Abstract

Under Section 525 of the 1987 amendments to the federal Clean Water Act, Montana initiated an intensive monitoring program to identify and rank the major point and nonpoint sources of nutrients to the Clark Fork River. A 51 station monitoring network was established, including 19 stations on the Clark Fork River, 22 stations on tributary streams, and 10 municipal and industrial wastewater discharges to the river. In the first year of monitoring, samples were collected 15 times and analyzed for total and soluble forms of phosphorus and nitrogen.

Several small tributaries to the upper Clark Fork (Gold, Flint, Lost, Racetrack, and Dempsey creeks and the Mill-Willow Bypass) and all 10 wastewater discharges exhibited elevated nutrient concentrations. The Missoula, Butte, and Deer Lodge municipal wastewater discharges were responsible for the largest nutrient concentrations in the Clark Fork. Inflows from good quality tributaries such as Rock Creek and the Blackfoot, Little Blackfoot, Bitterroot, and Flathead rivers were important in diluting nutrient concentrations in the Clark Fork.

Overall, soluble phosphorus loading to the Clark Fork originated about equally from tributary inflows and wastewater discharges. About two-thirds of the soluble nitrogen loading came from tributaries, with effluents contributing the remaining third. During the summer low flow period, an even greater share of the soluble nutrient loading came from effluents.

Tributary sources of soluble nutrient loading were dominated by the Flathead, Bitterroot, and Blackfoot rivers. Gold and Flint creeks ranked fourth in importance as tributary sources of soluble phosphorus and nitrogen, respectively.

The Missoula, Butte, and Deer Lodge municipal wastewater treatment plants and the Stone Container Corporation kraft mill discharged most of the soluble nutrient loading from effluents. However, the Warm Springs treatment ponds on Silver Bow Creek removed most of the Butte nutrient load prior to reaching the Clark Fork River.

Start Date

20-4-1990 9:40 AM

End Date

20-4-1990 10:00 AM

Document Type

Presentation

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Apr 20th, 9:40 AM Apr 20th, 10:00 AM

Nutrient Sources in the Clark Fork River Basin

Under Section 525 of the 1987 amendments to the federal Clean Water Act, Montana initiated an intensive monitoring program to identify and rank the major point and nonpoint sources of nutrients to the Clark Fork River. A 51 station monitoring network was established, including 19 stations on the Clark Fork River, 22 stations on tributary streams, and 10 municipal and industrial wastewater discharges to the river. In the first year of monitoring, samples were collected 15 times and analyzed for total and soluble forms of phosphorus and nitrogen.

Several small tributaries to the upper Clark Fork (Gold, Flint, Lost, Racetrack, and Dempsey creeks and the Mill-Willow Bypass) and all 10 wastewater discharges exhibited elevated nutrient concentrations. The Missoula, Butte, and Deer Lodge municipal wastewater discharges were responsible for the largest nutrient concentrations in the Clark Fork. Inflows from good quality tributaries such as Rock Creek and the Blackfoot, Little Blackfoot, Bitterroot, and Flathead rivers were important in diluting nutrient concentrations in the Clark Fork.

Overall, soluble phosphorus loading to the Clark Fork originated about equally from tributary inflows and wastewater discharges. About two-thirds of the soluble nitrogen loading came from tributaries, with effluents contributing the remaining third. During the summer low flow period, an even greater share of the soluble nutrient loading came from effluents.

Tributary sources of soluble nutrient loading were dominated by the Flathead, Bitterroot, and Blackfoot rivers. Gold and Flint creeks ranked fourth in importance as tributary sources of soluble phosphorus and nitrogen, respectively.

The Missoula, Butte, and Deer Lodge municipal wastewater treatment plants and the Stone Container Corporation kraft mill discharged most of the soluble nutrient loading from effluents. However, the Warm Springs treatment ponds on Silver Bow Creek removed most of the Butte nutrient load prior to reaching the Clark Fork River.