Hydro-Regional platform

Shifting to local, renewable water supplies to meet environmental and community needs

Adopted September 13, 2016

As water availability in the West becomes increasingly uncertain, the time is right for Tucson to develop and implement a holistic plan to ensure sustainable water supplies for our region. Hydro-regionalism refers to the principle and practice of meeting local water needs with renewable supplies from the local watershed.[1] With an established vision, cooperative coordination, and integrated management and policies, our region can balance water demand with local supply instead of relying on the resources of another region to meet our needs. Water policy should be firmly rooted in this hydro-regional concept and focus on local augmentation strategies in order to ensure a sustainable water supply and high quality of life for Tucson residents into the future.

Most of Tucson’s municipal water is imported from the distant Colorado River, more than 300 miles away, which has been facing drought conditions and a ‘structural deficit’ (more water is diverted than comes into the river each year) since 2003. The remaining supply comes primarily from locally-pumped groundwater. Both of these sources are problematic: importing water is energy-intensive, costly, and increasingly unreliable, while over-pumping of groundwater has depleted our aquifers and dried up our springs, creeks and rivers. The current water supply system operates under a ‘scarcity’ framework that detrimentally impacts residents’ quality of life by degrading riparian and aquatic systems that are critical to community and environmental health.

However, with a paradigm shift in how we value, manage, and use water, we can reduce dependence on imported Colorado River water while protecting our local groundwater supply. Hydro-regionalism involves a shift from the existing ‘scarcity’ framework to one of sufficiency and abundance. These concepts and practices have already taken root in Tucson and Pima County: we are national leaders in reclaimed water use, rainwater harvesting, green infrastructure, and native landscaping. To build on these successes and set the national standard for hydro-regionalism, Tucson needs to further cultivate a diverse water portfolio of renewable and recycled water supplies coupled with strong conservation programs.

More rain falls on the City of Tucson in one year than the entire amount of water the city uses from the tap. This abundant renewable water supply can be harnessed to offset our water needs and enhance recharge of our aquifers. Under a hydro-regional model, groundwater aquifers – aided by enhanced stormwater recharge strategies – can be restored to a fully renewable water supply. Additionally, by limiting groundwater pumping to the amount of water that is recharged annually, this finite resource can be restored and stabilized to support renewal of seasonal and annual flows in our springs, creeks, and rivers. Finally, recycled water sources are a critical piece of a balanced water budget. Greywater and reclaimed water can be used for irrigation and landscaping needs, reducing the strain on municipal supplies.

Hydro-regionalism offers direct economic benefits to our region. Though water security is a top priority for many Arizonans, the state’s future water resources remain uncertain. Our current reliance on the drought-stricken Colorado River may deter economic investment in Southern Arizona by investors wary of future water shortages, whereas increased water independence and security resulting from a hydro-regional water policy will support and encourage long-term economic investment in our communities.

A hydro-regional water policy that protects and restores riparian and aquatic systems will realize an increase in the value of ‘ecosystem services’ provided. A recent report by Seattle-based non-profit Earth Economics prepared for Watershed Management Group found that Lower Sabino Creek alone provides between $1.4 and $2.1 million dollars of ‘ecosystem services’ – clean water and air, urban heat island mitigation, outdoor recreation, groundwater recharge, and flood control – each year.

Moreover, under a hydro-regional policy, Tucson will gain stature as a regional and national leader in sustainable water use. Innovative conservation and augmentation strategies, technologies, and practices will both support local economic development and serve as examples for other communities working to increase municipal water security.

To ensure available water is secured to support future generations of healthy Tucsonans, water-dependent riparian and aquatic systems, and continued economic investment in our region, we propose the following actions and policies for the Upper Santa Cruz Subbasin in the Tucson Active Management Area:

  • Assess the potential for utilizing urban enhanced stormwater runoff to meet community water resource needs in the Tucson basin.
    • Estimate the difference between pre-development and post-development runoff for Tucson basin.
    • Identify potential areas with favorable soils for location green infrastructure practices to promote deep infiltration and estimate potential recharge benefit.
    • Identify potential for enhanced channel and floodplain infiltration and estimate potential recharge benefit.
    • Conduct monitoring of pilot green infrastructure infiltration basins as a proof of concept and to inform basin-wide estimates for recharge benefits.
  • Analyze seasonal and annual variability of aquifer recharge to determine sustainable use without depleting groundwater and impairing riparian and aquatic systems.
    • Develop a hydro-regional scenario for Bureau of Reclamation’s Tucson Basin Study groundwater model.
    • Analyze Tucson basin model results for both temporal and spatial shortages to inform water supply sharing coordination across basin groundwater users.
  • Develop water resource budgets based on renewable local water resources to meet present and future community needs.
  • Collaborate with agencies and governments to improve integrated stormwater management and set water conservation targets to shift the Tucson basin towards sustainable local water resource reliance and awareness of local drought conditions.

Check out the basic water budget below, or click here to see a more detailed budget with footnotes. 



[1] “Renewable supplies from the local watershed” does not include Colorado River water delivered hundreds of miles through CAP to southern Arizona. CAP water is unsustainable due to (1) The extractive cost on the Colorado River environment, (2) The high energy cost (~40% of Arizona's energy demand) to deliver this water, and (3) the additional water cost to produce the energy required to transport CAP water. The future of sustained CAP supplies is uncertain because Arizona has junior priority to California in times of Colorado River water shortage, and has begun voluntary reductions of CAP allocations to prevent a near-time shortage declaration at Lake Mead. By developing local water supplies, we move toward regional self-sufficiency, increase community resilience, and ensure water availability for future economic and environmental health.