Water Demand

Water is a vital resource for supporting healthy and prosperous communities, especially in the face of climate change. According to the United Nations, 97.5% of the world’s water is salt water and 2.5% is freshwater. Most of the freshwater on Earth is frozen in ice caps leaving roughly 0.7% of the world’s water available to support environmental and community needs.  Moreover, clean water is a resource in decline due to wasteful use, climate change, and pollution. With such a burdened and limited resource, finding a sustainable balance between human and environmental needs is increasingly difficult. However, many utilities and water managers are realizing the benefits of conservation, efficiency, and water reuse to maximize water supply and protect the environment.

What is Water Demand?

Water demand is the total amount of water required for ecosystem functions and processes (e.g. healthy base flows required to support fish and other life) and out-of-stream uses (e.g. domestic use, irrigation, and industrial activities, and energy production). Traditionally, utilities and water managers consider historic use rates, population data (current population and population growth projections), economic activity, seasonal fluctuations, the amount of available water, and return flows in water demand assessments.

Common Mistakes

• Assumption that clean, available water is abundant. A primary assumption in water demand calculations is that sufficient water will be available in the future to satisfy projected demand. In reality, water supplies around the country are increasingly uncertain due to climate change, rapid population growth, urban sprawl, and many other factors.
• Water conservation, efficiency, and reuse are not incorporated into demand projections. Demand calculations for all sectors (agricultural, municipal, etc.) are more accurate when conservation and efficiency measures are included in the assessment.  In particular, it is important to take into consideration “natural conservation” or natural changes in water demand that will occur without the support of targeted programs or policies. Natural conservation happens when water wasting fixtures break and are then replaced with low-flow toilets, showerheads, and more efficient fixtures.
• Communities overestimate demand projections. Communities seeking new water supply projects often overestimate demand projections and may ignore or underestimate conservation and efficiency measures in an attempt to “claim” as much water as possible. For example, according to the Pacific Institute, the Metropolitan North Georgia Water Planning District’s Water Supply and Water Conservation Plan from 2003 used inflated population projections, which overestimated water demand, and failed to include significant conservation, efficiency, and water reuse measures.

Good News

Reducing demand through water efficiency, conservation, and reuse is proven, cost-effective, and timely. Water managers and utilities have the technology and the tools to reduce demand and protect water resources now. Moreover, there is quite a bit of low hanging fruit just waiting to be harvested:

• For example, in the U.S. we use more clean water than the top 30 developed nations in the world.  The average U.S. per person water use is 100 gallons per day while in Brisbane, Australia it is 36 gallons per day – using far less water, with the same high quality of life. 
• As much as 35% of indoor household potable water use can be saved by retrofitting with water efficient fixtures alone. 
• According to the U.S. Geological Survey, over 6 billion gallons per day is lost to water distribution system leaks and other unaccounted for uses, an amount sufficient to supply the ten largest US cities.
• Moreover, according to the Pacific Institute, residential water use efficiency measures can save enough water to meet the needs of 5 million people by 2020. Irrigation efficiency practices can save another 450 thousand-acre-feet of water per year, which is enough to supply water to 3.6 million people.

[For more details on proven, cost-effective, and timely water efficiency programs and policies, see American Rivers’ Hidden Reservoir: Why water efficiency is the best solution for the Southeast.]

Key Components of Robust Water Demand Analysis

• Break out water demand by customer sector.  Typical categories include residential-single family, residential-multi-family, agricultural, industrial, commercial, irrigation, institutional, and public.
• Take into account natural conservation.  Calculating the rate of natural conservation must account for the percentage of inefficient plumbing fixtures (toilets, showerheads, washing machines) and the anticipated rate of replacement over the planning period.
• Accurate population data that accounts for a range of scenarios. Any water demand assessment should not be a single calculation based on census data. Rather, a range of population projections should be provided with appropriate water demands for a range of growth scenarios.
• Include additional environmental considerations.  Environmental factors such as predicted variations in climate and precipitation patterns must be included in a demand assessment to maximize accuracy and promote an adaptive system.   

Cities Decreasing Demand

More and more cities and utilities are recognizing the need for accurate demand management and working to find better water management solutions. Cities like Boston and Seattle are making significant strides in accurately calculating and controlling demand by incorporating conservation and efficiency measures into demand calculations and water supply plans. Here are just a few examples from around the country:

• Boston, Massachusetts:  After a long drought and significant increase in water consumption, the Massachusetts Water Resource Authority (MWRA) was created in 1985 to reduce per capita demand by 10% in three years.  The MWRA identified inefficiencies in the City’s infrastructure, formed a highly detailed audit system, assessed cultural and behavioral issues from domestic, commercial, and industrial water users, and addressed pricing issues. Twenty years after the program began, the MWRA dramatically reduced water demand to 205 million gallons per day, far below the original projection of 450 million gallons per day. By committing to water efficiency, Boston was able to grow its customer base by 2 million people, reduce its water consumption by one-third – to 1911 levels- and save $500 million by eliminating the need to build a dam.
• Seattle, Washington:  Even in rainy Seattle, a reliable water supply that satisfies demand in the face of rapid population growth and climate changes is a significant concern. In 1992, a drought led to mandatory water use restrictions and tiered pricing for consumers. In 2000, Seattle’s water supplier implemented a Regional 1% Water Conservation Program that sought to reduce water consumption by 1% every year for ten years. The water conservation measures used in Seattle’s water supply planning have reduced water consumption by 24% since 1990, even though the population increased by 11%.
• Waukesha, Wisconsin:  The small town of Waukesha, WI is located 20 miles west of Milwaukee. Waukesha’s water supply relies on withdrawing water from a deep underground aquifer that cannot recharge fast enough to maintain a sufficient amount of clean water. Since 1988, the City’s water use has declined by an estimated 25%, despite a 17% increase in population. Although Waukesha has a history of water conservation the City also initiated a campaign to reduce water demand by 20% by 2020 and a conservation program designed to achieve three goals: reduce water use, protect sourcewater from pollution, and protect stormwater recharge areas to help aquifer recharge. While these programs are fairly new, all signs indicate that the conservation measures will be successful.
• San Antonio, Texas:  To reduce the frequency and the severity of drought response measures, the city of San Antonio implemented year-round water efficiency and conservation measures in 1993 and  in 2005, passed a Conservation Ordinance that provided a roadmap for saving 1.3 billion gallons of water each year or 3 gallons per person per day. Water demand reduction programs combine regulations and incentives to change water use efficiency and behavior. One of the more innovative ways in which San Antonio develops water policy and achieves its water savings is through a citizen advisory committee with representation from environmental, landscape industry, and economic development groups, among others.  The group advises the water utility on water policies, regulations, and programs. One successful program that emerged from the group strategically targets inefficient commercial and industrial water use and funds retrofits through a commercial and industrial meter fee. Through this and other complementary water conservation and efficiency programs, San Antonio is able to secure needed water supply for growth and economic development.
• Cary, North Carolina:  In the last decade, the town of Cary, North Carolina began a water conservation program that included a grassroots public education campaign, three ordinances designed to prevent irrigation waste, tiered pricing, and an investment in new reclaimed water infrastructure. The water efficiency program is intended to reduce per-capita water consumption by 20% before the year 2020. Despite the fact that the town has grown by 5% for the past two years, water used has remained the same.

Key Questions to Ask

When your municipality or utility develops water demand projections, it is important to ask a few questions and prepare for indirect responses:

1. What is the projection of per capita water use for the next decade and what are the assumptions of the projection? What is the source of the population data?
2. How will the water management entity promote public education and ensure transparency?
3. How will instream flows and out-of-stream water uses be measured and monitored to ensure sustainable water supplies?
4. What conservation, efficiency, and water reuse commitments are made in the demand projection?
5. What projects depend on or relate to this demand projection? What entities will benefit from the water supply project or projects?

Additional Resources

Contact your local water utility to learn more about how water demand is calculated and considered for water supply projects in your area. For more ideas and information, contact Jenny Hoffner, director of the water supply program with American Rivers at jhoffner@AmericanRivers.org or (404) 373-3602.