The City of Bellingham manages the amount of water stored in the Lake Whatcom Reservoir to ensure that an adequate supply of drinking water is available throughout the year. A control dam at the head of Whatcom Creek, the only stream flowing out of the Lake Whatcom Reservoir, provides a mechanism for managing the surface level of the lake and therefore the amount of water stored in the lake.
Four primary factors influence the city’s lake-level management strategy.
- Maximum surface elevation: the maximum surface elevation set by a court order in the 1960s. When the lake reaches the court-set maximum surface elevation, the city must open the gates on the control dam and spill as much water as possible to avoid flooding lakeside properties.
- Water availability: determined by when and how much it rains in the Lake Whatcom watershed and diversions from the Middle Fork Nooksack River.
- Drinking water demand: how much water is consumed by City residents and businesses. Although this varies from year to year the daily drinking water consumption for the past 35 years has stayed at about 9 million gallons a day.
- Salmon habitat in Whatcom Creek: providing water flowing in Whatcom Creek to provide a healthy habitat for salmon and other fish using the stream.
Together these four operating constraints present a complex set of management options that are considered and incorporated into the strategy for managing the Lake Whatcom Reservoir.
The interactive dashboard below provides up-to-date information about current and historic lake levels, Whatcom Creek flow and rainfall.
Seasonal Lake Level Management
Each season has a target lake level based on the seasonal changes in rainfall. Careful management goes into keeping the lake levels within the target range.
With dry summers, spring rains are captured to keep the lake levels high enough through the summer. During the wet winter months, the lake levels need to be kept lower so the levels can rise during large rain events.
Transition to Summer Target – level gradually rises (February – March)
Beginning on or around February 15, the lake level is gradually raised to 314.5 feet above sea level to increase storage for the drier spring and summer months.
Summer Target – level maintained as long as possible (April – September)
During late spring and through the summer, a lake level target of 314.5 to 314.6 feet is maintained as long as possible into the summer season.
Transition to Winter Target – level gradually drops (September – October)
Starting on or around September 15, the lake level is gradually dropped to the target elevation of 311.5 feet. Control dam gates are opened to gradually bring the lake level down to this elevation.
Winter Target – level maintained, storm fluctuations (November – February) During the winter period a lake level of approximately 311.5 feet is maintained to allow for flood storage. It is expected the lake level will fluctuate above and below the target level due to storm events.
Whatcom Creek Flow Management
The instream flow in Whatcom Creek is partially influenced by the control dam and lake level management, and it is also influenced by the area below Lake Whatcom that drains precipitation, groundwater, and stormwater into lower Whatcom Creek. Like all streams and creeks in the region, Whatcom Creek flows decrease during late summer and increase through the winter.
Flow is managed to the extent possible based on available water, including increasing outflow from Lake Whatcom in the fall to maximize native fish habitat to the degree possible with available water, reducing peak flows in the winter to minimize impacts to salmon redds, and extending flows in late winter and early spring to facilitate steelhead migration. The amount of water available varies by year depending on annual precipitation and lake evaporation.
NOTE: The Water Level Elevations shown on this web page are reported in the City of Bellingham Vertical Datum (Bellingham Municipal Code 1.12). The City of Bellingham Vertical Datum Elevation is ~1.7 feet higher than the North American Vertical Datum of 1988 (NAVD88) Elevation.
