ScholarWorks at University of Montana

Water quality in the Flathead Lake drainage is of great concern. The potential of wetlands to reduce pollution has been established for certain aquatic pollution parameters, especially nitrates and phosphates. This study investigated the levels of nutrients that entered a storm drainage ditch approximately 100 meters long that empties into Ashley Creek. The source of water was a storm sewer that services most of east Kalispell, Montana. Nitrate and phosphate levels were determined at both ends of the ditch to see if nutrient levels were reduced as runoff passed through the vegetation in the ditch. Phosphates were reduced 54% while nitrates were reduced 90%. While I hypothesize Ceratophyllum demersum was responsible for most of the nutrient trapping, lab studies found Hippuris vulgaris to be the most efficient nutrient trapper of the native plants tested. Planting additional vegetation or meandering the ditch may be a viable option to increase the pollution filtering process.

If you ask Montanans which five Montana lakes are the most important or valuable, invariably Flathead Lake is in the top three picks. The lake's size, beauty, recreation benefits, and excellent water quality increase local real estate values and make it a popular destination. However, few Montanans know that Flathead Lake currently does not meet State water quality standards (ARM 17.30.637 (1)(e)General Prohibitions), and is undergoing the eutrophication process at an accelerated rate. Excess nutrients (phosphorus and nitrogen) stimulate algal blooms and serious oxygen depletion of the deep waters. Extensive lake and stream water quality monitoring document that nonpoint source pollution is degrading water quality, interfering with beneficial uses, and causing violation of water quality standards. As a result, Flathead Lake is included on the Clean Water Act’s Section 303(d) list of water-quality-impaired waterbodies, and is a high priority for developing a water quality restoration plan (called a Total Maximum Daily Load or TMDL). Such a plan is close to completion.

Probable sources of water quality impairment include atmospheric deposition, domestic wastewater lagoons, flow regulation/modification, municipal point sources, on-site wastewater treatment systems (septic tanks), urban sprawl, overland runoff, agriculture, silvaculture, and an upstream impoundment. Only 2 percent of the nutrient load in Flathead Lake is estimated to come from point sources. The vast majority of nutrients come from natural sources or human-caused nonpoint source pollution. To address nonpoint source pollution, the Flathead Basin Commission (FBC) developed the Voluntary Nutrient Reduction Strategy (VNRS), and linked it to the TMDL process. The goal of the VNRS is to achieve the 1978 lake primary productivity level of 80 grams carbon/m²/year. This level is expected to yield water quality that meets water quality standards and supports beneficial uses (including swimming and aquatic life support). To meet the target primary productivity, the FBC determined that nitrogen (including nitrate plus nitrite) and phosphorus loading must be reduced by 15 percent basin wide. Six principal components for successful implementation of the ongoing VNRS/TMDL program include:

(1) coordination and planning, (2) grant funding & contributions (3) partnerships and public outreach, (4) participation of watershed groups, (5) identification of opportunities, and (6) monitoring. History, implementation and achievements of the Flathead Basin VNRS/TMDL are described in this paper.

A variety of metrics were examined to find if there is consistency among them.

A selective withdrawal system was added to Hungry Horse Dam in 1994 to help downstream fish populations. To evaluate the effects of that system on perlid stoneflies of the South Fork, I replicated a study of the South Fork, Middle Fork, and Main Stem of the Flathead done before the installation of the system. I sampled in July, August, and October 1999 and in early and late March 2000. The system appeared to warm the South Fork waters significantly in late summer months by as much as 5oC. The temperature of the South Fork in 1999 was warmer than the temperatures of the Middle Fork and Main Stem. The numbers of Hesoperoperla pacifica and Claasenia sabulosa appeared to be lower than 1994 in all streams. No Perlidae were identified on the South Fork in August of 1999.

Although research suggests that Little Bitterroot Lake has some of the best water quality in the Flathead Valley, its quality is deteriorating due to increased development. This study analyzed aquatic macroinvertebrate communities to evaluate the impact of land use on lake condition. I hypothesized that macroinvertebrates more tolerant to pollution would be found in the more developed East Bay compared to the less developed South Bay.

On November 13, 1999, I sampled both sites for macroinvertebrates and water quality – including: temperature, dissolved oxygen, pH, nitrates, phosphates, alkalinity, turbidity, and E. coli (a bacteria associated with sewage). Macroinvertebrates were collected on artificial substrates. I found that mayflies and tubiflex worms were absent from the South Site, while amphipods were uncommon at the East Site. Of the water quality parameters, only alkalinity was found to be significantly different at the two sites.

This study gathered baseline data and compared water quality at two sites on Little Bitterroot Lake in northwestern Montana. Artificial substrates were placed on two bays of the lake and were sampled from September 12, 1999, until November 26, 1999. I determined the biomass of periphyton diatoms collected every few weeks as well as the relative number of Cymbella diatoms in that biomass. More Cymbella were collected from East Bay where more year-round homes are located. Water quality tests (including temperature, alkalinity, dissolved oxygen, phosphates, nitrates, E. coli, and turbidity) revealed a low level of phosphates and nitrates (nutrients). Sampling will continue this spring to determine seasonal variations in periphyton and water quality parameters.