Lake Whatcom is the source of water for approximately half of Whatcom County residents. The majority of these residents obtain water from the City of Bellingham although there are a number of others that also obtain water from the lake or watershed including:
Where does your drinking water come from?
Water flows to Lake Whatcom from two main sources:
  • Rainwater that falls in the Lake Whatcom Watershed and ends up in the lake

  • Water from the Deming Glacier on Mt. Baker that flows to the Middle Fork of the Nooksack River and is seasonally diverted into Lake Whatcom through a tunnel under Bowman Mountain.
How does your drinking water get from the Lake to your tap?
The drinking water for the City of Bellingham and the Lake Whatcom Water and Sewer District is supplied via two major intake structures in the lake.
The City of Bellingham treatment plant serves residents of Bellingham as well as five neighboring water districts and one tribal nation.
The City of Bellingham withdraws water from Basin 2 through a 1,200-foot wooden pipeline that leads to the screenhouse at Whatcom Falls Park. The treatment plant in Whatcom Falls Park is capable of producing 24 million gallons of drinking water per day.
The Lake Whatcom Water and Sewer District withdraws water out of Basin 3 to serve residents of Sudden Valley, Geneva, and portions of North Shore and South Bay.
The Water District's treatment process is similar to that of the City of Bellingham, but uses four multi-media filters and reaches a maximum output of 50,100 gallons per day.
What happens to your wastewater?
Sewers were first installed throughout the developed areas of Bellingham in 1892. These original sewers collected both sewage and rainwater and discharged them into Whatcom Creek and Bellingham Bay. 
Most of these early sewers are still in use. The ones carrying sewage are now separate from those carrying stormwater and send their flows directly to the wastewater treatment plant. The City first provided primary wastewater treatment in 1947, discharging effluent into a shallow party of Bellingham Bay, from a treatment plant located near the mouth of Whatcom Creek.
In 1974, Bellingham replaced the Whatcom Creek treatment plant with the Post Point Wastewater Treatment Plant at the foot of Harris Avenue. The Post Point Wastewater Treatment Plant provided primary treatment for up to a peak flow of 55 million gallons per day for the area's sewered population.
In 1993, Post Point was upgraded to include secondary treatment at a cost of $55 million. This upgrade to secondary treatment increased contamination removal to 95 percent before releasing wastewater into Bellingham Bay.

In 2014, additional plant improvements were completed to increase secondary treatment processes, upgrade to more efficient equipment, and to increase wastewater treatment capacity at the Post Point Plant.

Water Treatment Process
Wastewater Treatment Process
Source Water and Treatment Trends Report 2005