Monitoring the Casting Pond

The Mission Bay Preserve HOA is concerned about the water quality in the Casting Pond. The 3-acre pond is fed by the Flathead Irrigation System. The pond is about 300 yards from Flathead Lake, and any overflow is discharged through a natural riparian area into Flathead Lake. The concern was increased by a sudden algae event in September 2023

Historical land use was and remains an agricultural area with small grains and hay fields surrounding the pond. In approximately 2006, a subdivision of large lots was established. All lots are on city water and sewer. Potential pollution sources can be recycled irrigation water, field runoff, and residential fertilizers from numerous residential yards that the ditch meanders through. 

As there is no baseline water quality data on the water being discharged from the Casting Pond to Flathead Lake, Mission Bay Preserve HOA are attempting to establish the basis and monitor seasonal changes. It is their goal to create baseline data, monitor changes in the pond water, and create a plan to improve the quality of the water to minimize negative impacts on water quality entering Flathead Lake. Monitoring objectives are to evaluate current nutrient conditions in Casting Pond and establish a baseline for future comparisons. Nutrient samples of total nitrogen, total phosphorus, soluble reactive phosphorus, ammonia, and nitrate-nitrite will be collected at three sites near the Casting Pond.

Samples will be taken at three points in the surrounding area of the Casting Pond. The first sampling site is the Flathead Irrigation Ditch leading to Casting Pond. The second site is the Casting Pond itself, at the outlet. The third sampling point is the Cattails or backwater area of the Casting Pond before entering Flathead Lake, the marsh area downstream of the pond. Agriculture, followed by residential subdivisions, is the primary land use in the watershed area of the Casting Pond. The Casting Pond is also affected by runoff from residential inputs from housing and yards along the ditch supplying the Pond.   

 MMW helps citizen-led groups provide the critical data needed to make sound decisions and better sustain our freshwater resources and protect our native fish populations and angling industries for years to come.  Learn how you can help MMW provide critical support to citizen-led watershed groups throughout the state  .