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PI-Submitted Research Highlights for
Subsurface Biogeochemical Research Program

Building Confidence in Hydrologic Models

Ethan Coon
Oak Ridge National Laboratory

Highlight

25 April 2017

Model intercomparison project evaluates performance of seven different integrated hydrology models for solving challenge benchmarks.

The Science 
Understanding water availability and quality for large-scale surface and groundwater systems requires simulation, and many numerical models have been developed by scientists to address these needs.  A suite of common hydrologic benchmark challenges was developed, and seven different modeling teams from the U.S. and Europe exercised their models to achieve the benchmarks, and to thereby better understand how each of the models and model outputs agree and differ.

The Impact
Model intercomparison benchmark challenges build confidence in the choice of model used for a specific scientific question or application, and they illuminate the implications of model choice because they force modeling teams to better understand the strengths and weaknesses of their own and competing models.  This understanding leads to more reliable simulations and improves integrated hydrologic modeling.

Summary
Following up on a first integrated hydrologic model intercomparison project several years ago, seven teams of modelers, including two teams supported by the Interoperable Design for Extreme-scale Application Software (IDEAS) project, participated in a second intercomparison project.  Teams met at a workshop in Bonn, Germany, and designed a series of three model intercomparison benchmark challenges. The challenges were designed to focus on different aspects of integrated hydrology, including a hillslope-scale catchment, subsurface structural inclusions and layering, and a field study of hydrology on a small ditch with simple but data-informed topography.  Parameters were standardized, but each team used their own model, including differences in model physics, coupling, and algorithms.  Results were collected, stimulating detailed conversations to explain similarities and differences across the suite of models.  While each of the codes share a common underlying core capability, they are focused on different applications and scales, and have their own strengths and weaknesses.  This type of effort leads to improvement in all the codes, and improves the modeling community’s understanding of simulating integrated surface and groundwater systems hydrology.

Contacts
Ethan Coon
Oak Ridge National Laboratory
coonet@ornl.gov

Reed Maxwell
Colorado School of Mines
rmaxwell@mines.edu

Funding
Funding was provided by the DOE Office of Biological and Environmental Research, Subsurface Biogeochemistry Research (SBR) activity to the Interoperable Design for Extreme-scale Application Software (IDEAS) project.

Publications
S. Kollet, M. Sulis, R.M. Maxwell, C. Paniconi, M. Putti, G. Bertoldi, E.T. Coon, E. Cordano, S. Endrizzi, E. Kikinzon, E. Mouche, C. Mugler, Y.-J. Park, J.C. Refsgaard, S. Stisen, and E. Sudicky. “The integrated hydrologic model intercomparison project, IH-MIP2: A second set of benchmark results to diagnose integrated hydrology and feedbacks.” Water Resour. Res., 53, 867-890. (2017). [DOI: 10.1002/2016WR019191.]

This work featured LANL and Colorado School of Mines submissions.

Three co-authors (Coon, Kikinzon, Maxwell) were supported by the IDEAS program, funded by SBR, along with many other (US and international) funding sources supporting other co-authors.

Submissions included simulations by the Advanced Terrestrial Simulator (ATS) and ParFlow.


Approach: Surface elevation for one of three intercomparison problems in coupled surface/subsurface hydrology. This problem focused on comparing results for a rainfall/runoff experiment in a small drainage ditch to the participating model solutions.

 

Source: Water Resources Research, publication attached.  Copyright was not transferred to the journal due to lab contributions, and is held jointly by all participating institutions.  The PIs give permission for it to be used in the highlights database and any other BER use.

midsized version

Results and Impact: The top row of plots show subsurface water storage as a function of time, while the bottom plots show surface water and runoff.  While subsurface models largely agreed in both formulation and solution, surface models differ significantly, and so do surface results.  This comparison helped modelers understand how their work relates to others in the field, and indicates the need for model validation to ensure the correct model structure is chosen for a given study.  These types of effort are critical for building confidence in models.

 

Source: Water Resources Research, publication attached.  Copyright was not transferred to the journal due to lab contributions, and is held jointly by all participating institutions.  The PIs give permission for it to be used in the highlights database and any other BER use.

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