(from the introduction in the Users' Manual)
The Instream Flow and Aquatic Systems Group (IFASG), in cooperation with the U.S. Soil Conservation Service (SCS) and the U.S. Fish and Wildlife Service (FWS), has developed this model to predict instream water temperatures based on either historical or synthetic hydrological, meteorological, and stream geometry conditions. The model is applicable to any size watershed or river basin with a stream network of any stream order and complexity. The model incorporates several features, including:
The instream water temperature model was designed to predict the average daily temperature and diurnal fluctuations in water temperatues throughout a stream system network. It mostly uses readily available meteorological and hydrological data. Stream geometry information also is necessary, but often is collected as a part of previous or concurrent hydrologic studies. However, the model does not require the collection of new field data (e.g., stream temperature) over some period of time before the temperature regime of a stream system can be predicted. The use of previously collected data may help to calibrate the model, but is not necessary for most applications.
Meteorologic data required by the model consist of certain solar radiation coefficients, air temperature, relative humidity, sunshine ratio, and wind speed. These data often are available from published climatological and related data but generally require extrapolation to a point in the basin. The model includes features to transpose meteorology data from a single known point in the basin throughout the stream network.
Solar radiation is entirely modeled as a function of the latitude of the stream basin, time of the year, and prevailing meteorological conditions.
Shading, resulting from both topographic features and riparian vegetation, is modeled as a function of latitude, time, basin topographic characteristics, and riparian vegetation parameters.
Hydrological data required by the model consist of discharge or flow data throughout the stream system and initial water temperatures at the beginning points. The hydrological data needed, either the discharge, initial temperature, or both, can be developed from synthetic hydrological procedures or from known or assumed reservoir operation procedures, where applicable. The model includes regression techniques to smooth and/or complete water temperature data at points of at least some known water temperature.
Stream geometry information needed consists of the stream system network (mainstem and tributaries), stream widths, stream gradients, shading parameters, and hydraulic retardance. Data on all but the shading parameters are normally collected as part of a hydrological study.
The instream water temperature model can be conceptualized as three general parts: (1) input preprocessing; (2) heat flux relationships; and (3) a heat transport equation. Input preprocesssing includes the preliminary input generation, such as the adiabatic meteorological corrections, solar radiation, and regression models. The heat flux relationships deal with the heat sources and thermal processes involved in the exchange or generation of heat, including back radiation from the water. The heat transport equation describes the downstream movement of heat energy in the water and the actual exchange of heat energy between the water and its surrounding physical environment.
Instream models differ from lake models because the downstream water movement tends to mix the water. This turbulent mixing is assumed to evenly distribute the temperature both vertically and transversely and, therefore, is the basis for using a constant water temperature throughout a given cross section at any given instant. The purpose of the transport model is to predict the longitudinal temperature variation. While the temperature at a specific cross section may be constant at any given time, a downstream differential is expected and predicted.
The turbulent mixing, leading to a homogeneous distribution of temperature throughout a given cross section, simplifies the application of the heat flux relationships part of the model. All heat entering the water is assumed to be immediately distributed both vertically and transversely. All heat leaving the water is a function of the homogeneous water temperature. Flowing water generally mixes at a far faster rate as a result of the turbulence than due to either conduction or convection within the water.
The model can, and has been, used satisfactorily to evaluate the impact of the following factors on instream water temperature:
The model has been used in large basins (e.g., the Upper Colorado River Basin) to study the impact of water temperature on endangered species. It also has been used in smaller, ungaged watersheds to study the impacts of riparian vegetation on salmonid habitat. The model also has been used several times to evaluate the impact of reservoir releases on water temperature immediately below a dam.
Various solution techniques, ranging from hand-held calculator to computer programs, directly offer the user reasonable answers for each application. The selection of the proper solution technique depends on the complexity of the application, volume of computations involved, and availability of hardware to perform the calculations. The software for all the solution techniques is available to the user through IFASG.
(abstract excerpted from Bartholow, J.M., 1991: Environmental Management, vol. 15, no. 6, pp. 833-845)
Water temperature is almost certainly a limiting factor in the maintenance of a self-sustaining rainbow trout (Oncorhynchus mykiss, formerly Salmo gairdneri) and brown trout (Salmo trutta) fishery in the lower reaches of the Cache la Poudre River near Fort Collins, Colorado, USA. Irrigation diversions dewater portions of the river, but cold reservoir releases moderate water temperatures during some periods. The US Fish and wildlife Service's Stream Network Temperature Model (SNTEMP) was applied to a 31-km segment of the river using readily available stream geometry and hydrological and meteorological data. The calibrated model produced satisfactory water temperature predictions (R2=0.88, P<0.001, N=49) for a 62-day summer period. It was used to evaluate a variety of flow and nonflow alternatives to keep water temperatures below 23.3degC for the trout. Supplemental flows or reduced diversions of 3 m3/sec would be needed to maintain suitable summer temperatures throughout most of the study area. Such flows would be especially beneficial during weekends when current irrigation patterns reduce flows. The model indicated that increasing the riparian shade would result in little improvement in water temperatures but that decreasing the stream width would result in significant temperature reductions. Introduction of a more thermally tolerant redband trout (Oncorhynchus sp.), or smallmouth bass (Micropterus dolomieui) might prove beneficial to the fishery. Construction of deep pools for thermal refugia might also be helpful.
Bartholow, J.M., 1989: Stream temperature investigations: field and analytic methods. Instream Flow Information Paper No. 13. U.S. Fish Wildl. Serv. Biol. Rep. 89(17). 139 p.
Bartholow, J.M., 1990: Stream temperature model. Pages IV-20 to IV-47 in W.S. Platts ed. Managing Fisheries and Wildlife on Rangelands Grazed by Livestock: A guidance and reference document for biologists. W.S. Platts and Assoc. for the Nevada Department of Wildlife. December, 1990. v.p.
Bartholow, J.M., 1991: A modeling assessment of the thermal regime for an urban sport fishery. Environmental Management 15(6):833-845.
Bartholow, J.M. 1993: Sensitivity of the U.S. Fish and Wildlife Service's Stream Network Temperature Model. Pages 247-257 in Morel-Seytoux, ed., Proceedings of the Thirteenth Annual American Geophysical Union Hydrology Days. Fort Collins, CO.
Bartholow, J.M., 1995: The Stream Network Temperature Model: A decade of Results, Pages 57-60 in Ahuja, L., K. Rojas, and E. Seeley, editors. Workshop on Computer Applications in Water Management, Proceedings of the 1995 Workshop. Water Resources Research Institute, Fort Colins, Colorado. Information Series No. 79. 292 pp.
Bartholow, J.M., J.L. Laake, C.B. Stalnaker, and S.C. Williamson, 1993: A salmonid population model with emphasis on habitat limitations. Rivers 4(4).
Dinan, K.F. 1992: Application of the Stream Network Temperature Model (SNTEMP) to the central Platte River. Professional paper, Department of Fish and Wildlife, Colorado State University, Fort Collins, Colorado. 49 pp plus appendix.
Lifton, W.S., K.A. Voos, and D. Gilbert. 1987: Simulation of variable release temperatures from the Rock Creek-Cresta project using the U.S. Fish and Wildlife Service instream temperature model. Pages 610-619 in B.W. Clowes, ed. Waterpower 87 Int. Conf. on Hydropower, Portland, OR August 19-21, 1987..
Lifton, W.S., K.A. Voos, and D. Gilbert. 1985: The simulation of the Pit 3,4, and 5 Hydroelectric Project using the USFWS instream temperature model. Pages 1805-1814 in Waterpower 1985, Volume 3. Proceedings of an International Conference on Hydropower, Las Vegas, Nevada, September 25-27, 1985. Am. Soc. of Civil Engineers.
Mattax, B.L. and T.M. Quigley, 1989: Validation and sensitivity analysis of the stream network temperature model on small watersheds in Northeast Oregon. Pages 391-400 in W.W. Woessner and D.F. Potts, eds. Proceedings of the Symposium on Headwaters Hydrology, Am. Wat. Res. Bethesda, MD 20814-2192.
Meyer, P., K.A. Voos, and B. Valdez, 1983: Stream temperature modeling in the Susitina River Basin, Alaska. Paper presented at the Alaska Science Conference, Arctic Division of AAAS, Whitehorse, Yukon Territory, Canada.
Prewitt, C.G., K.A. Voos, and T. Waddle, 1981: Completion report-- IFG study of physical-chemical habitat conditions on the Green and Colorado Rivers in Colorado and Utah. Coop. Instream Flow Serv. Group, U.S. Fish Wildl. Serv., Fort Collins, CO. 44 p.
Stalnaker, C., B.L. Lamb, J. Henriksen, K. Bovee, and J. Bartholow, 1995: The Instream Flow Incremental Methodology. A primer for IFIM. National Biological Service Biological Science Report 95(29). 44 p.
Sullivan, K., J. Tooley, K. Doughty, J.E. Caldwell, and P. Knudsen, 1990: Evaluation of prediction models and characterization of stream temperature regimes in Washington. Timber/Fish/Wildlife Rep. No. TFW-WQ3-90-006. Washington Dept. of Nat. Resources, Olympia, Washington, 224 p.
Theurer, F.D., and K.A. Voos, 1982: IFG's instream water temperature model validation. Pages 513-518 in Conference on water and energy: technical and policy issues. ASCE Proc. of the Hydraulics Conf., Pittsburg, PA, and Fort Collins, CO, May and June, 1982.
Theurer, F.D., K.A. Voos, and C.G. Prewitt, 1982: Application of IFG's instream water temperature model in the Upper Colorado River. Pages 287-292 in International symposium on hydrometeorology, Denver, CO, June 13-17, 1982. Am. Wat. Resour. Assoc.
Theurer, F.D., K.A. Voos, and W.J. Miller, 1984: Instream Water Temperature Model. Instream Flow Inf. Pap. 16. U.S. Fish and Wildl. Serv. FWS/OBS-84/15. v.p.
Theurer, F.D., I. Lines, and T. Nelson, 1985: Interaction between riparian vegetation, water temperature, and salmonid habitat in the Tucannon River. Water Resources Bulletin. Am. Wat. Res. Assoc. 21: 53-64.
Tu, S. (Project Manager), 1991: Instream Temperature Model Evaluation. Pacific Gas & Electric Environment, Health, and Safety Report 009.4-90.17. June 7, 1991. Pacific Gas & Electric, San Ramon, CA v.p.
Tu, S. W. Mills, and S. Liu, 1992: Temperature model evaluation and application. Habitat Evaluation Notes and Instream Flow Chronicle. Colorado State University Conference Services. January 1992. 2(1):1-3.
Voos, K.A., Lifton, W.S., and D.A. Gilbert, 1987: Simulation of the Stanislaus Project: Performance of the U.S. Fish and Wildlife Service instream temperature model on a complex system. Pages 746-755 in B.W. Clowes, ed. Waterpower 87: Proceedings of Int. Conf. on hydrology. Portland, OR. Aug. 19-21, 1987.
Waddle, T.J., 1988: Water temperature data analysis and simulation for the Salmon River, New York, Summer 1986. Pages 201-211 in H.J. Morel-Seytoux and D.G. DeCoursey, eds. Proceedings of the eigth annual AGU front range hydrology days, Water Resources Publication, 1988.
Zedonis, P., 1994: Estimated influences of feather edge and side-channel projects on water temperatures of the upper Trinity River. U.S.D.I. Fish and Wildlife Service, Lewiston, Calif. 19 p.
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