Amidst Arizona’s growing population and demand for more water, many areas around the state, especially rural areas, are facing the harsh reality of groundwater depletion, some aspects of climate change, river impacts, water-quality issues, monumental infrastructure expenditures, and few alternative water supplies. These realities are placing limits on the water supplies that will be available and affordable in the future. The Sun Corridor, which extends from Yavapai County to western Cochise County, is now home to over 5 million people, and, by 2040, have population projections of over 10 million people. Is the Sun Corridor the next Chicago? Raising Arizona was the challenge of the 20th century, while sustaining Arizona is now the challenge of the 21st century (Morrison Institute, 2007). According to Michael Willis, 2006 president of International City/County Managers Association, “The answers to the issues of our age do not come solely from the global political arena, but also from the very things we do at the local level. For nowhere is change more achievable than at the individual and local levels. And in so many ways, it’s the things we do locally that really count.”
If we peer into the future, water sustainability looks more like an imperative than an option (Vickers, 2002). In 1999, the US National Academy of Sciences published its report, “Our Common Journey: A Transition Toward Sustainability.” This report outlined that sustainable development has now become central to the mission of international organizations; countries; and national institutions, corporations, cities, and some states. This report also defined the issues, “What is to be sustained?” The answer: nature, life support, and community. It also focused on “What is to be developed?” The answer: people, economy, and society.
Introduction
Chino Valley is like any other rural Arizona community that seems to be struggling with the growing pains of transitioning from a rural to urban community. However, Chino Valley is within the Prescott Active Management Area (AMA), where water supplies within the AMA are sparse and more critically managed.
The Prescott area aquifers were declared to be in overdraft in 1999, and currently the AMA is being overdrafted two to one. Chino Valley is located in the northern region of the AMA (Figure 1), and centrally located over the Little Chino Aquifer, which is the principal aquifer for the region and provides the water for the three communities. Chino Valley is 68 square miles, and larger than Prescott and Prescott Valley combined. However, 80% of the lands within Chino Valley have no water rights, and is why Chino Valley has principally grown through lot splits, exempt wells, and septic tanks.
For Chino Valley to create any sustainable water resource plans, water sustainability must be clearly defined along with any associated components. In this case, water resource sustainability will be defined as “a condition of existence or process that allows water to be maintained indefinitely; the principles of sustainability integrate three closely interlinked systems that include: the environment, the economy, and social systems.”
For any planning process it is important to understand the current conditions, the costs, and benefits for planning modifications, and a precise way to measure the efficiency and success.
Planning for the Future
Chino Valley, which resides at the northern extent of the Sun Corridor, is experiencing significant growth, which is exerting demands upon the precious limited and already-overdrafted water supply. Understanding long-term water demand projections and available water supplies is essential to determining a future water budget, while incorporating sustainability components to ensure those water supplies are maintained or enhanced in perpetuity.
The Town’s population has historically grown around 4% with periodic increases. Starting with today and looking into the future, regarding new growth, predictions for population and future water demands can be made. Using a prediction model, the estimated population for Chino Valley at 2055 is over 60,000 people, (Figure 3). Based on this population prediction model, an estimate for water supply requirements for this new growth can be calculated. As part of this iterative process, a complete inventory of all existing and future water supplies will be required to evaluate the future water budget.
The town currently has no appropriable surface water rights, 263 acre-feet (af) of assured water supply credits, 50 af of type-I and type-II non-irrigation rights, and is currently generating annually 150 af of long-term storage credits as part of its recently permitted underground storage facility. Since 1999, Chino Valley has been acquiring historically irrigated acres (HIA) water rights within the Big Chino sub-basin (an adjacent groundwater basin to the North), with the future commitment to import that water supply under ARS §45-555(A). To date, the town has acquired 3,750 af of importable water rights.
By evaluating new growth at 4%, the town is projecting to have an additional 50,000 people by 2058, (Figure 4). The future water demand can be calculated by multiplying the population projections by the estimated gallons per capita per day (GPCD) value. In this model, 130, 87, and 57 GPCD were used. For example, if the new population used 130 GPCD, an annual water budget of over 7,000 af would be required, while a 57 GPCD would require a much smaller annual water budget of a little more than 3,000 af.
AMA Water Supplies
Even though over 450,000 af fall within the AMA as precipitation, less than 2% actually find its way back into the aquifer as recharge, primarily due to runoff and evapotranspiration. Current water demands within the AMA and a very small amount of water being recharged have led to a significant overdraft, where for every acre-foot of water recharged into the aquifer, there are 2 af being withdrawn for use annually.
Water use throughout the year fluctuates as demand for water increases significantly. The summer month’s seasonal outdoor water use creates additional aquifer stresses at a time when recharge is at its lowest (Figure 5). This water use increase is primarily due to landscape watering. Because 40–50% of all water delivered is used for landscaping and lost, only half of that water supply is returned through a municipal sewer system for treatment and recharged back into the aquifer.
Achieving Water Resource Sustainability
If we evaluate the current water equation for water use within the AMA, there are two significant paradigm shifts that need to occur to achieve water sustainability. First, by closing the water loop for water delivery and collection systems this would eliminate water being served exteriorly, which is lost due to the previously mentioned processes. Closing the water loop will require an alternative water supply for exterior uses. Second, groundwater recharge can be increased within the AMA through planned retention/recharge projects as part of new requirements for development drainage plans and/or centralized or community retention/recharge projects. Figure 6 shows water supplies delivered for interior use only and the delivery being severed to exterior uses. Also, an alternative water supply is integrated to meet the needs of exterior water demands. Lastly, the figure illustrates a new stormwater retention system that provides water back to the aquifer in the form of recharge.
In May 2007, Chino Valley passed a resolution that only allows imported HIA water supplies to be served to the interior of any type of development that uses this assured water supply. Meaning, this water cannot be used for any exterior uses i.e., landscaping, etc. The town is currently finalizing the ordinance to administer this resolution and create better interior water efficiency standards through improvements to the plumbing and building codes. Also, this ordinance will specify the requirements for the retention/recharge systems.
Figure 6 shows the possibilities of graywater reuse from faucets or clothes washers for toilets. Any graywater reuse within the interior only would decrease the demand for potable water serving these specific fixtures, but graywater systems are well-regulated through the Arizona Department of Environmental Quality to ensure specific systems are allowed under the strictest plumbing certifications.
Alternative Water Supply Systems
The most common type of alternative water supply system is the residential rainwater harvesting system. These systems—when sized correctly and used in tandem with native low water use and drought-tolerant landscapes—provide all landscape watering requirements, are relatively inexpensive, and can be configured in many different ways (Figures 7 and 8). A 2,000-square-foot roof can collect 1,200 gallons of water for every inch of precipitation. Systems are sized in accordance with landscape watering requirements.
Water harvesting can be accomplished on a macro-scale through onsite development-wide systems or through participation in a city or regional scale water retention system. Some examples of these include Figure 9, illustrating a development-wide water harvesting system. These systems are incorporated into the already-required engineered stormwater drainage plans.
These water supplies are then used for exterior landscape uses. Xeriscape, not to be confused with “zeroscape,” are the types of landscapes that work well with water harvesting systems. Depending on the region, elevation, and climate, a xeriscape is an assortment of native low water use and drought-tolerant plants, trees, and shrubs that thrive in that particular climate (Figure 10). Water is applied from water harvesting systems only when plants are stressed during dry periods.
A regional retention/recharge system may be constructed onsite in a development-wide system or as part of a city or regional retention/recharge system. These systems would collect water through water harvesting techniques and direct that water through streets, curbs, and gutters, and/or stormwater collection systems where, ultimately, the water will quickly infiltrate back into the aquifer through a series of rapid infiltration basins or other rapid infiltration methods.
These systems would require an Arizona Department of Water Resources underground storage facility permit if long-term storage credits were to be quantified, and may require an aquifer protection permit to ensure water quality standards are protected.
Economic Benefits
There are a significant number of economic benefits to pursue water sustainability. If a developer can now develop seven or more units per acre-foot of water versus the current average of 3.5 units, and assured water costs $25,000 to $45,000 per acre-foot, there is a significant cost savings. Also, this significantly reduces the amount of assured water supply credits needed with growth. Development will be part of the solution in reaching safe-yield and water sustainability, and not part of the interpreted problem with growth in the region. Water harvesting systems and improved landscaped designs will create new niche markets that include water-harvesting systems, xeriscape nurseries and landscape design, landscape architects, improved irrigation systems and audits, new engineering designs, and improvements towards retention and recharge.
From a water utility standpoint, water system demands will grow much slower and minimize operations and maintenance costs. Also, because there is no seasonal water demands, water production will be flat-lined throughout the year. And, water and sewer expansion projects can be downsized or possibly even averted.
Water sustainability and efficiency plans will virtually double the initial water supply and stretch its use much further into the future; thus, new water supplies will not be needed until much further into the future. This allows more time to seek water supplies in a planned and forecasted fashion versus finding new water supplies when the tipping point is reached.
Environmental Benefits
There are significant environmental benefits to water sustainability. Because there is no net loss of water, aquifer storage will not be depleted nor create an aquifer overdraft condition, nor expand upon an already-occurring overdraft condition. Sustainability will keep new water supply aquifers in safe-yield and help reach safe-yield in overdrafted aquifers. Also, through the new requirements of retention/recharge systems, a net gain in aquifer storage may be realized. Within the Prescott AMA, if the 2% of recharge could be increased to 5%, safe-yield could be reached.
If water is used sustainably, adjacent rivers and lakes, crucial spring flows, critical habitats, and endangered species will not be impacted. Also, as impervious surfaces increase throughout developed areas, water harvesting systems and retention/recharge systems will help reduce contaminants from runoff and reduce sediment loading into river systems, thus maintaining or improving water quality. Plants thrive better when irrigated with lower pH rainwater, and soils perform better versus using potable, neutral pH and chlorinated water.
Social System Benefits
There are many benefits to water-related social systems. From a single residence to a large commercial or industrial complex, everyone has access to rainwater. Living and working within water harvesting developments or communities integrates the value and how we efficiently use water in our everyday lives. Sustainable water use links land owners to alternative water, microclimates, and the environments from where we live and work. Today, water harvesting is similar to other past ideas and concepts that were once rejected, but now fully accepted and integrated into everyone’s lifestyle, i.e., similar to the recycling program.
These systems bring about a more conscience interface regarding where our water is derived, how much we consume, how much we conserve, and think about water for future generations.
Conclusions
The town of Chino Valley has reached the tipping point regarding water resources and how it will use any future water supplies in the most efficient and sustainable ways. It is only a matter of time when many Arizona communities, regions, or the state will be facing similar challenges. Alternative water supply systems will become more accepted and common place within our society.
For any sustainable plan to be comprehensive and effective, it must include various components of the environment, economy, and our social systems to realize the true value. Conservation is the greatest untapped water supply we can utilize today. Sustainable water use and reuse is the second greatest untapped water supply. Eventually, only as a last resort, should we seek out new water supplies for the future.
A fundamental question needs to be asked when a community or region is willing to spend hundreds of millions or billions of dollars for new water supplies, “what have they invested to increase or enhance conservation, efficiency, and sustainability to ensure they are not at the same tipping-point soon into the future?”
Chino Valley recognizes how important water supplies are, not just for development, but also for the environment and the social systems we depend upon. More importantly, Chino Valley recognizes that how we use this water within our society reflects the value we place upon water and how it enriches all aspects of the community, region, and the state we live in.