Assessment of phosphorus and nitrogen sources in the Clark Fork River Basin, 1988-1991 : final report PDF
Preview Assessment of phosphorus and nitrogen sources in the Clark Fork River Basin, 1988-1991 : final report
574.52632 W3APNS 1992 ASSESSMENT OF PHOSPHORUS AND NITROGEN SOURCES IN THE CLARK FORK RIVER BASIN 1988-1991 FINAL REPORT SECTION 525 OF THE 1987 CLEAN WATER ACT AMENDMENTS mw vmmmn collection Prepared by: JUN 1 8 g92 t MONTANA STATE LIBRARY Gary L. Ingman 1515 E- 6th AVE. HELENA, MONTANA 59620 State of Montana Department of Health and Environmental Sciences Water Quality Bureau Cogswell Building Helena, Montana 59620 January 1992 ,1\ . x"• 5"*" j a ' "t i : * MONTANASTATELIBRARY S574.52632W3apsn1992c.1Ingman Assessmentofphosphorusandnitrogenso m*» 3 0864 00077779 1 TABLE OF CONTENTS SUMMARY ii 1.0 INTRODUCTION 1 2.0 MONITORING OBJECTIVES 2 3.0 MONITORING APPROACH AND METHODS 2 4.0 RESULTS 9 4 Nutrient Concentrations 9 . 4.1.1 Clark Fork River 9 4.1.2 Tributaries 11 4.1.3 Wastewater Discharges 13 4.2 Nutrient Loads 23 4.2.1 Clark Fork River 23 4.2.2 Tributaries 24 4.2.3 Wastewater Discharges 25 4.2.4 Nutrient Loading during Summer 25 5.0 CONCLUSIONS 35 6.0 MANAGEMENT STRATEGY 43 7.0 REFERENCES 44 8.0 ACKNOWLEDGEMENTS 47 APPENDICES Digitized by the Internet Archive 2013 in http://archive.org/details/assessmentofphos1992ingm SUMMARY From 1988 to 1991, the Montana Department of Health and Environmental Sciences conducted an intensive monitoring program to identify and rank the major point and nonpoint sources of phosphorus and nitrogen that were responsible for nutrient-caused use impairment in the Clark Fork River. The monitoring network included 19 stations on the Clark Fork River, 34 stations on tributary streams and 10 municipal or industrial wastewater discharges. Samples were collected from 14 to 45 times at each location and analyzed for total and soluble forms of phosphorus and nitrogen. Nutrient concentrations were compared to criteria for the control of nuisance algae. Nutrient loads were used to evaluate the relative importance of each tributary and effluent source. The Clark Fork and many of the wastewater discharges showed progressive declines in nutrient concentrations over the three years. Causes were higher streamflows and reductions in wastewater nutrient loading resulting from phosphorus detergent bans and nutrient control measures at the Stone Container Corporation kraft mill. There was evidence that phosphorus detergent bans had broader than expected effects, possibly by decreasing the availability of high phosphorus detergents in communities without bans. Despite the marked improvements, two reaches of the Clark Fork, Silver Bow Creek, and nearly half the other tributaries continued to show nutrient concentrations in excess of recommended levels. The Missoula, Deer Lodge, and Butte wastewater treatment plant discharges were the sources most responsible for high nutrient concentrations in the Clark Fork River. Inflows from tributaries with low nutrient concentrations were important in diluting nutrient concentrations in the river. When averaged over the year, soluble phosphorus loading from tributaries was about equal to that contributed by effluents. About three-fourths of the soluble nitrogen loading came from tributaries. During the summer low streamflow period when nutrient-related use impairment was most prevalent, wastewaters contributed the majority of the nutrient loading to the river. Tributary sources of soluble nutrient loading were dominated by the Flathead, Bitterroot and Blackfoot rivers. Mission and Crow creeks, Coleman Coulee, and the Little Bitterroot River contributed a large share of the soluble nutrient loading in the lower Flathead River. Discharges of contaminated groundwater from the Missoula area were responsible for a significant portion of the soluble nitrogen loading in the lower Bitterroot River, especially during base flow periods. Flint, Rock and Gold creek, and the Little Blackfoot and Thompson rivers were important sources of soluble phosphorus. The Bull River and Fish Creek were significant sources ii of soluble nitrogen. The Missoula, Butte, and Deer Lodge municipal wastewater discharges and the Stone Container Corporation kraft mill were responsible for most of the soluble nutrient loading from effluents. These findings established direction for the development of a basin-wide nutrient management plan. 111 1 INTRODUCTION . The Section 525 amendments to the 1987 federal Clean Water Act authorized a three-year comprehensive assessment of water quality in the Clark Fork/Pend Oreille Basin. Under the guidance of EPA Regions VIII and X, the states of Montana, Idaho and Washington were each directed to conduct water quality evaluations in portions of the basin within their states. An interstate steering committee was established to coordinate the project. Funding was appropriated with assistance from the Clark Fork Coalition and the project was formally initiated in July 1988. Prompted by a growing concern over nutrient (phosphorus and nitrogen) pollution in the basin and limitations in the available data, Montana developed a plan to identify, monitor and rank the major point and nonpoint sources of nutrients to the Clark Fork River in Montana. The Montana portion of the Clark Fork/Pend Oreille basin encompasses approximately 22,000 square miles, or about 85 percent of the total watershed. Consequently, activities which influence the water quality of the river in Montana have a major effect on the Idaho and Washington portions of the drainage. The upper and middle reaches of the Clark Fork are some of the most productive stream waters in Montana west of the Continental Divide from the standpoint of nutrient concentrations and the potential to grow algae (Bahls et al., 1979a, 1979b). Elevated concentrations of phosphorus and nitrogen promote the growth of nuisance levels of attached algae which adversely affects the use of well over 100 miles of the river (MDHES, 1990) Dense mats of . filamentous algae in the Clark Fork above Missoula and heavy growths of diatom algae below Missoula reduce dissolved oxygen levels below state water quality standards and impede irrigation and recreation (MDHES, 1988a; Johnson and Schmidt, 1988; Ingman and Kerr, 1989a) Seasonally, as the algae senesce and decay, water . clarity and visual appeal of the river is reduced. The decaying organic matter has also been implicated in the production of river foam which is an aesthetic nuisance of considerable magnitude. In the lower Clark Fork, concerns have focused on nutrient loading to Idaho's Lake Pend Oreille, which has experienced increased weed and algal growth in recent years (Watson, 1985; MDHES, 1985; Johnson and Schmidt, 1988; IDOHW, 1989; Frenzel, 1991) The Clark Fork supplies the lake with 90 percent of its . water and nearly 75 percent of its incoming nutrients. When the river leaves Lake Pend Oreille it is called the Pend Oreille River. In the state of Washington, the river is plagued with dense growths of rooted aquatic plants. Washington's interest has been in determining factors which promote the growth of the vegetation and developing weed control measures (Pelletier and Coots, 1990; Coots and Carey, 1991). The Section 525 study emphasizes the nutrient problem in the Clark Fork/Pend Oreille Basic because it is the primary interstate issue. Additionally, it was recognized that the 525 study would provide the resources to assess the nutrient problem on a basin- wide scale. This final report summarizes the results of Montana's three- year nutrient source assessment project and sets the stage for a forthcoming basin-wide nutrient management plan which will address nutrient and eutrophication problems in the three-state area. 2.0 MONITORING OBJECTIVES The objectives of Montana's Clark Fork Basin nutrient source assessment were to: • Document nutrient concentrations and loads in the Clark Fork from its headwaters to Idaho. • Document nutrient contributions from tributaries and wastewater discharges. • Identify the most important sources of nutrients. • Identify controllable sources of nutrients. • Develop management alternatives which address the nutrient- caused use impairment in the Clark Fork Basin. 3.0 MONITORING APPROACH AND METHODS Water quality data were collected 15 time annually (monthly from July through March and twice monthly from April through June) , between July 1988 and June 1991. The monitoring network included 19 stations on the Clark Fork River, 34 stations on tributary streams, and ten municipal and industrial wastewater discharges (Table 1 and Figure 1) . Some stations were discontinued after the first year of monitoring, while new stations were added in the second and third years. This approach was necessary as preliminary data allowed us to key in on the most important nutrients sources, while at the same time maximizing limited resources. Forty-two of the 63 stations were monitored in all three of the years. The tributaries monitored accounted for 86 percent of the Clark Fork drainage area upstream from the Idaho border (Figure 2) . The remaining 14 percent of the watershed was indirectly monitored through the evaluation of data for mainstem Clark Fork stations. Thus, the vast majority of nonpoint source nutrient loading from tributary watersheds was inventoried. The ten wastewater discharges represented the majority of those in the basin. Four municipal discharges were not monitored (Towns of Philipsburg, Lolo, Stevensville, Hamilton) However, all of the four discharged .
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