Lake Whatcom is the source of drinking water for more than 100,000 people. 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 Lake Whatcom, allows us to manage the surface level of the lake and therefore the amount of water stored in the lake. We monitor the lake level 24/7 and operate the dam gates to maintain seasonal lake level targets.
Four primary factors influence how we manage the lake level:
- 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 into Whatcom Creek 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. Lake Whatcom water levels are mostly impacted by rainfall in the watershed, so we closely track weather patterns and historical trends.
- Drinking water demand: how much water is consumed by City residents and businesses. Although this varies, the daily drinking water consumption for the past 35 years has stayed around 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, and careful management helps keep the lake within that range.
In dry summers, spring rains are stored to maintain an adequate lake level. During the wet winter months, the lake is kept lower to leave room for water from 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.
Flood Elevation
FEMA sets the 100‑year flood level for Lake Whatcom at approximately 319 feet above sea level, measured in City of Bellingham Vertical Datum (or 317.2 feet above sea level using NAVD88). This elevation is used for understanding flood risk around the lake.
Whatcom Creek Flow Management
The instream flow in Whatcom Creek is shaped by how the control dam manages Lake Whatcom’s water level and by the area below the lake that drains precipitation, groundwater, and stormwater into lower Whatcom Creek. Like other urban streams in the region, Whatcom Creek typically has lower flows in late summer and higher flows through the winter.
The flow is managed as effectively as possible based on what is available. This includes increasing outflow from Lake Whatcom in the fall to support native fish habitat, reducing peak flows in winter to protect salmon redds (nests), and extending flows in late winter and early spring to help steelhead migrate. The amount of water available each year depends on annual precipitation and lake evaporation.
More Information
NOTE: The Water Level Elevations shown on this webpage 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.
