HGS RESEARCH HIGHLIGHT – Groundwater recharge from overbank floods
Doble, R. C., Crosbie, R. S., Smerdon, B. D., Peeters, L., & Cook, F. J. (2012). Groundwater recharge from overbank floods. In Water Resources Research (Vol. 48, Issue 9). American Geophysical Union (AGU). https://doi.org/10.1029/2011wr011441
“While the nature of HydroGeoSphere did not allow the recharge to the water table to be calculated explicitly, it is inferred by the volume of infiltration, and is equal to the infiltration volume minus the volume of water remaining in the unsaturated zone.”
Fig. 2. Aquifer cross section used in this study (z dimension exaggerated). Clogging layers over the river and floodplain are denoted by dark gray and light gray shading, respectively.
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This study explores the process of overbank flood recharge using a fully coupled surface-subsurface HydroGeoSphere (HGS) flow model. Overbank flooding can cause a significant amount of groundwater recharge, making at an important process to quantify when estimating aquifer sustainable yield. The research highlights the interactions between surface sediment, aquifer parameters, and flood characteristics in determining the volume of infiltration through floodplains. At the center of the investigation is HydroGeoSphere (HGS), a modelling platform known for its ability to simulate coupled surface water-groundwater interactions with high accuracy. By using HGS, the researchers examined how factors such as flood wave height, peak duration, and aquifer transmissivity impact the infiltration process.
A major benefit of HGS is its flexibility, allowing for detailed simulations of various hydrological processes. From modelling flood scenarios to analyzing the effects of different sediment types and floodplain irregularities, HGS enabled researchers to investigate various scenarios thoroughly. The researchers used HGS to test 66 different scenarios, examining the sensitivity of overbank flood recharge to factors such as the conductance of the clogging layer, flood wave characteristics, aquifer transmissivity, and irregularities in floodplain elevation. They found that infiltration volume increases with higher conductance of the clogging layer, greater flood wave height, longer peak duration, and higher aquifer transmissivity, but decreases with increasing water table gradient.
Fig. 8. Modeled infiltration volume plotted against the infiltration volume calculated from the relationship developed in this paper.
One really interesting aspect of modelling hydrologic systems with HGS is highlighted in the quote at the top of this blog post. Groundwater “recharge” as a concept is something that really only comes about when considering groundwater systems from a fully-saturated view point. When modelling with HGS, the arbitrary distinction between groundwater and surface water (or conceptualizing groundwater as distinct saturated and unsaturated regions) disappears!
Abstract:
Overbank flood recharge is increasingly acknowledged as important for estimations of aquifer sustainable yield. The physics of this process in areas with shallow groundwater, however, is not well understood and typically is not included in river or groundwater models. Modeling of the overbank flood recharge process was undertaken using a fully coupled, surface-subsurface flow model to compare the volume of infiltration through a floodplain with varying surface sediment, aquifer, and flood parameters. The infiltration volume was found to increase with the conductance of the clogging layer (represented by a thin veneer of sediments across the floodplain and river bed), flood wave height, peak duration, and aquifer transmissivity and to decrease with increasing water table gradient (positive toward the river). The influence of the flood wave and aquifer hydraulic parameters was more pronounced in systems with sand or loam clogging layers. Irregularities in floodplain elevation had a large effect on infiltration volume. A dimensionless analysis of the flood recharge process identified the factors that limited flood infiltration for each of the modeled scenarios: the clogging layer conductance, unsaturated aquifer storage, or aquifer transmissivity. A dimensionless number F* was used to predict the limiting factor in floodplain systems. An analytical equation was developed to estimate the infiltration volume for catchments where full numerical modeling is not warranted or applicable. Results from the analytical equation compared favorably with recharge modeled using a more complex numerical model.
“Assistance from Philip Brunner, Rob McLaren, and [Aquanty’s] Young-Jin Park with the HydroGeoSphere modeling was invaluable.”