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Interdisciplinary Modeling Exercise: Climate and Fish

  • IntroductionSnow

    This page describes one of several culminating exercises designed for GEOS 697 Interdisciplinary Modeling: Water-Related Issues and Changing Climate.  Exercises are team-based projects designed to promote interaction between students in different disciplines. Teams will plan out an interdisciplinary modeling project pertaining to water-related issues in Idaho and New Mexico. Details and expectations are described here.

    This project focuses on the impacts of changing climate on fish habitat in an upland, semiarid watershed. Students are expected to design, and implement to the extent possible, a modeling strategy to assess the impacts of climate warming on the hydrology of a snowmelt-dominated stream, and the consequences of those changes on the quality of redband trout habitat.


    This goal of this interdisciplinary modeling project is to determine the impact of climate warming on fish habitat in Dry Creek.

  • Small mountain watersheds provide critical habitat for fish. Habitat quality is dictated by environmental conditions including water temperature, dissolved oxygen, and nutrient availability. All of these conditions are sensitively adjusted to the hydrologic regime. In the semiarid mountains of the intermountain west, stream hydrology and consequently fish habitat, are directly related to the timing and magnitude of mountain snowmelt. The mountain snowpack is changing [Mote et al., 2005]. Although the total amount of precipitation that a watershed receives in a year may not be changing, the proportion that falls as snow is diminishing, and the snow that accumulates on the ground is melting earlier leading to lower summer flows and potentially late-season stream cessation[Luce and Holden, 2009].

    The Dry Creek Experimental Watershed (DCEW) has served as a hydrometeorological research testbed in the semiarid rain-snow transition zone since 1999 ( The mission of the DCEW is to provide temporally continuous and spatially distributed hydrometeorological and geographical data from point to watershed scales for researchers and educators. Long-term monitoring and short-term research campaigns have focused on a wide range of topics on the interactions among climate, landforms, ecology, and hydrology.

    Dry Creek hosts a native, genetically pure population of Columbia River redband trout, which is a subspecies of rainbow trout native to high desert streams of the western US, east of the Cascades [Richins, 2014]. The American Fisheries Society, United States Forest Service, and Bureau of Land Management recognize Columbia River redband trout as a species of “special concern” An attempt to list the species under the Endangered Species Act failed due to a lack of information—as Columbia River redband trout is the least studied of Idaho’s salmonids.  Thus, there is a pressing need to document population genetic status (i.e., “purity”) and determine the adaptive basis for this trout’s unique ability to survive in harsh (extreme fluctuations in flow, high temperature, and low dissolved oxygen) desert streams [Thurow et al., 1997].

    The redband trout in Dry Creek are isolated from the mainstem  Boise River due to regular downstream summer drying of the channel and channel barriers (artificial waterfall). Richins [2014] tagged approximately 500 fish in Dry Creek and have collected genetic samples from the population over the past 3 years.  These data provide insight on redband trout distribution, movement patterns, as well as fine-scale population genetic and family structure.

    Dry Creek is fed by high elevation springs that most throughout the year most years. In very dry summers such as was observed in 2013 and 2014, Dry Creek contracts upwards, retreating towards its spring sources. In 2013, redband trout migrated upstream as Dry Creek contracted, but the ability of the species to disperse was limited by mountain topography, channel structure, and man-made barriers. Thus, habitat was greatly reduced and fish suffered high mortality, leading to a population reduction and loss of genetic diversity. Individuals which suffered the highest mortality were found in isolated pool habitats with extremely low levels of dissolved oxygen. Survivors established themselves in flowing upstream reaches [Richins, 2014].


    Luce, C. H., and Z. A. Holden (2009), Declining annual streamflow distributions in the Pacific Northwest United States, 1948–2006, Geophysical Research Letters, 36(16), L16401.

    Mote, P. W., A. F. Hamlet, M. P. Clark, and D. P. Lettenmaier (2005), Declining mountain snowpack in western North America.

    Richins, S. (2014), Ecology of Columbia River Redband Trout, Oncorhynchus mykiss gairdneri, in Dry Creek, Idaho (Lower Boise River Drainage), 74 pp, College of Idaho.

    Thurow, R. F., D. C. Lee, and B. E. Rieman (1997), Distribution and status of seven native salmonids in the interior Columbia River basin and portions of the Klamath River and Great basins, North American Journal of Fisheries Management, 17(4), 1094-1110.

  • Case Study Challenge: Earlier spring snowmelt, higher proportions of precipitation as rain, and warmer temperatures are impacting redband trout habitat in Dry Creek. Your challenge is to apply interdisciplinary modeling concepts to assess the impact of climate warming on the quality of redband trout habitat. The team should take into account the skills and interests of individual team members to develop a modeling approach to examine climate change impacts on redband trout in Dry Creek.

    The modeling system should transfer atmospheric inputs of mass (i.e., precipitation) and energy through a hydrologic model to evaluate the reliance of aquatic habitat on climate and landscape properties. Some things to think about for this project:

    1. How will warming temperatures change the spatial and temporal distribution of snow in the watershed?
    2. How will altered snow conditions impact streamflow?
    3. What specific habitat metrics may be sensitive to climate-driven hydrologic change?
    4. How will altered streamflow impacts habitat metrics?

    Modeling Guidelines and Questions: Participants are free to develop the modeling system as they see fit, given the skills and knowledge of the modeling team. A few points to consider:

    • Climate models are extremely complex. The model developed in this project should not model climate scenarios. Rather, scenarios should be obtained elsewhere, or simply invented.
    • The movement of water through a watershed is governed by basic physics and spatially distributed landscape properties. Physics-based models can be used to describe independent process (i.e. snowmelt and infiltration), but it may be difficult to distribute the processes over a watershed. Index approaches offer simplicity but can also suffer from the loss of spatial variability. The modeling team should consider an approach that represents the hydrologic processes operating in watersheds while maintaining computational efficiency.
    • Ideally, the modeling system should be able to discern snow and rain precipitation inputs. Thus, the hydrologic model will likely need air temperature and precipitation mass as inputs. The model may also accumulate and melt snow, and combine snowmelt and rain into a time series of surface water input (SWI). SWI should then infiltrate and flow through the subsurface to become streamflow or groundwater recharge.
    • The modeling team must consider how to transfer information between models or different modeling processes. For example, a snowmelt model can deliver water to the surface in discrete time steps, which is then available for drainage and evapotranspiration. Which process “takes” the water first? Further, how are hydrologic model outputs used in a fish habitat model?
    • An organized database and creative visualizations to aid data and model interpretations will be an important component of this project.

  • Most of the hydrometeorological data required to complete this exercise are available within the various pages of the DCEW website. However, modelers will need to look elsewhere for climate change projections, as well as for supporting information about fish habit.

    Hydrologic Data: The site contains links to real time and historical data for several hydrometeorologic stations distributed throughout the DCEW. These data can be used for model calibration and validation.

    Geospatial Data: DEM’s and other GIS coverages can be found here:

    Climate Change Scenarios: No scenarios are provided.

    Fisheries data: There are no publicly available data on the redband trout in Dry Creek. However, important information is contained in the thesis by Shelby Richins. Shelby’s thesis along with all other theses conducted in Dry Creek is accessible here:

    Model examples: An example excel-based snowmelt-infiltration-evapotranspiration model is provided. Participants can use this model as a learning tool, but will have to figure out how to perform similar modeling tasks at larger watershed scales.

    Other: drycreek.ppt