Water for Seattle’s Future

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Cedar River Reservoir. Most of Seattle’s water comes from the Cedar River Watershed. (Courtesy Seattle Municipal Archives)

Seattle Public Utilities has developed an updated water plan covering 2013-2018, with some analysis and projection for future years as far out as 2060.  It’s a good news plan, demonstrating that Seattle’s commitment to water conservation has been extraordinarily successful, and projecting continued success in the future.

The bottom line is that total average demand is forecast to remain at or below current levels of approximately 133 million gallons per day through 2060.  That’s 20% below the projections made in the last water plan issued in 2007.  Actual demand is now lower than in the 1950’s.  Since 1990, consumption has decreased by about 30% while population in the service area has increased by 15%.  Population is expected to grow by more than 20% during the next 3 decades, with no increase in consumption.

Since Seattle’s current water supply system produces 172 million gallons per day, there is no need for additional water sources as far as SPU can project.  This is true even taking into account the most severe possible impacts from climate change.   Under the warmest scenario analyzed, supply would be reduced by about 13% by 2075, which is when the supply would exceed projected demand.  SPU projects that even at this point, there would be low or no cost system improvements that would enable the system to meet demand.

This good news means that only very modest improvements and renovations will be needed to the supply side of the Seattle water system over the next few decades.  The quality of our water supply continues to be very high, and current drinking water quality facilities will probably not need major new increments.  That’s more good news for water drinkers – and for ratepayers.

There are other parts of the system that will need work, however.  SPU has completed permanent covers for eight reservoirs and plans to try decommissioning the two remaining open reservoirs, Roosevelt and Volunteer.  However, the first two reservoirs to be covered, Bitter Lake and Lake Forest Park, had floating covers rather than permanent ones, and the plan is to replace these when the floating covers have reached the end of their useful life.

Then there’s the distribution system.  This is where there is likely to be a long range need to continue to invest in maintenance and replacement of aging infrastructure.  Capital spending is expected to level off and decline by about one third over the next decades.  The hope is that the new evaluation, maintenance, and scheduling methodology that SPU has been developing and implementing will mean that this level of investment will create a system that is well-maintained and capable of being sustained over time at this level of expenditure.  This will mean more stable water rates in the future, especially as the utility pays off the major capital investments made in the last few years in quality treatment and habitat conservation.

Seattle is known around the world for the quality of our water, the effectiveness of our conservation programs, our innovative approach to habitat conservation, and our proactive approach to infrastructure maintenance.  The Seattle water system is an example of how we have not just imagined sustainability, but achieved it in this critical area.