Characteristics of Extreme Precipitation and Associated Streamflow in the Reynold's creek Experimental watershed, Idaho

The USDA-ARS, Northwest Watershed Research Center operates a precipitation gauge network on the Reynolds Creek Experimental Watershed in southwest Idaho. Analysis of the 37-yr (1962-1998) record from this watershed showed that the average annual precipitation ranged from 240mm on the low elevation (1180 m) areas of the watershed to 1130 mm on the high elevation (2160 m) areas. Maximum average monthly precipitation was about the same for November, December, January and June at the lowest elevation sites and for November, December and January at the high elevation sites. The minimum average monthly precipitation occurred in July at all sites. There was a good linear relationship between elevation and mean annual or seasonal precipitation for the sites used in this study. This paper discusses depth-duration-frequency and other precipitation characteristics as they relate to season, elevation and location within the watershed. Information in the paper shows the relationships between the major runoff events that have occurred in the Reynolds Creek Watershed and the season, amount and distribution of the associated precipitation. The information shows that engineers and hydrologists need to do an in-depth evaluation of climatic conditions at project sites because generalized maps may not represent local conditions.