Table Of Content574.52632
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
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Prepared by:
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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
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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
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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
.
