The significance of groundwater flow processes on surface water flow
Background
Groundwater is the largest source of available freshwater on Earth and plays a vital role in the hydrologic cycle. With numerous hydrological models available to simulate the interaction between groundwater and surface water, it can be hard for users to know how complex a model needs to be to support the decision making in their watershed.
In this project, researchers used a hydrologic model called HydroGeoSphere (HGS) to examine the significance of groundwater flow processes on surface water flow within the Alder Creek Watershed (ACW), a small watershed in southwestern Ontario, Canada. They compared the results of five modeling scenarios of increasing levels of subsurface complexity to field data to determine the spatial and temporal variations in surface water and groundwater fluxes. They also used the model to investigate the impact different groundwater pumping scenarios on surface and groundwater interaction to provide insights relevant to municipal wellfield management.
Modelling results revealed several new insights including:
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Models with different subsurface representation yield dramatically different results. The model with the most detailed representation of the subsurface produced the best results.
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The way a model treats the shallow subsurface is critical when determining surface water-groundwater interaction and streamflow.
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Municipal well operations can significantly impact both surface water and groundwater flows.
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When predicting hydraulic head at various depths, the heterogeneity of the subsurface in the model can greatly impact results.
Principal Investigator:
Walter Illman, Professor, Earth and Environmental Sciences
Project duration:
2017-2020
GWF funding support:
$85,000
Key messages for watershed organizations and modellers
- Detailed representation of the shallow subsurface is essential for surface water-groundwater interaction and streamflow estimation. This will lead to more accurate hydrologic modelling results and improved management of watershed fluxes.
- Monitoring of streamflow and groundwater flow at several locations within a watershed may be needed to better compare simulation results to field data.
- Baseflow needs to be carefully estimated and monitored for better management of surface water-groundwater interaction and maintenance of healthy aquatic ecosystems.
Key messages for municipal wellfield administrators
- Consider the impact of municipal well operations on surface water and groundwater flows in hydrological models, especially those with simplified subsurface representations.
- Sustained monitoring and management of municipal well operations and its impact on streamflow and groundwater flow is important.
Key publications
Cheng, S., Tong, X., & Illman, W. A. (2022). Evaluation of baseflow separation methods with real and synthetic streamflow data from a watershed. Journal of Hydrology, 613, 128279. https://doi.org/10.1016/j.jhydrol.2022.128279
Tong, X., Illman, W. A., Park, Y. J., Rudolph, D. L., & Berg, S. J. (2023). Significance of groundwater flow processes in hydrologic models: A model comparison study in a small watershed. Manuscript submitted for publication.
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