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Driving east on Highway 36, Main Stem (MS) Weares
is located in the middle of the Lower Basin between Fox Creek
and Flanigan Creek monitoring sites but is actually very close
to Flanigan Creek. MS Weares is located on the main stem Van Duzen
River, where samples were taken for turbidity and suspended sediment.
The site is situated 40° 30.519' North and 123° 59.580'
West, and above the site, but within the project boundary, is
a large catchment area with approximately 142 miles of stream
network. Elevations in this basin range from 160 feet at the base
to over 3,450 feet in the upper reaches, and the monitoring site
is approximately 160 feet in elevation. Other than a few areas
designated as part of Grizzly Creek State Park, the watershed
is in private ownership with about half of the timber holdings
(in the lower part of the watershed) and timber harvests operated
by Humboldt Redwood Company (HWC), formerly owned by PALCO. In
the upper half of the watershed timber harvests are conducted
by various private operators considerably smaller than HWC. Vegetation
is predominantly mixed and evergreen Redwood forest in the lower,
western part of the sub basin, giving way to fir and pine forest
in the upper eastern part (see map of MS Weares Catchment Area).
The catchment area of a monitoring site is important when considering
upslope factors that affect water quality in the stream. This
area represents the true watershed that lies above the point where
water from the stream is sampled, and from which all rain and
sediment are channeled into the stream down to the point where
water is withdrawn for turbidity and suspended sediment analysis.
Stream discharge is directly proportional to the
size of the catchment area - the greater the area, the more water
is carried by the stream during storm events. Within the boundary
of the project MS Weares is the second largest of the 11 catchment
areas, and above this point in the river, the catchment area drains
approximately 167.4 square kilometers which is equivalent to 64.6
square miles. During the first year of sampling (HY07) volunteers
recorded a maximum discharge of 8,420 cubic feet per second (CFS)
and an average discharge of 1,394 CFS, a maximum turbidity of
1,576 Nephlometric Units (NTU) and an average turbidity of 99
NTU. In HY08, there was a maximum discharge of 24,662 CFS and
an average discharge of 2,495 CFS, a maximum turbidity of 3,888
NTU and an average turbidity of 261 NTU over the winter sampling
season. Over the two seasons combined (HY07-HY08), the maximum
discharge was in HY08 at 24,662 CFS with an average of 1,844 CFS,
maximum turbidity was also in HY08 at 3,888 NTU with an average
of 167 NTU. This translates to an average of 814 tons of suspended
sediment per square mile per year.
The main stem Van Duzen River runs year round
through most of the lower basin, and is therefore referred to
as a perennial stream (as opposed to an ephemeral stream, which
runs dry in the summer). However, in recent years, the stream
has begun to go dry, or goes underground in the alluvial plain
before it reaches the Eel River. These conditions are directly
due to the vast deposits of course sediment (sand, gravel, and
cobble) that have been deposited and continue to be deposited
in the river over time. Maximum weekly average temperature (MWAT)
in the summer of 2007 at MS Weares was 22.55 C, and in 2008 it
was 20.71 C. Over the sampling period, temperatures were extremely
high compared to all of the other streams sampled within the lower
basin project area, and even higher than Yager Creek, which was
the warmest of all tributaries sampled within the lower basin.
MS Weares catchment area has a road density of about 6.8 miles
of roads per square mile of watershed. As with all of the catchment
areas within the lower basin, this density of road networks receives
a rating of extremely high. In the 17-year period from 1991 through
2007, the proportion of the area harvested for timber equaled
48.5%, with clear cutting accounting for 9.9% of the total watershed
area. Similar to Yager Creek, a large portion of the MS Weares
catchment area (in the eastern higher elevations) is non-forest
grassland and grazing land, which therefore makes it difficult
to quantify the impact of timber harvest in the coniferous forests
of the region, which are primarily Redwood in the lower reaches
and Fir in the upper reaches of the watershed.
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