Natural Security: Seattle, Washington
Reducing Demand through Conservation and Efficiency
Challenge
Seattle faces a challenge similar to many other cities in the western U.S.: a growing population and limited water supply. King County, home to much of the Seattle metropolitan area, has experienced population growth of over 95 percent since 1960. Such rapid growth inevitably results in increased demand for limited water supplies. Summer months present the greatest water supply challenge for the city, as rainfall is scarce and demand soars due to outdoor watering and irrigation.
Limited water availability can have far-reaching impacts on economies, ecosystems and quality of life. Economic losses due to drought average $6-8 billion nationwide every year. Washington State has declared drought emergencies five times since 1977, most recently in 2005.
Approach
Driven by growing water demand and environmental concerns, Seattle started to invest in water efficiency and conservation in the late 1980s. The city began by altering water rates to encourage conservation, especially during the summer when supplies are lowest. The city also altered plumbing codes to require efficient fixtures in new construction and remodeling projects and invested in its water supply infrastructure to reduce losses from leaks. Seattle has further reduced water use through a variety of incentives designed to encourage replacement of antiquated plumbing fixtures and change wasteful behavior. Early programs included the Home Water Savers Program, through which the city gave away 330,000 efficient showerheads and provided free installation of water-saving showerheads, faucets and toilets to residents of apartments and condominiums. The city also gives out thousands of rebates for efficient washing machines, showerheads and sprinkler systems.
In 1999, the Saving Water Partnership, a group of 18 regional water utilities, created the 1% Water Conservation Program, designed to reduce personal and business water consumption in the region by one percent each year through 2010. Reaching this goal would save 14.5 million gallons of water per day (mgd) and offset the increased demand from projected population growth. Through the partnership, participating utilities have implemented nearly 70 cost-effective conservation and efficiency measures.
Finally, Seattle does an exceptional job of safeguarding its source waters, the Cedar River and the South Fork of the Tolt River. The city owns the majority of these watersheds and has banned agricultural, industrial and recreational activities in order to protect water quality. By limiting the disturbance in critical water supply areas, Seattle has maintained the forests and wetlands that ensure a safe and consistent supply of water, thereby limiting treatment costs and reducing vulnerability to drought.
Benefits
Seattle’s innovative water supply programs have been highly successful, allowing the city to reduce annual water consumption despite a steadily increasing population. Between 1990 and 2007, water consumption dropped 44 mgd, or 26 percent, despite a 16 percent increase in population. Water use per capita has fallen from 150 gallons per day to less than 100 gallons per day. The region is also on track to achieve the 2010 target under the 1% Program. These initiatives have also proven more cost effective than the construction of new water supply infrastructure. While neighboring Tacoma has invested $237 million in its water supply expansion, Seattle has avoided capital-intensive projects such as new pipelines or reservoirs.
Finally, water conservation and efficiency have also helped the city protect vital ecosystems and wildlife. Reduced water consumption leaves more water in the river for aquatic organisms. While Seattle has historical water claims to 350 mgd from the Cedar River, it typically uses only a third of its claim and allows the river to keep the rest.
Adapting to a Changing Climate
Seattle’s water supply challenges are complicated significantly by climate change. Projections show that temperatures will rise sharply and precipitation will decrease 15-20 percent in summer months. Most critically, snowpack in the Cascade Mountains that feeds rivers and streams throughout summer months could decline 32-71 percent by 2059. The decreases will affect the volume of water that flows into Seattle’s primary reservoirs on the Cedar and Tolt rivers, and climate models suggest that Seattle’s water supply could decrease 14 percent by 2040. The combination of population growth and climate change will make it very difficult to guarantee a safe and consistent supply of water.
Fortunately, by embracing source water protection, conservation and efficiency and a flexible planning approach that incorporates global warming, Seattle has built a water supply system with the ability to respond to the unpredictable impacts of a changing climate. While most water sources in the west are already over-allocated, leaving little room for adjustment as flows decrease, Seattle has excess supply and a commitment to efficiency that will provide an inexpensive insurance policy against the uncertainty of a warming climate. Furthermore, by reducing water withdrawals, Seattle is maintaining healthy watersheds that can continue to supply clean water even as water quality problems grow. The city’s source water protection efforts provide additional resilience in the city’s water supply system. The intact streams, wetlands and forests absorb rainfall and release it slowly, buffering against droughts and extreme storms.
Finally, Seattle has embraced a planning approach that will allow it to effectively respond to global warming. SPU works to continuously identify and evaluate all possible impacts to its existing supply system and potential responses. The city has a network of sensors that provides real-time snowpack measurements which are used to guide operations, project conservation targets and adjust water rates. In a highly variable and unpredictable climate, these planning and monitoring efforts will be essential to ensuring a consistent supply of clean water and maintaining healthy ecosystems.
