spring flow to pass through the delta in order to re-work sediments and create conditions ideal for natural regeneration. It also means guaranteeing smaller, yet consistent, flows that keep the wetland and riparian ecosystems moist during the hot, dry months of the summer.
Calculations based on vegetation analysis suggest that even 1 percent of the natural flow of the Colorado River could provide the means for conserving and enhancing riparian and wetland areas in the delta. Ideally, a hydrologic management system would be created to provide a continuous flow that would maximize the number of days with discharge larger than 2 m3/s (4 X 107 m3/year). This would be complemented with pulse floods every 4-5 years at 80-120 m3/s (3 X 108 m3/year) to foster recruitment of native plants, wash salts, and rework sediments in the floodplain (Glenn et al. 2001, Zamora-Arroyo et al. 2001).
The socio-political situation is such that achieving these relatively modest flows will be challenging. Numerous steps involving social, political, and ecological considerations will have to be taken before the United States and Mexican governments, delta residents, and other stakeholders can agree on what the overarching goal of restoration is, and which strategies would be most effective in accomplishing the restoration goals.
Sources and Amounts of Funding
The restoration projects at Campo Mosqueda and Laguna del Indio have been funded in part by the North American Wetlands Conservation Council. Additional support was provided by the National Fish and Wildlife Foundation, the Sonoran Joint Venture (U.S. Fish and Wildlife Service), the Sonoran Institute, the Upper Gulf of California and Colorado River Delta Biosphere Reserve, Campo Mosqueda, AEURHYC, the Cucapá Community, and Ejido Johnson. The activities conducted in the Río Hardy wetlands were coordinated through the AEURHYC, and funds and in-kind support were provided mainly by the Río Hardy tourist camps and local community members.
The Sonoran Institute
Sonoran Joint Venture