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Tang Y.,Sun Yat Sen University | Xi S.,Sun Yat Sen University | Xi S.,Shenzhen Water Resources Planning and Design Institute | Chen X.,Sun Yat Sen University | Lian Y.,University of Illinois at Urbana - Champaign
Advances in Meteorology

Coastal flood regimes have been irreversibly altered by both climate change and human activities. This paper aims to quantify the impacts of multiple factors on delta flood. The Pearl River Delta (PRD), with dense river network and population, is one of the most developed coastal areas in China. The recorded extreme water level (m.s.l.) in flood season has been heavily interfered with by varied income flood flow, sea-level rise, and dredged riverbeds. A methodology, composed of a numerical model and the index R, has been developed to quantify the impacts of these driving factors in the the PRD. Results show that the flood level varied 4.29%-53.49% from the change of fluvial discharge, 3.35%-38.73% from riverbed dredging, and 0.12%-16.81% from sea-level rise. The variation of flood flow apparently takes the most effect and sea-level rise the least. In particular, dense river network intensifies the impact of income flood change and sea-level rise. Findings from this study help understand the causes of the the PRD flood regimes and provide theoretical support for flood protection in the delta region. Copyright © 2016 Yihan Tang et al. Source

Liu D.,Tianjin University | Xuan P.,Tianjin University | Li S.,Purdue University | Huang P.,Shenzhen Water Resources Planning and Design Institute
Journal of Computing in Civil Engineering

Schedules are fundamental parameters for decision making in the design phase of tunnel construction projects. Schedule estimates of tunnel construction projects are subject to major uncertainties caused by uncertain geologic conditions and risks. This research presents an adaptive cyclic operation network simulation (CYCLONE) simulation technique to predict the schedule of tunnel boring machine (TBM) tunneling and quantifies the impacts of geologic risks along a tunnel in the design phase. A geologic prediction model is integrated with expert judgments to evaluate the probabilistic geologic risks along the tunnel alignment. An adaptive CYCLONE simulation technique is developed to flexibly adjust the durations, arrangements, and modes of construction operations in response to the occurrences of geologic risks and changes of geologic conditions. The applicability of the proposed method was demonstrated by an illustrative case study - Jinping (JP) hydraulic tunnel project in southwest China. The simulation results indicate that this project has a high risk of delays caused by geologic hazards. The analysis of the simulation results reveals that the schedules of tunneling and the uncertainty in the schedules will be underestimated if geologic risks are not considered well in the simulation. The incorporation of geologic risks and the adaptability of the simulation model would lead to a more accurate and robust simulation. © 2014 American Society of Civil Engineers. Source

Wu H.,Xian University of Technology | Huang Q.,Xian University of Technology | Xu W.,Chongqing Jiaotong University | Xi S.,Sun Yat Sen University | Xi S.,Shenzhen Water Resources Planning and Design Institute
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering

Reservoirs optimal operation can improve the efficiency of water allocation and supply. Gongming water supply project is taken as an example, which is subsystem of Shenzhen urban water supply. The project constituted by hybrid reservoirs, including Gongming reservoir, Qiankeng reservoir, Ejing reservoir and Shiyan reservoir. In this project, Gongming reservoir is used to prevent continuous dry years or serious water pollution incidents, which might take great threat to urban water supply. Thus, the storage water of Gongming reservoir is taken as reserved water source for Shenzhen city water supply. For this special task, the Gongming reservoir need keeping at a relatively high water storage level for a long time, and the reservoir requires a certain amount of exchange water to maintain water quality health. The water supply benefit of the hybrid reservoirs and the amount of exchange water of Gongming reservoir are the key objectives. To study the optimal operation of Gongming water supply project for inter-basin water diversion and water supply operating, firstly, aggregation method is applied to aggregate the reservoirs into a "virtual reservoir", which is used for simplifying topological structure of hybrid reservoirs. The dead storage and usable storage of "virtual reservoir" is formed by superposing the dead storage and usable storage of hybrid reservoirs respectively. Then based on "virtual reservoir", the hybrid reservoirs operation rules for water diversion and water supply are established. Further, the multi-objectives genetic algorithm NSGA-II is applied to optimize the operation rules, and the multi-objectives of the operation are the minimum amount of diversion water and the maximum amount of supply water. The water supply operation rule curves divide the storage of "virtual reservoir" into 3 functional areas, which are normal water supply area, reduced water supply area and reserved water supply area. When total water storage of "virtual reservoir" keeps during normal water supply area, the urban demand water can be supplied adequately. When total water storage of "virtual reservoir" keeps during reduced water supply area, it indicates that the reservoirs are lacking of water, urban demand water can not be satisfied and water supply needs to reduce appropriately. The third situation is when continuous dry years or serious water pollution incidents occur, reserved water of Gongming reservoir is used to satisfy the urban demand water. The water diversion operation rule curves divide the storage into 2 functional areas, which are reduced water diversion area and normal water supply area. When total water storage of "virtual reservoir" keeps during reduced water diversion area, it indicates that the reservoirs have enough water to satisfy urban demand. The reserves reduce diversion water to prevent abandoned water. However, when total water storage of "virtual reservoir" keeps during normal water supply area, the reserves are lacking of water storage that should do water diversion. Pareto optimization technique is embedded in NSGA-II, which makes NSGA-II deal with multi-objectives at the same time. Firstly, Pareto optimization technique is applied to obtain 400 multi objective feasible solution sets that can meet water supply guarantee rate. In these sets, 183 optimal feasible solutions with different weights are selected. Then according to the 183 Pareto solutions, operation processes of water diversion and water supply are simulated. Based on the simulated results, the amounts of water diversion, exchange water, abandoned water and guarantee rate are counted as indicators, and the fuzzy method is used to analyze the relative membership degree of 183 Pareto solutions. In the scheme selecting process, water diversion and exchange water are assumed to be equal. Thus the highest relative membership degree of solution B is selected as satisfying scheme for real-time operation. Comparing and analysis the results, it demonstrates that optimization operation can improve efficiency of water supply and water exchange. © 2016, Chinese Society of Agricultural Engineering. All right reserved. Source

Both fresh and saline groundwater may be of some value to coastal communities. A comprehensive simulation-optimization model was developed to identify optimal solutions for managing both types of groundwater in coastal areas. The model may be used for conventional management problems of fresh groundwater development and of seawater intrusion control. In addition, the model can be used for problems of concurrent development of fresh and saline/brackish groundwater for beneficial uses. A set of hypothetical examples is given to demonstrate the applicability of the proposed model. In the protection of an over-exploiting freshwater pumping well, the saltwater pumping scheme was less efficient than the freshwater injection scheme. Although the former scheme may be more advantageous in some limited cases, the latter should be considered first as it retains more freshwater in the aquifer. The example of the concurrent development of fresh and brackish groundwater exhibited two different sets of optimal solutions: one with a large amount of freshwater and a small amount of brackish water with high salinity, and the other with a small amount of freshwater and a large amount of brackish water with low salinity. © 2015, Springer-Verlag Berlin Heidelberg. Source

Jiao J.J.,University of Hong Kong | Shi L.,University of Hong Kong | Shi L.,Shenzhen Water Resources Planning and Design Institute | Kuang X.,University of Hong Kong | And 3 more authors.
Hydrogeology Journal

Offshore hydrogeology has been much less studied compared to onshore hydrogeology. The marine Quaternary system in Hong Kong (China) consists of interlayers of aquitards and aquifers and was part of the Pearl River Delta when the sea level was low before the Holocene. Core samples from six offshore boreholes were collected to measure the chloride concentration in the system by adding deionized water. A method was proposed to convert the sediment chloride into that of the original pore water. A one-dimensional sedimentation-transport model was developed to simulate the historical conservative transport of the reconstructed pore-water chloride. The model integrates present knowledge of stratigraphy and the historical evolution of the geological system. The chloride concentration profiles show that the chloride decreases from an average of 13,800 mg/L in the first marine unit to an average of 5,620 mg/L in the first aquifer. At the bottom of one borehole, the concentration is only 1,420 mg/L. The numerical model shows that the vertical chloride distribution is due to diffusion-controlled downward migration of seawater. The second marine unit obstructs the downward migration, indicating its low permeability and good aquitard integrity. The relatively fresh or brackish water in deep aquifers protected by the aquitard has the potential to be used as drinking water following some treatment, or at least as raw water with much cheaper desalinization compared with using seawater. The methodology and findings in this study are instructional for other coastal areas with similar geology and history in the South China Sea. © 2014, Springer-Verlag Berlin Heidelberg. Source

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