Stopped by Mirror lake while on journey elsewhere. Mirror Lake is where water diverted from Middle Fork Nooksack River is discharged before it flows via Anderson Creek to Lake Whatcom, the drinking water source for Bellingham. The lake was in fully muddy mode from the diverted water that is derived from glacial melt water.
Mirror Lake turbidity
Aerial view of diversion and pipe (blue line) (USGS)
The City of Bellingham diverts water with a diversion dam on the Middle Fork Nooksack River. The Middle Fork headwaters flow out of the Deming Glacier on the southwest flank of Mount Baker - a 10,000-foot strato volcano covered with glaciers. During the mid summer to fall the Middle Fork becomes cloudy as the glacial meltwater becomes the dominant source of flow. The diversion is only used part of the time to augment the lake levels in Lake Whatcom, a natural lake and the city's drinking water source. The city also supplies water to non city residences.
Lower Demming Glacier. Blue line marks terminus of the glacial in 1993.
All that silt and mud in Mirror Lake is a source of phosphorus, a natural occurring problem for Lake Whatcom water quality. Phosphorus can lead to algae growth and results in low oxygen levels in shallow part of the lake. The low oxygen levels also cause phosphorus in the lake bottom sediments to be released making the problem worse. Algae utilize the phosphorus and also utilize available nitrates to the point that algae that can directly utilize nitrogen from the water start to become dominant leading to possible toxic blooms. The phosphorus loads to the lake have caused the lake to become degraded, particularly at its northern end.
As such the City of Bellingham and Whatcom County have been required to lower the amount phosphorus entering the lake by Washington State Department of Ecology under the Clean Water Act. The reductions are spelled out in a TMDL (total maximum daily load) (All and more HERE). But the requirements do not apply the the diversion as it is exempted. The requirements have also not been applied to the Washington State Department of Natural Resources or other forest property managers. Ecology decided to treat commercial forest land as natural background despite ample scientific evidence that forest roads are a major source of sediment discharge.
Hence, two major sources of phosphorus inputs to the lake - the diversion of water full of grounded up volcanic andesite and logging roads are included in the calculation of phosphorus inputs to the lake, but are excluded from being required to be reduced.
When Whatcom County took over management of the 8,000 plus acres of Lake Whatcom Forest Board Lands from the DNR, the County was given no credit in phosphorus reduction to the lake despite the fact that reconveyance will prevent 22 miles of new road building in the watershed and will greatly maintain the forest cover relative to DNR management.This issue of no credit points to a weakness of the TMDL process and to a broad challenge of Ecology oversite of water quality related to forest practices. Perhaps a result of competing natural resource issues.
The release of phosphorus via the diversion also presented a perception problem with the rules. For County government facing very stringent rule making and very expensive stormwater fixes to incrementally reduce phosphorus loads while at the same time a major source is allowed does raise some questions and perhaps some resentment.
The above said, the bigger problem for the lake has been at the north, shallow end of the lake where urban levels of development were permitted by the City of Bellingham for decades. Urban development and rural development permitted by the County at the north end of the lake has also contributed to elevated phosphorus discharge to the sensitive north end of the lake. The shallow waters at the north end of the lake are susceptible to algae blooms due to elevated nutrient levels. Fortunately, the discharges of phosphorus at the south end of the lake from the city diversion and off of commercial forest lands is into deep water where low oxygen is not an issue and most of the phosphorus remains unavailable for algae. But it may have been better if Ecology could have somehow managed to separate out this problem.