100 



sage efficiency standard (that is, 80 percent of the fish pass through non-turbine 

 routes). 



NMFS supports voluntary spill because studies have shown that passage through 

 spillways is the safest route for juvenile salmon migrating past a hydroelectric 

 proiect. The spill program reduces the number of young fish passing through tiie 

 turbines at a dam, increasing overall survival of fish migrating in-river. 



DISSOLVED GAS 



Water spilled at dams entrains large amounts of air and forces it into a dissolved 

 state. Thus, spill may cause total dissolved gas (TDG) levels in the river to exceed 

 saturation — resulting in gas supersaturated water. When migrating juvenile (or 

 adult) salmon are exposed to areas with high levels of total dissolved gas, they can 

 develop a condition luiown as gas bubble trauma (GBT). The condition is character- 

 ized by air bubbles (embolisms) forming in various tissues of the affected fish (e.g., 

 in fins, vascular svstems, and gills, and along the lateral lines). In extreme cases, 

 the condition can lead to death. At lower levels gas bubble trauma can result in re- 

 duced ability to avoid predators, increased susceptibility to disease, and impaired 

 swimming performance. Reflecting their concerns about the effects of gas bubble 

 trauma on resident and migrant fish, the states have adopted water qutdity stand- 

 ards consistent with EPA guidelines. 



THE SPILL PRCXJRAM IN 1996 



In developing the 1995 spill program, NMFS biologists used scientific literature 

 regarding gas Bubble trauma, spillway and turbine survived, fish guidance, and by- 

 pass and transportation operations. The NMFS analysis included peer-reviewed re- 

 ports, unpublisned government reports, a spill evaluation conducted by the state 

 and tribal fishery agencies, and all the data collected through monitoring the 1994 

 spill program. NMFS also convened a panel of experts in gas bubble trauma on two 

 separate occasions. The panel's purpose was to help interpret the 1994 monitoring 

 results, to aid in developing protocols for a 1995 monitoring program, and to identify 

 critical research needs. Much of the literature reviewed in developing the 1995 spill 

 program is listed in the FCRPS Biological Opinion and in the State and Tribal Fish- 

 ery Agencies' spill evaluation reference sections. 



In addition, NMFS relied on the professional judgment of its biologists and re- 

 ceived extensive input fi"om other Federal Government scientists. The review drew 

 on scientists fi-om the Corps of Engineers, the U.S. Fish and Wildlife Service 

 (USFWS), and the National Biological Survey (NBS) and utilized their expertise in 

 the fields of dissolved gas supersaturation, fish biology, limnology, and many other 

 disciplines in developing the scientific conclusions regarding the technical elements 

 of the spill program. ^ 



The spills on the Columbia and Snake River system have three components: Vol- 

 untary spill at non-collector projects in order to improve downstream migrant sur- 

 vival, voluntary spill at fish collector projects to determine the relative merits of 

 transportation versus in-river migration, and involuntary spill caused by high runoff" 

 events combined with limited hym-aulic capacities at some of the projects. 



In the case of voluntary spill at non-collector projects (those projects where juve- 

 nile salmon are not collected for transportation), there is little debate regarding its 

 value to the fish. Spill has long been used at these projects as safer than routing 

 the fish through the turbines. The difference is that under the Proposed Recovery 

 Plan, the spill level is somewhat higher than under past operations. 



Voluntary spill at collector projects occurs only under high flow conditions, when 

 conditions are better for in-river survival. This spill provides important information 

 needed in NMFS' adaptive management strategy. By companng the survived to 

 adults of in-river migrants to that of transported migrants, NMFS obtains critical 

 data on how to improve overall survival of salmon, which is NMFS' ultimate goal. 

 Voluntary spill at both collector and non-collector projects is limited in NMFS' pro- 

 gram to ensure that dissolved gas levels do not pose a danger to migrating fish. 



Involuntary spill occurs due to high flows fi-om snow melt and heavy rains. The 

 storage (reservoir) facilities in the system have limited capacity to contain these 

 flows. The flows which cannot be routed through the turbines are spilled. The vol- 

 ume of this involuntary spill increases when generating capacity at the Federal 

 projects is impaired, for example during turbine outages. 'This uncontrolled spill 

 causes the greatest challenge for the management of dissolved gases. 



1 (The details of the review are given in the last section of this dociunent: Responses to Ques- 

 tions by Senator Kempthome.) 



