Exploring the ability of reservoir infrastructure to mitigate climate
change compounded impacts on stream temperature and water availability
in the Southeastern United States
Abstract
Over 270 major dams have been constructed in the Southeastern United
States (SEUS) during the past century, changing natural flow patterns
and affecting stream temperatures. Projected increases in air
temperature combined with changes in precipitation may result in water
scarcity and affect maximum stream temperatures during the summer for
some regions in the SEUS. Currently existing reservoirs mitigate water
shortages during drought by releasing more water but reducing residence
time, the ratio of reservoir volume to inflow. Regulating stream
temperature in the summer can be done by either increasing residence
time or releasing more water. In this study, we investigate the extent
to which the current reservoir infrastructure can be used to mitigate
the impacts of climate change under current reservoir regulations as
well as the range of operating rules that could minimize climate change
impacts on both streamflow and river temperature. We use the Variable
Infiltration Capacity (VIC) hydrological model to simulate runoff, which
is then used as input to a large-scale river routing-reservoir model
(MOSART-WM) to simulate reservoir operations and produce regulated
streamflow. VIC and MOSART-WM outputs are then used as input to a stream
temperature model that accounts for thermal stratification in reservoirs
(RBM-res). Climate change projections are based on two representative
concentration pathways (RCPs) and multiple global climate models from
the Coupled Model Intercomparison Project Phase 5 (CMIP5). We compare
modeled changes with those from a model implementation that does not
include any reservoirs and which therefore lacks any flow regulation
(VIC->MOSART-RBM) to evaluate the resilience of current
reservoir infrastructures. We also evaluate different reservoir
operating rules (residence time versus low flow mitigation) to
investigate the extent to which the current reservoir system can be used
to mitigate the impacts of climate changes on both streamflow and stream
temperature.