Liu, Lei
Permanent URI for this collectionhttps://hdl.handle.net/10222/39727
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Item Open Access Assessing the Effects of Land Use Changes on Non-Point Source Pollution Reduction for the Three Gorges Watershed Using the SWAT Model(2013-09) Chen, Y.; Cheng, S. Y.; Liu, L.; Guo, X. R.; Wang, Z.; Qin, C. H.; Hao, R. X.; Lu, J.; Gao, J. J.This study presents a new attempt of applying the hydrological model SWAT to the Three Gorges watershed in China for addressing its non-point source (NPS) pollution control issues. The model was calibrated and validated using the monitoring data collected during 2002-2008, and satisfactory values of R-2 and ENS (Nash-Suttclife Efficiency) were obtained. The calibrated SWAT model was then used to simulate 6 different land use scenarios for investigating the effects of each scenario on the non-point source (NPS) pollution control in the watershed. Six scenarios were designed with distinct land use focuses and include five newly-designed scenarios (Q1-Q5) representing 5 different land use alternatives and a baseline scenario (Q6) representing the land use pattern the watershed had in 2005. It was identified that the farmland is the dominant contributor to the NPS pollution in the watershed in terms of yields of sediment, TN and TP. If the farmland is changed to the woodland, grassland or shrubland, a better control and reduction over the NPS pollution could be achieved. This study provides a good understanding of the interactions between different land use patterns and the NPS pollution control for decision-makers to make sound decisions. Changing the land use pattern and implementing alternative management practices could help reduce the non-point source pollution effectively and thus play a significant role in improving reservoir water quality of the watershed.Item Open Access A Coupled MM5-CMAQ Modeling System for Assessing Effects of Restriction Measures on PM10 Pollution in Olympic City of Beijing, China(2012-06) Zhou, Y.; Cheng, S. Y.; Liu, L.; Chen, D. S.In this paper, a coupled MM5-CMAQ modeling system was employed to investigate the PM10 pollution issue in Beijing, China, with a focus on assessing the effects of different restriction policies implemented during and after the 2008 Olympic Games. The simulations under designed scenarios were implemented over a 2-level nested grid domain for comparing the difference of PM10 concentrations under restriction and no-restrictions situations. The restriction measures include alternate-day vehicle driving, construction activities, trans-boundary emissions from neighboring provinces, and vehicle restrictions during the post-Olympic period. Meteorological contributions to the air quality improvement were also examined. The results show that significant improvement of air quality in Beijing during the 2008 Games was attributed largely to these restriction measures, although favorable weather conditions play an important role. Also, during the post-Olympic period, daily vehicle restrictions implemented temporarily under extreme weather conditions played a crucial role in alleviating Beijing's air pollution. Beijing not only needs to take continuing efforts to addresses its own PM10 problem, but also has a clear self-interest in demanding better environmental performance from neighboring provinces. It is suggested that Beijing would work collectively with neighboring provinces to develop a long-term multi-region initiative and strategy aimed at emission reduction for providing the citizens in this region a healthy and clean air in the long run.Item Open Access A Hybrid Perturbation and Morris Approach for Identifying Sensitive Parameters in Surface Water Quality Models(2008-12) Huang, Y. T.; Liu, L.Surface water quality models (SWQM) are always developed as universal frameworks so that they can be flexibly employed to simulate a large variety of water bodies. These models are often over-parameterized (more parameters than needed are included in these models). As a result, it is necessary to identify sensitive parameters when these models are applied to the simulations of specific water bodies. Sensitivity analysis has been widely used as an effective tool to undertake the task. In this study, a hybrid approach was developed through integrating the parameter perturbation method and the Morris method into a general SWQM-parameter sensitivity analysis framework. The approach was applied to Lake Maumelle in Arkansas with its hydrodynamics and water quality being simulated by the model CE-QUAL-W2. The sensitivities of the 96 model parameters were firstly evaluated by the parameter perturbation method in the simulation of the variables including temperature, ammonium, nitrate-nitrite, dissolved oxygen, total phosphorus and chlorophyll a, and 51 of them were found sensitive. The sensitivities of the 51 parameters were further investigated using the Morris method. It was found that each output variable was strongly sensitive to a distinctive set of parameters. It is also observed that the highly sensitive parameters display nonlinear relationships with the model outputs or strong correlations with other parameters. The obtained results from this study could provide a scientific base and solid start for the calibration, validation and application of the model.