. Big Hole River Arctic Grayling Restoration Project annual report : 1992. Arctic grayling. RESULTS Discharge Discharge and Water Temperature The April through September hydrograph from the USGS gage at Wisdom illustrates extreme drought conditions in the Big Hole basin in 1992 (Figure 6). The instantaneous peak flow was 610 cfs on June 17, 1992, which was 65% lower than the peak of 1,080 cfs recorded in 1988, another year of record drought. In 1991, discharge peaked at 4,300 cfs. No major pulse of run-off flows occurred in 1992. Several periods of extreme low flow were observed in 1992. On Ma
. Big Hole River Arctic Grayling Restoration Project annual report : 1992. Arctic grayling. RESULTS Discharge Discharge and Water Temperature The April through September hydrograph from the USGS gage at Wisdom illustrates extreme drought conditions in the Big Hole basin in 1992 (Figure 6). The instantaneous peak flow was 610 cfs on June 17, 1992, which was 65% lower than the peak of 1,080 cfs recorded in 1988, another year of record drought. In 1991, discharge peaked at 4,300 cfs. No major pulse of run-off flows occurred in 1992. Several periods of extreme low flow were observed in 1992. On May 18, flows decreased from 20 to cfs during the normal period of runoff. Just prior to this decline grayling fry should have emerged from the gravel, and the sudden flow reduction probably reduced rearing habitat and impeded recruitment. In response to earlier solicitations, local water-users decreased withdrawals which increased flows from a low of cfs to 32 cfs by May 26. A second major flow reduction occurred between June 9 and 10, when discharge decreased from 15 to 7 cfs. June rains provided relief as flows increased to the peak flow on June 17. Rains continued until mid- to late-August when flows began to decrease to a low of cfs on September 4. The lowest flow recorded in 1988 was 0 cfs in August, and in 1991 was 11 cfs on September 4 and 6. fl 22 — 1988 Pl991 38^1992. *£^^..^ -">-frmMrfM 4^1 4/16 4/29 0/19 0/37 e/10«a4 7/0 7/32 8/S 8/19 W2 WIS 9/30 D«t9 Figure 6. Big Hole River hydrograph measured at the USGS Wisdom gage, 1988, 1991, and 1992. 14. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Byorth, Patrick A. (Patrick Arthur); Fluvial Arctic Grayling Workgroup; Beaverhead National Forest (Mont. ). Dillon? : Montana Dept. of Fish, Wildlife, and Parks
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