All of the water temperature monitoring sites on the mainstem Big River had MWATs that varied from moderately to fully unsuitable (67-70 °F) with maximum daily temperatures (73-77 °F) in excess of the lethal limit for salmonids. High diurnal fluctuations were also recorded (7.5-12.8 °F), suggesting poor canopy and/or low flows;
Data from lower Two Log Creek indicated water temperatures were between fully suitable, with a minimum observed MWAT of 58 °F, and undetermined with a maximum observed MWAT of 64 °F. However, large diurnal temperature fluctuations (6.7-12.0°F) were recorded at both lower Two Log Creek sites, which may indicate poor canopy and/or low flows;
The only monitored tributary to Two Log Creek, Beaver Pond Gulch, had fully suitable water temperatures, but based on the thermograph, the monitoring device may have been placed in a thermally stratified pool or a site with a significant groundwater component;
Hatch Gulch had fully suitable water temperatures with minimal diurnal fluctuations. It is likely that Hatch Gulch provides some cooling effect to the mainstem Big River;
It is also probable that Two Log Creek has a cooling effect on the mainstem Big River. However, the magnitude of that effect is unknown as it is dependant on the temperature differentials and flows;
There is no water chemistry data for this subbasin.
Areas of dry channel in Kidwell and Hatch gulches found during CDFG stream surveys may indicate fish passage problems.
McNeil core sediment samples in Two Log Creek indicated excessive amounts of fine material in this stream. This could indicate unsuitable conditions for salmonids;
Canopy cover was suitable for salmonids on all surveyed tributary reaches within this subbasin, but unsuitable on surveyed reaches of the mainstem Big River as expected on a larger order stream.
A high incidence of shallow pools, and a lack of cover and large woody debris have contributed to a simplification of instream salmonid habitat in surveyed reaches of Kidwell Gulch, Two Log Creek, and the mainstem Big River between Tramway Gulch and the North Fork Big River;
Cobble embeddedness values in Hatch Gulch, Saurkraut and Ayn creeks were unsuitable for salmonid spawning success. In addition, the MRC characterized spawning gravels as fair quality on all seven segments they surveyed;
Permeability sampling in the Big River below the North Fork Big River indicated low to moderate amounts of fine material. This could indicate suitable to somewhat unsuitable conditions for salmonids.
Salmonid habitat conditions in this subbasin on surveyed streams are generally rated as medium potential refugia;
Two Log Creek provides the best salmonid refugia in this subbasin;
The mainstem Big River serves as critical contributing area.
Flow and Water Quality Improvement Activities
Protect instream flows in Two Log Creek and Hatch Gulch to help moderate or cool the warmer mainstem Big River in the summer.
Erosion and Sediment Delivery Reduction Activities
Continue efforts such as road improvements, and decommissioning throughout this subbasin to reduce sediment delivery to Big River and its tributaries. CDFG stream surveys indicated Kidwell Gulch, Two Log Creek, and Saurkraut Creek have road sediment inventory and control as a top tier tributary improvement recommendation.
Riparian and Instream Habitat Improvement Activities
Where feasible, add LWD to develop habitat diversity in the mainstem channel and to increase shelter complexity for salmonids. CDFG stream surveys indicated Kidwell Gulch, Two Log Creek, and Big River from Tramway Gulch to North Fork Big River have increase escape cover as a top tier tributary recommendation;
Ensure that this high quality habitat is protected from degradation. The highest stream reach conditions as evaluated by the stream reach EMDS and refugia analysis were found in the mainstem Big River, Two Log Creek, Ayn Creek, Tram way and Hatch gulches.
Education, Research, and Monitoring Activities
Continue water temperature monitoring at current locations where high temperatures have been detected on the mainstem Big River;
In lower Two Log Creek, both MRC and HTC have temperature monitoring sites in nearly the same location. It may be more effective if one company monitored the site and shared the information with the other while the second monitoring device is deployed at another location.