Introduction
The 2009 Regional Municipal Water Supply Outlook (2009 Outlook) presents a regional overview of municipal water demands, provides an inventory of existing water supplies, and identifies and summarizes potential future water supply and conservation projects for King, Pierce, and Snohomish Counties. The 2009 Outlook was prepared by the Water Supply Forum (Forum) over a three-year period, with significant involvement from the region's water utilities, county governments, state agencies, and environmental and tribal interests.   |
Water Supply Forum
The Water Supply Forum, created in July 1998 as the central Puget Sound Water Supply Forum, is a voluntary organization comprised of representatives from public water systems and local governments from King, Pierce, and Snohomish Counties. The water utilities represented by the Forum provide municipal water to most of the three-county population. The Forum developed the firstregional municipal water supply planning document — the 2001 Regional Water Supply Outlook (2001 Outlook), which presented information on regional public water supplies, regional municipal water needs, potential stream flow issues, and future supply options for the entire three-county area. After completing the 2001 Outlook, the Forum committed to continue collaborative planning for municipal water supply and coordinate with others on regional water resource issues. Membership of the Water Supply Forum:
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Purpose of 2009 Outlook
Water Supply Forum initiated the process to produce the 2009 Outlook in response to requests for updated information on municipal water demand and supply by local governments. In addition, the update process provided the Forum an opportunity to allow a better understanding of the ongoing work of water utilities to address the current and future water supply needs and address issues raised since the publication of the 2001 Outlook.
The key steps to update the Outlook began with recent regional demographics, primarily from the Puget Sound Regional Council (PSRC). Current water use information was obtained by an extensive survey of local water providers. Information collected also included utility experience with water conservation and water curtailments implemented to address unique supply or system challenges. All of this information was used to prepare a regional demand forecast model that would forecast municipal water needs by decade, from 2010 through 2060. In addition, the water demand forecast for the region as a whole was extrapolated to the year 2110.
In developing the Outlook, the Forum had speci al bjectives. The demand forecast had to be consistent across the region. Consistency was assured by using the same computational techniques for all purveyors, sub-regions counties and the region for demand forecasting. A second objective was that the demand forecast should address uncertainty. The Municipal Water Demand Forecast Model (Demand Model) features an approach to illustrate uncertainties in water demands by including di erent demographic growth projections, alternative weather and economic conditions, and the implications of climate change.
A third objective was to provide transparency to the planning process by encouraging meaningful participation of interested stakeholders. To provide transparency, the Forum created two Advisory Committees, one focused on municipal water demand and another focused on the water supply assessment. Using the Advisory Committees allowed the Forum to identify where more clarity was necessary both in the planning process used and how it was described. The Advisory Committees also played a vital role in developing the scope of the project and ES-3 in selection of the Consultant to prepare the 2009 Outlook.
The membership of these committees and the project team for the 2009 Outlook are presented on the last page of this executive summary report. A fourth objective was to document existing water supplies within the region, along with future water supply options that may be available for development as needed. In addition, the work included development of appropriate criteria and a credible evaluation technique that could be used by any water resource agency or stakeholder when considering future water supply needs. And lastly, future municipal water demands were compared to existing water supplies to document potential shortfalls. |
The Planning Area
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The 2009 Outlook planning area - comprised of King, Pierce, and Snohomish Counties-is remarkable in its richness in natural resources, strong economy, and high quality of life. The Seattle-Tacoma-Bellevue metropolitan area consistently ranks among the top places in the United States to live and work. Residents living in this region also place a very high value on the environment and recreation, as evident by the laws and regulations that emphasize sustainable development and strategies to proactively protect and recover endangered and threatened species. |
Demographics, Economy, and Land Use
The attractiveness of the region has resulted in significant population growth. Population has doubled from 1960 to 2000 according the U.S. Census. As a result, housing, industry, and commerce have all increased-putting pressure on the natural environment.
Most of the households in the region are currently single-family (66 percent). Multifamily households-comprised of apartments, condominiums, duplexes and attached townhomes - represent 34 percent of the total. Average family size in the region is around 2.6 persons per household.
From 1995 to 2005, the region's employment grew 18 percent, which represented greater growth than most large metropolitan areas in the nation. However, during this same period, manufacturing employment decreased by 18 percent. This decline was due to several factors, but mostly attributed to the loss of many paper/wood mills and other heavy industry. The largest gain was in construction (tied to the signi cant increase in housing) and nancial and services sectors.
Since future demographics are key to forecasting water demands, projections of population, households and employment were obtained from the Puget Sound Regional Council (PSRC) through the year 2040 and extrapolated to 2060. PSRC is the designated agency to provide local governments with detailed demographic data for the planning area. |
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Water Providers and Sources of Water Supply
There are more than 118 water utilities in the three-county region that have greater than 500 service connections, and these utilities provide water supply to more than 94 percent of the region's population. The largest water utilities (in terms of customer accounts) are Seattle Public Utilities, Tacoma Public Utilities, Alderwood Water District, Bellevue, Lakehaven Utility District, and Everett. These six utilities directly serve over 45 percent of the region's population and serve another 29 percent indirectly through wholesale supplies.
Approximately 66 percent of the region's water supply comes from the region's rivers. The major sources of surface water supplies are:
The remaining 34 percent of the region's water supply comes from groundwater, which is produced by wells located primarily in King and Pierce Counties. |
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How Water is Used
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Municipal water is used in the region for households, industry and commerce, irrigation of parks and other public spaces, fire protection, and other miscellaneous uses. For purposes of this 2009 Outlook, municipal water demands were categorized into: (1) single-family residential; (2) multifamily residential; (3) nonresidential, which includes industrial, commercial, and public; and (4) non-revenue water. Non-revenue water includes unauthorized as well as authorized uses, such as re ghting, utility system ushing, reservoir operations, meter, error, and system leakage.
Most of the municipal water used in the region (almost 60 percent) is for residential purposes. Non-residential uses account for about 32 percent of the water, and non-revenue water is about 11 percent of water use.
Water is used for di erent purposes, both indoors and outdoors. In this region, most of the water (about 84 percent of the annual consumption) is used for indoor purposes. For households, this includes toilet ushing, showers, clothes washing, dishwashing, cooking, and drinking. For non-residential customers, water is used indoors for some of the same purposes as households, but also includes food processing, industrial processing, and cooling.
Outdoor water use (about 16 percent of the annual consumption) consists mainly of landscape irrigation for households, commercial properties, golf courses and public parks. Almost all of this outdoor water use occurs during the summer and early fall.
Across the region, single-family households, on average, use 215 gallons of water per home per day and multifamily households use an average of 138 gallons of water per household per day. Regionally, the average non-residential (both industrial and commercial) customer uses 58 gallons of water per employee per day. There is however a broad range in these regional values depending on the lot sizes, income levels, density of multifamily housing (duplexes to multi-story apartment buildings) and other factors. |
Since the 1980s, several large water utilities have implemented conservation programs as a way to stretch existing water supplies and defer system expansions required to serve new customers. A severe drought in 1992 resulted in short-term seasonal mandatory water use restrictions (temporary curtailments) by several of the region’s utilities. This curtailment resulted in a sharp but temporary drop in summertime water use. The drought campaign and public education associated with the curtailment also lowered water demands for other utilities not implementing curtailment programs in 1992.
After the 1992 drought, public attitudes changed regarding water use and conservation. Utilities began implementing more aggressive long-term conservation programs including activities such as low- ush toilet rebates and retro ts, low- ow showerhead replacements, water conservation pricing, landscape audits, system leak detection and repair, and other means to reduce demand. In 1993, a new state plumbing code established e ciency standards for all new toilets, showerheads, and faucet aerators. As a result, all new construction and remodels have more water-efficient plumbing fixtures.
In 2003, the Municipal Water Law placed additional water conservation requirements on water utilities in Washington. These included a requirement that water systems set water-saving goals and annually evaluate and report their progress in meeting their goals. Most large utilities in the region have conservation goals to save about 10 percent by 2020. These goals are in addition to historic reductions in water use over the past decade.
All of these conservation e orts have resulted in a signi cant decrease in water demands in the region since 1990. The reduction in municipal water use over time is illustrated by the fact that wholesale and retail systems in Seattle, Tacoma, and Everett each use less water today than they did 40 years ago despite signi cant population growth.
Available data indicates that the average single-family household water use has decreased from 276 gallons per day in 1990 to 197 gallons per day in 2005 — almost a 30 percent decrease in consumption. This water use e ciency trend was also observed in multifamily and non-residential water use, and in overall per capita water use. The reasons for this downward trend in water consumption include utility conservation programs and plumbing code changes, as well as reductions in water use by the region’s industries.
Forecast of Municipal Water Demands
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A Municipal Water Demand Forecast Model (Demand Model) was developed as part of the 2009 Outlook. This Demand Model uses actual water use data (customer consumption rates) from a large sample of water utilities in King, Snohomish, and Pierce Counties. The utility sample represents 95 percent of the total water customers in the region. Consumption rates were modi ed over time to re ect variables that are known to in uence water use:
Price of Water: The price paid for water is known to in uence water demands, where the greater the price of water, the less water is consumed. National and regional empirical studies have shown that water consumption could go down by as much as three percent for every 10 percent increase in price. Household Income: Generally, if household income increases so does water consumption. This occurs because homes with greater income tend to have larger lot sizes requiring irrigation, and more water using xtures. National and regional empirical studies have shown that water consumption could increase by as much as four percent for every 10 percent increase in household income. Weather and Climate: Generally, hot and dry weather conditions will increase water consumption due to more irrigation for landscaping of homes and commercial businesses, as well as increased cooling processes for industry. The 2009 Outlook Demand Model measured the impact of historical weather variability and concluded that hot and dry weather in the summer can result in annual water demands being up to six percent greater than average weather.
Conservation: As water utilities continue to implement water conservation programs water use will decrease. The forecast of water demands for the 2009 Outlook assume that conservation programs similar to those of the largest utilities will occur regionally for the duration of the planning period (through 2060). In addition, the Demand Model includes several forecast scenarios that were developed to test the sensitivity of the demand model. These forecast scenarios included demographic growth and climate change. |
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Baseline Demand Forecast
The baseline municipal water demand forecast is estimated by multiplying the water consumption rates (with adjustments described earlier) and baseline demographic projections (obtained from the Puget Sound Regional Council through 2040 and extrapolated to 2060 by the project Consultant). The baseline demand forecast also assumes projected levels of water conservation savings that result from existing plumbing codes and current and projected water utility conservation programs. The baseline forecast also assumes historical average weather conditions, along with the historical variability in weather.
Municipal water demands are expected to increase from 397 million gallons per day in 2005 to 609 million gallons per day in 2060 under average weather conditions. Conservation from both plumbing codes and water utility conservation programs are expected to reduce demand from what it would otherwise be by over 120 million gallons per day (or 17 percent) by 2060.
Water demands in Pierce and Snohomish Counties are projected to increase by 63 percent over the next 50 years, while King County’s water demand is forecast to increase by approximately 47 percent. |
Water demand will react to di erent assumptions about future conditions, which is generally referred to as the “sensitivity” to changes in those assumptions. To illustrate the sensitivity in future water demands, several scenarios were analyzed for the year 2060. Alternative demographic growth projections resulted in the greatest variability in forecasted water demands. The Puget Sound Regional Council developed alternative demographic projections to the baseline (high and low) and these were input to the Demand Model to determine the impacts on the regional forecast. The high demographic growth scenario would increase projected water demands by 22 percent (when compared to the baseline), while the low demographic growth scenario would reduce the forecast of water demands by 18 percent.
Variability in weather also impacts water demands. Under historical hot and dry summer weather, projected annual water demands would be approximately ve percent greater than under historic average weather; while cool and wet weather would decrease water demands by four percent.
Climate change could increase projected water demands by 12 percent under the warmest climate change scenario (as compared to historical average weather). The warm climate change scenario could increase projected water demands by five percent.
Water Supply Outlook
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One of the major goals for the 2009 Outlook was to assess the adequacy of the region’s water supply, even under uncertainty. To accomplish this, projected water demands were compared to existing, rm water supplies under a variety of scenarios for the future.
Existing Water Supplies
Surface water provides the largest portion of the region’s municipal water supply and is the primary source for the three largest municipal water suppliers—the City of Everett, SPU and TPU. These surface water sources exist in the form of reservoir impoundments on major rivers located on the western slopes of the Cascade Mountains.
Groundwater, which is the region’s other major source of water supply, is widely distributed throughout the region. The municipal groundwater sources are tapped by wells with depths ranging from less than 100 feet to more than 1,000 feet. Most of the municipal groundwater use occurs in the central and southern portions of King and Pierce Counties. Some regional groundwater purveyors have interties with major surface water purveyors to supplement their groundwater supply sources.
An inventory of existing municipal water supply sources was assembled from a survey of more than 100 utilities. Many utilities, especially smaller ones, rely exclusively on groundwater. Some utilities have no water supplies of their own and purchase water from other utilities such as SPU, TPU, and the City of Everett.
The existing water supply for the region totals 648 million gallons per day. Of this total, surface water supply represents 424 million gallons per day and groundwater supply represents 224 million gallons per day. The greatest available water supply in the region is in King County; almost double that of Pierce and Snohomish Counties. |
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There are a number of challenges in maintaining these existing water supplies, including:
» Balancing increasing water demands for water supply while protecting senior water rights and protecting aquatic habitat and fish. » Meeting the changing and additional water quality regulations; taste and other aesthetic quality/public perception issues; and the blending of regional supplies with various degrees of treatment and watershed protection » Adapting to the potential threat of climate change
To determine the potential implications of climate change, SPU, TPU, and the
Comparison of Existing Water Supplies and Projected Demands
Existing water supplies were compared to projected municipal water demands to assess the region’s overall supply-demand condition. This comparison was made under baseline conditions as well as for other scenarios such as high demographic growth and climate change.
Under baseline assumptions, the region has approximately 39 million gallons per day more water supply than projected water demands by 2060.
The baseline conditions are based on projections of demographics (population, households, and employment through 2040) from the Puget Sound Regional Council (PSRC) and a projection of demographic data from 2040 through 2060.
The PSRC also identi ed two alternative scenarios for future growth (high and low). Under the high demographic scenario, the region’s existing water supply could meet projected water demands through 2050. Using the high growth projections, water supply is estimated to fall short in meeting projected water demands by approximately 94 million gallons per day around 2060. Conversely, under the low growth demographic scenario, existing supplies could meet projected water demands well beyond 2060.
Comparing water demands and existing supplies under historical weather conditions indicates that even under hot and dry weather the region will have enough water supply through 2060. |
Global Climate Change and Its Importance in Water Planning
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A variety of studies indicate that the Central Puget Sound Region—with its reliance on snowpack for seasonal storage of water and high utilization of its rivers and streams for hydropower, water supply, irrigation, and sh habitat — has been and will continue to be impacted by climate change. As a result, climate change should be considered in estimating future water demands and evaluating water supplies for the region. Scenarios of Climate Change
Climate change evaluations included in the 2009 Outlook are based on the work of the Climate Change Technical Committee, which was formed as part of King County’s water planning process. The Climate Committee worked with stakeholders that included water utilities, county government, and environmental and tribal interests to develop climate change scenarios for use for Outlook water supply planning e ffort.
The Climate Committee used three scenarios, to represent a full range of potential impacts to the region’s surface water supply hydrology. Climate change studies to date have not addressed the potential impacts to the region’s groundwater water supply Impacts of Climate Change
Climate change will likely impact water demands and water supplies in the region. To estimate the potential impacts on water demands, future estimates of temperature and precipitation from the three climate change scenarios were input into the Demand Model developed as a part of the 2009 Outlook. All three climate change scenarios resulted in future water demands that would be greater than would be expected based on historical average weather conditions. By 2060, it is projected that water demands could be as much as 12 percent greater under climate change. |
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Using the same data, analysis was done to determine the potential change to stream ows. Runo model for speci c basins were used to estimate the potential changes in stream ow. All three climate change scenarios indicate that stream ows will would be greater in the winter and fall months, but lower in the spring and summer months (when compared to historical conditions). This climate change impact increases over time.
Under potential climate change, existing water supply is expected to decrease and projected water demands increase. Under all three of the climate change scenarios evaluated for this 2009 Outlook, existing water supplies are adequate to meet projected water demands through the year 2050. However, by 2060 it is estimated that supply shortfalls would occur—ranging from 18 to 100 million gallons per day. This shortfall computation assumes no system improvements, no changes to reservoir operations or management, and no new water supplies or additional conservation.
It is important to note that many of the region’s water utilities have adapted in the past to uctuations in water supplies under signi cant dry periods and droughts through reservoir management and system adaptations, implementing long-term conservation programs, and through short-term demand curtailments. Climate change will undoubtedly present new challenges for these utilities, but they have demonstrated in the past they have the tools to address such uncertainty, as well as plan for long-term supply availability. |
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Future Water Supplies and Conservation
Another major goal of the 2009 Outlook was to identify potential future water supplies and conservation opportunities. This e ort involved summarizing known new water supply projects that water utilities have been studying and planning, as well as identifying and analyzing other new potential projects. The purpose of this water supply assessment is to provide the region with information, but not to make recommendations as to which projects, if any, should be developed. The results of the analysis suggest there is no urgency in planning for new regional supply sources, given the status of existing supplies and future municipal water demand. Development of future water supplies is the responsibility of individual water utilities (or groups of utilities) based on what best meets their actual local conditions and needs. The future water supply projects were categorized into the following types: surface water, groundwater, desalination, reclaimed water and green options.
Twenty-eight water supply and conservation projects were summarized, with a total potential water supply of 428 million gallons per day. For each of these projects, the preliminary construction and annual operational costs were estimated and other descriptive information was documented, including location, water quality characteristics, and potential impacts on the environment.
To compare these projects on a common cost metric, the total annualized cost was divided by the supply yield (in million gallons) to develop a unit cost. The unit costs ranged from $50 per million gallons of water produced to more than $43,000 per million gallons. This large variation in costs is in part due to the fact that some supply projects only supply water for summer demands and therefore costs cannot be recovered through water sales throughout the year. Other projects provide water year around and for any municipal use, and consequently the extra utility and additional availability of the supply lowers the unit cost.
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Need for Consistent Method to Compare Future Projects
As such, the 2009 Outlook identi ed analytical tools to compare supply projects that preserves local decisions, but takes a consistent approach that is fully transparent to the public and stakeholders. This approach is based on the principles that single-objective planning no longer re ects the realities of today. Cost and supply yield are not the only important criteria.
Essential to the implementation of this method is the identi cation of evaluation criteria. For the 2009 Outlook, the Advisory Committee provided input in the selection of these criteria:
1. Supply Reliability This criterion is to evaluate ability to meet current and future municipal water supply needs with a high degree of reliability.
2. Water Quality This criterion is to evaluate ability to provide for safe drinking water through the development and use of supplies with the best available source water quality for the proposed use.
3. Environment This criterion is to evaluate ability to minimize impacts to the natural environment from supply development through mitigation and other methods; and to seek opportunities to enhance the natural environment.
4. Implementation This criterion is to evaluate ease of or ability to maximize implementation of supply projects that accounts for permitting, tribal treaty interests, institutional barriers and public support.
5. Cost This criterion is to evaluate the overall unit cost (e.g., $/mg) of a supply project, including both capital construction costs and operational costs.
This evaluation method will help decision-makers see the trade-o s among alternatives. It also allows for conducting sensitivity analysis easily. |
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Conclusions and Recommendations
The key findings of the 2009 Outlook are:
Adequate Existing Water Supply: Existing water supplies in the region are adequate to meet projected water demands through 2050 under all planning scenarios evaluated. In some scenarios, such as the baseline scenario or the low demographic scenario, existing supplies could meet projected water demands through or well beyond 2060. However, localized water shortages may exist due to a lack of infrastructure to move water from places that have more supply than needed through the planning period to locations that would have short-falls during the same period. (This computation does not include the Lake Tapps Project currently under development by the Cascade Water Alliance.)
Shortages Possible Beyond 2050 Under Certain Conditions: Beyond 2050, there may be shortages in existing water supply if demographic growth projections are signi cantly greater than baseline demographic forecasts and/or if climate change materializes as forecasted without adaptive management of supply resources. The maximum water supply shortage could be as much as 100 million gallons per day in 2060 if no supply improvements are constructed or new supplies are brought on-line.
Many New Supplies Identified: Over 400 million gallons per day from new water supply and conservation projects have been identi ed in this 2009 Outlook, more than four times what is needed—even under the warmest climate change scenario. A multi-criteria evaluation method was developed for the 2009 Outlook that can be used by decision-makers in the region to compare the many new supplies using a consistent and transparent approach.
Adequate Time Available to Make Decisions: There is adequate time to make decisions on large water supply projects because existing water supplies are su fficient to meet regional needs at least until 2050.
The Forum believes that continued regional coordination and e orts such as the Regional Water Supply Outlook are important for water supply planning. A number of recommendations have been made for future Outlooks by the Advisory Committee stakeholders who participated in the preparation of the 2009 Regional Water Supply Outlook. These recommendations include:
- Continue to involve regional stakeholders in the development of the Outlook.
- Build on the existing water demand models and supply evaluation tools for the next Outlook; do not start the process over.
- Work with utilities to improve data collection and reporting — one of the most labor-intensive aspects of the 2009 Outlook.
- Improve our understanding of climate change and, in particular, the impacts to water demands and supplies. This would include estimating potential impacts of climate change on groundwater, which was not evaluated in the 2009 Outlook.
- Review the Outlook on a 10-year time interval to determine when an update is needed.
