Frequently Asked Questions

Instructions:    Click on questions to read answers.

What is the difference between adult ladder counts starting March 15 and those starting January 1?

Starting in 2000 the Army Corp of Engineer’s began posting both direct observation and video counts on their website. Below is a table showing the dates for each type of observation. The COE previously had just reported the direct observation data starting March 15th, and therefore this is what is used in the ten-year average.If you are a fisherman and are just concerned with the number of fish passing each dam, then use the Counts Starting January 1st. Be aware that any of our reports or queries that use the ten-year average, such as the Cumulative Adult Passage Report that appears in our weekly report and the Adult Graph, use theCounts Starting March 15.

Dam Direct Observation Reporting Dates Video and Direct Observation Reporting Dates
Bonneville Dam March 15 to November 15 January 1 to December 31
The Dalles Dam April 1 to October 31 February 20 to December 7
John Day Dam April 1 to October 31 February 20  to December 7
McNary Dam April 1 to October 31 March 1 to December 31
Ice Harbor Dam April 1 to October 31 March 1 to October 31
Lower Monumental Dam April 1 to October 31 January 1 to December  31
Little Goose Dam April 1 to October 31 January 1 to December 31
Lower Granite Dam March 1 to December 15 March 1 to December 15
Priest Rapids Dam April 15 to November 15 April 15 to November 15
Rock Island Dam April 15 to November 15 April 15 to November 15
Rocky Reach Dam April 15 to November 15 April 15 to November 15
Wells Dam May 1 to November 15 May 1 to November 15

What is the difference between the daily average flows used in the smolt passage index and those that appear in the two week flow & spill report, finalized flow query, and in reports on DART and on the USACE’s web site?

The daily average flows used in the passage index and that appear in the catch report and in the smolt data queries are hourly flows averaged for the sampling hours of that particular batch. The sampling period for most SMP sites is typically from 7:00am – 7:00am daily, and at other SMP sites the sampling period is typically from 9:00am – 9:00am daily. This sampling period allows for fish to be worked up and examined at a time of day when there is usually very little fish passage, and at a time of day when it is possible to have SMP sampling personnel on duty at the SMP sites. The daily flows displayed in the Two Week Flow Report and in the Finalized Flow Query are a midnight to midnight daily average. Other web sites such as DART and the USACE only display the midnight to midnight averages.

Where can I find the hatchery releases?

Our hatchery release information can be found in several formats. We publish a Hatchery Releases for the Last and Next Two Weeks as part of our weekly report. We also offer many ways of querying the data (by migration year, species, river zone, hatchery, sub-basin, Hydrologic Unit Code, etc.) or you can view Yearly Totals. Querying by Migration year or River Zone is often the quickest way to obtain all the current releases for the year, either across the whole hydrosystem or in a particular geographic area.

Why are the shad ladder counts higher at The Dalles Dam than Bonneville?

When the shad first appear in May they tend to go through the locks at Bonneville, rather than using the fish ladder and therefore are not counted. As the season progresses the numbers will rise at Bonneville, bringing it more in line with the count at The Dalles Dam.

Why are steelhead counts sometimes higher at John Day Dam than The Dalles Dam even though it is further upstream?

The Army Corp of Engineers did a study to try and discover the root of the discrepancy. Their findings were summarized as being due to many factors including: errors in visual counting (as compared to video), problems with conversion rates (to extrapolate count to full hour), errors at the north counting stations at both dams, and large numbers of fall backs at John Day Dam (meaning the same fish is counted multiple times).
For more detailed information you can view the report here.

The Ives water level is not a depth, it is just water depth over the gauge. Is the gauge in contact with the substrate to make it a true depth?

The gage is 0.2 feet under the substrate and at the same elevation as the hydraulic control between Ives Island and Hamilton Island. Thus if the gage reads 1.0 feet there will be one foot of water over the control at the thawleg.

If I add 13.27 to the Ives water level I usually get an elevation that is greater than the Bonneville tailwater elevation. How can I account for this difference? How it possible that Bonneville elevation is actually lower that Ives elevation when Ives is downstream of Bonneville?

The USACE still uses the older vertical datum of NGVD29 for most of there gages on the Columbia River. To correct for the difference between NGVD29 and NAVD88 (Ives Gage) you would subtract 3.34 feet from the Ives Gage.

Are the adult counts for wild steelhead a subset of the adult steelhead counts? How are wild steelhead identified at the Corp of Engineers Dams?

Wild steelhead are a subset of steelhead. Wild steelhead are counted separately from hatchery steelhead at Corps dams on the Columbia and Snake Rivers. Wild steelhead are identified as fish with an intact adipose fin. However, a small number of hatchery fish may not have had their adipose fin removed.




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Page last updated on: April 26, 2011

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