Clark Fork River Figures
Clark Fork River Figures summers of 1999 and 2000
Bitterroot River Figures May to September, 2000
Clark Fork Non-Point Source
Nutrient Sampling
Report for Summers of 1999
and 2000
Submitted by,
John Lhotak and Vicki
Watson
University of Montana,
Environmental Studies
Submitted to,
Peter Nielsen
Missoula County Water
Quality District
Funding for this study
provided by,
Smurfit/Stone Container
thru the Missoula County Water Quality District
Clark Fork River Figures summers of
1999 and 2000
Bitterroot River Figures May to
September, 2000
The Voluntary Nutrient Reduction Program (VNRP) for the Clark Fork River has
set a target of reducing non-point source nutrient inputs by 20%. In-stream target levels are 20 ppb for total
phosphorus and 300 ppb for total nitrogen.
In order to assess whether this was being worked towards and to identify
areas of concern, long-term monitoring was of nutrient input to the Clark Fork
River and tributaries of concern was proposed in the spring of 1998. Monitoring began in the fall of 1998, and
has continued to the present. In 2000,
some sites on the Bitterroot River were added.
TWQC’s contractor Land and Water Consulting is monitoring the mainstem and
major tributaries. WQD’s intern is
monitoring some smaller tributaries in the upper river that look to be
significant sources and/or have proposed conservation projects where nutrient
reduction may be realized. The sampling
dates were chosen by WQD’s intern to coincide with Land and Water Consulting's
mainstem water chemistry sampling in an effort to compare nutrient loadings
from tributaries and mainstem levels.
Nutrient sampling from tributaries of the Clark Fork River is intended
to assess nutrient levels and loads.
WQD’s upper river sampling sites were chosen considering various historical
assessments and include: streams identified in Ingman's Section 525 Report
(1992), streams impaired for nutrients on the 303d list for TMDL development, and
sites identified by UM studies. In addition to sampling near the mouth of the
tributaries, several sites were visited to identify specific areas in the
watershed of concern. Lost Creek was sampled to assess subdivision development
west of the Galen Road and ranching impacts to the lower reach. Outflow from a
wetland within the new riverside park in Deer Lodge was sampled to measure its
load. Historically, this site, identified by a UM graduate student, caused a
sharp increase in N levels in the mainstem, thought to be a result of
hydrological modification of the wetland. Gold Creek and its tributaries were
also sampled to determine phosphorus levels and loads and to determine whether
irrigation practices continue to increase P loads as found by Carey 1991.
In the field, two
grab samples were taken at each site by wading into the stream and dipping a
250 mg bottle into the water. The
bottle was lowered to the streambed so that water collected was a mixture of
different levels of the stream. 1+1 sulfuric
acid was added to one sample as a preservative. The other sample was run through a .45mm filter.
All samples were then placed in a cooler containing dry ice. In addition, rough estimates of stream
discharge were made where USGS stream gauges were not present, in order to
estimate daily nutrient loading.
The Montana
Department of Public Health and Human Services, Environmental Lab in Helena
performed all sample analyses. Sampling
methods and laboratory analysis conform to DEQ’s QAQC specifications. Filtered samples were analyzed for soluble
for soluble reactive phosphorus and preserved samples were analyzed for total
phosphorus, Kjeldahl N, and nitrite and nitrate.
Summary of the results for the summers of 1999 and 2000 are presented in the
attached figures. Figures
1 to 4 show total nitrogen loads and total phosphorus loads with Clark Fork
tributaries and the mainstem. To show
how tributary loads contribute to the mainstem’s loads, tributary loads are
“stacked” on top of the main stem sampling site located upstream of the
tributary. Figures
5 to 10 show the mean concentrations of nutrient levels in Clark Fork
tributaries and the main stem of the Clark Fork. Figures 5 to 10 combine data taken in the
summers of 1999 and 2000. Figures 11 to 16 show the mean concentration of nutrient
levels in the Bitterroot River for the summer of 2000. Figures 5 to 16 have a dashed line
indicating the VNRP target levels, 20 ppb TP and 300 ppb TN. All the figures show sample sites running
from upstream to downstream with upstream at the figure’s left.
These figures show a
good correlation between tributary loads and loads in the main stem. When the tributary loads are stacked on top
of the main stem site upstream of it, this combined level correlates closely
with the load of the next main stem site.
The City of Deer Lodge
started to land apply its wastewater in the fall of 1999. Figures 3 and 4 show an increase in loading between sampling sites at
Deer Lodge and the Little Blackfoot River.
The rise in nutrient loading correlates with the load input from the
Deer Lodge effluent. In the year 2000
there is no rise in loading between Deer Lodge and the Little Blackfoot
River. The nitrogen loading even drops
between these to sites. Deer Lodge’s
effluent loading was estimated from sampling done in 1989, 1990, and 1991.
Nutrient levels in
most sites of the sampled tributaries are below or at the target level for
Total Nitrogen (300 ppb) and Nitrate/Nitrite (30 ppb) concentrations. Sites exceeding targets include Racetrack
Creek, Dempsey Creek and Arrow Stone Park.
Arrow Stone Park is sampled at the outflow of a wetland site and is
significantly above the target levels.
All sites are at or above total nitrogen concentrations. The only tributary site just below VNRP
target levels is the Little Blackfoot River.
However, even though the Little Blackfoot River’s concentrations are
low, it still contributes a significant load to the Clark Fork River. Other tributaries contributing a significant
load of TN include Gold Creek, Lost Creek and Flint Creek.
The only tributaries
below the VNRP target levels for soluble reactive phosphorus (6 ppb) and total
phosphorus (20 ppb) include Lost Creek, Racetrack Creek and Arrow Stone
Park. However, Lost Creek provides a
significant load to the Clark Fork River.
Gold Creek, Flint Creek and the Little Blackfoot River show high
concentrations of total phosphorus and also contribute significant loads to the
Clark Fork River.
All sites sampled
along the Bitterroot River were below the VNRP target level for total nitrogen
(300 ppb). However, of the seven sites
sampled, five sites were above the VNRP target levels for phosphorus. These sites include Hamilton Bridge,
Florence Bridge, below the Lolo waste treatment plant, Miller Creek and
Buckhouse Bridge. Miller Creek dried up
early in the summer and was only sampled once.
Currently it is hard
to estimate loading for the Bitterroot River because there are only active USGS
gauging stations at Buckhouse Bridge and Darby. However, the average load for the Bitterroot River at Buckhouse
Bridge was 1129 kg/day for total nitrogen and 55 kg/day for total
phosphorus. Since it was a low flow year,
a rough estimate of Lolo Creek’s discharge could be measured in July, August
and September. The average loads for
these months in Lolo Creek were 7.6 kg/day for total nitrogen and .2 kg/day for
total phosphorus. This represents .7%
and .4% of the Bitterroot’s TN and TP load respectively.
Based on the results
we conclude that the most significant non-point source nutrient loads in the
Upper Clark Fork River come from the Little Blackfoot River, Flint Creek, Lost
Creek and Gold Creek. Since Land and
Water Consulting are already monitoring the Little Blackfoot and Flint Creek,
we propose monthly sampling only on Lost Creek and Gold Creek during spring
high flow we will attempt some synoptic sampling on these tributaries and on
Dempsey Creek and Cottonwood Creek which have NRCS conservation projects
underway. We will also continue
sampling the Bitterroot River sites sampled last year.
Carey, Jennifer. 1991. Phosphorus Sources in Gold Creek, a tributary of the Clark Fork River in Western Montana. Masters Thesis, U. of Montana Dept. of Environmental Studies.
Ingman, G.L. 1992b. Assessment of phosphorus and nitrogen sources in the Clark Fork River Basin. State of Montana, Department of Health and Environmental Sciences. Section 525 of 1987 Clean Water Act Amendments.