@misc{MagbalotFernandezHeMolkenthin, author = {Magbalot-Fernandez, Alminda and He, Qianwen and Molkenthin, Frank}, title = {Effect of Climate Change in the Stream Flow, Crop Yields and NP Levels at White Oak Bayou Watershed Using SWAT simulation: A Case Study}, series = {Asian Journal of Geographical Research}, volume = {2}, journal = {Asian Journal of Geographical Research}, number = {2}, pages = {1 -- 9}, abstract = {Projected changes in temperature due to global climate change may have serious impacts on hydrologic processes, water resources availability, irrigation water demand, and thereby affecting the agricultural production and productivity. Therefore, understanding the impacts of climate change on crop production and water resources is of utmost importance for developing possible adaptation strategies. The White Oak Bayou, one of the several waterways that give Houston, Texas, United States its popular nickname "The Bayou City" was selected in this case study. SWAT model is process based and can simulate the hydrological cycle, crop yield, soil erosion and nutrient transport. It is operated with an interface in ArcView GIS using raster or vector datasets including the digital elevation model (DEM), soil properties, vegetation, LULC, and meteorological observations observed which were derived from the Consortium for Geospatial Information, National Cooperative Soil Survey, National Land Cover Database 2006, NCEP Climate Forecast System Reanalysis and USGS website in 2005-2008. The climate change scenario was based on the projected increase in temperature by the IPCC by 2100. This case study showed a decrease in streamflow from observed actual scenario (2005-2008) to projected increase of 4°C temperature in future climate change scenario by 2100. The evapotranspiration increased but there was a decrease in surface runoff and percolation. Moreover, there were greater average plant biomass and more average plant yields. Hence, the nitrogen and phosphorus uptake and removed in yield increased. Thus, the total nitrogen decreased while the total phosphorus is zero indicating loss of the Phosphorus content in the soil. Yet, this case study needs to be validated and calibrated with actual data to support the projected outcome.}, language = {en} } @misc{HeWendlandMolkenthin, author = {He, Qianwen and Wendland, Frank and Molkenthin, Frank}, title = {The analysis of nitrogen load and simulation uncertainty using SWAT in a catchment with paddy field in China}, series = {Water Science \& Technology Journal}, volume = {80}, journal = {Water Science \& Technology Journal}, number = {4}, issn = {0273-1223}, doi = {10.2166/wst.2019.326}, pages = {806 -- 816}, language = {en} } @misc{HeMolkenthin, author = {He, Qianwen and Molkenthin, Frank}, title = {Improving the integrated hydrological simulation on a data-scarce catchment with multi-objective calibration}, series = {Journal of Hydroinformatics}, volume = {23}, journal = {Journal of Hydroinformatics}, number = {2}, issn = {1464-7141}, doi = {10.2166/hydro.2021.132}, pages = {267 -- 283}, abstract = {The process-based hydrological model Soil and Water Assessment Tool ensures the simulation's reliability by calibration. Compared to the commonly applied single-objective calibration, multi-objective calibration benefits the spatial parameterization and the simulation of specific processes. However, the requirements of additional observations and the practical procedure are among the reasons to prevent the wider application of the multi-objective calibration. This study proposes to consider three groups of objectives for the calibration: multisite, multi-objective function, and multi-metric. For the study catchment with limited observations like the Yuan River Catchment (YRC) in China, the three groups corresponded to discharge from three hydrometric stations, both Nash-Sutcliffe efficiency (NSE) and inversed NSE for discharge evaluation, and MODIS global terrestrial evapotranspiration product and baseflow filtered from discharge as metrics, respectively. The applicability of two multi-objective calibration approaches, the Euclidean distance and nondominated sorting genetic algorithm II, was analyzed to calibrate the above-mentioned objectives for the YRC. Results show that multi-objective calibration has simultaneously ensured the model's better performance in terms of the spatial parameterization, the magnitude of the output time series, and the water balance components, and it also reduces the parameter and prediction uncertainty. The study thus leads to a generalized, recommended procedure for catchments with data scarcity to perform the multi-objective calibration.}, language = {en} }