HGS RESEARCH HIGHLIGHT – Using depth specific electrical conductivity estimates to improve hydrological simulations in a heterogeneous tile-drained field
Boico, V. F., Therrien, R., Højberg, A. L., Iversen, B. V., Koganti, T., & Varvaris, I. (2022). Using depth specific electrical conductivity estimates to improve hydrological simulations in a heterogeneous tile-drained field. In Journal of Hydrology (Vol. 604, p. 127232). Elsevier BV. https://doi.org/10.1016/j.jhydrol.2021.127232
This paper is available for download until January 16th, 2022! Click here to access the paper.
A new study, which is part of the PhD project of Vinicius Boico and co-authored by Aquanty co-founder Rene Therrien, uses HydroGeoSphere to explore the impact of soil heterogeneity on simulated hydrology of a highly-instrumented, tile-drained agricultural field in Denmark. Results of the integrated hydrologic simulations indicate that homogeneous soil layers can effectively reproduce overall drainage and flow volumes at this scale. However, the inclusion of clay layers provides a much better representation of hydraulic heads throughout the field, a necessity for the accurate simulation of solute transport in agricultural catchments.
While HydroGeoSphere has been used to simulate the integrated hydrology of this system, the true focus of the paper is on the use of depth-specific electrical conductivity estimates to delineate the low-permeability clay layers.
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Abstract:
In agricultural fields, tile drains represent potential pathways for the migration of solutes, such as nitrates, in groundwater and surface water bodies. Tile drain flow is controlled by the temporal and spatial dynamics of the shallow groundwater table, which results from complex interactions between climate, topography and soil heterogeneity. Studies on the effect of topsoil heterogeneity on shallow water and drainage dynamics by fully 3D surface water and groundwater flow modeling are limited. The objective of our study is to demonstrate the use of depth specific electrical conductivity (EC) estimates to improve hydrological simulations in a tile drained field. The model was applied to a field site in Denmark where times series of drainage discharge and water table elevations are available. Clay-rich soil zones were identified in a tile-drained field using depth specific electrical conductivity estimates generated by the inversion of apparent electrical conductivity data measured using an electromagnetic induction instrument. One model that included the low-permeability clayey zones in the soil layers down to a depth of 1.2 m was compared to a simpler model that assumed homogeneous soil layers.
3D HydroGeoSphere Model of the Study Area
Both models simulate drainage discharge that compares well to the observations. However, including the clayey zones improves the simulation of hydraulic heads, and water table fluctuations, and generates flooded areas that are more representative of those observed during the wet seasons. Our results suggest that the simulation of water table fluctuations can be improved when the soil heterogeneity determined from depth specific EC estimates is included in integrated hydrological models. A better representation of the subsurface flow dynamics will also improve subsequent simulations of the transport and fate of agrochemical substances leaching from fields such as nitrate, which may deteriorate the quality of groundwater and surface water bodies.