Tag Archives: Casad Dam

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.


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.


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.”


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.


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.


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.

Bremerton water system to get added UV protection

Bremerton will receive more than $6 million in federal “stimulus” money to add a new ultraviolet treatment system to its waterworks below Casad Dam on the Union River.

Kathleen Cahall, Bremerton's water resources manager, takes a look at Casad Dam on the Union River.
Kathleen Cahall, Bremerton's water resources manager, takes a look at Casad Dam on the Union River.

The city will keep its chlorination system, which is good at destroying bacteria and viruses. Chlorine also stays in the water lines to protect the water throughout the city’s distribution system.

The new UV system is better at killing protozoa, such as giardia and cryptosporidium — although the city has never detected these two single-celled organisms in its water, according to Kathleen Cahall, water resources manager for the city.

Cryptosporidium, which can be found in the guts of infected warm-blooded animals, has been a concern of the Environmental Protection Agency since a major outbreak occurred in Milwaukee in 1993. Read a report in the New England Journal of Medicine and check the EPA’s factsheet on requirements for unfiltered systems (PDF 248 kb).

So far, Bremerton has been able to avoid building a filtration plant, because the city owns 98 percent of the land area in its watershed, with the remainder on other protected lands. A filtration system could cost $30 million plus significant operation and maintenance costs. If such a system were required, Bremerton residents could expect to see another increase in their utility bills.

Bremerton has sufficient well capacity to switch over to groundwater sources when its surface supply behind Casad Dam becomes too turbid to be used as drinking water. Cities without such options are usually forced to filter their water. During the record storms of December 2007, Bremerton switched to groundwater supplies for three months — something that had never happened before, Cahall said.

Heavy rains stir up clays in the soil and can make the water murky for a long time, she noted. During winters when the rains don’t stir up the sediments, the city has been able to use its surface water supplies all year long. Normally, the Union River supplies about two-thirds of the city’s water.

Funding for the UV plant is coming out of the Washington State Department of Health’s $38.5 million share of economic stimulus funding from the Environmental Protection Agency. See reporter Chris Henry’s story in today’s Kitsap Sun.

Other federal money for clean water, including funding for sewage-treatment plants, will come through the Washington Department of Ecology. News of that funding should come within two weeks, Cahall said.