Integrated modeling of groundwater–surface water interactions in a tile‐drained agricultural field: The importance of directly measured flow route contributions

Abstract

[1] Understanding the dynamics of groundwater-surface water interaction is needed to evaluate and simulate water and solute transport in catchments. However, direct measurements of the contributions of different flow routes from specific surfaces within a catchment toward the surface water are rarely available. For this study, we physically separated the tile drain discharge toward a 43.5 m ditch transect from the groundwater-plus-overland flow routes. Direct groundwater flow and ephemeral overland flow were jointly captured in three sheet pile in-stream reservoirs, while the effluent from three tile drain outlets was collected in vessels. Our flux measurements showed that, in response to a rainfall event, the tile drain contribution to the total ditch discharge decreased from 80% to 28%. We used these flow route measurements to calibrate a field-scale integrated water transport model. The HydroGeoSphere code was used because it simultaneously solves the flow regimes in the variably saturated domain, the tile drain domain, and the surface flow domain. This simultaneous solution is needed for a correct representation of the mutual interactions between groundwater flow, tile drain flow, and ditch water flow. Our model produced a flow distribution between the flow paths which deviated only 2% from the measured flow distribution. A sensitivity analysis showed that model parameters related to tile drain entrance resistance and to the resistance to water flow through the surface water system controlled the water flow route distribution but with little effect on groundwater levels. This indicates that a model calibration based on groundwater levels alone does not necessarily produce a correct representation of the flow route contributions.

Analyzing subsurface drain network performance in an agricultural monitoring site with a three-dimensional hydrological model

“…Turunen et al (2015a) discussed the possibility of lateral groundwater flow entering a clayey field section in southern Finland. Similar results were reported by Rozemeijer et al (2010) who conducted short-term simulations with data from a tile-drained field in the Netherlands with the HydroGeoSphere model. Hansen et al (2013) reckoned that insufficient representation of the local heterogeneities in the geological model and lack of spatial variation in hydraulic conductivities within the geological units were the main reasons that the model (MIKE SHE) was not able to reproduce the spatial dynamics in hydraulic heads in a catchment area with till soil in Denmark.…”

“…Three-dimensional (3D) hydrological models can explicitly describe the different branches of the drainage network and topographical variations in the area, and the resulting lateral flow processes such as water redistribution due to groundwater flow (e.g. Rozemeijer et al, 2010;Turunen et al, 2013Turunen et al, , 2015aTurunen et al, , 2015bFilipović et al, 2014;Warsta et al, 2013aWarsta et al, , 2014. Alternatively, drainage network can be presented adequately e.g.…”

High-frequency monitoring of water fluxes and nutrient loads to assess the effects of controlled drainage on water storage and nutrient transport

“…The drains discharge into the ditch at 90 cm below the field surface level. Over their 200 m length the tubes slope upward by 20-60 cm away from the ditch, depending on the local topography (Rozemeijer et al, 2010b). Rozemeijer et al (2010a) quantified that the tube drains contributed 80 % of the total yearly water discharge to the surface water and 90 % of the total yearly NO 3 -N and P export.…”

Improving catchment discharge predictions by inferring flow route contributions from a nested-scale monitoring and model setup

“…All three time series were simulated with a NashSutcliff (NS) coefficient (Nash and Sutcliff, 1970) exceeding 0.8. Rozemeijer et al (2010b), who used the same dataset and a fully distributed HydroGeosphere (Therrien et al, 2009) model to simulate flow routes during a single discharge event, demonstrate that the relatively simple LGSI-model concepts can simulate the discharges of individual flow routes at least equally well as the HydroGeosphere model and hence constitute a very powerful tool for simulation and prediction of flow routes at a field site. Like , we found that measurements of both the storage of groundwater within the field and the corresponding discharge of flow routes are indispensible for an accurate model representation of the groundwater-surface water interaction.…”