Tennessee Project: Implementing and optimizing a structured decision making model for regulated rivers

Tennessee Project

Implementing and optimizing a structured decision making model for regulated rivers

July 2013 - December 2014

Personnel

Participating Agencies

U.S.G.S.

In a recently-completed project, a structured decison making model was developed for the operation of Tims Ford Dam on the Elk River. In this follow-up project, we are: 1. Initiating training and support for TVA and USFWS personnel to improve their understanding of how the decision model works, how to use it, and how to update it. 2. Investigating options for proceeding with optimization of the decision model. Optimization is a complex component of the Structured Decision Making process that, although not required to effectively use existing, fully-parameterized decision models, helps managers identify long-term optimal decisions. Optimization is a rapidly-changing area of research in the decision-making world. Colin has limited experience with optimization, but has discussed the topic with colleagues more familiar with the process. Identifying the best method for optimization (there are many) and conducting optimization analyses would require a year or more of additional work. However, even if optimization cannot be accomplished during six additional months of support, it would be useful to begin this process.

Research Publications

Research Publications	Publication Date
Shea, C.P., P.W. Bettoli, K.Potoka, C.F. Saylor, and P.W. Shute. 2015. Use of dynamic occupancy models to assess the response of darters (Teleostei: Percidae) to varying hydrological and hydrothermal conditions in a southeastern United States tailwater. River Research and Appplications 31:676-691. \| Abstract	May 2015	River regulation and water resource development are important problems threatening stream-dwelling fishes and other aquatic biota. During the past 100 y, most large rivers in North America have been altered for flood control, hydropower, navigation, or water supply development. Although these activities clearly provide important human services, their associated environmental disturbances can profoundly affect stream-dwelling organisms. Nowhere in North America is this more evident than the Tennessee River drainage in Alabama, Georgia, Tennessee, and Virginia, where the Tennessee Valley Authority operates 11 dams on the mainstem Tennessee River and 27 dams on major tributaries. We used multi-species dynamic occupancy models to evaluate the influence of site- and species-level characteristics on metapopulation dynamics rates for 15 darter species native to the Elk River, Tennessee. Modeling results indicated that darter colonization was strongly and positively related to water temperature and body size, but crevice spawning species were substantially less likely to colonize previously unoccupied study reaches. Modeling results also indicated that the risk of extinction was strongly and negatively related to stream temperature. Additionally, the presence of populations in neighboring upstream study reaches contributed to a lower risk of extinction for existing populations. A series of metapopulation simulations based on parameter estimates from the best-approximating models were conducted to evaluate the consequences of alternative hypotheses on darter dispersal capabilities. The simulation results revealed that failure to account for alternative plausible hypotheses of influential properties, such as dispersal, could mask the range of possible outcomes, both positive and negative. Our study demonstrates the usefulness of trait-based approaches and a metapopulation framework to assess the dynamics of darters in a heavily-regulated stream system. Results from our study will provide a baseline for evaluating the ecological consequences of alternative dam operations under an adaptive management framework.
Potoka, K.M., C.P. Shea, and P.W. Bettoli. Multi-species occupancy modeling as a tool for evaluating the status and distribution of darters in the Elk River, Tennessee. Transactions of the American Fisheries Society 145:1100-1121. \| Abstract \| Download	August 2016	Sixteen darter species, including the federally endangered Boulder Darter Etheostoma wapiti, are known to occur in the Elk River, a large, flow-regulated Tennessee River tributary in Tennessee and Alabama. Since the construction of Tims Ford Dam (TFD) in 1970, habitat modification caused by cold, hypolimnetic water releases and peak-demand hydropower generation have contributed to population declines and range reductions for numerous aquatic species in the mainstem Elk River. We developed multi-species occupancy models to determine the influence of site-, habitat-, and species-level characteristics on darter occurrence using presence-absence data for 15 species collected from 39 study reaches. Modeling results indicated that the large river obligate species, such as Boulder Darters, were 7.53 times more likely to occur for every 37 km increase in downstream from TFD. In contrast, small stream and cosmopolitan species were 2.04 and 1.82 times less likely, respectively, to occupy stream reaches for every 37 km downstream from TFD. The probability of occurrence for darter species also was strongly and negatively related to the absence of cobble and boulder substrates and the presence of high silt levels, particularly for species that require boulder substrates during spawning. Although total darter species richness was similar across all 39 sample sites, the composition of darter assemblages varied substantially among locations, presumably owing, in part, to species-specific habitat affinities and hydrothermal conditions. Results from this study provide a baseline for managers to assess future changes in the status and distribution of darter species following recent operational changes at TFD.

Cooperative Fish and Wildlife Research Units Program: Tennessee Education, Research and Technical Assistance for Managing Our Natural Resources