Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Model evaluation paper
16 Jun 2017
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Geoscientific Model Development (GMD).
A Hydrological Emulator for Global Applications
Yaling Liu1, Mohamad Hejazi1, Hongyi Li2, Xuesong Zhang1, and Guoyong Leng1 1Joint Global Change Research Institute, Pacific Northwest National Laboratory, 5825 University Research Court, College Park, Maryland 2 0740, United States
2Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT 59717, United States
Abstract. While global hydrological models (GHMs) are very useful in exploring water resources and interactions between the Earth and human systems, their use often requires numerous model inputs, complex model calibration, and high computation costs. To overcome these challenges, we construct an efficient open-source and ready-to-use hydrologic emulator (HE) that can mimic complex GHMs at a range of spatial scales (e.g., basin, region, globe). We constructed both a lumped and a distributed scheme of the HE based on the monthly abcd model, for users' choice – minimal computational cost with reasonable model fidelity, or heavier computational load with better predictability. Model predictability and computational efficiency were evaluated in simulating global runoff from 1971–2010 with both the lumped and distributed schemes. The results are compared against the runoff product from the widely-used Variable Infiltration Capacity (VIC) model. Our evaluation indicates that the lumped and distributed schemes present comparable results regarding annual total quantity, spatial pattern and temporal variation of the major water fluxes (e.g., total runoff, evapotranspiration) across the global 235 basins (e.g., correlation coefficient r between the annual total runoff from either of these two schemes and the VIC is >0.96), except for several cold (e.g., Arctic, Interior Tibet), dry (e.g., North Africa) and mountainous (e.g., Argentina) regions. Compared against the monthly total runoff product from the VIC (aggregated from daily runoff), the global mean Kling-Gupta efficiencies are 0.75 and 0.79 for the lumped and distributed schemes, respectively, with the distributed one better capturing spatial heterogeneity. Notably, the computation efficiency of the lumped scheme is two orders of magnitude higher than the distributed one, and seven orders more efficient than the VIC model. Our results suggest that the revised lumped abcd model can serve as an efficient and acceptable HE for complex GHMs and is suitable for broad practical use, and the distributed scheme is also an efficient alternative if spatial heterogeneity is of more interest.

Citation: Liu, Y., Hejazi, M., Li, H., Zhang, X., and Leng, G.: A Hydrological Emulator for Global Applications, Geosci. Model Dev. Discuss.,, in review, 2017.
Yaling Liu et al.
Yaling Liu et al.


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Short summary
This hydrologic emulator provide researchers an easy way to investigate the variations in water budgets at any spatial scale of interest, with minimum requirements of efforts, reasonable model predictability and appealing computational efficiency. We expect that it will have profound influence on scientific endeavors in hydrological modeling, and will excite the immediate interest of researchers working on climate impact assessments, uncertainty/sensitivity analysis and integrated assessment.
This hydrologic emulator provide researchers an easy way to investigate the variations in water...