Groundwater Journal's Special Section on Integrated Hydrologic Modeling

The following is the press release from NGWA’s website announcing the issue.

January 17, 2019

Recently published scientific articles detail fresh perspectives regarding the future of groundwater modeling.

The articles were published in a special section within the January-February 2019 issue of NGWA’s flagship technical journal, Groundwater®.

The special section focuses on integrated hydrological modeling. In the past, saturated groundwater flow, unsaturated near-surface flow, and streamflow were all simulated independently from each other by separate computer programs. However, four research papers and two methods notes in this special section show the advances that have been made and future areas for research and development with integrated models representing the hydrological processes.

Within the section, there is a timely research paper on a coupled surface-subsurface hydrological model that includes winter processes to assess the impact of climate change. Another paper details a coupled surface-subsurface model for multiple flood events.

The section was put together with the aid of guest editors, Dr. Edward A. Sudicky of the University of Waterloo and Dr. Steven J. Berg, P.Geo. from Aquanty Inc., a science and technology firm in Waterloo, Ontario, Canada.

Groundwater Editor-in-Chief Dr. Henk Haitjema says, “guest editors Sudicky and Berg have been leaders in the field of integrated hydrological modeling. They collected four research papers and two methods notes in this special section to illustrate the state of the art as well as the challenges of this integrated approach to modeling. I hope that this special section will inspire young researches to further develop integrated hydrological modeling and bring it to maturity.”

Since 1963, Groundwater has published a dynamic mix of papers on topics focused on groundwater such as flow and well hydraulics, hydrogeochemistry and contaminant hydrogeology, application of geophysics, management and policy, and the history of hydrology.

HGS RESEARCH HIGHLIGHT - Simulating Climate Change Impacts on Surface Water Resources within a Lake Affected Region using Regional Climate Projections


This study aims to assess the impact of climate change on water resources in a large watershed within the Laurentian Great Lakes region, using the fully‐integrated surface‐subsurface model HydroGeoSphere. The hydrologic model is forced with an ensemble of high‐resolution climate projections from the Weather Research and Forecasting model (WRF). The latter has been extended with an interactive lake model (FLake) to capture the effect of the Great Lakes on the regional climate. The WRF ensemble encompasses two different moist physics configurations at resolutions of 90km, 30km, and 10km, as well as four different initial and boundary conditions, so as to control for natural climate variability. The integrated hydrologic model is run with a representative seasonal cycle, which effectively controls natural climate variability, while remaining computationally tractable with a large integrated model. However, the range of natural variability is also investigated, as are the impact of climate model resolution and bias correction. The two WRF configurations show opposite climate change responses in summer precipitation, but similar responses otherwise. The hydrologic simulations generally follow the climate forcing; however, due to the memory of the subsurface, the differences in summer propagate throughout the entire seasonal cycle. This results in a set of dry scenarios with reduced streamflow and water availability year‐round; and a set of wet scenarios with increased streamflow for all times excluding the spring peak, which does not increase. Most of the analysis focusses on streamflow, but changes in the seasonal cycle of baseflow and groundwater recharge are also analyzed.


HGS RESEARCH HIGHLIGHT - Natural stimuli calibration with fining direction regularization in an integrated hydrologic model


The interaction between surface water and groundwater during flood events is a complex process that has traditionally been described using simplified analytical solutions, or abstracted numerical models. To make the problem tractable, it is common to idealize the flood event, simplify river channel geometry, and ignore bank soil heterogeneity, often resulting in a model that only loosely represents the site, thus limiting its applicability to any specific river cross-section. In this study, we calibrate a site-specific fully-integrated surface and subsurface HydroGeoSphere model using flood events for a cross-section along the South River near Waynesboro, VA. The calibration approach presented in this study demonstrates the incorporation of fining direction regularization with a highly parameterized inversion driven by natural stimuli, to develop several realistic realizations of hydraulic conductivity fields that reflect the depositional history of the system. Specifically, we calibrate a model with 365 unique material zones to multiple flood events recorded in a dense well network while incorporating possible fining sequences consistent with the depositional history of the riverbank. Over 25,000 individual simulations were completed using calibration software and a cloud platform specifically designed for highly parallelized computing environments. The results of this study demonstrate the use of fining direction regularization during model calibration to generate multiple calibrated model realizations that account for the depositional environment of the system.

Figure 5. a) Finite element mesh including boundary conditions and material zonation based on the hydrostratigraphic interpretation of the site; b) 365 material zones for calibration of hydraulic conductivity (colouration indicates zone location and not material properties); and c) quadrants to which different fining preferences (shown by arrow directions) for model calibration were assigned.

Figure 5. a) Finite element mesh including boundary conditions and material zonation based on the hydrostratigraphic interpretation of the site; b) 365 material zones for calibration of hydraulic conductivity (colouration indicates zone location and not material properties); and c) quadrants to which different fining preferences (shown by arrow directions) for model calibration were assigned.

The 25th Latornell Conservation Symposium


“The Great Lakes and St. Lawrence River are critically important to Ontario’s environment and economy. They are also a source of joy for many Ontario residents in terms of scenic views, recreational opportunities, and spiritual significance and renewal.

The relationship between the Great Lakes and St. Lawrence River, and the surrounding landscape, is complicated. Many efforts have been made, and continue to be made, to understand, protect and restore these important water resources and to manage the impacts our activities have on them.


The 25th Latornell Conservation Symposium will explore the status of the Great Lakes and St. Lawrence River and the lands that connect them in order to assess the work currently underway to protect, conserve and enhance them. What progress is being made, and what more needs to be done?”


World Water-Tech North America 2018

“Six Start-Ups Revealed for World Water-Tech North America 2018 -- Toronto, October 24-25

World Water-Tech North America has revealed six US and Canadian start-ups who have been selected to unveil their cutting-edge technologies and breakthrough innovations at the summit.

The water-tech start-ups will present in the renowned Technology Showcase sessions to an audience of over 250 global water leaders, technology integrators, engineers, utilities and investors.”


45th IAH conference in Korea

"We have an exciting and inspiring the 45th Congress of IAH 2018 on September 9-14, 2018 in Daejeon, South Korea. The IAH 2018 Scientific Committee welcomes the submission of abstracts from worldwide experts in the fields of hydrogeology.

In order to make IAH 2018 successful, please submit abstract through the website The deadline of abstract submission is March 31, 2018. Don’t let your science and technology be left out due to late submission!

If you have any questions or need assistance, please reach out to the IAH 2018 Secretariat Office at

We look forward to seeing you all this coming September in Daejeon, South Korea."


HGS RESEARCH HIGHLIGHT - Understanding the water balance paradox in the Athabasca River Basin, Canada


This study demonstrates the importance of the including and appropriately parameterizing peatlands and forestlands for basin-scale integrated surface–subsurface models in the northern boreal forest, with particular emphasis on the Athabasca River Basin (ARB). With a long-term water balance approach to the ARB, we investigate reasons why downstream mean annual stream flow rates are consistently higher than upstream, despite the subhumid water deficit conditions in the downstream regimes. A high-resolution 3D variably saturated subsurface and surface water flow and evapotranspiration model of the ARB is constructed based on the bedrock and surficial geology and the spatial distribution of peatlands and their corresponding eco-regions. Historical climate data were used to drive the model for calibration against 40-year long-term average surface flow and groundwater observations during the historic instrumental period. The simulation results demonstrate that at the basin-scale, peatlands and forestlands can have a strong influence on the surface–subsurface hydrologic systems. In particular, peatlands in the midstream and downstream regimes of the ARB increase the water availability to the surface–subsurface water systems by reducing water loss through evapotranspiration. Based on the comparison of forestland evapotranspiration between observation and simulation, the overall spatial average evapotranspiration in downstream forestlands is larger than that in peatlands and thus the water contribution to the stream flow in downstream areas is relatively minor. Therefore, appropriate representation of peatlands and forestlands within the basin-scale hydrologic model is critical to reproduce the water balance of the ARB.

3-D subsurface model for the Athabasca River Basin.

3-D subsurface model for the Athabasca River Basin.

a) Spatial distribution of aridity index (AI) and b) Spatial distribution of actual aridity index (AAI) based on long-term steady state simulation results: JA=Jasper; HT=Hinton; WF=Windfall; AT=Athabasca; FM=Fort McMurray; and EA=Embarras Airport sub-basin.

a) Spatial distribution of aridity index (AI) and b) Spatial distribution of actual aridity index (AAI) based on long-term steady state simulation results: JA=Jasper; HT=Hinton; WF=Windfall; AT=Athabasca; FM=Fort McMurray; and EA=Embarras Airport sub-basin.

HGS RESEARCH HIGHLIGHT - Analytical Approach to Estimate Salt Release from Tailings Sand Hummocks in Oil Sands Mine Closure


Integrated surface water and groundwater models are well suited for evaluating the long-term performance of oil sands mine closure landscapes to optimize reclamation designs that satisfy performance criteria. However, the scale of the problem makes it difficult to evaluate a large number of design alternatives using numerical models, while at the same time satisfying numerical criteria, such as the courant and peclet numbers. The problem becomes particularly challenging in the design of permeable sand tailings hummocks overlying relatively impermeable composite tailings, where vertical advective flushing of process-affected water through the tailings hummocks is coupled to lateral transport of diffusive release from the underlying composite tailings. We developed an analytical solution that rapidly estimates long-term mass loadings from the sand tailings without the challenges typically associated with numerical modelling. Advection and dispersion in the flushing zones, progressive diffusion into underlying low permeability layers, and purely diffusive release are all considered. A comparison of the analytical solutions to numerical simulations for a series of simple hypothetical cases demonstrated that the analytical solutions provide a reasonable simulation of the mass loadings from the reclaimed landscapes over the design life. Although the approach needs to be further verified and validated for more realistic complex mine reclamation conditions, the analytical framework provides a foundation for hydrologic analysis in mine reclamation and closure in the northern boreal environment.

Link to the published article.

HGS RESEARCH HIGHLIGHT - Full Coupling Between the Atmosphere, Surface, and Subsurface for Integrated Hydrologic Simulation


An ever increasing community of earth system modelers is incorporating new physical processes into numerical models. This trend is facilitated by advancements in computational resources, improvements in simulation skill, and the desire to build numerical simulators that represent the water cycle with greater fidelity. In this quest to develop a state-of-the-art water cycle model, we coupled HydroGeoSphere (HGS), a 3-D control-volume finite element surface and variably saturated subsurface flow model that includes evapotranspiration processes, to the Weather Research and Forecasting (WRF) Model, a 3-D finite difference nonhydrostatic mesoscale atmospheric model. The two-way coupled model, referred to as HGS-WRF, exchanges the actual evapotranspiration fluxes and soil saturations calculated by HGS to WRF; conversely, the potential evapotranspiration and precipitation fluxes from WRF are passed to HGS. The flexible HGS-WRF coupling method allows for unique meshes used by each model, while maintaining mass and energy conservation between the domains. Furthermore, the HGS-WRF coupling implements a subtime stepping algorithm to minimize computational expense. As a demonstration of HGS-WRF's capabilities, we applied it to the California Basin and found a strong connection between the depth to the groundwater table and the latent heat fluxes across the land surface.

Link to the published article.

HGS RESEARCH HIGHLIGHT - Advancing Physically-Based Flow Simulations of Alluvial Systems Through Atmospheric Noble Gases and the Novel 37Ar Tracer Method


To provide a sound understanding of the sources, pathways, and residence times of groundwater water in alluvial river-aquifer systems, a combined multi-tracer and modeling experiment was carried out in an important alluvial drinking water wellfield in Switzerland. 222Rn, 3H/3He, atmospheric noble gases, and for the first time, the novel 37Ar -method were used to quantify residence times and mixing ratios of water from different sources. With a half-life of 35.1 days, 37Ar allowed to successfully close a critical observational time gap between 222Rn and 3H/3He for residence times of weeks to months. Covering the entire range of residence times of groundwater in alluvial systems revealed that, to quantify the fractions of water from different sources in such systems, atmospheric noble gases and helium isotopes are tracers suited for end-member mixing analysis. An updated illustration of available tracer methods, now including the new 37Ar method, is provided below:


The tracer-based mixing ratios were subsequently compared to mixing ratios simulated with the fully-integrated, physically-based flow model HydroGeoSphere. In order to simulate the propagation of the different sources of water in HydroGeoSphere, the Hydraulic Mixing Cell method (HMC) of Partington et al. (2013) was extended for this study to incorporate not only streamflow separation, but also tracking in the subsurface. Simulations of three different scenarios (poorly permeable, permeable and strongly permeable riverbed) are illustrated below. Both the exchange flux pattern on the surface and the fraction of surface water in the subsurface are illustrated.


The comparison between tracer-based and simulated mixing ratios revealed that models, which are only calibrated against hydraulic heads, cannot reliably reproduce mixing ratios or residence times of alluvial river-aquifer systems. However, the tracer-based mixing ratios allowed the identification of an appropriate flow model parametrization. Consequently, for alluvial systems, we recommend the combination of multi-tracer studies that cover all relevant residence times with fully-coupled, physically-based flow modelling using HGS and HMC-based flow tracking to better characterize the complex interactions of river-aquifer systems.

Link to the published article.