Weekly Report #98-21
August 7, 1998

 

 

SUMMARY OF EVENTS:

Water Supply: There was no significant precipitation in the area during the past week. Central basins were hot with temperatures ranging from 12 to 17 degrees above normal, some even reaching or exceeding 100 degrees. Above normal temperatures were also measured in the Western Snake Basin System Storage: US reservoirs continue summer augmentation drafting for endangered Snake River salmon.

A summary of actual elevations on August 6, 1998 is shown in the following table:

US reservoirs:

Upper Snake reservoirs:
Reservoirs are operating to meet high irrigation demands. Temperatures continue to be high and irrigation withdrawals are continuing to increase.

Jackson Lake is drafting for irrigation at a rate of about 5 kcfs.

Palisades continues slow drafting, about 2 kcfs higher than inflow, for Upper Snake diversion irrigation withdrawal at a rate of 8.5 kcfs.

American Falls continues intensive drafting to provide irrigation diversion of 10.9 kcfs downstream at Minidoka. Current outflow is 12.9 kcfs, about 10.4 kcfs higher than inflow.

Millner outflow continues at a constant rate of about 1.5 kcfs since July 7. Irrigation withdrawal at Upper Snake diversions above Blackfoot continue between 9-10 kcfs.

Boise River Basin:
Anderson and Arrowrock continue intensive drafting for irrigation withdrawals. Current reservoir capacities are 90% of full and 69% of full. The flow at Glenwood Bridge remained about 1.3 kcfs.

System Streamflow: The weekly average flows due to dry and hot weather are receding all over the basin. Flows at Lower Granite and McNary continue to be below summer target flows required by BiOp. The summary of average weekly flows for run of the river projects during the July 24-August 6 period is shown in the following Table:

Spill: Spill above hydraulic capacity continues at Dworshak Dam as flow augmentation is implemented. In the Lower Snake River the summer spill program is being implemented at Ice Harbor Dam. Spill averaged 38.9 kcfs at Ice Harbor Dam over the past week.

The lower Columbia River summer spill program began on July 1, 1998. Spill ended at McNary on July 30 as hydraulic capacity was no longer exceeded. Spill continued at lower river projects. Spill averaged 44.1 kcfs at John Day Dam, 69.2 kcfs at The Dalles Dam, and 85.1 kcfs at Bonneville Dam over the past week.

The summer spill program is being implemented at the Mid Columbia projects.

Total Dissolved Gas Supersaturation and Gas Bubble Trauma Monitoring:
TDGS levels have been at, or below, the gas waivers at all monitoring sites. Gas bubble trauma monitoring has ended for the season at the Snake River monitoring sites. Sampling will continue through the summer at Rock Island, McNary, John Day and Bonneville dams. Three juvenile subyearling chinook salmon have been detected with signs over the past week out of 845 examined.

Smolt Monitoring Program: In the Snake River and Columbia River drainages, the passage indices of subyearling chinook dropped from 31 to 72% below last week's average level. In the Snake River, wild subyearling chinook passage indices at Lower Granite Dam averaged 511 fish per day, a drop of 37% from last week's average. Wild subyearling chinook passage indices averaged 371 fish per day at Little Goose Dam and 107 fish per day at Lower Monumental Dam, down 50% and 72%, respectively, from last week's average. In the Mid-Columbia River, subyearling chinook passage indices at Rock Island Dam averaged 141 fish per day, about 40% lower than last week's average. In the lower Columbia River, subyearling chinook passage indices at McNary dropped to an average of 26,752 fish per day, down 31% from last week's average. Subyearling chinook passage indices averaged 7,587 fish per day at John Day Dam and 1,601 fish per day at Bonneville Dam, down 61% and 69%, respectively, from last week's average.

Adult Fish Passage: The final counting of summer chinook at Bonneville Dam was completed on July 31, with the season total being 21,433. The count of summer chinook at McNary Dam was 15,707 with the turnoff into the Snake River (Ice Harbor Dam count) less than 5,500 for the season. Daily counts of adult summer chinook continued at less than 10 fish per day through the week at the Snake River projects (similar to last week). The cumulative count of summer chinook at Priest Rapids Dam was 13,524 through August 6 with approximately 10,750 passing Rock Island Dam. Of these, about 53% have continued past Rocky Reach Dam.

The steelhead run at Bonneville Dam varied more than usual through the week with numbers that ranged between 800 to above 2,000 fish per day for this passage week. The season count at Bonneville Dam (March 15 - August 6) pushed above the 53,000 mark. Of these steelhead above Bonneville Dam, less than 13,000 have passed The Dalles Dam about 25% of the Bonneville total. With the hot water temperatures that exist in the lower Columbia River, many steelhead are seeking cooler water in tributary streams above Bonneville Dam. Daily counts of steelhead at all projects above Bonneville Dam on August 6 for example were less than 100. The steelhead count at McNary Dam through August 6 was 9,851, at Ice Harbor Dam (5,934) and at Priest Rapids Dam (1,070).

Sockeye passage is nearly completed for the 1998 season with numbers reducing to near 20 per day by the end of the reporting week at Rock Island and Wells dams on the Mid-Columbia River. This year's run past Rock Island Dam will be near 9,400 for the season. Sockeye destined for Lake Osoyoos should exceed those migrating to Lake Wenatchee as about 59% of the sockeye past Rock Island have been counted at Rocky Reach Dam (5,500).

Note that the Fish Passage Center began listing the "Wild" steelhead in the Adult Fish Passage Table. In time we will add the historic counts for the "Wild" steelhead. The Wild component of the run, based on the absence of the adipose fin, was 17,826 or about 33% of the total steelhead passing Bonneville Dam.

Coho are arriving at Bonneville Dam for the season, albeit less than two dozen have been counted to date, and no adult coho counted at the projects upstream yet.

Hatchery Releases: Columbia Basin hatcheries completed release of subyearling summer and fall chinook for the year. Spring Creek Hatchery personnel will release 500,000 subyearling spring chinook into the Big White Salmon River in mid August. Other releases of subyearling spring and summer chinook will be outplanted in Idaho tributaries during this summer and fall. Most will migrate in spring 1999.