HGS RESEARCH HIGHLIGHT - Efficient Uncertainty Quantification in Fully-Integrated Surface and Subsurface Hydrologic Simulations

AUTHORS: K.L. Miller, S.J. Berg, J.H. Davison, E.A. Sudicky, and P.A. Forsyth

Although high performance computers and advanced numerical methods have made the application of fully-integrated surface and subsurface flow and transport models such as HydroGeoSphere common place, run times for large complex basin models can still be on the order of days to weeks, thus, limiting the usefulness of traditional workhorse algorithms for uncertainty quantification (UQ) such as Latin Hypercube simulation (LHS) or Monte Carlo simulation (MCS), which generally require thousands of simulations to achieve an acceptable level of accuracy. In this paper we investigate non-intrusive polynomial chaos for uncertainty quantification, which in contrast to random sampling methods (e.g., LHS and MCS), represents a model response of interest as a weighted sum of polynomials over the random inputs. Once a chaos expansion has been constructed, approximating the mean, covariance, probability density function, cumulative distribution function, and other common statistics as well as local and global sensitivity measures is straightforward and computationally inexpensive, thus making PCE an attractive UQ method for hydrologic models with long run times. Our polynomial chaos implementation was validated through comparison with analytical solutions as well as solutions obtained via LHS for simple numerical problems. It was then used to quantify parametric uncertainty in a series of numerical problems with increasing complexity, including a two-dimensional fully-saturated, steady flow and transient transport problem with six uncertain parameters and one quantity of interest; a one-dimensional variably-saturated column test involving transient flow and transport, four uncertain parameters, and two quantities of interest at 101 spatial locations and five different times each (1010 total); and a three-dimensional fully-integrated surface and subsurface flow and transport problem for a small test catchment involving seven uncertain parameters and three quantities of interest at 241 different times each. Numerical experiments show that polynomial chaos is an effective and robust method for quantifying uncertainty in fully-integrated hydrologic simulations, which provides a rich set of features and is computationally efficient. Our approach has the potential for significant speedup over existing sampling based methods when the number of uncertain model parameters is modest ( ≤ 20). To our knowledge, this is the first implementation of the algorithm in a comprehensive, fully-integrated, physically-based three-dimensional hydrosystem model.

Link to the published article.

Read full manuscript here.

 

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HGS RESEARCH HIGHLIGHT - Wetlands and Flood Mitigation in Ontario: Natural adaptation to extreme rainfall

AUTHOR: MASON MARCHILDON, P. Eng. Oak Ridges Moraine Groundwater Program

Wetlands are often recognized for their flood control value, but little research exists specific to Ontario, where extreme weather causing flooding poses ever-greater threats to urban areas. Ducks Unlimited Canada has undertaken new research to better understand the role of wetlands in storing and attenuating flood flows in an urban/rural watershed. The second phase of this research, reported here, employs advanced hydrologic modelling to address the questions of where and how wetlands are most effective at retaining water, what consequences further wetland loss may have on flooding, and what potential wetland restoration could have to improve flood storage within a watershed. The modelling was accomplished using fully-integrated, three-dimensional variably saturated hydrologic model built for the entire Credit River watershed at a high spatiotemporal resolution.

For more information click here.

HGS RESEARCH HIGHLIGHT - Limits of heat as a tracer to quantify transient lateral river-aquifer exchanges

AUTHORS: YUEQING XIE, AND JORDI BATLLE-AGUILAR

The application of heat as a tracer for assessing river-aquifer exchanges has been mainly limited to vertical flow through the riverbed. Lateral river-aquifer exchanges may be more important than vertical riverbed exchanges if the river is deeply incised into an aquifer. Few studies have examined lateral river-aquifer exchanges and the ability of heat to constrain such exchanges. This study aims to perform a robust assessment of the limits of heat as a tracer to quantify lateral river-aquifer exchanges. It is largely based on a section of the Meuse River in Belgium (Figure 1), a river predominantly gaining in the studied area that only becomes intermittently losing in the winter time.

Figure 1. Location of the study site adjacent to the Meuse River, monitored wells U5 and U3 (114 and 207 m distance from the river, respectively) and groundwater head contours as measured in April 2006.

Figure 1. Location of the study site adjacent to the Meuse River, monitored wells U5 and U3 (114 and 207 m distance from the river, respectively) and groundwater head contours as measured in April 2006.

A site-based transect model established with HydroGeoSphere was first calibrated using both hydraulic head and temperature time series from two monitoring wells over 100 m away from the river (U5 and U3). However, the temperature time series were not helpful in calibrating the model because of the large distance from the river and the gaining nature of the river.

The best-calibrated model was then utilised as the base case for assessing the usefulness of temperature at closer distances from the river. We extracted both head and temperature time series at a number of locations much closer to the river (i.e. 4, 5, 6, 7, 8, 9, and 10 m from the river) from the best-calibrated model. Then we analysed how the use of different synthetic heat and temperature time series as calibration targets impacts on the uncertainty of integrated river-aquifer exchange volume using the Monte Carlo approach (the river-aquifer exchange volume uncertainty is attributed to parameter uncertainties). Our results suggest that the ability of heat to reduce the uncertainty of lateral river-aquifer exchanges is directly proportional to the distance of the monitoring location from the river. In our case, the uncertainty range of the net exchange volume was reduced by approximately a factor of 3 from 4 m to 9 m (Figure 2a). This ability of course is limited to a certain range. For instance, heat cannot be used at 0 – 4 m in our case because of the occupation of the river bank, and was not useful beyond 8 m as the effect of river temperature becomes insignificant. The optimal distance is where groundwater temperature variation is no longer affected by river temperature (8 m in this study), or temperature variation is below the resolution limit of the temperature sensor. Our study also indicates that heat alone cannot constrain lateral river-aquifer exchanges better than the commonly used hydraulic head (compare Figures 2a and 2c). However, once combined with hydraulic head, heat can reduce the uncertainty of lateral river-aquifer exchanges significantly (compare Figures 2a and 2e). A factor of 3 – 6 reduction in the net exchange volume was observed in our synthetic case.

Figure 2. Net river-aquifer exchange volume statistics for using hydraulic head and temperature time series in different manners. The left panel shows results when time series were used at individual locations (i.e., 4, 5, 6, 7, 8, 9, 10 m from the river), whereas the right panel includes results when time series were used at specific ranges of locations (e.g., 4-5 m indicates locations at both 4 and 5 m, and 4-6 m indicates locations at 4, 5 and 6 m). In each boxplot, the upper and lower bounds show maximum and minimum values, the top and bottom of the box indicate 75 and 25 percentiles, and the red bar within the box is the median value. The dotted lines show the net exchange volume for the base case model.

Figure 2. Net river-aquifer exchange volume statistics for using hydraulic head and temperature time series in different manners. The left panel shows results when time series were used at individual locations (i.e., 4, 5, 6, 7, 8, 9, 10 m from the river), whereas the right panel includes results when time series were used at specific ranges of locations (e.g., 4-5 m indicates locations at both 4 and 5 m, and 4-6 m indicates locations at 4, 5 and 6 m). In each boxplot, the upper and lower bounds show maximum and minimum values, the top and bottom of the box indicate 75 and 25 percentiles, and the red bar within the box is the median value. The dotted lines show the net exchange volume for the base case model.

Job Notice - Intermediate/Senior Numerical Modeller (Hydrology/Hydrogeology)

Aquanty is looking for an intermediate/senior Numerical Modeller to join our growing team in Waterloo, ON. The ideal candidate has a background in hydrogeology and numerical modelling at the regional scale.

Location: Waterloo, ON, Canada

Education: Masters/PhD degree hydrogeology or related field

Experience: Minimum 5 - 10 years

Position Description:

The successful applicant will be involved in all aspects of project delivery including; project management, reporting, data processing, GIS, hydrostratigraphic interpretation, 3D model construction, numerical model setup and simulation.

Desired Skill Set:

·         Demonstrated project management and report writing experience

·         Experience building numerical models for hydrogeology/hydrology applications

·         Experience interpreting regional scale hydrostratigraphy

·         Experience with HydroGeoSphere/FEFLOW/MODFLOW is an asset

·         Experience mentoring junior staff

 

Please send your resume to hr@aquanty.com

About Aquanty

Aquanty Inc., is a research spin-off company from the University of Waterloo specializing in computer simulations of how water moves through the natural environment. Our best-in-class simulation platform, HydroGeoSphere, is used in a number of industries including; agriculture, oil and gas, mining, watershed management, contaminant remediation, and nuclear storage and disposal to support water related decision making. Check out our Case Studies to see examples.

Statement of Commitment

Aquanty’s is an equal opportunity employer that does not unlawfully discriminate against any employee or applicant on the basis of race, ancestry, place of origin, colour, ethnic origin, citizenship, religion, gender identity, gender expression, creed, sex, sexual orientation, age, record of offences, marital status, family status or disability. Aquanty is committed to a fair and inclusive work environment. We will endeavor to accommodate the needs of qualified applicants in all parts of the hiring process.

Australasian Groundwater Conference 2017

Aquanty is proud to support the Australasian Groundwater Conference this year. Swing by our booth to talk to us. We will also have two talks durring the Wednesday session on Groundwater Modelling.

River basin-scale integrated surface-subsurface hydrologic modelling to support agricultural risk management.

Simulating complex surface water/groundwater interactions during flood events with a fully-integrated physics based hydrologic model.

René Therrien -- Fellow of the Canadian Academy of Engineering

Aquanty is very pleased to announce that Professor René Therrien in the Département de géologie et de génie géologique at Laval University has been elected as a Fellow of the Canadian Academy of Engineering for his contributions to the advancement of hydrogeological science and the development of advanced mathematical models. Dr. Therrien is a co-founder of Aquanty and a co-developer of Aquanty's simulation platform HydroGeoSphere. He also serves on the Board of Directors of Aquanty. Dr. Therrien is the second co-founder of Aquanty elected to this prestigious honour. Dr. Sudicky was elected to the Academy in 2003.

For more information...

HGS RESEARCH HIGHLIGHT - Integrating hydrological modelling, data assimilation and cloud computing for real-time management of water resources

Authors: Wolfgang Kurtz, Andrei Lapin, Oliver S. Schilling, Qi Tang, Eryk Schiller, Torsten Braun, Daniel Hunkeler, Harry Vereecken, Edward Sudicky, Peter Kropf, Harrie-Jan Hendricks Franssen, and Philip Brunner

Online data acquisition, data assimilation and integrated hydrological modelling have become more and more important in hydrological science. In this study, we explore cloud computing for integrating field data acquisition and stochastic, physically-based hydrological modelling in a data assimilation and optimisation framework as a service to water resources management. For this purpose, we developed an ensemble Kalman filter-based data assimilation system for the integrated hydrological model HydroGeoSphere, which is able to run in a cloud computing environment. A synthetic data assimilation experiment based on the widely used tilted V-catchment problem showed that the computational overhead for the application of the data assimilation platform in a cloud computing environment is minimal, which makes it well suited for practical water management problems. Advantages of the cloud-based implementation comprise the independence from computational infrastructure and the straightforward integration of cloud-based observation databases with the modelling and data assimilation platform. 

For more information click here.

HydroGeoSphere Language Grammar

Syntax highlighting is now available for Grok input files! Dr. Claus Haslauer from the University of Tübingen created the syntax highlighting functionality. Claus' highlighting functionality works on both TextMate and SublimeText editors (OSX and Windows machines) and the features include:

  • "Skip on" and "Skip off" is greyed out.
  • "Problem description" at the beginning is greyed out.
  • "!" are greyed out (as comments).
  • Input files are coloured.
  • Numbers are highlighted.
  • Domain names (porous medium, surface, etc.) are highlighted.
  • Keywords ('end', 'clear', 'choose') are highlighted.

To find out more information on the Syntax Highlighting please visit Claus' github page.

Job Notice - Intermediate Numerical Modeller (Hydrogeology/Hydrology)

Aquanty is looking for a intermediate Numerical Modeller to join our growing team in Waterloo, ON. The ideal candidate has a background in hydrogeology and numerical modelling at the regional scale.

Location: Waterloo, ON, Canada

Education: Bachelors or Masters level degree in hydrogeology or related field

Experience: 2 - 10 years

Position Description:

The successful applicant will support the Aquanty team with the construction of basin scale numerical models. Tasks are expected to include: data processing, GIS, hydrostratigraphic interpretation, 3D model construction, numerical model setup and simulation.

Desired Skill Set:

·         Experience building numerical models for hydrogeology/hydrology applications

·         Experience interpreting regional scale hydrostratigraphy

·         Strong GIS and data processing skills

·         Experience with HydroGeoSphere/FEFLOW/MODFLOW is an asset

·         Ability to work in a team

 

Please send your resume to hr@aquanty.com

About Aquanty

Aquanty Inc., is a research spin-off company from the University of Waterloo specializing in computer simulations of how water moves through the natural environment. Our best-in-class simulation platform, HydroGeoSphere, is used in a number of industries including; agriculture, oil and gas, mining, watershed management, contaminant remediation, and nuclear storage and disposal to support water related decision making. Check out our Case Studies to see examples.