Article Features Judy CorbettJake Mackenzie

Ahwahnee Water Principles Provide a Blueprint for Ensuring Future Clean Water Supplies

Judy Corbett is executive director of the Local Government Commission (LGC) and can be reached at Jake Mackenzie is a council member for the City of Rohnert Park and can be reached at For more about LGC, visit

California’s growing population, $1.4 trillion economy and natural resources all depend on clean, reliable and affordable water. Many cities and counties are facing major challenges related to water pollution and stormwater runoff as well as concerns about whether there is enough reliable water for current and future residents.

In a natural setting, runoff water is temporarily detained by the leaves of trees, absorbed by the soil, and held in streams and ponds.Besides slowing the flow of water and preventing flooding, these processes also cleanse and replenish the water supply.

In today’s typical suburban development, however, streets and parking lots cover about 60 percent of the land. The thousands of acres of paved surfaces that comprise the urban landscape prevent rain and other sources of water from penetrating the soil and replenishing groundwater supplies. Instead, water rushes over paved surfaces with increasing speed and volume, picking up a “stew” of pollutants along the way. Ultimately this polluted water flows into gutters, channels and pipes and is delivered untreated into local waterways, such as creeks and rivers. Water pollution from urban runoff has escalated as more and more natural areas have been developed.

With 12 million more residents expected in California by 2030, the water-related challenges of flooding, polluted urban runoff and lack of reliable water supplies are increasingly serious. New residents will bring additional demands on the supply of potable (drinkable) water. Furthermore, auto-oriented growth that covers additional land with impermeable surfaces will further reduce the ability of watersheds to provide us with clean water, increasing the possibility of floods.

Ahwahnee Water Principles Offer Solutions

Fortunately, there are some practical steps that cities and counties can take now to ensure that new development and redevelopment minimize the risk of future water contamination and flood damage. At the same time, these steps can help ensure that communities will have the water they need to serve new businesses and residents.

These strategies are “least cost” options. They avoid the necessity of cities undertaking costly cleanup measures or being dependent on potentially unreliable or expensive water supplies from outside the region.

To identify the most effective and viable least cost options, the Local Government Commission (LGC) invited a group of forward-thinking water experts from the federal, state and local levels to craft a set of land use principles that would provide guidance to communities concerned about future water supplies. In March 2005, the principles were presented at the Ahwahnee Hotel in Yosemite to an audience of more than 100 elected officials. They consist of nine community principles and five implementation principles (see “The Ahwahnee Water Principles for Resource-Efficient Land Use”)

In short, the Ahwahnee Water Principles advocate a change in land use planning to create the compact, walkable, mixed-use neighborhoods and town centers that are growing in popularity with young adults and seniors as a place to live. They promote the preservation of untouched watersheds because this is the land that collects and cleanses water, replenishes groundwater supplies and provides us with potable water.

The principles call for stretching the water we do have via water recycling and conservation strategies, such as low-flow toilets and drought-tolerant landscapes. They advocate urban planning that reduces paved, nonporous areas by using narrower streets and smaller or multi-storied parking lots, and they recommend using newly available porous concreteand asphalt.

The principles promote recessed (slightly below ground level) recreation areas and attractive water features where water can be held temporarily during periods of heavy rainfall. And they encourage more natural methods of channeling and cleansing water by using drainage swales, streams and ponds.

Growing in the Appropriate Manner

The Ahwahnee Water Principles focus primarily on how California cities might provide for a growing population while covering over a minimal amount of land. It’s a strategy to ensure that new growth is accommodated without destroying the precious watersheds that supply our water.

Some of the groundwork for the water principles was laid earlier by the LGC’s Ahwahnee Land Use Principles and the League’s Smart Growth Principles. The compact, walkable, transit-oriented communities called for in these documents (created by the LGC in 1991 and the League in 2000) focus growth primarily in already developed areas. They prescribe land use patterns where people can get around without depending solely on the car. This minimizes the amount of land that is paved and the associated water-related problems.

Research has confirmed the value of this strategy. Rutgers University professors analyzed the water quality impacts from current development trends and compared them to the water quality impacts of a proposed, compact development. The study found that compact development would generate 30 percent less runoff and 40 percent less water pollution than would a lower-density scenario. Numerous additional studies have yielded similar results, adding credibility to the premise that more compact development will have fewer negative impacts on water quality.

Because watersheds cross jurisdictional lines, the Ahwahnee Water Principles recommend that local governments sharing the same regional watershed make their land-use decisions in concert with one another. This is critically important. Every time a city council or county board of supervisors approves a new development, the resulting stormwater runoff has an impact on the entire watershed.

Water-Friendly Site Design

The Ahwahnee Water Principles also deal with site design. The “least cost” way of handling water on-site is to mimic the natural patterns that existed on the land before it was developed.

These features can enhance the landscape by incorporating naturalistic, site-scale features. They can take many forms, including swales, rain gardens and recessed turf areas, and can be used in parks, private yards, public spaces, parking areas, along the street, in traffic islands and below roof spouts.

Because a major portion (up to 75 percent) of water use in California is for irrigating plants, the principles specify that all aspects of the landscape should be designed to reduce water demand. This includes selecting native or drought-tolerant plants and using newer, technologically advanced watering systems.

The Village Homes development in Davis, Calif., is often cited as an example of water-friendly site design. Pavement is minimized through the use of narrow streets. Creek-like drainage channels and ponds take the place of underground concrete drainage. In addition to enhancing the aesthetics of the development, the water features hold all runoff water that falls on the site and allow it to penetrate the soil. Perhaps just as important, the system was far less expensive to build than the concrete alternative.

Looking at the Building

Not all the water used in a home, office or landscape needs to be potable. Treated wastewater can be safely used for flushing toilets, watering plants, parks and golf courses, and industrial uses. The Ahwahnee Water Principles call for installing purple pipe (pipe that carries recycled water) in all new construction, in anticipation of the future availability of recycled water.

Water-efficient technologies, such as low-flow toilets, efficient clothes washers and water-using industrial equipment, should be incorporated in new and remodeled construction. This has been shown to be highly effective in Los Angeles where, despite an increase in population, the city is using the same amount of water today as it used 30 years ago. This was accomplished through a citywide campaign to retrofit all homes with low-flow toilets.

Implementing the Principles As Policy

At the October 2005 League of California Cities Annual Conference, members voted to send the Ahwahnee Water Principles to every city, accompanied by a resolution that encourages cities to consider adopting them. The California Association of Counties took similar action at its annual conference.

In addition, the Bay Area Water Forum and Association of Bay Area Governments CalFed Task Force sent a letter to boards of supervisors and mayors in the region encouraging the use of the Ahwahnee Water Principles when updating local planning documents. Meanwhile, the principles have been adopted by the Water Policy Task Force of the Southern California Association of Governments and are moving through the process of adoption by its members.

Both the Marin and Ventura county boards of supervisors are among the entities that have adopted the Ahwahnee Water Principles as policy. Cities taking similar action include San Luis Obispo, Petaluma, Menlo Park, Palo Alto, Morgan Hill, Ventura, Richmond and Rohnert Park.

Communities that adopt the Ahwahnee Water Policies may reap financial rewards in the future. The California State Water Resources Control Board is looking to link the provisions of the Ahwahnee Water Principles to qualification for their grants and loans. But according to Executive Director Celeste Cantu, “Local jurisdictions will be responsible for the cleanliness of their runoff. This could be very costly.” Cantu adds that cities would be well advised to implement the Ahwahnee Water Principles in their land use practices today in order to avoid having
to take remedial action later.

Cantu says, “If done right, sustainable projects will deliver National Pollutant Discharge Elimination System (NPDES) compliance.” This will eliminate possible fines and spending taxpayers’ dollars to clean up problems that could have been avoided.

The Multiple Benefits of Informed Stewardship

Preserving natural water systems and fostering appropriate, water-sensitive new growth will have multiple benefits. These include an adequate supply of clean water, reduced flooding, a stronger economy, more livable communities and a better quality of life. 

Editor’s note: In 1991, a group of stakeholders met at the Ahwahnee Hotel in Yosemite to develop a set of principles addressing land use and planning issues. These were called the Ahwahnee Principles for Resource-Efficient Communities. In 2005, another group met there to develop similar complementary principles for water, which appear below.

The Ahwahnee Water Principles for Resource-Efficient Land Use Preamble

Cities and counties are facing major challenges with water contamination, stormwater runoff, flood damage liability, and concerns about whether there will be enough reliable water for current residents as well as for new development. These issues impact city and county budgets and taxpayers. Fortunately there are a number of stewardship actions that cities and counties can take that reduce costs and improve the reliability and quality of our water resources.

The Water Principles below complement the Ahwahnee Principles for Resource-Efficient Communities that were developed in 1991. Many cities and counties are already using them to improve the vitality and prosperity of their communities.

Community Principles

  1. Community design should be compact, mixed use, walkable and transit oriented so that automobile-generated urban runoff pollutants are minimized and the open lands that absorb water are preserved to the maximum extent possible (see the Ahwahnee Principles for Resource-Efficient Communities).
  2. Natural resources such as wetlands, flood plains, recharge zones, riparian areas, open space and native habitats should be identified, preserved and restored as valued assets for flood protection, water quality improvement, groundwater recharge, habitat and overall long-term water resource sustainability.
  3. Water holding areas such as creek beds, recessed athletic fields, ponds, cisterns and other features that serve to recharge groundwater, reduce runoff, improve water quality and decrease flooding should be incorporated into the urban landscape.
  4. All aspects of landscaping, from the selection of plants to soil preparation and the installation of irrigation systems, should be designed to reduce water demand, retain runoff, decrease flooding and recharge groundwater.
  5. Permeable surfaces should be used for hardscape. Impervious surfaces such as driveways, streets and parking lots should be minimized so that land is available to absorb stormwater, reduce polluted urban runoff, recharge groundwater and reduce flooding.
  6. Dual plumbing that allows grey water from showers, sinks and washers to be reused for landscape irrigation should be included in the infrastructure of new development.
  7. Community design should maximize the use of recycled water for appropriate applications, including outdoor irrigation, toilet flushing, and commercial and industrial processes. Purple pipe [used to carry recycled water] should be installed in all new construction and remodeled buildings in anticipation of the future availability of recycled water.
  8. Urban water conservation technologies such as low-flow toilets, efficient clothes washers and more efficient water-using industrial equipment should be incorporated in all new construction and retrofitted in remodeled buildings.
  9. Groundwater treatment and brackish water desalination should be pursued when necessary to maximize locally available, drought-proof water supplies.

Implementation Principles

  1. Water supply agencies should be consulted early in the land use decision-making process regarding technology, demographics and growth projections.
  2. City and county officials, the watershed council, Local Agency Formation Commission (LAFCO), special districts and other stakeholders sharing watersheds should collaborate to take advantage of the benefits and synergies of water resource planning at a watershed level.
  3. The best, multi-benefit and integrated strategies and projects should be identified and implemented before less integrated proposals, unless urgency demands otherwise.
  4. From start to finish, projects and programs should involve the public, build relationships, and increase the sharing of and access to information.
  5. Plans, programs, projects and policies should be monitored and evaluated to determine if the expected results are achieved and to improve future practices.

This article appears in the July 2006 issue of Western City
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