Understanding and Responding to Future Change in Hydrologic Variability in Wyoming’s Watersheds
- Project Number: 70
- PIs: Bart Geerts
- Period: July 2026 - June 2029
Abstract:
Through separate funding, we have conducted a series of high-fidelity, fine-resolution
numerical simulations of the regional climate, coupled to the land surface, seasonal
snowpack, and watershed hydrology for Wyoming and surrounding areas. These simulations
cover the historical period, as well as futures decades out to 2100. The spatial resolution
of these simulation is unprecedented, and is necessary to capture Wyoming’s mountains,
and the weather and precipitation over the mountains. In general, any regional climate
simulation has uncertainty in the predictions due to climate variability and uncertainty
in the representation of processes in the atmosphere, at the surface, and in rivers.
These uncertainties are tackled through the use of an ensemble of driver datasets,
which provides a spread of possible solutions and enables an assessment of risk. The
driver datasets include the output from 15 CMIP6 global climate models, plus multiple
model perturbations. All simulations are at 9 km grid resolution, bias-corrected,
and validated against recent history, and seasonal streamflow at natural flow gauges
is used for calibration. Our finest resolution simulation, at an unprecedented 1.3
km grid spacing, currently in production, is expected to capture terrain-driven snowfall
distribution more accurately than the observational network in the historical period.
This is a single deterministic simulation, driven by the CMIP6 ensemble mean to predict
out to 2063.
We will couple these simulations of the weather and land surface (both the 9 km ensemble and the 1.3 km deterministic run) to stream hydrology in all HUC 8 watersheds in Wyoming, using the WRF Hydro model calibrated against gauge data during the historical period. These river routing simulations will be used to examine long-term changes in seasonal streamflow patterns, probabilities of flooding due to rapid spring snowmelt (often rain-on-snow events), and probabilities of seasonal and multi-year hydrological drought. We will identify watersheds most susceptible to these challenges. These data will be made available publicly, and graphically displayed at https://wyadapt.org. Our work so far has examined natural flow in watersheds only, i.e., unaffected by built infrastructure. In this project, we will work with the Wyoming Water Development Office (WWDO) , the State Engineer’s Office (SEO), and other interest groups, to examine specific water management scenarios that can mitigate the impact of flooding (and associated channel erosion, water turbidity, and sedimentation) and the impact of late summer low-flow.
