Tres Rios, Arizona Ecosystem Restoration Project

Phoenix , Phoenix (FUA), United States

City population: 5268907

Duration: 2003 – 2012

Implementation status: Completed

Scale: Meso-scale: Regional, metropolitan and urban level

Project area: 3136310 m²

Type of area: Agricultural area or farmland, Previous derelict area

Last updated: November 2024

The Tres Rios Ecosystem Restoration Project is an ambitious initiative aimed at revitalizing a seven-mile stretch of the Salt and Gila Rivers in Phoenix, Arizona. The Tres Rios Environmental Restoration project involves the rehabilitation of nearly 700 acres in and around the Salt River, restoring a vital wetland and riparian habitat. Initially conceived in 1993 to tackle water quality issues and improve flood control, the project gained significant traction in the 2000s through a partnership between the City of Phoenix and the U.S. Army Corps of Engineers (USACE). Funding was structured with 65 percent from the USACE and 35 percent from the City of Phoenix and the Sub-Regional Operating Group Members, including Scottsdale, Tempe, Glendale, and Mesa. The Tres Rios project encompasses habitat restoration, flood control, and recreational development, with the primary objectives being to restore a degraded ecosystem, enhance water quality, and provide new recreational spaces. Construction involved relocating 1.6 million cubic yards of earth to shape three large wetland zones and two deep-water retention basins. Additionally, 18,000 feet of underground water lines and 600 feet of 84-inch fiberglass effluent pipelines were installed. To establish a thriving wetland habitat, the project coordinated the planting of over 300,000 aquatic and terrestrial plants. Habitat restoration efforts re-establish native vegetation and create wetland areas that support local biodiversity. The lush and scenic Tres Rios is now home to more than 150 different species of birds and animals like muskrats, raccoons, skunks, coyotes, bobcats, and beavers. By using treated wastewater to sustain the ecosystem, the project reduces dependency on natural water sources, thereby helping to mitigate water scarcity. The Tres Rios Ecosystem Restoration Project serves as a model for sustainable urban ecological initiatives, combining environmental health with community benefits. (1-8, 10-13)

A descriptive map of the accessible pedestrian areas at the Tres Rios Wetland

Tres Rios Wetland Map

City of Phoenix

Overview

Nature-based solution

Blue infrastructure
Rivers/streams/canals/estuaries
In-land wetlands, peatlands, swamps, and moors
Green areas for water management
Other

Key challenges

Green space, habitats and biodiversity (SDG 15)
Green space creation and/or management
Habitat and biodiversity restoration
Water management (SDG 6)
Flood protection
Improvements to water quality
Water security
Health and well-being (SDG 3)
Creation of opportunities for recreation
Enabling opportunities for physical activity
Inclusive and effective governance (SDG 16)
Inclusive governance
Social justice, cohesion and equity (SDG 10)
Social justice and equity
Environmental education

Principal problems in Functional Urban Area (FUA)

Climate-Related Hazards
River flooding
Environmental Degradation
Biodiversity loss
Poor water quality
Health, Well-being and Social cohesion
Inadequate access to recreational opportunities
Resource Scarcity and Competition
Water stress (increased demand)

Key priorities

Biodiversity (conservation and/or restoration), Social Justice and community

Focus

Creation of semi-natural blue areas, Creation of artificial wetlands, Management and improved protection of rivers and other blue areas, Restoration of riparian vegetation, Ecological restoration of ecosystems, Restoration of wetlands (other types than peatlands and mangroves, e.g. seagrass), Restoration and protection of ecosystems (including water ecosystems), Protection of natural ecosystems, Protecton and enhancement of wetlands (other types than peatlands and mangroves, e.g. seagrass), Habitat restoration, Monitoring and maintenance of habitats and/or biodiversity, Clearing out invasive alien species and allow natural regeneration maintaining the functionality the ecosystem

Project objectives

1. To restore degraded riparian and wetland habitats along the Salt River (including control of invasive species and rehabilitation of native ones) 2. To address flood risk management by protecting the surrounding community from flooding through levee construction 3. To provide recreational opportunities by creating public access points, trails, and amenities for visitors 4. To address water management issues by implementing efficient water use practices, including the use of treated wastewater for wetland maintenance 5. To include environmental education activities by providing opportunities for public learning and awareness about the ecosystem 6. To involve Native communities in decision making processes and asses needs of the surrounding communities and Tribal Nations (1-7).

Implementation activities

The Tres Rios, Arizona Ecosystem Restoration Project has implemented several key activities to address the existing problems of habitat loss, flood risk, water quality degradation and lack of recreational opportunities. An Environmental Impact Statement was completed in 2000 as part of the initial phase of the project (2). This includes environmental compliance approvals under the National Environmental Policy Act (NEPA), Endangered Species Act (ESA), Clean Water Act (CWA), state water quality certification, and National Historic Preservation Act (NHPA)(2). To achieve its goals and address the existing problems in the Salt River area the project has: 1. Wetland creation: Three large wetland areas were constructed to replicate the historical wetland ecosystem. These wetlands provide habitat for a variety of wildlife species and help to filter pollutants from the water (1-7). 2. Plant restoration: Over 300,000 aquatic and terrestrial plants were installed to recreate the natural vegetation of the area. This helps to improve water quality, provide habitat for wildlife, and reduce erosion (1, 3, 7, 13). 3. Water management: Reclaimed wastewater is used to nourish the wetlands (1-8, 10-13, 15). Trees were planted to reduce storm water runoff (1, 7) 5 pumps installed to maintain the marshlands and irrigate trees and bushes (1, 7) 4. Recreational infrastructure: The project has developed trails, and other recreational facilities to encourage public use (2, 10-13).

Climate-focused activities

Climate change adaptation:

Implement measures that prevent/manage desertification, soil erosion and landslides
Increase urban vegetation cover to reduce urban heat island effect
Restore mangroves, marshes, reefs and wetlands to dissipate the effects of storms and floodwaters
Restore rivers and other fresh water bodies to reduce flood or drought risk

Communities vulnerable to environmental hazards or climate change impacts

Yes

Specification of climate or environmentally vulnerable communities

Indigenous or tribal communities, Minority or marginalized ethnic groups

Biodiversity conservation or restoration-focused activities

Biodiversity restoration:

Rehabilitate and restore damaged or destroyed ecosystems
Restore native species
Clear and control invasive alien species
Restore ecological connectivity

Main beneficiaries

Local government/Municipality
Citizens or community groups
Marginalized groups: Indigenous communities

Governance

Management set-up

Government-led

Type of initiating organisation

Local government/municipality

Participatory approaches/ community involvement

Co-planning (e.g. stakeholder workshops, focus groups, participatory mapping)
Taskforce groups
Dissemination of information and education
Joint implementation (e.g. tree planting)
Co-management/Joint management

Details on the roles of the organisations involved in the project

The Tres Rios Ecosystem Restoration Project brought together a coalition of federal, state, and local organizations, each playing a vital role in its success. The U.S. Army Corps of Engineers (USACE) was instrumental, providing a significant portion of the project’s funding as well as leading the design and overseeing its development. The Environmental Protection Agency (EPA) contributed expertise in environmental permitting and regulatory compliance. The Arizona Department of Environmental Quality (ADEQ) took charge of water quality monitoring. The City of Phoenix led the Tres Rios Project, managing its implementation and upkeep, while Maricopa County’s Flood Control District ensured flood management. The project was supported by the SROG - Sub-Regional Operating Group (Glendale, Mesa, Scottsdale, Tempe). Needs of the surrounding communities and Tribal Nations were assessed and specific concerns addressed. Volunteers helped with cleaning efforts (2-5, 7, 13).

Project implemented in response to ...

... an EU policy or strategy? Unknown

... a national policy or strategy? Yes (Water Resources Development Act of 2000 (2). )

... a local policy or strategy? Unknown

Type of enablers

Funds, subsidies or investment for GI/NBS in the city (available for the city or provided by the city)

Financing

Total cost

More than €4,000,000

Source(s) of funding

Public local authority budget
Public national budget

Type of funding

Earmarked public budget

Non-financial contribution

Type of non-financial contribution

Provision of expertise

Who provided the non-financial contribution?

Citizens (e.g. volunteering)

Impacts and Monitoring

Environmental impacts

Water management and blue areas
Improved water quality
Achieved improved water quality
Increased protection against flooding
Achieved increased protection against flooding
Enhanced protection and restoration of freshwater ecosystems
Achieved enhanced protection and restoration of freshwater ecosystems
Green space and habitat
Increased green space area
Achieved increased green space area
Increase in protected green space areas
Achieved increase in protected green space areas
Increased conservation or restoration of ecosystems
Achieved increased conservation or restoration of ecosystems
Increased ecological connectivity across regeneration sites and scales
Achieved increased ecological connectivity across regeneration sites and scales
Increased conversion of degraded land or soil
Achieved increased conversion of degraded land or soil
Reduced biodiversity loss
Achieved reduced biodiversity loss
Increased number of species present
Achieved increased number of species present
Increased presence and recovery of wild species
Achieved increased presence and recovery of wild species

Economic impacts

Unknown

Socio-cultural impacts

Social justice and cohesion
Improved access to urban green space
Achieved improved access to urban green space
Increased involvement of locals in the management of green spaces
Achieved increased involvement of locals in the management of green spaces
Health and wellbeing
Gain in activities for recreation and exercise
Achieved gain in activities for recreation and exercise
Cultural heritage and sense of place
Improvement in people’s connection to nature
Expected improvement in people’s connection to nature
Education
Increased support for education and scientific research
Achieved increased support for education and scientific research
Increased knowledge of locals about local nature
Expected increased knowledge of locals about local nature

Type of reported impacts

Presence of formal monitoring system

Yes

Presence of indicators used in reporting

Yes

Presence of monitoring/ evaluation reports

No evidence in public records

Availability of a web-based monitoring tool

Yes

Potential risks of implementation and trade-offs

Unknown

References

City of Phoenix (n.d.). Welcome to Tres Rios!. [Source link];

U.S. Army Corps of Engineers (2024). MEMORANDUM FOR ASSISTANT SECRETARY OF THE ARMY (CIVIL WORKS) . [Source link];

The Walsh Group (n.d.). Tres Rios Environmental Restoration. [Source link];

Alamar (n.d.). Welcome to Tres Rios. [Source link];

U.S. Army Corps of Engineers (2011). Review Plan for Tres Rios Environmental Restoration Construction Project, Arizona. [Source link];

U.S. Army Corps of Engineers (n.d.). Tres Rios Environmental Restoration Project. [Source link];

City of Phoenix (n.d.). History of Tres Rios. [Source link];

Arizona State University (n.d.). Tres Rios Wetland Dynamics. [Source link];

The Birding Resource of the West Valley (2021). Planting Native Plants for Tres Rios Wetlands Volunteers. [Source link];

10.

Perry, Z. (2024). Wetlands in Arizona? Tres Rios Wetlands is Phoenix’s hidden nature gem. [Source link];

11.

Support Public Lands (n.d.). Tres Rios Wetlands. [Source link];

12.

Brown, J., Start, B., Stanisic, D., Ternack, M., Wass, R., and Coughenour, J. (2011). Tres Rios constructed wetlands: maximizing beneficial reuse while balancing demands of diverse stakeholder needs . WIT Transactions on Ecology and the Environment,;

13.

Elkins, R. (2011). Tres Rios – Water for the Desert. Lakeline, [Source link];

14.

City of Phoenix (n.d.). Tres Rios - FAQs.;

15.

Aponte, G. (2012). Tres Rios Constructed Wetland System. [Source link];

16.

MAG - Arizona Demographics (n.d.). MAG - Arizona Demographics. [Source link];