Neil H. Berg

Cool Water Formation and Trout Habitat Use in a Deep Pool in the Sierra Nevada, California

Abstract We documented temperature stratification in a deep bedrock pool in the North Fork of the American River, described the diel movement of rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta, and determined whether these trout used cooler portions of the pool. From July 30 to October 10, 1992, the main study pool and an adjacent pool were stratified (temperature differences between surface and bottom were as great as 4.5°C) on all but two days. Six rainbow and one brown trout equipped with temperature-sensitive radio transmitters used water with temperatures ranging from 12 to 19.3°C. During the late afternoon, when the widest range of water temperature was available, trout were found in temperatures up to 19.3°C even though cooler (14.5°C) water was available. Radio tracking indicated that fish were significantly more active and had significantly larger home ranges at night; fish were least active during the day. Because we found no evidence of subsurface seepage into the pool and water ...

Ion elution and release sequence from deep snowpacks in the central Sierra Nevada, California

Elution of Cl−, SO42−, NO3−, and H+ often occurred in that order at a site in the central Sierra Nevada, California, that receives an annual average of 1000 cm of snowfall which is low in acidic components. During eight winter periods of above-base level snowpack outflow, and one spring melt period, on the average 25% of the ions were discharged at the following percentages of outflow volumes: Cl− at 11%, NO3− at 13%, SO42− at 18%, and H+ at 20%. Seven of eight winter outflows were associated with low ionic strength rainfall onto the snowpack. Mean solute concentrations during the first 25% and first 50% of the total outflow were significantly greater than during the last 75% and last 50% of the total outflow for Cl−, NO3−, and SO42−, but not for H+. Maximum solute concentrations were up to 2.9 times the overall event volume-weighted mean concentrations for Cl−, 3.7 times for NO3−, 3.0 times for SO42−, and 2.9 times for H+.

Ice in Stream Pools in California's Central Sierra Nevada: Spatial and Temporal Variability and Reduction in Trout Habitat Availability

Abstract Ice in streams can be detrimental to fish in many ways, including physical exclusion offish from habitat. Stream pools along an elevational gradient in Californias central Sierra Nevada were monitored during winters 1990–1991 and 1991–1992 for ice thickness, coverage by ice, and below-ice water depth. Both ice thickness and duration in pools increased with site elevation. Because minimum water depths were below a 6-cm criterion for adult trout movement for only a l0-d period in only 1 of 30 pools monitored over the two winters, 1 concluded that physical exclusion offish from habitat by ice was not a problem. Validated methods to predict the presence and thickness of ice in mountain streams are needed. Ice presence along the elevational gradient and ice thickness at the one pool evaluated were predicted moderately well from air temperature, There is a need for refined models that incorporate the effects of snow cover and stream velocity on ice formation.

Rain-induced outflow from deep snowpacks in the central Sierra Nevada, California

Abstract In many mountainous areas of the Pacific coast of North America, rainfall onto snowpacks causes massive floods, probably the single greatest cause of changes in channel morphology and lotie habitats. To understand and model this hydrometeorological phenomenon better, process-response hypotheses were developed for snowpack outflow amount, duration and rate and the time lags from the beginning of rainfall to initial and peak outflow. The hypotheses were evaluated by correlation and regression analyses based on measurements of 20 rainon-snow events monitored between 1984 and 1990 at forested and open plots near Lake Tahoe, California. Outflow amount correlated significantly with precipitation amount, duration and rate, snow depth and melt potential. Many of these variables also correlated significantly with outflow duration and rate and lag time to peak outlfow. Regression models expalined 80–90% of the variation in outflow amount and duration. Significant differences were not identified between the...

Bare soil and rill formation following wildfires, fuel reduction treatments, and pine plantations in the southern Sierra Nevada, California, USA.

Accelerated erosion commonly occurs after wildfires on forested lands. As burned areas recover, erosion returns towards prefire rates depending on many site-specific characteristics, including fire severity, vegetation type, soil type and climate. In some areas, erosion recovery can be rapid, particularly where revegetation is quick. Erosion recovery is less well understood for many fuel load reduction treatments. The rate of post-disturbance erosion recovery affects management options for forested lands, particularly when considering the combined ramifications of multiple disturbances on resource recovery rates (i.e. cumulative watershed effects). Measurements of percentage bare soil and rilling on over 600 plots in the southern Sierra Nevada with slopes less than 75% and within 1 km of roads were made between 2004 and 2006. Results suggest that after high-, moderate- or low-severity wildfire, rilling was seldom evident more than 4 years after fire. Percentage bare soil generally did not differ significantly between reference plots and wildfire plots greater than 6 years old. Little rilling was evident after treatment with a variety of fuel reduction techniques, including burning of machine- and hand-piled fuel, thinning, mastication, and crushing. Percentage bare soil at the fuel load reduction treatment plots also did not differ significantly from reference conditions. Percentage bare soil at pine plantation plots was noticeably higher than at reference sites.

The influence of meteorology on rime and snow chemistry at a mountaintop site in northern California

Samples of rime and snow were collected from 36 storm events during three winters at a high-elevation site in northern California. Trajectories for the 36 events were segregated into types characterized by either large zonal or large meridional extent. The hypothesis that events dominated by meridional flow (potentially bringing pollutants to the study site from pollutant source areas to the south) were associated with elevated ion concentrations in time was not substantiated. For both the combined 3-year period, and winter 1988–89 alone, Cl−, NO3−, SO42−, and H+ concentrations in rime were greater generally than in snow, with the 3-year median concentrations for these ions ranging from 7 to 11 μeq L−1 in rime, vs. 2 to 8 μeq L−1 in snow. Intra-year variation in ion concentrations in rime was high during all three winters, with maximum concentrations during events in winter 1988–89 at least 16 times the magnitude of the minimum concentration for each ion.