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00248: and agencies. Extensive data have been presented in various reports and publications. Detailed studies of the distribution of precipi- tation rates and hours of precipitation, as related to elevation, latitude along the Sierra Nevada barrier, the 500-millibar (mb) temperature, and the 700-mb wind direction, as determined by the Oakland, California sounding, were performed by Bailey8 for selected American River stations. MBA said that when this information was combined with other CENSARE data and reanalyzed, the following results emerged. Precipitation duration increases from the valley to the Sierra Nevada crest. Average precipitation rates are generally highest over the lower slopes (800 to 1400 m or 2600 to 4600 ft) of the Sierra Nevada and decrease to produce an average maximum somewhere between the 1500 and 1800 m (4900 and 5900 ft) mean sea level along the windward slopes. The latitudinal gradients of precipitation rate and duration (hours of precipitation) are in the same direction. Both show a maximum in the Northern Sierra Nevada, decreasing southward. The difference in precipitation duration along the western slope from north to south is roughly a factor of 2:1. The ratio of north to south precipitation rates is about 4:3. MBA reported that while the isopleth of maximum precipitation does tend to curve with the curvature of the barrier in the Feather River Basin, the amount drops off relatively rapidly as the barrier continues to curve into an east-west orientation. Orographic characteristics are e~silY correlated with the precipitation isopleths as presented by Bailey and indicate a difference in precipitation characteristics between the American and Feather River Basins with the Feather having the lesser accumulations. The isopleths of maximal precipitation for the entire Sierra Nevada Range lie below the barrier on the windward side, extending from the South Fork of the American River up to the northeastern reaches of the Yuba. These differences are supportive of MBA's conclusion that the Feather River is an over-the-barrier precipitation catchment as opposed to the American and Yuba River Basins which have windward catchments. Streamflow simulation analyses were conducted to obtain the expected increase in streamflow resulting from 10 and 50 percent increases in the snowpack, bracketing the increases forecast by the Twelve Basin Investigation. These simulation results were not very different on the average than one could obtain from using the percent of the total basin catchment that retains the snowpack through the winter (in the case of the American Basin, 30 percent) and multiplying by 8. Bailey, D. L. (1973). "Climatological Assessment of Winter Precipitation over the Sierra Nevada," Final Report, Project CENSARE, Vol. III, California State University, Fresno Foundation. 12