MEASURING INORGANIC CARBON FLUXES FROM CARBONATE MINERAL WEATHERING FROM LARGE RIVER BASINS: THE OHIO RIVER BASIN

Author(s):  
Autumn B. Turner ◽  
2015 ◽  
Vol 12 (7) ◽  
pp. 6755-6797 ◽  
Author(s):  
S. Zuliziana ◽  
K. Tanuma ◽  
C. Yoshimura ◽  
O. C. Saavedra

Abstract. Soil erosion and sediment transport have been modeled at several spatial and temporal scales, yet few models have been reported for large river basins (e.g., drainage areas > 100 000 km2). In this study, we propose a process-based distributed model for assessment of sediment transport at a large basin scale. A distributed hydrological model was coupled with a process-based distributed sediment transport model describing soil erosion and sedimentary processes at hillslope units and channels. The model was tested on two large river basins: the Chao Phraya River Basin (drainage area: 160 000 km2) and the Mekong River Basin (795 000 km2). The simulation over 10 years showed good agreement with the observed suspended sediment load in both basins. The average Nash–Sutcliffe efficiency (NSE) and average correlation coefficient (r) between the simulated and observed suspended sediment loads were 0.62 and 0.61, respectively, in the Chao Phraya River Basin except the lowland section. In the Mekong River Basin, the overall average NSE and r were 0.60 and 0.78, respectively. Sensitivity analysis indicated that suspended sediment load is sensitive to detachability by raindrop (k) in the Chao Phraya River Basin and to soil detachability over land (Kf) in the Mekong River Basin. Overall, the results suggest that the present model can be used to understand and simulate erosion and sediment transport in large river basins.


2018 ◽  
Author(s):  
Yongping Yuan ◽  
Ruoyu Wang ◽  
Ellen Cooter ◽  
Limei Ran ◽  
Prasad Daggupati ◽  
...  

Abstract. This study describes and implements an integrated, multimedia, process-based system-level approach to estimating nitrogen (N) fate and transport in large river basins. The modeling system includes the following components: 1) Community Multi-Scale Air Quality (CMAQ); 2) Water Research and Forecasting (WRF); 3) Environmental Policy Integrated Climate (EPIC); and 4) Soil and Water Assessment Tool (SWAT). The previously developed Fertilizer Emission Scenario Tool for the Community Multiscale Air Quality (FEST-C) system integrated EPIC with the WRF model and CMAQ. FEST-C, driven by process-based WRF weather simulations, includes atmospheric N additions to agricultural cropland, and agricultural cropland contributions to ammonia emissions. Watershed hydrology and water quality models need to be integrated with the system (FEST-C), however, so it can be used in large river basins to address impacts of fertilization, meteorology, and atmospheric N deposition on water quality. Objectives of this paper are to describe how to expand the previous effort by integrating a watershed model with the FEST-C (CMAQ/WRF/EPIC) modeling system, as well as demonstrate application of the Integrated Modeling System (IMS) to the Mississippi River Basin (MRB) to simulate streamflow and dissolved N loadings to the Gulf of Mexico (GOM). IMS simulation results generally agree with USGS observations/estimations; the annual simulated streamflow is 218.9 mm and USGS observation is 211.1 mm and the annual simulated dissolved N is 2.1 kg/ha. and the USGS estimation is 2.8 kg/ha. Integrating SWAT with the CMAQ/WRF/EPIC modeling system allows for its use within large river basins without losing EPIC’s more detailed biogeochemistry processes, which will strengthen assessment of impacts of future climate scenarios, regulatory and voluntary programs for nitrogen oxide air emissions, and land use and land management on N transport and transformation in large river basins.


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