Proposal for a Regional Water Temperature Monitoring Plan and Protocol for the Snake River

Prepared by the Water Temperature Monitoring Committee of the Water Quality Team

Background

Water temperature conditions have a complex array of effects on salmonids. Intergravel water temperatures affect the rate of embryonic development, with about 500 degree days needed for emergence (Weatherley and Gill 1995). Post-emergence growth rates are directly related to water temperature. Water temperatures experienced by out migrating juvenile salmon have been shown to affect survival (Connor, et al. 1998, Smith 1998, Muir, et al. 1999). An emerging issue is potential water temperature effects on juvenile out-migration timing. The working hypothesis is that Snake River juvenile fall chinook out-migration timing is delayed by cooler than historical water temperatures during incubation and early rearing life stages. This effect may be exacerbated by delayed spawning due to excessively warm fall temperatures. Because water temperature conditions and juvenile salmon mortality rates increase from mid-July through mid-September, delaying out-migration timing reduces juvenile fall chinook survival through Lower Granite Reservoir.

Immigrating adults can be delayed by excessively warm water temperatures (Karr et al. 1998). In addition, fall chinook spawning is inhibited by temperatures above 61E F (McCullough). Delay can reduce the ability of adult fish to survive to spawning and vigor and fecundity during spawning.

Water temperature also indirectly affects salmon survival. Foraging rates of piscivorus fish are directly related to temperature (Vigg and Burley 1991) and the rates of infectivity and mortality of several diseases are known to be directly related to temperature (NMFS 1998).

Reservoir existence and operation can have strong effects on water temperatures, both within the reservoir and in downstream reaches. Snake River basin reservoirs are known to affect water temperatures (Yearsley 1999), by greatly extending water residence times and by changing the heat exchange characteristics of affected river reaches. Thus, operation of these reservoirs affects both the thermal characteristics of the river and the thermally-regulated aspects of salmon survival. For this reason, the thermal effects of reservoir operation are an important consideration in developing system operations aimed at protecting and restoring listed salmonids.

Purpose

The issue of managing Snake River basin reservoir operations to minimize adverse water temperature effects has been investigated for many years. A wide array of data have been collected and there are extensive water temperature data available (Appendix A). Several mathematical models have been developed to examine the water temperature effects of the reservoirs (Yearsley 1999, COE 2000).

Concomitantly, fisheries biologists have been investigating the effects of water temperature conditions on salmon. These studies have focused on adult migration delays (Karr et al. 1998) and juvenile survival (Connor et al. 1998, Smith 1998, Muir et al. 1999).

Two basic questions drive our interest in this issue: What effects do Snake River basin reservoirs have on water temperatures and associated salmon survival?; and, How should reservoir operations be managed to avoid or minimize those effects?

The water temperature monitoring committee surveyed regional interested parties to identify particular issues and concerns (Appendix B). Both through this effort and internal discussions we determined that the spatial and temporal dynamics of water temperature conditions in Lower Granite Reservoir and the effects of upstream reservoir operations on those temperatures are of particular concern. Therefore, this report focuses on a proposal to develop a study for this issue.

Modelers familiar with the available data also identified an issue with the quality of available data (John Yearsley, personal communication). As shown in Appendix A, there are copious data available. Unfortunately, the quality of these data varies substantially. There is also a lack of detailed meteorological data to define the near-river heat flux conditions forcing modelers to estimate key parameters. The issue of water temperature modeling is also affected by a lack of consistent data on project operations at the time of data collection.

Thus we propose that the region:

Neither of these proposals have been developed to the point where they are ready to implement. Rather we suggest the characteristics we believe important in the final designs and the steps necessary to complete and implement the proposals.

Rationale for Focusing on Water Temperature Effects at and above Lower Granite Reservoir

Lower Granite Reservoir occupies the Snake River from river mile (RM) 108 to RM 148 and backs water into the Snake and Clearwater Rivers a few miles upstream from their confluence near Lewiston, Idaho. It is the first major reservoir encountered by emigrating Snake River juvenile salmon and the last major reservoir negotiated by immigrating adults. A substantial portion of juvenile fall chinook salmon mortality occurs in Lower Granite Reservoir (Smith 1998, Connor 1998, Muir et al. 1999).

During the summer, all emigrating juveniles collected at Lower Granite Dam are transported to release points downstream from Bonneville Dam, the lowermost dam on the Columbia River. In recent years up to 50 percent of the outmigrating Snake River fall chinook juveniles passing Lower Granite Dam have been collected and transported (Peters et al. 1999). For these transported fish, Lower Granite Reservoir is the last reservoir occupied on their seaward migrations.

Survival of pit-tagged juvenile fall chinook salmon from release points in the Snake and Clearwater Rivers to Lower Granite Dam is strongly correlated with water temperature in Lower Granite Reservoir (Figure 1). To minimize water temperature-related impacts on juvenile fall chinook, Dworshak Dam on the North Fork Clearwater, about 2 river miles upstream from the Clearwater River and 60 miles from Lower Granite Reservoir, is routinely operated to release relatively large amounts of cool water to reduce water temperatures in Lower Granite Reservoir and downstream reaches. Dworshak Reservoir is a deep impoundment (over 600 feet at full pool) that stratifies in the summer and Dworshak Dam is equipped with a variable intake depth release structure that facilitates selecting a specific discharge water temperature. During July and August reservoir managers typically release water at 48E to 50E F at the request of regional salmon managers. Cooler releases are possible but may result in adverse juvenile salmon growth conditions at a downstream hatchery and the Clearwater River.

This operation of Dworshak Reservoir has created controversy among local interests and fishery professionals. The principal concerns are that summer drafting at Dworshak diminishes the aesthetic, cultural, and recreational value of the lake; may adversely affect fish populations in the reservoir and downstream river reaches; and, reduces the amount of water available to provide temperature protection and attraction flows to adult salmon (primarily steelhead) in the early fall.

Water temperatures in Lower Granite Reservoir are also strongly affected by water temperatures in the Snake River upstream. (The Snake River provides about 2/3 of the summer inflow to Lower Granite Reservoir.) Snake River water temperatures in turn are affected by the discharge water temperature from Hells Canyon Dam, the lowermost dam of Idaho Power Company=s Hells Canyon Complex and the current upstream limit of occupied salmon habitat on the Snake River. Temperatures approaching the Upper Incipient Lethal Temperature for salmonids (68E F) are common in this portion of the Snake River during the summer (Karr et al. 1998).

The role of Lower Granite Reservoir in processing these heat inputs is not well known. Data collected during a previous study (Karr et al. 1998) shows that Lower Granite Reservoir stratifies during the summer. For example, on August 27, 1991 there was a 6E F difference in water temperatures between the upper 50 feet of the reservoir ( 70E F) and water at depths greater than 100 feet (64E F). It is likely that even stronger temperature gradients occur during hot summer periods when cool water is being discharged from Dworshak Dam (1991 was prior to these operations). This stratification can also be inferred from temperature data collected upstream of each dam at shallow depth (c. 12 feet) as part of the dissolved gas monitoring program. For example, on August 17, 1995 the water temperature upstream from Lower Granite Dam was 75.2E F. Yet temperatures recorded at Little Goose Reservoir over the next week never exceeded 69E F. It is unlikely that this difference in temperature was due to cooling in Little Goose Reservoir. Rather, this difference was likely primarily due to release water temperature at Lower Granite Reservoir being substantially cooler than the surface temperature. The powerhouse intake is located at the bottom of the reservoir and captures water from the bottom 50 feet of the reservoir, the coolest water available.

Early results of a juvenile fall chinook salmon radio-tracking study show that juveniles occupying Lower Granite Reservoir in the summer are typically found within 20 feet of the surface (David Venditti, USGS, personal communication). This suggests that emigrating fall chinook are often exposed to the warmest water temperatures found in the reservoir.

The three downstream Snake River reservoirs exhibit progressively weaker stratification, becoming virtually homothermic in Lower Monumental and Ice Harbor Reservoirs (Karr et al. 1998).

Efforts are underway to understand the thermal characteristics of the Hells Canyon Complex (Myers and Pierce 1999) with the intent of identifying measures to minimize that project=s adverse temperature effects on salmon survival.

We conclude that understanding the thermal characteristics of the Snake River from Hells Canyon Dam to Lower Granite Dam, including Lower Granite Reservoir and the Clearwater River downstream from Dworshak Dam, is of primary concern in devising operations and other measures to protect listed fish from adverse temperature conditions in the lower Snake River. Existing data and models are useful, but available 1-dimensional models are not sufficient to explain phenomena that vary in three dimensions. The reduced spatial variation in temperatures downstream from Lower Granite Dam and the shorter fish residence times in downstream reaches suggest that existing 1-dimensional approaches may be adequate downstream from Lower Granite Dam. Given limitations in research budgets, ongoing efforts (e.g. IPC relicensing studies) that could be incorporated into the study design, and the level of impact and concern, detailed investigation of the water temperature characteristics of this portion of the Snake River is clearly warranted.

Water Temperature Study

Purpose: To develop a model or series of models capable of estimating water temperatures of the Snake River from Hells Canyon Dam to Lower Granite Dam and from Dworshak Dam to Lower Granite Dam, including Lower Granite Reservoir within " 0.5E F on a bulk average flow basis based on reservoir discharge water temperatures and meteorological data. The model would be capable of simulating the outcomes of alternative operations and discharge temperatures at Hells Canyon, Dworshak, and Lower Granite Dams.

A two-dimensional (or three-dimensional) model of Lower Granite Reservoir=s temperature characteristics should also be developed. The level of accuracy achievable for such a model is unknown, but to be useful it should be capable of estimating bulk average temperatures within 0.5E F and provide estimated temperatures on a relatively small 2-d scale (say 10 foot depth H 100 foot longitudinal). The distribution of flow (velocities) is another important component to understanding and modeling reservoir temperature characteristics. A density current could develop along the bottom of the reservoir, conveying the coldest water through the reservoir with little effect on the temperature conditions in the occupied near-surface waters.

Until a modeling technique is selected, defining a data collection scheme is somewhat risky. That is, better data could possibly be developed at lower cost if the data needed to effectively drive the model was perfectly understood. Statistical tests may be available to identify the data needs (John Yearsley, personal communication). However, it is clear that both additional water temperature and meteorological data are needed.

As the Snake and Clearwater are rapid, turbulent rivers it is reasonable to assume that the free-flowing portion of the rivers are relatively homothermic at any given point and time. Existing tri-level thermograph data (Karr et al. 1998) from the Clearwater River inlet also supports this assumption. Thus, a single well-placed temperature probe at each selected station in the free-flowing portions of the study streams would accurately define the water temperature at that point.

It is difficult to estimate the number of additional meteorological stations needed to achieve the desired model accuracy. Given that the geographic scale of weather variations can be quite small, particularly during the summer (e.g summer convective storms), it is unlikely that all errors associated with extrapolation of site specific conditions could be eliminated with any reasonable number of new stations. Again, a statistical analysis should be conducted to define the most important locations for new meteorological stations. All additional stations should discretely measure all of the meteorological variables necessary to construct a deterministic model of heat flux. Measured variables should include: air temperature, relative humidity, barometric pressure, wind speed and velocity, solar radiation, and evaporation rates.

We cannot at this time reasonably define the methods, or data needs for this proposal. However, Appendix B outlines the sort of water temperature data collection network needed for development of a multi-dimensional view of Lower Granite Reservoir water temperatures.

Product: The model(s), when completed should be usable in the public domain. A wide array of interested parties should have access to the model (or an input interface) through a website or other distribution mechanism. Because the model initially would necessarily be based on limited data, an interesting possibility would be to make the model continually calibrate itself based on available verified data.

Data Collection Protocols

Available water temperature data throughout the basin has been collected by various entities for an array of purposes (Appendix A). For some data, quality assurance/quality control programs ensure that data are collected with sufficient precision, accuracy, and frequency to serve a variety of purposes. For other data, this is not the case. Much of the data collected is from relatively imprecise instruments and may be subject to errors in accuracy. For example, turbine scroll case water temperatures may be collected sporadically, using instruments capable of reading to the nearest 1E F, subject to inaccurate reading by observers (dial-type thermometers subject to parallax errors).

Further, few researchers perceived the need to correlate temperature conditions with current and antecedent reservoir operations information. As can be clearly illustrated by the temperature information given above, temperatures in downstream reaches are affected by reservoir operations. Water temperatures downstream from Lower Granite Dam could vary at a given point in time depending on the relative contribution of spill (which comes from warmer near-surface water) to total discharge. If viewed alone, temperature data from such operational effects could appear to be errors in a 1-dimensional model.

Thus, we recommend that the various entities collecting and using water temperature data strive to develop a single water temperature data collection protocol. At a minimum such a protocol should include descriptions of instrument precision and accuracy, measures to ensure quality control, consistent and reliable recording of time and date; and, for data collected in reservoirs, depth. The U.S. Environmental Protection Agency is the logical entity to develop such a protocol with inputs from state, private, and tribal interests. We see no need to further elaborate this issue here but would suggest that once developed, such a protocol be adopted as a minimum standard for water temperature data collected under projects supported by the NPPC=s Fish and Wildlife Program.

This recommendation should not be construed to infer that existing data would not be useful in developing the water temperature models described above. Existing data have successfully been used to model Snake River water temperatures in a bulk-flow 1-dimensional manner (Yearsley 1999). It is these data that we anticipate using to define the extent and locations of new data collection sites. A detailed inventory of these data has been conducted and much of this information would be useful in calibrating the model(s).

Next Steps

If the Water Quality Team and the Implementation Team support this concept, a detailed study plan should be developed. Such a plan could be developed by WQT participants (given sufficient access to the time of principal scientists familiar with water temperature modeling), or a contract could be let to develop the plan. Detailed plan development should be completed by May 2000.

Tentative Schedule:

Research on the distribution, timing, and mortality of salmonids passing through Lower Granite Reservoir should also be continued and expanded. Of particular interest is the distribution of fish relative to temperature conditions in the reservoir. Investigation of the location, diet, and consumption rate of piscivorus fish should also be conducted. Given that temperature-related mortality in Lower Granite Reservoir is a substantial concern, we are interested in investigating potential mitigative measures. Improved biological data are needed to define the likely biological effects of potential mitigative measures prior to implementation.

References:

Connor, W.P., H.L. Burge, and D.H. Bennett. 1998. Detection of PIT-tagged subyearling chinook salmon at a Snake River dam: implications of summer flow augmentation. North American Journal of Fisheries Management 18:530-536.

Karr, M.H., J.K. Fryer, and P.R. Mundy. 1998 Snake River Water Temperature Control Project - Phase II. Methods for Managing and Monitoring Water Temperatures in Relation to Salmon in the Lower Snake River. Columbia River Inter-Tribe Fish Commission. 209 pp.

Myers, R. and S. Pierce. 1999. Descriptive Limnology of the Hells Canyon Complex (Project

Progress Report, November 1999). Idaho Power Company, Environmental Affairs: Draft

Report.

McCullough, D.A. 1999. A Review and Synthesis of Effects of Alterations to the Water

Temperature Regime on Freshwater Life Stages of Salmonids with Special Reference to

Chinook Salmon. Report to the Environmental Protection Agency - Region 10. p 210.

Muir, W.D., S.G. Smith, E.E. Hockersmith, M.B. Eppard, W.P. Connor, T. Andersen, and B.D. Arnsberg. 1999. Fall Chinook Salmon Survival and Supplementation Studies in the Snake River and Lower Snake River Reservoirs, 1997. Prepared for U.S. Dept. of Energy, Bonneville Power Admin. 66 pp.

National Marine Fisheries Service (NMFS). 1998. Factors Contributing to the Decline of Chinook Salmon: An Addendum to the 1996 West Coast Steelhead Factors for Decline Report. NMFS Protected Resources Division. 8 pp.

Peters, C.N., D.R. Marmorek, and I. Parnell (eds.). 1999. PATH Decision Analysis Report for Snake River Fall Chinook. Prepared by ESSA Technologies Ltd. Vancouver, BC. 332 pp.

Smith, Steven G. 1998. Review of recent survival study results: presentation of NMFS Northwest Fisheries Science Center to the Implementation Team, October 1, 1998.

U. S. Army Corps of Engineers (COE). 1999. Draft Lower Snake River Juvenile Salmon Migration Feasibility Report/ Environmental Impact Statement. Appendix C - Water Quality. 147 pp.

Vigg, A. and C.C. Burley. 1991. Temperature dependent maximum daily consumption of juvenile salmonids by northern squawfish (Ptchocheilus oregonensis) from the Columbia River. Canadian Journal of Fisheries and Aquatic Sciences 48: 2491-2498.

Weatherley, A.H. and H.S. Gill. 1995. Growth. In C. Groot, L. Margolis, and W.C. Clarke eds. Physiological Ecology of Pacific Salmon. UBS Press, Vancouver.

Yearsley, John. 1999. Columbia River Temperature Assessment: Simulation Methods. U. S. EPA, Region 10, Seattle, WA. 77 pp. + app.