@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} } @inproceedings{HeMolkenthinWendlandetal., author = {He, Qianwen and Molkenthin, Frank and Wendland, Frank and Herrmann, Frank}, title = {Evaluation of different interpolation schemes for precipitation and reference evapotranspiration and the impact on simulated large-scale water balance in Slovenia}, series = {European Geosciences Union, General Assembly 2016, Vienna, Austria}, booktitle = {European Geosciences Union, General Assembly 2016, Vienna, Austria}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {Precipitation and reference evapotranspiration (ET0) are two main climate input components for hydrological models, which are often recorded or calculated based on measuring stations. Interpolation schemes are implemented to regionalize data from measuring stations for distributed hydrological models. This study had been conducted for 5 months, with the aim of: (1) evaluating three interpolation schemes for precipitation and reference evapotranspiration (ET0); (2) assessing the impact of the interpolation schemes on actual evapotranspiration and total runoff simulated by a distributed large-scale water balance model - mGROWA. The study case was the Republic of Slovenia, including a high variability in topography and climatic conditions, with daily meteorological data measured in 20 stations for a period of 44 years. ET0 were computed by both FAO Penman-Monteith equation and Hargreaves equation. The former equation is recommended as the standard equation, while the ET0 calculated by the latter one for Slovenia had a certain deviation (+150 mm/a) from it. Ordinary Kriging, Regression Kriging and Linear Regression were selected to regionalize precipitation and ET0. Reliability of the three interpolation schemes had been assessed based on the residual obtained from cross-validation. Monthly regionalized precipitation and ET0 were subsequently used as climate input for mGROWA model simulation. Evaluation of the interpolation schemes showed that the application of Regression Kriging and Linear Regression led to an acceptable interpolation result for reference evapotranspiration, especially in case the FAO Penman-Monteith equation was used. On the other hand, Regression Kriging also provided a more convincing interpolated result for precipitation. Meanwhile, mGROWA simulation results were affected by climate input data sets generated by applying difference interpolation schemes. Therefore, it is essential to select an appropriate interpolation scheme, in order to generate a convincing climate input.}, language = {en} } @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{HeMolkenthin, author = {He, Qianwen and Molkenthin, Frank}, title = {A Modeling Approach for Critical Source Areas Identification and Sources Apportionment for Nitrogen Load in Yuan River Catchment, China}, series = {Advances in Hydroinformatics - SimHydro 2019 - Models for Extreme Situations and Crisis Management}, journal = {Advances in Hydroinformatics - SimHydro 2019 - Models for Extreme Situations and Crisis Management}, editor = {Gourbesville, Philippe and Caignaert, Guy}, publisher = {Springer Nature}, address = {Singapore u.a.}, isbn = {978-981-15-5435-3}, issn = {2364-6934}, doi = {10.1007/978-981-15-5436-0_51}, pages = {659 -- 671}, abstract = {Excessive load of nitrogen from anthropogenic sources is a threat to a healthy aquatic ecosystem. The analysis of nitrogen load, in terms of identifying the critical source areas and apportioning the instream nitrogen to individual sources is supportive to the catchment management. The difficulty of the analysis spatially and seasonally, including the processes of transformation and transportation, has made the Soil and Water Assessment Tool (SWAT), a physically-based hydrological model, a useful tool to quantify the nitrogen load at the catchment scale. This study is focused on the application of the SWAT model at the Yuan River Catchment (YRC), which has been under the threat of extensive nitrogen load in the previous years. The major nitrogen sources identified in the research are urban drainage, as the point source; fertilizer, rural feedlot and rural household, as the diffusive sources. The calibrated hydrological model indicated that the downstream plain region with paddy field and denser rural population released the highest rate of total nitrogen. Fertilizer and waste from feedlots contributes to the 85\% of the nitrogen in the stream. The results show the applicability of the SWAT model at the YRC in terms of nitrogen load simulation, and indicate the necessity to tackle the nitrogen from diffusive sources and the critical areas at the YRC.}, language = {en} } @phdthesis{He, author = {He, Qianwen}, title = {Evaluating the effect of multi-objective calibration on the modeling of catchment-scale hydrology and nitrogen load}, publisher = {Brandenburgische Technische Universit{\"a}t Cottbus-Senftenberg}, address = {Cottbus}, doi = {10.26127/BTUOpen-5233}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-52330}, pages = {191}, 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} }