Consultants say Weiser Lake has extreme summer phosphorus, propose short‑ and long‑term fixes

Whatcom County Health and Community Services staff and outside consultants presented a draft lake management plan for Weiser Lake at a virtual public meeting, saying monitoring shows summer phosphorus concentrations far above recommended levels and offering a mix of short‑term and long‑term options.

The consultants said the lake’s West Basin recorded phosphorus concentrations “over 300 micrograms a liter” and the East Basin over 200 micrograms a liter, compared with a typical target of about 20 micrograms per liter to limit nuisance algal growth (Mark Rosenkrantz, Aquatic Insight). The presentation tied those elevated summer phosphorus levels primarily to internal loading—phosphorus released from lake sediments under low‑oxygen conditions—plus continuing inputs from upstream watershed flows, septic systems and seasonal waterfowl movements.

Why it matters: summer cyanobacteria blooms at Weiser Lake have caused very low water clarity and concentrated mats at popular access points, affecting recreation and shoreline use. The plan’s combined monitoring and modeling approach suggests some interventions could reduce blooms quickly, while others—septic upgrades and agricultural best management—would be longer term.

Key findings and evidence

- Monitoring and lab work: County staff and contractors collected seasonal water‑quality samples, sediment cores and biological samples. Consultants used those data in simple lake models (Vollenweider and Nurnberg approaches) and a nutrient budget to estimate sources and likely drivers of blooms.

- Extreme summer phosphorus and internal loading: “We have a phosphorus concentration over 300 micrograms a liter in our West Basin and over 200 micrograms a liter in the East Basin,” said Mark Rosenkrantz, who led the data review.…