The assertion that spilling more water at four lower Snake River and four lower Columbia River dams would result in more salmon and steelhead returning to the rivers is now being argued in the Ninth Circuit Court.

While spill has been a leading strategy for more than a decade for increasing salmon survival through the Columbia River hydropower system, providing even more spill was proposed last year by plaintiffs in a case that in 2016 had resulted in a remand in U.S. District Court of the NOAA Fisheries 2014 salmon/steelhead biological opinion for the federal hydrosystem.

However, even as it is opposing spill in the appeals court, NOAA Fisheries is also developing two designs to test the assertion that higher spill -- specifically spilling to the upper limits of what would be allowed for total dissolved gas at the dams – would improve smolt-to-adult survival.

NOAA developed two broad categories of experimental designs to evaluate the effects of higher spill compared to the baseline spill level, a level of spill adopted by the 2008 BiOp, but which actually began in 2006 and has been used at some level every year since at the eight dams. The second spill level is the proposed increase to 120/115 percent gas cap that was developed through the Regional Implementation and Oversight Group (RIOG) last year in response to the court-ordered spill.

The two experimental spill designs proposed by NOAA are a before/after design and a block design.

NOAA submitted the designs to the Independent Scientific Advisory Board in January for review and the ISAB just completed that review this week, submitting its report March 19. The ISAB report is here. 

NOAA’s draft proposal, “A Power Analysis of Two Alternative Experimental Designs to Evaluate a Test of Increased Spill at Snake and Columbia River Dams, Using Smolt-to-Adult Returns of Anadromous Salmonids,” was completed in January and can be found here.

In that draft report, NOAA said that it could see four potential response variables to higher spill:

1. smolt to adult return rate for smolts that migrate in-river

2. smolt survival rate through the hydropower system

3. smolt travel time through the hydropower system

4. SAR of transported smolts relative to SAR of in-river migrants

The first possibility for studying spill to the gas cap level would be to implement the action through the entire migration season, NOAA said in its proposal.

“Response variables could be computed on an annual basis, and compared to corresponding annual measures from retrospective years,” it says. “We refer to this experimental strategy as the ‘Before/After’ approach. In this approach, there is no variation in the ‘treatment’ – the new management action – within prospective years and evaluation is essentially based on annual measures.”

The second possibility for studying spill is to vary, or manipulate, the treatment level within the migration season in prospective years, the proposal says.  “In the case of the Spill Test, this implies that one spill level would be used during designated subset(s) of each migration season, and the other level used in the rest of the season. We refer to this experimental strategy as the ‘Block - Spill Design’ or simply ‘Block Design’ approach.”

Staff at the Northwest Fisheries Science Center proposed an example of a block design and conducted a preliminary power analysis indicating that such a design will generally be better able to detect benefits from increased spill compared to a before/after approach.

The ISAB agreed, saying that it found that the “NOAA’s analysis is a standard assessment of the power to detect effects and appears to be structured appropriately. The methodology and conclusions are conceptually sound, and the block design provides advantages to a before/after study.”

The key advantage to the block design is that high year-to-year variation is controlled for by conducting both spill regimes in the same year, the ISAB said. “However, the advantages are somewhat tempered because of several sampling and estimation issues. In addition, the success of the proposed experiment may depend on a number of factors including the availability of sufficient water and tagged fish to actually implement the experiment, the assumption that past fish behavior (in the retrospective years) is indicative of what will happen under the new spill regime, and other operational issues that would need to be resolved before an actual experiment is implemented.”

The operational issues are:

1. the expected improvement in smolt-to-adult returns (SARs) associated with particular spill levels

2. the impacts of low and high flow years on the study’s implementation

3. whether the proposed spill regime is equally beneficial for fish of all sizes/ages when they start their migration

4. impacts of the proposed spill regime on fish travel speed

5. effects of new spillway detectors on the study design

6. identification of adaptive management triggers, and

7. the experiment’s effects on migrant survival when only half of the year is at higher spill levels compared to a full year at higher spill levels.

So, while a theoretical implementation (i.e., NOAA’s block spill paper) may show high statistical power, an actual implementation may have less power because of these problems. These issues and several topics that should be explored to strengthen NOAA’s analysis are described in the full report, the ISAB said.

The request for injunctive relief for more spill was enjoined with the earlier case argued in U.S. District Court of Oregon, with Judge Michael H. Simon presiding. The initial case resulted in a May 2016 remand of the federal Columbia River power system biological opinion for salmon and steelhead listed under the Endangered Species Act.

The spill plea was brought to Simon in January 2017, asking the court to begin ordering spill to maximum total dissolved gas levels beginning April 3, 2017 and to continue for each year of the BiOp remand. Simon agreed that more spring spill would benefit ESA-listed fish, but delayed the action until 2018 while federal agencies completed a spill plan for lower Snake and Columbia river dams.

However, an appeal of Simon’s spill injunction was filed in the appeals court in early June 2017 by federal agencies, Northwest RiverPartners, the Kootenai Tribe of Idaho, the states of Idaho and Montana, and the Inland Ports and Navigation Group.