Main Stem Weares Catchment Area

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stream is sampled, and from which all rain and sediment are channeled into the stream down to the point where water is withdrawn for turbidity and suspended sediment analysis.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.

Location of staff plate at MS Weares monitoring site. Photo by P. Trichilo.
Location of staff plate at MS Weares monitoring site.
(Photo by P. Trichilo)
MS Weares at high water after a major winter storm event. Note the high turbidity. Photo by K. Bromley.
MS Weares at high water after a major winter storm event. Note the high turbidity. (Photo by K. Bromley)

MS Weares after a moderate spring storm event. Photo by K. Bromley.
MS Weares after a moderate spring storm event.
(Photo by K. Bromley)

Site of one of the temperature data loggers placed in the stream at MS Weares during the summer of 2008. Photo by P. Trichilo.
Site of one of the temperature data loggers placed in the stream at MS Weares during the summer of 2008.
(Photo by P. Trichilo)

Friends of the Van Duzen River
PO Box 315
Carlotta, CA 95528