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About SPU
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Water System
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History & Overview
Demographics and Water Use Statistics
The service area for Seattle Public Utilities
Seattle Public Utilities provides direct retail water service to about 630,000 people in the City of Seattle, parts of Shoreline and small areas just south of the city limits.
Seattle Public Utilities also sells water wholesale to 25 neighboring cities and water districts serving another 720,000 people. The total population of the area receiving water service from Seattle Public Utilities is 1,350,000.
2004 Population, Households, and Employment in the Seattle Public Utilities Water Service Area
Demographics
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Retail
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Wholesale
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Total
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Population
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630,000
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720,000
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1,350,000
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Households
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298,300
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282,400
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581,700
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Single Family
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151,300
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192,800
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344,100
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Multifamily
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138,000
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99,600
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237,600
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Employment
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584,000
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484,000
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1,068,000
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Wholesale Customers of Seattle Public Utilities Cities:
• City of Bellevue*
• City of Bothell
• City of Duvall
• City of Edmonds
• City of Kirkland*
• City of Mercer Island
• City of Redmond*
• City of Renton
• City of Tukwila*
Water Districts:
• Cedar River Water & Sewer District
• Coal Creek Utility District
• Highline Water District
• Lake Forest Park Water District
• Northshore Utility District
• Olympic View Water & Sewer District
• Shoreline Water District
• Skyway Water & Sewer District*
• Soos Creek Water & Sewer District
• Woodinville Water District
• Water District No. 20
• Water District No. 45
• Water District No. 49
• Water District No. 90
• Water District No. 119
• Water District No. 125
* Members of Cascade Water Alliance
Water Demand
Seattle and purveyor water demand totaled 155 million gallons a day (mgd) in 2003. Of that, 140 mgd came from the SPU supply system and 15 mgd was obtained from other purveyor sources of supply. Various components of Seattle and purveyor demand are shown in the chart and table, below. Seattle demand was 70 mgd including 8 mgd of non-revenue water¹. Total purveyor demand of 84 mgd consisted of 69 mgd from Seattle (68 mgd purchased and 1 mgd transmission non-revenue water) and 15 mgd obtained from other sources. Included in purveyor demand but not shown separately on the chart is about 5 mgd of distribution system non-revenue water.
Components of Seattle and Purveyor Water Demand: 2003
¹ Non-revenue water is calculated by subtracting total metered water sales (both retail and wholesale) from total water supplied from Seattle's sources. Meter water sales are less than total water supplied for various reasons including: system operations (reservoir overflowing, draining and cleaning, and watermain flushing), non-metered public uses (construction, fire fighting, sewer flushing, street cleaning), meter inaccuracies, and reservoir and pipeline leaks.
Retail, Wholesale, and Total Seattle System Water Demand: 2003
In Millions of Gallons per Day (mgd)
Water Consumption
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Retail
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Wholesale
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Total
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Average Annual*
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70 mgd
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69 mgd
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139 mgd
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Annual Billed
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62 mgd
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68 mgd
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130 mgd
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Peak Season (4 month)
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89 mgd
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10 mgd
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187 mgd
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Peak Day
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N/A
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N/A
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250 mgd
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*Average annual consumption for wholesale customers includes water purchased from Seattle only and excludes water obtained from sources other than Seattle (such as purveyors' own wells). The 15 mgd from other sources is shown on the bar chart, above.
How Seattle system water consumption has changed over time can be seen in the graph below. While population has risen steadily since 1975, total water demand leveled off during the 1980's at about 170 mgd before dropping off sharply due to a severe drought and mandatory water use restrictions in 1992. For the rest of the decade, the combined effects of higher water rates, the 1993 plumbing code, conservation, and improved system operations kept total consumption at or just under 150 mgd – well below pre-drought levels. Since 2000, an economic slowdown, voluntary curtailment in 2001 and continued conservation further dampened water demand which has now dipped down into the 135-140 mgd range.
Since 1990, the population of Seattle’s service area (retail and wholesale) has increased by 15%. At the same time, total water supplied by Seattle decreased by 17%. As a result, water consumption per capita plummeted 27% (from 145 gpd per capita to 105 gpd per capita) between 1990 and 2004.
Related links
Water Usage 1975-2004
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