Reservoir operations

Fall Creek Reservoir at drawdown (Source: D. Tullos). What is drawdown? Lowering the reservoir to let the river act like a river again for a few days to weeks.

Climate and land use change are modifying inflows to reservoirs, which have potential to impact the ability of reservoirs to reduce flood risk, produce hydropower, supply water to cities and industries, provide recreation, and release flows to support downstream ecosystems. Furthermore, the growing population, aging infrastructure, and changing regulations and socioeconomic values place additional pressure on water resources systems. Under a collection of grants, the Rivers Lab has been using a suite of coupled models to evaluate how changing environmental conditions and aging infrastructure impact reservoir operational performance, and how reservoir operations can be adapted to mitigate the effects of changing conditions on people and the environment.  Key outcomes from the work so far include:

  • Lowering the water level of reservoirs for flushing sediment, flushing fish, and dam maintenance or decommissioning exposes accumulated sediment to erosion and downstream transport. Typically, models of the reservoir’s geomorphic response have been limited to 1D incisional erosion without the incorporation of widening, but our work demonstrates that the drawdown scenario plays an important role in the processes leading to, and relative importance of, lateral erosion (Artruc et al.  2022).
  • hydrologic model selection for climate change analysis (Surfleet et al. 2012), uncertainty in projections of future reservoir inflows (Surfleet and Tullos 2012), and effects of climate change on rain-on-snow events (Surfleet and Tullos 2013) (NSF #0846360);
  • the role of hydrogeology in the sub-basin sensitivity to land use and climate change (Mateus et al. 2015), and the reliability, vulnerability, and sensitivity of reservoir operations to climate change (Mateus and Tullos 2016a, b) (NSF #0846360, #1038925);
  • Deeply multidisciplinary modeling, stakeholder engagement, and scenario analysis around climate change responses, produced through the Willamette Water 2100 project. Results highlight the role of regulations and conveyance costs in producing scarcity (Jaeger et al. 2017) and the impacts of changing storage on reservoir operations across a network of reservoirs (Tullos et al. 2020) (NSF #1038925).
  • Matlab scripts for reservoir operations metrics