Supplies Update

Water Supply


Bremerton's water sources are surface water from the Union River Reservoir and groundwater from production wells located in the Bremerton area. All sources are managed in accordance with Washington State Department of Health and federal EPA regulations and best management practices for water supply systems. Bremerton owns and protects the 3,000-acre watershed surrounding the Union River supply. Access to the watershed is secured and limited to water supply and forestry management. Each year the Washington State Department of Health inspects the surface supply. Groundwater wells are also safeguarded through efforts to protect critical areas around the wellheads. Water quality information can be found in the Annual Drinking Water Quality Report.

Water Use


The Bremerton water system serves about 56,000 people and the Bremerton Naval Complex. On average, the Bremerton Water Utility supplies about 7 million gallons each day. Each person uses about 100 gallons of water each day.

Water demand in Bremerton generally increases over 30% in the summer due to outdoor uses. On particularly hot days water use can double. To use less water outside, it is recommended to water lawns in the morning or evening no more than 1” per week, wash cars at a commercial car wash that recycles, use a broom instead of a hose to clean sidewalks, and use native, drought tolerant plants for landscaping. For conservation information, please visit Waterwise Guidelines.

Water Supply Measurement


Bremerton’s water sources rely entirely on precipitation and not snow pack. Water managers measure precipitation on a “water year” which is October through September. Bremerton measures precipitation at the Union River Intake. Water year 2021 began on October 1, 2020 and runs through September 30, 2021. Water Year 2021 precipitation is currently 101% average.

Bremerton currently has sufficient supplies in both surface water and groundwater sources to meet expected water demands. Customers would be informed should the situation change. Customers are advised to always use water wisely. The Bremerton Water Utility carefully monitors surface supplies and groundwater levels and alerts customers when increased conservation measures are needed.  

Monthly Precipitation vs Average Precipitation
The Union River Reservoir forms behind Casad Dam. The dam is designed for water supply storage, not for flood control. McKenna Falls downstream of the dam is a natural barrier to migrating fish. When the reservoir fills to capacity, any further flows from precipitation to the reservoir pass downstream to the Union River, just as it would if the reservoir were not there. The chart below shows the level of the reservoir at the first of the month (blue) compared to the desired water level (green).
Union River Reservoir vs Firm Yield Curve
The water level in the Union River Reservoir as of July 1st was 10.25 feet below overflow. The reservoir is full by spring with good supply for the upcoming summer and fall. When the reservoir level is above the overflow, the lake is full to capacity and the system is designed to allow additional precipitation to flow downstream in the Union River. Information for residents living below the Union River Reservoir can be found in the Union River Flood Notification System brochure or visit Mason County's Emergency Management Division website.
Casad Dam
Last updated July 15, 2021