2501 SW First Avenue, Suite 230, Portland, OR 97201-4752

Phone:(503)230-4099 Fax:(503)230-7559


e-mail us at fpcstaff@fpc.org

Weekly Report #98-11
May 29, 1998




Water Supply: Cumulative precipitation for the October through May period increased for the entire region because May was a very wet month. Precipitation continues to vary from 82% at Flathead to 127% at the Klamath basin and 141% in the Harney/Malheur basin. Precipitation distribution for May 1 through 26 continues to have high variations, with the highest precipitation on the Upper Deschutes/Crooked river at 368%, the Klamath Basin at 363% and the Harney/Malheur Basin at 324%. The lowest precipitation in the NW Slope was in the Washington Cascades at 68%. The Snake River basin and Lower Deschutes/Hood area continue to be the areas with the highest precipitation, in the range of 242% to 360%. Precipitation in the Columbia above the Coulee was 127%, the Columbia above the Dalles was 168% of the average and the Snake River above Ice Harbor was 230% of the average.

System Storage and Streamflow: The flows in the system continued to be high during last week. Unusual high precipitation in the Snake Basin refilled reservoirs and resulted in a high runoff. The upper Columbia reservoirs continue to be in refill at a much slower rate this season, except Libby and Hungry Horse which accelerated refill during last week.

A summary of actual elevations is shown in the following table:
















Hungry Horse



Grand Coulee










  • Mica is in refill to an end of July full pool elevation. Currently it is releasing 10 kcfs from Treaty storage. Actual outflow is zero, because the water is stored into Non Treaty Storage (NTS), per 5 kcfs on BPA and BC accounts. It is expected that it will continue with storage into NTS to the middle of June. It is not expected that the reservoir will be full by the end of July. The projected end of July Treaty elevation is 14 ft below full pool. Treaty elevation on May 28 is 2415.9 ft. The Non Treaty Storage account on May 26 is: BPA-812 ksfd and BC Hydro-846 ksfd. It is projected that by the end of June it will be: at BPA-account 942 ksfd and BC Hydro account - 1-11 ksfd.
  • Arrow is also in refill to the end of July full pool elevation. Current actual elevation is about 9 ft below Treaty required elevation. The reservoir is operated with minimum actual outflow of 14 kcfs for trout spawning below the dam. The Treaty projected outflow is 21.6 kcfs. The difference is stored into Non Treaty Storage.
  • Duncan is in refill to the end of July full pool elevation. The actual outflow is 0.1 kcfs because of accelerated refill.
  • Libby was operated with outflows of 18-19 kcfs during last week and will be operated to provide 25 kcfs at Bonners Ferry.
  • Hungry Horse continues to be at a minimum outflow of about 170 cfs to 270 cfs, controlling the flow of 3.5 kcfs at Columbia Falls. During period of May 25-27, the outflow was increased to 1.2-3.35 kcfs because of unstable weather conditions. But after it, it will continue to refill to the BiOp required end of June elevation.
  • Grand Coulee was refilled from 1281.4 ft to 1284.6 ft and fishery agencies requested to Priest Rapids of 135 kcfs.
  • Brownlee is full. Increased precipitation in the Snake basin increased inflows to the reservoir up to 80 kcfs. The reservoir is currently passing inflow.
  • Dworshak is almost full and was releasing outflows up to full powerhouse capacity of 14 kcfs. It will continue with high outflows due to high precipitation in the region.

Upper Snake reservoirs: Although the system is in the irrigation season, the outflow from the reservoirs is well beyond the irrigation demands because of the continued increased precipitation in the basin. The system continues to be operated for flood control.

Jackson Lake was in slight refill with outflow rates up to 4.9 kcfs during last week and it is expected to continue with similar flows during next week. Currently the reservoir is 88% full.

Palisades was in slow refill during last week due to flood control operations and it is expected to pass inflow to the end of next week. Currently, the outflow is 15.5 kcfs and the reservoir is 73% full.

American Falls is full and is passing inflow of 21.9 kcfs.

Milner flow at the lowest point of the Upper Snake system is peaking at 16.4 kcfs (higher for 1 kcfs compared to the flow of last week). Irrigation withdrawal upstream at Minidoka remained the same as last week, about 5 kcfs.

System Streamflow:The weekly average flows in the Snake River were at it’s seasonal peak during last week while continued with recess in the mid Columbia. The summary of average weekly flows for run of the river projects during the May 15 through 28 period is shown in the table below:


ProjectMay 22-28May 15-21
Priest Rapids141.7 kcfs180.8 kcfs
McNary323.9 kcfs310.9 kcfs
Lower Granite178.8 kcfs125.7 kcfs
Bonneville335.5 kcfs326.9 kcfs

Spill: Recent rains and the lack of irrigation withdrawals has resulted in significantly higher flow and spill in the Snake and Columbia rivers over the past week. All spill currently occurring at the lower Snake River Projects was in excess of hydraulic capacity. Dworshak outflow was increased above hydraulic capacity to prevent the reservoir from reaching full capacity. Spill at Dworshak averaged 2.8 kcfs over the past week. Spill averaged 75 kcfs, 70.1 kcfs, 80.5 kcfs and 100.6 kcfs at Lower Granite, Little Goose, Lower Monumental and Ice Harbor dams, respectively. Spill at the lower Columbia projects was significantly greater than last week, and averaged 165.3 kcfs at McNary Dam, 127.6 kcfs at John Day Dam, 171.4 kcfs at The Dalles Dam (averaging 52% of total flow), and 133 kcfs at Bonneville Dam over the past week. Spill continues at all the Mid-Columbia projects.

Total Dissolved Gas Supersaturation and Gas Bubble Trauma Monitoring:As expected total dissolved gas levels exceeded the water quality waivers at all the lower Snake Projects due to the spill in excess of hydraulic capacity. Tailwater concentrations of TDGS were near, or in excess of, 130% at all these projects. The Hells Canyon project has been passing inflows of 70-90 kcfs. The hydraulic capacity of that project is only 30 kcfs and, consequently, significant amounts of spill have been occurring. No data on total dissolved gas levels has been released and, therefore, it is difficult to assess the impact of this project operation on the rearing subyearling fall chinook in the river reach below the project.

The gas levels in the lower Columbia are also above the gas waivers due to a combination of a lack of hydraulic capacity and excess generation spill. Limited data is available for the Mid-Columbia sites at this time, but levels at the sites monitored show dissolved gas levels below the waiver limits. It is unlikely that the other sites remain below the waivers. Gas bubble trauma monitoring has occurred at all sites over the past week. Few juvenile fish are showing signs throughout the system, with the percentage of signs remaining well below the action criteria. It is interesting to note that some fish are being detected at Lower Granite Dam with signs of GBT. This could be a result of the elevated dissolved gas levels below the Idaho Power Company’s Hells Canyon Project. One adult salmon out of 32 was reported at Lower Granite Dam with signs of GBT during the last reporting period.

Smolt Monitoring Program: Snake River Drainage.The Lewiston, Whitebird and Imnaha Traps are not operational due to the high River flows. They will resume fishing when the high river flows recede. The Grande Ronde Trap has completed fishing for the 1998 season. The trap has incurred damage and the needed time to effect the repairs will extend beyond the anticipated end of normal sampling. The decreasing trend in passage indices for yearling chinook, steelhead, coho and sockeye at Lower Granite, Little Goose, and Lower Monumental dams referred to last week was reversed by the recent increases in flow. Numbers of all species increased and peaked at Lower Granite Dam around the 23-25 of May before returning to the levels that were observed last week. Wild subyearling chinook were also detected at all the mainstem Snake sites this past week.

Columbia River Drainage.The passage indices at Rock Island Dam have been fairly stable for yearling chinook, coho, and wild steelhead, and over the week have shown decreasing trends for hatchery steelhead and wild sockeye. The trend in passage indices this week at McNary Dam has been one of decreasing coho and yearling chinook, and decreasing wild and hatchery steelhead and sockeye. However, subyearling chinook passage indices at McNary Dam have been increasing over the past week. Similar trends in passage indices occurred at John Day and Bonneville dams for steelhead and sockeye, while both yearling chinook and coho passage indices remained little changed from last week’s levels. Subyearling chinook from the Spring Creek Hatchery tule fall chinook release began passing Bonneville Dam on May 16 and continued with indices increasing towards the end of the reporting period.

Adult Fish Passage: At Bonneville Dam, daily counts of adult spring chinook ranged between 244 and 410 for the week with a cumulative total of 37,415. The spring chinook count for Bonneville Dam will end on May 31 with summer chinook counts beginning on June 1. This year’s spring chinook count will rank as one of the lower for the 1990’s with the 1998 count only 33.6% of the 1997 count and 52.9% of the 10-year average. The COE was able to start the second fish turbine at the new powerhouse on May 28, and the additional turbine will supply more attraction flows to the WA shore fishway.

The adult spring chinook count at Ice Harbor Dam (Snake River) through May 28 totals 11,018, well below the 1997 count (34.5%) and nearer the 10-year average (72.2%) than was the Bonneville count. The high flows in the Snake River resulted in very reduced numbers of fish passing the dams during the end of the week. As an example, the total passage for the four Snake River projects on May 28 was 11 chinook adults. In fact, the fish pumps that supply auxiliary water to the fishways have been shut down until flows are reduced. The turbidity of the water was nearly .3 ft, and almost chocolate color.

Passage of fish into the Mid-Columbia has not been impeded as in the Snake River, but river flow increased to about 190 kcfs on May 28 from levels nearly 140 to160 kcfs earlier in the week. The cumulative count of adult spring chinook at Priest Rapids Dam was 3,644, with Rock Island reporting more than 2,400. As indicated in last week’s report, the WDFW will be trapping all spring chinook that attempt passing Wells Dam. The steelhead run for the 1998/99 cycle is beginning to pick up at Bonneville Dam. Numbers of migrating adult fish have increased through the week to a high daily tally of 111 for the week, with the count for the season now up to 2,666. A large share of the early run fish could be destined for the Bonneville pool tributaries, but now the fish are continuing above The Dalles Dam.

Hatchery Releases: Juvenile subyearling summer and fall chinook will be released from mid-May through late June from hatcheries and acclimation facilities. The Priest Rapids and Ringold Hatchery fall chinook will be released in June as will the summer chinook from Wells and Turtle Rock Hatcheries. Subyearling fall chinook released in the Snake River will be from Pittsburg Landing and Big Canyon Acclimation Sites with no fish released from Lyons Ferry Hatchery (on-site). Subyearling releases of fall chinook from the Umatilla River Basin were completed with the Klickitat Hatchery opening their screens in mid-May and allowing the fish to volitionally emigrate from the ponds. Little White Salmon fall chinook are scheduled for release in June. Subyearling spring chinook were released in the Klickitat (500k) and Entiat (157k) rivers during the past two weeks. One item of interest is that, with the higher flow below Bonneville Dam, the new juvenile bypass outfall appears to be damaged to some extent. The damage to date is limited to the pilings and platform (work area). The COE and contractors are presently evaluating what can be done to stabilize the existing work platform.