October 09, 2018

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Representing Microtopography Effects in Hydrology Models

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.

Principal Investigator

Ahmad Jan
Oak Ridge National Laboratory
jana@ornl.gov

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

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.

References

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). https://doi.org/10.1029/2017WR021898.