8006 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I RESULTS Discharge and water temperature During the 1994 water year, total discharge was very low in the Little Snake River. Annual runoff was 207,300 acre feet, about half of the 70-year average. Winter baseflow prior to runoff was about 3 m3/sec from November through March and was ice covered. Runoff started in March and continued until mid-June. Daily discharge peaked at 68 m3/sec on April 25 and again at 58 m3/sec on May 15 (Figure 2). Discharge decreased rapidly in June and from mid-July through mid-September, discharge was less than 0.03 m3/sec, including 19 days of near zero discharge (Ugland et al. 1995). In August and September, localized rain caused two spates that increased discharge from near zero to about 2.0 m3/sec for several days and deposited large amounts of clay and silt within the river bed. During runoff, mean daily discharge on the two sampling trips ranged 55-57 m3/sec and 10-19 m3/sec. During baseflow, mean daily discharge on the two trips ranged 3-4 m3/sec and 0.02-0.03 m3/sec (Figure 2). Associated with runoff was high turbidity caused by the large sediment load. This turbidity cleared during baseflow except during temporary spate events. Conductivity increased as discharge declined. During runoff, conductivity ranged 163-220 jJS and during baseflow it ranged 500-1080 jJS. Water pH was only collected during baseflow and was 8.4 in June and 8.9 in July. In May and June, during runoff, water temperatures in the Little Snake River were generally higher than in the Yampa River; even minimum daily temperatures in the Little Snake River exceeded maximum daily temperatures on the Yampa River (Appendix Figures B.1-B.2). From July through October, daily average temperatures were similar between both rivers, but the Little Snake River typically had greater die' temperature fluctuations (Appendix Figures B.3-B.6). 10