Beijing Institute of Water
Beijing Institute of Water
Liu J.,Beijing Institute of Water |
Fang S.,Beijing Institute of Water
Environmental Earth Sciences | Year: 2017
The potential risk from cyanobacteria blooms is the basis for predicting, preventing, and managing eutrophication. Poyang Lake lies on the southern bank of the middle and lower reaches of the Yangtze River. This lake is a large shallow lake connected to the Yangtze River and is affected by monsoon. The comprehensive evaluation index system, evaluation model, and method of the potential risk from cyanobacteria blooms were constructed based on the nutrient zoning in Poyang Lake, and the potential risk from cyanobacteria blooms was evaluated in 2013. (1) The evaluation index system comprises physical, chemical, and biological indicators. The physical indicators consist of blocking degree, lake region location, transparency (Secchi disk depth, SD), and temperature; the chemical indicators consist of total nitrogen (TN) and total phosphorus (TP); and the biological indicators consist of chlorophyll a (Chla) and phytoplankton biomass. Among the indicators, blocking degree and lake region location along with the prevailing wind direction were selected to represent the indicators affected by water retention time and wind direction. (2) We established a comprehensive evaluation method for assessing the potential risk from cyanobacteria blooms by adopting both analytic hierarchy process weighting and a comprehensive evaluation method. (3) Results show that the high-risk periods for cyanobacteria blooms were August, July, and December, and the high-risk regions were in the Northeastern Lake Region, Western Lake Region and Northern Lake Region. The Northeastern Lake Region is particularly in high risk in August and July. These cyanobacteria blooms presented heavy risk or close to heavy risk. Based on the risk evaluation indicators, outbreaks of cyanobacteria blooms are limited by temperature and location. Chla and phytoplankton biomass were the key indices affecting the level of potential risk from cyanobacteria blooms during the high-water-level period (July and August). In contrast, TN and TP are the key indices affecting the level of harm during the low-water-level period. Within a year, Chla, phytoplankton biomass, and TP are key indicators for the prediction of cyanobacteria blooms in Poyang Lake. © 2017, Springer-Verlag Berlin Heidelberg.
Guo C.-S.,China Institute of Water Resources and Hydropower Research |
Liu D.-B.,Beijing Institute of Water
World Environmental and Water Resources Congress 2017: International Perspectives, History and Heritage, Emerging Technologies, and Student Papers - Selected Papers from the World Environmental and Water Resources Congress 2017 | Year: 2017
The Yangshan Sea area which locates in the Qiqu Archipelago is a typical offshore area with muti-island and muti-channel. In this paper, taking Yangshan Sea-area of the Qiqu Archipelago as an example, a 3D numerical model of tidal currents and sediments is established to study the change of the current and sediment field. The validity of the model is verified by the observation data including the tidal flow and suspended sediment concentration in the vicinity of the harbor. The verification of calculation shows the calculated values are in good agreement with the measured data. The field of tidal currents, suspended sediment concentration and the seabed deformation can be successfully simulated. Finally, one layout is simulated to study the changes of the current and suspended sediment field. And the seabed evolution is predicted with the model. © ASCE.
Yang X.-H.,Beijing Normal University |
Mei Y.,Beijing Normal University |
She D.-X.,Beijing Normal University |
Li J.-Q.,Beijing Institute of Water
Computers and Mathematics with Applications | Year: 2011
The embedding dimension and the number of nearest neighbors are very important parameters in the prediction of chaotic time series. To reduce the prediction errors and the uncertainties in the determination of the above parameters, a new chaos Bayesian optimal prediction method (CBOPM) is proposed by choosing optimal parameters in the local linear prediction method (LLPM) and improving the prediction accuracy with Bayesian theory. In the new method, the embedding dimension and the number of nearest neighbors are combined as a parameter set. The optimal parameters are selected by mean relative error (MRE) and correlation coefficient (CC) indices according to optimization criteria. Real hydrological time series are taken to examine the new method. The prediction results indicate that CBOPM can choose the optimal parameters adaptively in the prediction process. Compared with several LLPM models, the CBOPM has higher prediction accuracy in predicting hydrological time series. © 2010 Published by Elsevier Ltd. All rights reserved.
Yang X.H.,Beijing Normal University |
Zhang X.J.,Beijing Normal University |
Hu X.X.,Beijing Normal University |
Yang Z.F.,Beijing Normal University |
Li J.Q.,Beijing Institute of Water
Nonlinear Processes in Geophysics | Year: 2011
There is much uncertain information which is very difficult to quantify in the water resource renewability assessment (WRRA). The index weights are the key parameters in the assessment model. To assess the water resource renewability rationally, a novel nonlinear optimization set pair analysis model (NOSPAM) is proposed, in which a nonlinear optimization model based on gray-encoded hybrid accelerating genetic algorithm is given to determine the weights by optimizing subjective and objective information, as well as an improved set pair analysis model based on the connection degree is established to deal with certain-uncertain information. In addition, a new calculating formula is established for determining certain-uncertain information quantity in NOSPAM. NOSPAM is used to assess the water resource renewability of the nine administrative divisions in the Yellow River Basin. Results show that NOSPAM can deal with the uncertain information, subjective and objective information. Compared with other nonlinear assessment methods (such as the gray associate analysis method and fuzzy assessment method), the advantage of NOSPAM is that it can not only rationally determine the index weights, but also measure the uncertain information quantity in the WRRA. This NOSPAM model is an extension to nonlinear assessment models. © Author(s) 2011.
Gao J.,Beijing Institute of Water |
Gao J.,Tsinghua University |
Gao J.,University of Colorado at Boulder |
Williams M.W.,University of Colorado at Boulder |
And 3 more authors.
Remote Sensing of Environment | Year: 2012
The spatial and temporal distribution of snow and its response to changes in climate were investigated from 1979 to 2005 in eastern Tibet. The Lhasa River basin, Niyang River basin and Changdu region cover an area of approximately 15×10 4km 2 and ranges in elevation from 2000 to more than 7000m. This large area necessitates innovative procedures for estimating potential spatial and temporal changes in snow cover. For this analysis we used the microwave long-term snow cover dataset of China with a spatial resolution of 25km and temporal resolution of 1day. After data validation between the microwave dataset and MODIS snow product, we defined two parameters for each pixel: (1) median date of the snow-free period (T m); and (2) duration of the snow-free period (δT). After removing transient-snow dominated areas, we find that the duration of the snow-free period was inversely correlated with elevation (R=-0.651, p<0.001). TFPW-MK (Trend-free pre-whitening Mann-Kendall) was then used to examine and highlight the trend of δT with time. At lower-elevation sites, the length of the snow-free season increased. In contrast, at higher-elevations, it decreased. Mann-Kendall tests on monthly air temperature and annual precipitation for the period 1979 to 2005 from seven climate stations in the region operated by the China Meteorological Data Sharing Service System show a significant increase in annual precipitation and an increase in monthly air temperatures for the fall through spring months. Thus, the length of the snow covered season appears to be decreasing at lower elevation because of the increase in air temperatures. However, at higher elevations the increase in precipitation appears to compensate for the increase in air temperature such that the snow-free period has decreased. © 2012 Elsevier Inc.
Huang J.,CAS Nanjing Institute of Geography and Limnology |
Gao J.,CAS Nanjing Institute of Geography and Limnology |
Liu J.,Beijing Institute of Water |
Zhang Y.,China National Environmental Monitoring Center
Ecological Modelling | Year: 2013
Kalman filter has been successfully used in assimilating observations into the existing models, and has been continually adjusted for its wider use. In this study, one of the Kalman filter techniques (ensemble Kalman filter) was used to assimilate measured data into a spatial hydrodynamic-phytoplankton model for predicting dynamics of phytoplankton biomass in Lake Taihu. In order to investigate the effects of the initial conditions (chlorophyll a) and the model parameter on the model fit, we carried out three simulations with different update strategies of parameter and variable using ensemble Kalman filter. Two simulations updated both of model parameter and state variable once and twice a week, respectively. Another simulation updated the state variable once a week, respectively. The simulation results show that the model fit was improved when the state variable (chlorophyll a) was updated by measured data in a shorter term, and was slightly improved with time-varying parameter. In this respect, good estimates of initial chlorophyll a conditions are critical to achieve good predictions of chlorophyll a dynamics in Lake Taihu. This study demonstrates the success of the ensemble Kalman filter technique in improving models' predictive skill, and implementing time-varying parameters for ecological models. © 2013 Elsevier B.V.
Xu S.,Dalian University of Technology |
Ma T.,Dalian University of Technology |
Liu Y.,Beijing Institute of Water
Aquatic Botany | Year: 2011
This paper introduces a multi-cylinder evapotranspirometer method, which can directly measure evapotranspiration (ET) from emergent plants in different species and states as well as simultaneously measure evaporation (EW) from an open water surface. Values of daily ET from three contrasting reed (Phragmites australis) stands, with different leaf area indexes (LAI), were obtained through in situ measurements of the Baiyangdian wetland using this method during the growing seasons in 2008 and 2009. The results showed that the ET rate of the reed belt was very high, even exceeding 20mmd-1 under extreme weather conditions. Depending on the LAI change, the annual ET from the different reed canopies ranged from 970 to 2035mm, whereas the ET/EW ratios ranged from 2.05 to 3.98. Accuracy analysis results showed that the errors of the measurement from this method were no more than 2mm. The relative errors of the measurement were correspondingly from 0.04% to 0.33%. It is indicated that the accuracy of our measurement is good enough for the requirements of the ET measurement. © 2011 Elsevier B.V.
Hu C.,Beijing Institute of Water
Shuili Xuebao/Journal of Hydraulic Engineering | Year: 2016
Sediment deposition in a reservoir constructed in a sediment-laden river has a direct impact on the reservoir's lifespan and its comprehensive benefits of flood control, power generation, navigation and water supply. In 1970s the reservoir operation mode of 'Storing Clear Water and Discharging Muddy Flow' was put forward by Chinese scientists for coping with serious sedimentation problem in the Sanmenxia Reservoir, and further applied and developed in several key water control projects such as the Xiaolangdi Reservoir on the Yellow River and the Three Gorges Reservoir on the Yangtze River. This operation mode successfully solves the problem of the conflict between sedimentation and benefits of a reservoir on a sediment-laden river by reducing its sediment deposition and maintaining its effective storage capacity for long-term use. It gives full play to the comprehensive benefits of a reservoir and presents an effective new way to cope with reservoir sediment problem for a sediment-laden river. The operation mode of 'Storing Clear Water and Discharging Muddy Flow' will be constantly optimized and improved in practice along with the knowledge deepening on reservoir sediment problems. Base on the actual situation of changes on runoff and sediment loads of rivers, the paper puts forward suggestions on further optimizing operation mode for the Three Gorges Reservoir and Xiaolangdi Reservoir to ensure the projects'safety and comprehensive benefits and to provide scientific support for promoting development on the theory and technology of reservoir sedimentation. © 2016, China Water Power Press. All right reserved.
Guan C.M.,Beijing Institute of Water
Applied Mechanics and Materials | Year: 2014
The project of substituting small hydropower for fuel (SHPF project in short) in China has been implemented for ten years and has achieved significant economic, social and ecological benefits. The construction, completion situations, results and major experience of the SHPF project are summarized. The existing problems are analyzed. Some suggestions are given for the construction and management of similar projects in future. © (2014) Trans Tech Publications, Switzerland.
Xinshan S.,Donghua University |
Qin L.,Donghua University |
Denghua Y.,Beijing Institute of Water
Procedia Environmental Sciences | Year: 2010
This paper carried on a series of experiments with coupled vertical subsurface flow constructed wetlands(VSSFCWs) and horizontal subsurface flow constructed wetlands(HSSFCWs) for the nitrogen removal of the high concentration nitrogenous domestic sewage. According to the transformation results of inorganic nitrogen in VSSFCWs and HSSFCWs, the paper analyzed the key factors to influence inorganic nitrogen, and discussed the nitrogen removal effects under the conditions of external carbon source addition. The results show that: First point, the VSSFCWs has more powerful nitrification ability, and HSSFCWs has more powerful denitrification ability. Under the condition of excessive high concentration nitrogen in inlet water, not enough carbon source become the restriction of denitrification in HSSFCWs. Second point, in VSSFCWs, when DO is greater than 1.5 mg/L, hydraulic retention time is about 2 days, and ammonia nitrogen concentration in inlet water is less than 80 mg/L, the ammonia nitrogen concentration in inlet water can be transformed sufficiently into nitrate nitrogen. And so on, in HSSFCWs, adding external carbon source can cause a lower DO level system, and that is helpful to denitrificate successfully. When TOC(Total Organic Carbon)/TN(Total Nitrogen) in inlet water of HSSFCWs is greater than 2.5, the carbon source for denitrification is sufficiently, and the excessive TOC/TN is not constantly advantageous to increase nitrogen removal efficiency. © 2010 Published by Elsevier Ltd.