The City of Bellingham manages the amount of water stored in the Lake Whatcom Reservoir in order 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.
The maximum surface elevation of the lake was set by a court order in the 1960’s. 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.
The amount of water that is available for storage and treatment. The amount available for storage is determined as much by when it rains as it is by how much it rains in the Lake Whatcom Watershed. The second part of the availability equation is the timing and amount of water available from the Middle Fork diversion.
The demand for drinking water is based on 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 10 million gallons a day.
The fourth primary factor influencing lake management is the outflow into Whatcom Creek. Controlling the amount of water flowing into Whatcom Creek is necessary as we attempt to provide healthy habitat for Chinook salmon and other fish using the stream. NOAA Fisheries, a federal agency, has listed Puget Sound Chinook on the Endangered Species Act list as a Threatened Species.
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.