Sustainable Hydropower: Ecological Tradeoffs with Contrasting Water Level Regimes

EPA Grant Number: FP917824
Title: Sustainable Hydropower: Ecological Tradeoffs with Contrasting Water Level Regimes
Investigators: Murphy, Christina Amy
Institution: Oregon State University
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2015 through August 31, 2018
Project Amount: $132,000
RFA: STAR Graduate Fellowships (2015) RFA Text |  Recipients Lists
Research Category: Academic Fellowships


We aim to understand ecological interactions within reservoirs located in headwaters of the Willamette River. We are studying how changes in water level regimes affects 1) trophic relationships within reservoir food webs, 2) zooplankton communities, which support ESA listed juvenile salmonids and 3) water quality (phytoplankton, nutrient and physical parameters).


This research uses a case study design of four reservoirs in the upper Willamette Basin: Blue River, Fall Creek, Lookout Point and Hills Creek Reservoirs. Fall Creek Reservoir has undergone early winter drawdowns to run-of-river and Lookout Point Reservoir experienced a summer drawdown for repairs to infrastructure. Within each reservoir, we measure nutrient concentrations, dissolved oxygen, temperature, chlorophyll a, primary production, and light transmission, at multiple depths and fixed locations at the start, middle, and end of summer full pool. We sample fish and collect caudal fin clips, and quantify their plankton and invertebrate food resources at beginning and end of full pool in each reservoir. We analyze natural abundance of isotopes [carbon (13C) and nitrogen (15N)] to identify trophic relationships for the reservoir communities, which include both native and exotic fishes. These field data will be used to design and parameterize models to evaluate species and community responses to changes in reservoir water management. The models include Structural Equation Models (SEMs) to examine strength of linkages and trophic relationships and fish foraging and bioenergetics models of Chinook Salmon growth in response to resource availability and limnological conditions in each study reservoir.

Expected Results:

The major products will include better understanding of effects of water level management on reservoir food webs and tools to evaluate tradeoffs and sustainability of ESA listed salmonids where Pacific Northwest river headwaters have been modified by large dams. More specifically the products include: 1) comparison of physical, chemical and biological conditions in these reservoirs, 2) decision trees for managers to help them evaluate effects of timing, magnitude and duration of drawdowns on reservoir aquatic communities, 3) a foraging and bioenergetics model to examine relative growth of juvenile Chinook Salmon under a range of scenarios with anticipated or observed in-reservoir conditions, and 4) peer-reviewed publications analyzing and presenting the products above and also publications evaluating the strength of feeding interactions based on stable isotope analyses and a food web model with focus on Chinook Salmon and critical predator, competitor, and prey interactions and feedback loops.

Supplemental Keywords:

Dams, reservoirs, salmon, water level fluctuations, food webs

Progress and Final Reports:

  • 2016
  • 2017
  • Final