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Title: Development of a distributed biosphere hydrological model and its evaluation with the Southern Great Plains Experiments (SGP97 and SGP99)

item Wang, L
item Koike, T
item Yang, K
item Jackson, Thomas
item Bindlish, R
item Yang, D

Submitted to: Journal of Geophysical Research Atmospheres
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2009
Publication Date: 6/1/2009
Citation: Wang, L., Koike, T., Yang, K., Jackson, T.J., Bindlish, R., Yang, D. 2009. Development of a distributed biosphere hydrological model and its evaluation with the Southern Great Plains Experiments (SGP 97 and SGP 99). Journal of Geophysical Research Atmospheres.

Interpretive Summary: Global climate changes may have significant impacts on regional river runoff and water availability, which is most important for water resource managers and policy makers. It is critical to integrate the knowledge of atmosphere and hydrology communities for improved prediction capability of available water resources and possible hazards (floods and droughts) and to validate models to provide confidence in predictions. A new biosphere hydrological model was developed by coupling a realistic land surface model with a distributed hydrological model. It was validated using comprehensive field observations from the Southern Great Plains Hydrology Experiments in 1997 and 1999. The model demonstrated the ability to reproduce point-scale energy fluxes, the ability to predict discharges (both peak and base flows), and the ability to predict the basin-scale surface soil moisture evolution in a spatially distributed manner. The advances provide by the model will contribute to improving the ability to make hazard (flood and drought) predictions under climate changes.

Technical Abstract: A distributed biosphere hydrological model, the so called water and energy budget-based distributed hydrological model (WEB-DHM), has been developed by fully coupling a biosphere scheme (SiB2) with a geomorphology-based hydrological model (GBHM). SiB2 describes the transfer of turbulent fluxes (energy, water, and carbon fluxes) between the atmosphere and land surface for each model grid. The GBHM redistributes water moisture laterally through simulating both surface and subsurface runoff using grid-hillslope discretization and then flow routing in the river network. The WEB-DHM was calibrated and validated for the Little Washita Basin using field observations from Southern Great Plains Hydrology Experiments (SGP97 and SGP99). For the SGP97 period, the model was calibrated and it shows an ability to reproduce point-scale energy fluxes (RMSE < 50 W m-232) as well as CO2 flux (RMSE = 4.6 µ mol m-2s-133). At basin-scale, the WEB-DHM can simulate a reasonable hydrograph (Nash = 0.956) and spatial soil moisture distribution with calibration of only a few soil hydraulic parameters for discharge. The model was then validated using SGP99 datasets and observed discharge. For the validation period, the model shows good performance in reproducing the soil surface temperature at 11 sites and the spatial distribution of surface soil moisture, as well as long-term discharges (Nash = 0.715) in the hydroyear from 1 September 1998 to 31 August 1999 that covers both the annual largest flood peak of 1999 and the SGP99 period. To our knowledge, this work is the first to undertake the development and evaluation of a distributed biosphere hydrological model using such comprehensive field observations.