Simulating Groundwater-Streamflow Connections in the Upper Colorado River Basin

Area of Science:

• Hydrology
• Environmental Science
• Geosciences

Background:

• Mountain catchments rely on snowmelt for spring river streamflows.
• Groundwater's contribution to streamflow in these complex environments is poorly understood.
• Deep aquifers in mountain regions pose monitoring challenges.

Purpose of the Study:

• To quantify the effect of lateral groundwater flow on annual and peak streamflow.
• To assess groundwater's role in predevelopment conditions within the Upper Colorado River Basin (UCRB).
• To improve hydrologic model accuracy by incorporating lateral groundwater dynamics.

Main Methods:

• Utilized an integrated hydrologic model for numerical experiments.
• Focused simulations on the Upper Colorado River Basin (UCRB).
• Conducted sensitivity analysis on hydraulic conductivity.

Main Results:

• Lateral groundwater flow increased peak streamflow by up to 57%.
• Model-observation correlation for mean annual flows improved from 0.84 to 0.98 with lateral flow.
• Impacts were more pronounced in steeper topography and varied across UCRB sub-basins.

Conclusions:

• Lateral groundwater flow significantly influences streamflow, especially peak flows, in mountain catchments.
• The inclusion of lateral groundwater flow enhances hydrologic model performance.
• Findings are relevant to headwater systems globally, highlighting the importance of subsurface processes.