Tag Archives: Hydrogeology

Rainfall drops below average, but deep wells should be fine this year

Rainfall in most of Kitsap County was fairly normal or slightly above average until April, when the spring rains basically stopped. The lack of rain has led to extreme conditions, as anyone can see by looking at the dry vegetation across Western Washington.

Silverdale

The total rainfall has now fallen below normal in most areas of Kitsap County, as shown by the maps on this page. That below-average condition is unlikely to change without some uncharacteristic rainstorms between now and the end of the “water year” on Oct. 1.

The Kitsap Peninsula, like islands throughout Puget Sound, does not rely on snowpack for its water supplies, so a shortage of drinking water is unlikely. The one exception might be residents who rely on private shallow wells, some of which could start to dry up by the end of summer, according to Bob Hunter, manager of Kitsap Public Utility District.

Deeper aquifers used by most major water systems on the peninsula are not affected by a single year’s weather. It takes time for the water to trickle down to the deeper layers, where groundwater levels reflect the pattern of rainfall occurring over several years.

Holly

The soils and topography vary so greatly from one place to another that nobody can say how soon shallow wells will be affected. Some wells depend on springs or surface infiltration, while others tap into aquifers with adequate supply. The rate of withdrawal, including the number of homes in a given area, can have an effect on water supply.

Although the deeper aquifers are not likely to be affected this year, what if we are at the beginning of a dry period that lasts three years or more? I would hate to look back on my current water usage and regret not saving water when I had the chance. To a varying extent, conserving water can protect our water supplies and help the overall ecosystem.

In addition to affecting aquifers, the lack of rain has reduced streamflows in creeks and rivers to below-normal rates throughout the county. The resulting low flows could affect coho salmon, which spend a year in freshwater. The fall salmon migration will be mostly affected by whether rains show up to saturate the soils and raise stream levels in September and October.

Hansville

Bob Hunter says the per-capita use of water has been dropping, but he’s not sure how much of the change is a result of personal choices and how much is a result of new kitchen and bathroom fixtures required by plumbing codes. Low-flush toilets and low-flow faucets can really make a difference, he said.

People use large amounts of water on their lawns, so one long-term effort is to reduce the amount of grass and thirsty vegetation that homeowners maintain while improving the soil to increasing its water-holding capacity.

“This year, people are irrigating a lot earlier than they were in the past,” Bob told me. “That has to have an impact, especially if the summer stays dry the whole way.”

The key to protecting future water supplies on the Kitsap Peninsula is for everyone to change their habitats over time by finding ways to use less water. If people understand the trickle-down theory of aquifers, they might be less inclined to take our water for granted.

For more information, see the Kitsap PUD’s webpage on “Groundwater and Aquifers,” including an informative piece from the Environmental Protection Agency called “Build Your Own Aquifer.” The PUD also offers a list of “Frequently Asked Questions.” For details about lawns, see King County’s “Natural Lawn Care.”

Streams in Kitsap County have dropped significantly in their flows (cubic feet per second). ALL GRAPHICS FROM KITSAP PUBLIC UTILITY DISTRICT
Streams in Kitsap County have dropped significantly in their flows (cubic feet per second).
ALL GRAPHICS FROM KITSAP PUBLIC UTILITY DISTRICT

Rainfall and aquifers keep drought away from the Kitsap Peninsula

UPDATE: April 24, 2015
Cliff Mass, professor of atmospheric sciences at the University of Washington, says in his blog that it is too early to be predicting severe drought in Western Washington this summer because of possible late-spring rains:

“I believe the media and some local politicians have gotten a bit too worried about our ‘drought.’ We have NOT had a precipitation drought at all….we are in a snow drought due to warm temperatures. The situation is unique and I suspect we will weather this summer far better than expected.”

—–

The word seems to be getting around about the record-low snowpack in the mountains, which could create a shortage of drinking water and even lead to problems for salmon swimming upstream. Read about Gov. Jay Inslee’s expanded drought emergency, issued today, as well as the last update from the U.S. Department of Agriculture.

CK

Kitsap Peninsula and the islands of Puget Sound are in their own worlds, fairly insulated from what is happening in the higher elevations. In these lower elevations, the key to water supplies is rainfall, not snow, and the outlook for the year is normal so far.

As you can see from the charts on this page (click to enlarge), this year’s rainfall has been tracking closely the long-term average. If the rains are light and steady, much of the water will soak into the ground and recharge the aquifers where most area residents get their water. The aquifer levels tend to rise and fall over multiple years, depending on the rainfall.

Hansville

Casad Dam on the Union River, which supplies a majority of Bremerton’s water, filled in January, well ahead of schedule, said Kathleen Cahall, water resources manager for the city. The dam is scheduled for a normal drawdown, and Kathleen said she does not expect any water shortage.

“We filled the reservoir fairly early this year,” she said. “We are looking pretty good for the summer.”

Holly

October, the first month of the water year, was unusually wet, Kathleen said. December precipitation also was high. The other months were fairly normal for precipitation.

Precipitation in the Puget Sound region is expected to be below average for June, July and August, according to models by the NOAA’s Climate Prediction Center. Interestingly, large portions of the Central and Southwest U.S., Alaska and Florida can expect above-average precipitation. See U.S. map.

precip

Streams on the Kitsap Peninsula are fed by surface water flows and shallow aquifers. At the moment, most of the streamflows are near their historical average. That’s not the case for the larger rivers in the Northwest, which rush out of the mountains. Most are well below their normal flows, as shown by the map with the dots.

Low streamflows usually mean higher temperatures and stress for salmon. Low flows also can affect fish passage in some stretches of the rivers while also reducing spawning areas.

Streamflows

While things look fairly good on the Kitsap Peninsula now, things can change quickly. We have different vulnerabilities than elsewhere. Climate-change models predict that rains will grow more intense in the future without changing annual precipitation very much. That means more of the water will run off the land and less will soak in, potentially reducing aquifer levels over time. Managing those underground water supplies will become more and more critical.