Eagle Harbor, Bainbridge Island (née Winslow)
Kitsap County, Washington, Winter 2004
©EOP
When thinking about the problem of inadequate water supply for urban and slurban areas in the U.S., one usually thinks about the sprawling cities of the desert, probably including Albuquerque, Las Vegas and Phoenix. Even without climate change, those cities are likely to "run dry," that is outgrow feasible sources of inexpensive water, should growth resume after the Cheney-Bush economic crash. Only draconian restrictions on water use or immensely expensive new water projects will allow growth to continue at anything approaching the rate of the 1990-2005 period. One is not inclined to think of Seattle with its somewhat undeserved reputation for heavy rainfall (undeserved because Seattle actually receives less rain in a typical year than a number of East Coast and Midwest cities - Seatac Airport (SEA) receives about 930 mm of rain per year, while Washington National Airport (DCA) gets 1011 mm and St. Louis Airport (STL) gets 956 mm). In fact, in common with other U.S. cities in humid regions, Seattle, and especially some of its slurban territory, also faces problems of future water supply. This is especially true for those areas dependent on ground water, on aquifers, for a large part of that water.
The Kitsap Peninsula, a ferry ride from downtown Seattle on western side of Puget Sound, is a rapidly slurbanizing part of the Seattle metropolitan area. Despite its many cloudy days, Kitsap County (more or less coterminous with the Kitsap Peninsula plus Bainbridge Island) is facing potential water shortages over the next two decades. It grew from about 84,000 people in 1960 to about 240,000 in the fifty year period 1960-2010, by Sunbelt standards a moderate rate of growth. During that growth the county shifted from a mostly rural area with a small industrial city (Bremerton) to a largely slurban area. First to slurbanize was Bainbridge Island, a 35 minute ferry ride to downtown Searttle. A bit later, the expansion of military facilities, in particular the submarine base at Bangor on Hoods Canal, Naval Base Kitsap, contributed to slurban development of the peninsular part of the county. Most recently lower prices for real estate in comparison to the eastern shore of Puget Sound, especially for parcels with shoreline access or views of water and mountains, attracted many to the county.
Seattle and other cities on the eastern shore of the Sound depend primarily on surface streams fed by melting Cascade snowpack for their water supplies. Even though there are high mountains with glaciers and heavy winter snows both east and west, the Kitsap Peninsula is separated by salt water from those mountains, and its water supply is mostly from ground water supplemented by a few surface streams. The costs of piping water to Kitsap County from the Olympics or the Cascades have been considered prohibitive in an area where cheap water is taken for granted.
Most of the Puget Sound Basin was glaciated in the last ice age, and the area was near the southern terminus of the great continental glaciers, the depositional zone for glacial detritus. In consequence, much of the surface is underlain by permeable sand and gravel forming an excellent aquifer.The West Coast of the coterminus U.S. has a Mediterranean type climate with most precipitation falling in the months from October to April and a summer drought. Because there is ample winter precipitation in most years (unlike much of California where winter precipitation is uncertain), the Puget Sound aquifers store enough water to allow for summer growth of the lush evergreen forests which once blanketed the Peninsula. At moderate rates of usage, the aquifers also allow for agriculture with some supplemental irrigation and human settlements. Common to all aquifers, however, the rate of withdrawal can exceed the rate of recharge and cause the water level to drop.
Surrounded by salt water, some Puget Sound aquifers form lenses of fresh water floating atop denser salt water. When enough fresh water is withdrawn, salt water intrudes into those lenses. Beyond some critical level of withdrawal, the aquifer can be damaged or even destroyed for future use.The image below was drawn for the San Juan Islands, a little further north in Puget Sound, but the situation is almost identical on the Kitsap Peninsula (and as we shall see in a later posting, Bainbridge Island).
The combination of contaminated aquifers, salt water intrusions, and the possibility of draining the aquifers by too much use define the limits of water use in Kitsap County, as they do everywhere that ground water is used as the major water source. In a future posting we shall examine the water use in the City of Bainbridge Island (coterminus with the island), the most densely developed slurb in the county.
Kitsap County (pink area Naval Bases), Bainbridge Island at the Center of the Map
Source: Wikimedia Commons
