Session: Water Temperature Compliance and Modeling
Thursday, February 8, 2007 - 12:15 to 2:05 PM
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| In this session: | |
| Meeting Water Temperature Objectives in the Trinity River - A Post- ROD Review | Paul Zedonis |
| Trinity River Flow and Temperature Modeling | Ibrahim E Sogutlugil |
| Thermodynamics of Trinity and Lewiston Reservoir | Michael Deas |
| Trinity Reservoir Cold Water Pool: Historical Analysis and Future Outlook | Tom Stokely |
| Discussion Session: Water Temperature Compliance and Modeling | |
Meeting Water Temperature Objectives in the Trinity River - A Post- ROD Review
Paul Zedonis, U.S. Fish and Wildlife Service, paul_zedonis@fws.gov, (707) 822-7201
Seven years of water temperature data were examined to determine the success of flow management in meeting the temperature objectives as identified in the Trinity River Record of Decision, the foundation document from which the Trinity River Restoration Program is based. The spring objectives vary by hydrologic year type, time of the year, and salmonid species (Figure 1). Compliance of the objectives is defined by the average daily temperature at the mouth of the Trinity River . Of the seven years, flow schedules for 2003 to 2006 were purposely devised with a 2,000+cfs bench to meet optimal temperatures of the Trinity River at Weitchpec. These years coincided with colder water temperatures compared to those that were not managed for optimal temperatures (e.g., 2000 to 2002). Of these four years, in only 2006 were optimal temperatures achieved nearly 100% of the time. Optimal objectives were frequently met prior to mid- June in 2003 to 2005 but not thereafter; water temperatures were typically 2 to 3 °F warmer than the desired optimal condition.
Figure 1. Spring Objectives
Comparisons of the temperature differences of the Trinity River and the Klamath River from 2002 to 2006 reveal the Trinity River is a coldwater source to the Klamath River during the spring and early summer. Temperature differences (5 to 9 °F) occurred in late June and early July in years when flows of 2,000+ cfs were released from Lewiston Dam. In these years, the Trinity River was cold enough relative to the Klamath River to effectively reduce the average daily water temperature of the Klamath River by up to 3 °F, as in 2006. In contrast, in 2002, a year in which optimal temperatures were not sought, the temperature differences were less (1.8 °F) from June to early July, with only a relatively small temperature influence on the mainstem Klamath River .
The flow prescription of 450 cfs was generally sufficient to meet the temperature objectives of the upper Trinity River, also known as the Basin Plan objectives of the North Coast Regional Water Quality Control Board; 60 °F at Douglas City from July to September 14, 56 °F from September 15 to September 30 at Douglas City, and 56 °F from October 1 to December 31 at the confluence of the North Fork Trinity River. Dam release temperatures greater than ~ 50 °F and warmer than average air temperatures account for time periods when the temperature objectives were exceeded. Since 2000, exceedance has typically been infrequent and typically less than 1 °F.
Presentation notes:
Temperatures did not always reach objectives. During the first years of 2000 to 2002, Trinity water temperatures were generally cool, but reached "unsuitable" for Chinook in late June and July. By 2003 to 2005, late season temperatures were better, but still reached "marginal" for Chinook. In 2006, temperatures were optimal through July 8 (end of Chinook out-migration).
Questions concerned biological responses to flow and temperatures and whether these are natural. No clear answer. It was again questioned whether the 2000 cfs bench is really needed. Reports for 2002 through 2006 are available on the FWS website: www.fws.gov/arcata/fisheries.
Trinity River Flow and Temperature Modeling
Ibrahim E Sogutlugil, Watercourse Engineering, Inc., Ert.Sogutlugil@watercourseinc.com
(530) 750-3072 ext 102
The objective of this study is to develop a sub-daily flow and temperature model for the Trinity River system to assist in cold water management for anadromous fish restoration efforts. The system is represented by two numerical models. The flow component is represented with RMA-2, a finite element hydrodynamic model capable of representing highly dynamic flow regimes at short space and time scales. The output from this model includes velocity, depth, and water surface and bed areas, which are subsequently passed to the water quality model, RMA-11. RMA-11 is a full water quality finite element model, simulating the fate and transport of a wide range of physical, chemical, and biological constituents. Temperature and a conservative tracer are simulated in this application. Although the RMA models are capable of multiple dimensional modeling, the Trinity River application is a one-dimensional, longitudinal representation, i.e., laterally and vertically averaged.
The suite of river models is applied on a sub-daily time step (hourly) to capture the short-term response of flow and, in particular, temperature. The model domain includes the Trinity River, from Lewiston Dam (River Mile (RM) 110 TR ) to the confluence of the Klamath River at Weitchpec (RM 0 TR ) and the Klamath River from Orleans (RM 57.5 KR ) to Terwer (RM 5 KR ). Sixteen major tributary inflows are represented in the Trinity River reach of the model, and six major tributaries in the Klamath River reach. The confluence of the Trinity and Klamath River occurs at approximately RM 42.5 on the Klamath River . Geometric representation of the river - the latitude and longitude, as well as the bed slope - was based on several sources including USGS topographic data and USDA FSA Aerial Photography Field Office aerial (digital) photographs. Additionally, topographic shading information was incorporated into the modeling framework based on a 10 meter DEM.
Meteorological, flow, and temperature data were required to drive the model. Meteorological data from Lewiston Fish Hatchery/Trinity Camp stations data were used to represent the upper and middle Trinity River reaches, whereas the Hoopa station data was used for lower Trinity River and Klamath River reaches. Flow data were obtained from USGS gages to define boundary conditions for the main stem and tributaries (where available), to estimate accretions from ungaged tributaries, and to provide calibration data. Temperature data were obtained from USGS and CDEC, as well as information provided by TRRP. These data were used to formulate boundary conditions and to serve as calibration data for the model. A challenging aspect of this project has been the formulation or representative boundary conditions for tributaries lacking year round temperature data. Where data were lacking, initial estimates of influent tributary temperatures were based on an equilibrium temperature method. However, temperatures associated with snowmelt runoff in the spring suggest that tributaries do not attain equilibrium temperature prior to reaching the Trinity. An empirical relationship was developed based on field observations to adjust spring period inflow temperatures.
Calibration refinement, preliminary model application, and documentation are current tasks in this project. The project is sponsored by Trinity County Planning and Natural Resources and funded through the TRPP.
Presentation notes:
Many tributaries did not have data for the entire year. This had to be estimated using a equilibrium model. Corrections were introduced for snow melt and for north side and south side tributaries. For example, the equilibrium model overestimated tributary temperatures by 9 C at the midpoint of snowmelt (Julian day 125). Model predicts Trinity River temperatures well. Current work includes more calibration, application and documentation. Anticipated that model will be helpful to predict Trinity flows on the Klamath.
Thermodynamics of Trinity and Lewiston Reservoir
Michael L. Deas, Watercourse Engineering, Inc., Mike.Deas@watercourseinc.com, (530) 750-3072
Trinity Reservoir is the principal component of the Trinity Division of the United States Bureau of Reclamation. Maximum reservoir storage capacity is 2,448,000 acre-feet and mean annual inflow is about 1,200,000 acre-feet. Trinity Reservoir discharges to Lewiston Reservoir (14,660 acre-feet) that regulates Trinity River diversions to the Central Valley via Clear Creek Tunnel, and downstream releases to the Trinity River . The quality and quantity of water released from Trinity Reservoir define important upstream conditions for Lewiston Reservoir, releases to the Trinity River, and diversions to the Sacramento River Basin . Extra-basin diversions and releases to the Trinity River help maintain cool water temperatures for anadromous fishes in the Sacramento River and Trinity River, respectively.
Trinity Reservoir stratifies seasonally with surface temperatures exceeding 70 o F. However, the reservoir is sufficiently large that cold water releases (typically < 50 o F) can be sustained through the summer and fall months under normal operating conditions. However, two conditions can diminish the benefit of these cold waters on downstream reaches (both in the Trinity and Sacramento Rivers ): low storage in Trinity Reservoir and heating within Lewiston Reservoir.
Low storage conditions can diminish the cold water pool and lead to entrainment of near surface waters into the powerhouse intake during the summer and fall months - leading to increased release temperatures downstream. Such conditions have occurred historically. However, under such conditions storage alone may not solely determine the ultimate release temperatures. The initial reservoir temperature, initial storage, rate of withdrawal, and time of year can also be important. Such factors should be considered in carryover studies and operations planning.
Heating in Lewiston Reservoir is a second process that increases water temperatures in waters released to the Trinity River as well as those waters diverted to the Sacramento River Basin . During summer and fall months, typical flow rates in through Lewiston range from 1000 to 3000 cfs or more on a daily average. At 3000 cfs the residence time of the reservoir is approximately 2.5 days, but increases to approximately 7.5 days at 1000 cfs. Thus, operations at Lewiston, Carr Powerhouse, and downstream facilities in the Sacramento Basin may play a role in water temperature releases to the Trinity River. A temperature control curtain has been installed at Lewiston to improve temperature management in both the Trinity and Sacramento River.
Temperature models of the reservoirs and the river have been constructed to provide further insight into temperature management alternatives. These models are undergoing continued revision and refinement as additional information and field data are obtained.
Presentation notes:
Trinity Dam is 538 feet high and the lake is 450 feet deep. This creates lots of cold water, which is valuable for downstream releases to rivers that are too warm for fish. Deas showed several graphs of water temperatures versus depth over the season. The patterns of temperature change over the season and can change from year to year. These have implications for how water can be drawn out and how cool water may still be maintained. Lewiston Dam, by comparison is small-91 feet high with a 50-foot pool depth. Deas recommended switching to operations of these reservoir to a "year-type" operation to optimize use of cool water according to the year-to-year temperature variation. He suggested that the temperature curtain has limitations in its ability to manage temperatures. There are carry over storage considerations. Simulation models are useful for management of temperatures.
Questions: Could fall outflow temperatures be lowered? Possibly, but it depends on inflow temperatures. Models show temperatures are extremely sensitive to prior conditions.
Trinity Reservoir Cold Water Pool: Historical Analysis and Future Outlook
Tom Stokely, Principal Planner, Trinity County Planning Dept.; (530) 623-1351, X3407
California 's major rivers dammed by the Bureau of Reclamation's (BOR) Central Valley Project (CVP) system in California include, but are not limited to the Trinity River, Sacramento River, American River , Stanislaus River and the San Joaquin River . Other major rivers in California have also been dammed by either the California Department of Water Resources' (CDWR) State Water Project (SWP) such as the Feather River, or local agencies such as the Yuba County Water Agency (YCWA) on the Yuba River (to name just a few). While anadromous fishery runs have been adversely affected by construction of the dams through loss of habitat and historic flows, these large reservoirs also contain large amounts of cold water that are now essential for the preservation, propagation and rehabilitation of salmon and steelhead fisheries in California.
However, current and proposed water delivery schedules by BOR, CDWR and other agencies include plans to deliver unprecedented amounts of water during wet, normal and dry water years, such that large reservoirs will likely be drained to mud puddles during the next multi-year drought. In addition to widespread water shortages for agriculture, municipal, industrial and hydropower, the depletion of cold water supplies in major reservoirs will lead to reproductive failure and major fish kills of important commercial, recreational and tribal salmon fisheries. The end result will undo decades of salmon restoration work, wasting of hundreds of millions of dollars of restoration dollars and water allocated for fisheries, along with devastating economic, social and cultural impacts to fishery-dependent communities. The over-allocation of managed water supplies, combined with Global Warming will ultimately have a devastating effect on California 's remaining salmon and steelhead populations.
Trinity Reservoir's cold water pool is generally reliable, coming out of the dam at 44-45 degrees F. However, it requires water exports from the Trinity River basin to the Sacramento River basin to keep the Trinity River cold. Lewiston Reservoir, the 7 mile-long shallow regulation reservoir immediately downstream of Trinity Dam, requires a constant flow of approximately 1800 cfs during the hot summer months to keep temperatures at the "headwaters" of the anadromous Trinity River fishery at Lewiston Dam at approximately 48-50 degrees F. Since summer base flows in the Trinity River are 450 cfs, this means that approximately 1,350 cfs is required to be sent to the Sacramento River during summer in order for the Trinity River to stay cold. In the absence of exports to the CVP, even with cold temperatures at Trinity Dam, Lewiston Reservoir and the Trinity River will rapidly heat and lead to lethal temperatures downstream.
The droughts of 1976-77 and 1987-93 resulted in substantial depletion of cold water storage in Shasta and Trinity reservoirs and elevated water temperatures in the Trinity River . Relatively minor violations of State temperature objectives occurred during the more recent drought in the early 1990's, but the experience of the 1977 drought will be examined in greater detail to remind us of the imminent danger to our fisheries that continues to exist. Unless major policy changes are made in CVP operations and planned water deliveries, we can expect that the next multi-year drought in California will prove devastating to the Trinity River's fisheries, and those of every other dam-controlled river in California .
Presentation notes:
Temperature objectives for the Trinity River (vary between 56 and 60 F) have been typically met. However, Stokely is concerned that this will not guaranteed once a seasonal drought recurs and given the growing desire for water and confusion between documents that declare the use of water. CALFED and the NAPA agreement are looking to increase their share of water over that allowed by the ROD and Trinity EIS decisions. Stokely showed text of other documents/agreements that appear to show discrepancies for water that is intended to be diverted. He called these the "two faces of Bruce Babbitt." Stokely recommended 900,000 acre-feet of storage be reserved to September 30 in Trinity Lake . Water banking should be allowed. Exports of water south of the Sacramento Delta should be reduced.
Discussion Session: Water Temperature Compliance and Modeling
Participants: Paul Zedonis, Ibrahim Sogutlugil, Michael Deas, and Tom Stokely
How firm was this NAPA decision? It is being slowed down. For example, salinity objectives of the delta will slow down exports out of the Delta. There will likely be litigation.
What about changes in snowmelt as affecting reservoir temperatures? Modeling global warming is difficult, but models are a good way to constrain the questions and they allow you to dismiss some scenarios. Models can give insights to what might happen and then you can use risk analyses.
Should money be spent to update the Lewiston and Trinity temperature models? Stokely: The current model works ok unless we have drought conditions. Then a more finely tuned model may be useful. Deas: You should use models to provide information at one finer time step than you need your answers. The new model has an hourly time-step and 100-m spatial resolution. Zedonis: We used to think models were good enough, though we are a point where we can examine the physical components better than biological components. Temperature models might help to ask questions about the release bench.
An example of how cool water was used in 1991: Shasta Reservoir ran out of water; Trinity River was run to Whiskeytown and over the spillway to Clear Creek and then the Sacramento River to decrease water temps by 1 degree to help the winter Chinook.