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PI-Submitted Research Highlights for
Terrestrial Ecosystem Science Program

Representing Microtopography Effects in Hydrology Models

Ahmad Jan

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19 September 2018

A novel subgrid model improves the representation of hydrologic processes.

The Science
Microtopography is known to be an important control on surface water retention, evaporation, infiltration, and runoff generation. Unfortunately, direct representation of microtopography effects in models of those processes is typically not feasible because of the high spatial and temporal resolution required. A subgrid model was developed to include microtopography effects in lower-resolution models, thus improving the representation of key hydrologic processes.

The Impact
The newly developed subgrid model is broadly applicable to disparate landscapes and significantly improves the representation of runoff generation and inundation compared with neglecting small-scale topography. The subgrid model enables process-resolving models of permafrost thermal hydrology to expand to catchment scales and decadal time frames.

Summary
Fine-scale simulations using high-resolution digital elevation models highlight the importance of microtopography and its effects on integrated hydrology in polygonal tundra, hummocky bogs, and hillslopes with incised rills. A subgrid model that modifies the flow and accumulation terms in lower-resolution models replicates the microtopography-resolving simulations at orders-of-magnitude smaller computation cost. The subgrid model makes it possible to incorporate thaw-induced dynamic topography in simulations addressing the evolution of carbon-rich Arctic tundra in a warming climate.

Contacts
BER Program Managers
David Lesmes and Daniel Stover
SC-23.1
David.Lesmes@science.doe.gov (301-903-2977) and Daniel.Stover@science.doe.gov (301-903-0289)

Principal Investigator
Ahmad Jan
Climate Change Science Institute
Oak Ridge National Laboratory
Oak Ridge, TN 37831
jana@ornl.gov (865-576-8175)

Funding
This work was supported by the Interoperable Design of Extreme-scale Application Software (IDEAS) project and by the Next-Generation Ecosystem Experiments (NGEE)–Arctic) project, supported by the Office of Biological and Environmental Research (BER) within the U.S. Department of Energy Office of Science.

Publications
Jan, A., E.T. Coon, J.D. Graham, and S.L. Painter. “A subgrid approach for modeling microtopography effects on overland flow.” Water Resources Research 54(9), 6153–6167 (2018). [DOI:10.1029/2017WR021898]

This work was supported by Interoperable Design of Extreme-scale Application Software (IDEAS) project and by the Next Generation Ecosystem Experiment (NGEE-Arctic) project.

Simulator used: Advanced Terrestrial Simulator (ATS)

University collaborator: Jack Graham, Boise State University funded by SPRUCE project

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