The great spatial and temporal variability in hydrological conditions and nitrogen(N)processing introduces large uncertainties to the identification of N sources and quantifying N cycles in plain river network regions...The great spatial and temporal variability in hydrological conditions and nitrogen(N)processing introduces large uncertainties to the identification of N sources and quantifying N cycles in plain river network regions. By combining isotopic data with chemical and hydrologic measurements, we determined the relative importance of N sources and biogeochemical N processes in the Taige River in the East Plain Region of China. The river was polluted more seriously by anthropogenic inputs in winter than in summer. Manure and urban sewage effluent were the main nitrate(NO-3) sources, with the nitrification of N-containing organic materials serving as another important source of NO-3. In the downstream, with minor variations in hydrological conditions, nitrification played a more important role than assimilation for the decreasing ammonium(NH+4-N) concentrations.The N isotopic enrichment factors(ε) during NH+4utilization ranged from- 13.88‰ in March to- 29.00‰ in July. The ratio of the increase in δ18O and δ15N of river NO-3in the downstream was 1.04 in January and 0.92 in March. This ratio indicated that NO-3assimilation by phytoplankton was responsible for the increasing δ15N and δ18O values of NO-3in winter. The relationships between δ15N of particulate organic nitrogen and isotopic compositions of dissolved inorganic nitrogen indicated that the phytoplankton in the Taige River probably utilized NH+4preferentially and mainly in summer, while in winter, NO-3assimilation by phytoplankton was dominant.展开更多
The water distribution network is an important part of the plain water environment improvement system. To make efficient use of the regional water diversion source, scientifically distribute the water diversion flow a...The water distribution network is an important part of the plain water environment improvement system. To make efficient use of the regional water diversion source, scientifically distribute the water diversion flow and improve the water environment carrying capacity of Haishu Plain, the river network hydrodynamic model is used in this paper to simulate the water intake location, reasonable water quantity and influence range of water transfer in Haishu Plain. The simulation results have high accuracy, which can provide a scientific basis for the scale, water transfer mechanism and project layout of water transfer construction in Haishu Plain and show a strong reference value for the study of water diversion and distribution scheme of coastal plain river network.展开更多
China’s low-carbon development path will make significant contributions to achieving global sustainable development goals.Due to the diverse natural and economic conditions across different regions in China,there exi...China’s low-carbon development path will make significant contributions to achieving global sustainable development goals.Due to the diverse natural and economic conditions across different regions in China,there exists an imbalance in the distribution of car-bon emissions.Therefore,regional cooperation serves as an effective means to attain low-carbon development.This study examined the pattern of carbon emissions and proposed a potential joint emission reduction strategy by utilizing the industrial carbon emission intens-ity(ICEI)as a crucial factor.We utilized social network analysis and Local Indicators of Spatial Association(LISA)space-time trans-ition matrix to investigate the spatiotemporal connections and discrepancies of ICEI in the cities of the Pearl River Basin(PRB),China from 2010 to 2020.The primary drivers of the ICEI were determined through geographical detectors and multi-scale geographically weighted regression.The results were as follows:1)the overall ICEI in the Pearl River Basin is showing a downward trend,and there is a significant spatial imbalance.2)There are numerous network connections between cities regarding the ICEI,but the network structure is relatively fragile and unstable.3)Economically developed cities such as Guangzhou,Foshan,and Dongguan are in the center of the network while playing an intermediary role.4)Energy consumption,industrialization,per capita GDP,urbanization,science and techno-logy,and productivity are found to be the most influential variables in the spatial differentiation of ICEI,and their combination in-creased the explanatory power of the geographic variation of ICEI.Finally,through the analysis of differences and connections in urban carbon emissions under different economic levels and ICEI,the study suggests joint carbon reduction strategies,which are centered on carbon transfer,financial support,and technological assistance among cities.展开更多
The land area in a river network is divided into certain-scale square cells for the sake of precision,and,based on the physical mechanisms of rainfall-runoff processes and runoff pollution,the non-point source polluti...The land area in a river network is divided into certain-scale square cells for the sake of precision,and,based on the physical mechanisms of rainfall-runoff processes and runoff pollution,the non-point source pollution from cells is estimated using the export coefficients of different land use types.The non-point source pollution from a land cell should all go into the closest river reach,so it is distributed according to the terrain of the plain river network area and the positions of land cells and river network reaches.A relationship between a single land cell and its pollution-receiving reach can be determined using this system.In view of the above,a spatial distribution model of the rainfall runoff and non-point source pollution in reaches of a plain river network area was established.This model can provide technological support for further research on the dynamic effects of non-point source pollution on water quality.展开更多
This study examined the spatio-temporal trajectories of the international freight forwarding service(IFFS) in the Yangtze River Delta(YRD) and explored the driving mechanisms of the service. Based on a bipartite netwo...This study examined the spatio-temporal trajectories of the international freight forwarding service(IFFS) in the Yangtze River Delta(YRD) and explored the driving mechanisms of the service. Based on a bipartite network projection from an IFFS firm-city data source, we mapped three IFFS networks in the YRD in 2005, 2010, and 2015. A range of statistical indicators were used to explore changes in the spatial patterns of the three networks. The underlying influence of marketization, globalization, decentralization, and integration was then explored. It was found that the connections between Shanghai and other nodal cities formed the backbones of these networks. The effects of a city's administrative level and provincial administrative borders were generally obvious. We found several specific spatial patterns associated with IFFS. For example, the four non-administrative centers of Ningbo, Suzhou, Lianyungang, and Nantong were the most connected cities and played the role of gateway cities. Furthermore, remarkable regional equalities were found regarding a city's IFFS network provision, with notable examples in the weakly connected areas of northern Jiangsu and southwestern Zhejiang. Finally, an analysis of the driving mechanisms demonstrated that IFFS network changes were highly sensitive to the influences of marketization and globalization, while regional integration played a lesser role in driving changes in IFFS networks.展开更多
Four units and twenty-four zones of diatom have been discerned in the Borehole ZK5 in the estuarine plain of the Jiulong River, Fujian Province. Comprehensive analysis of these, together with microbiological assemblag...Four units and twenty-four zones of diatom have been discerned in the Borehole ZK5 in the estuarine plain of the Jiulong River, Fujian Province. Comprehensive analysis of these, together with microbiological assemblages and age determinations in some other boreholes, shows that during the Late Wurm Glacial, sea level of the study area rose and fell frequently, but had principally been in the environments of estuary-bay. This mainly resulted from the tectonic subouction. In this period 3 low sea levels occurred. at 18, 16 and 12 kaBP respectively. During Holocene, sea weter intruded massively and the sea level over the transgnaion maximum had been 5-10 m higher than that of the present.展开更多
In this study, we simulated water flow in a water conservancy project consisting of various hydraulic structures, such as sluices, pumping stations, hydropower stations, ship locks, and culverts, and developed a multi...In this study, we simulated water flow in a water conservancy project consisting of various hydraulic structures, such as sluices, pumping stations, hydropower stations, ship locks, and culverts, and developed a multi-period and multi-variable joint optimization scheduling model for flood control, drainage, and irrigation. In this model, the number of sluice holes, pump units, and hydropower station units to be opened were used as decision variables, and different optimization objectives and constraints were considered. This model was solved with improved genetic algorithms and verified using the Huaian Water Conservancy Project as an example. The results show that the use of the joint optimization scheduling led to a 10% increase in the power generation capacity and a 15% reduction in the total energy consumption. The change in the water level was reduced by 0.25 m upstream of the Yundong Sluice, and by 50% downstream of pumping stations No. 1, No. 2, and No. 4. It is clear that the joint optimization scheduling proposed in this study can effectively improve power generation capacity of the project, minimize operating costs and energy consumption, and enable more stable operation of various hydraulic structures. The results may provide references for the management of water conservancy projects in complex river networks.展开更多
Concern on alteration of sediment natural flow caused by developments of water resources system, has been addressed in many river basins around the world especially in developing and remote regions where sediment data...Concern on alteration of sediment natural flow caused by developments of water resources system, has been addressed in many river basins around the world especially in developing and remote regions where sediment data are poorly gauged or ungauged. Since suspended sediment load (SSL) is predominant, the objectives of this research are to: 1) simulate monthly average SSL (SSLm) of four catchments using artificial neural network (ANN);2) assess the application of the calibrated ANN (Cal-ANN) models in three ungauged catchment representatives (UCR) before using them to predict SSLm of three actual ungauged catchments (AUC) in the Tonle Sap River Basin;and 3) estimate annual SSL (SSLA) of each AUC for the case of with and without dam-reservoirs. The model performance for total load (SSLT) prediction was also investigated because it is important for dam-reservoir management. For model simulation, ANN yielded very satisfactory results with determination coefficient (R2) ranging from 0.81 to 0.94 in calibration stage and 0.63 to 0.87 in validation stage. The Cal-ANN models also performed well in UCRs with R2 ranging from 0.59 to 0.64. From the result of this study, one can estimate SSLm and SSLT of ungauged catchments with an accuracy of 0.61 in term of R2 and 34.06% in term of absolute percentage bias, respectively. SSLA of the AUCs was found between 159,281 and 723,580 t/year. In combination with Brune’s method, the impact of dam-reservoirs could reduce SSLA between 47% and 68%. This result is key information for sustainable development of such infrastructures.展开更多
The Hutuo River alluvial-proluvial fan is located in North China Plain, and groundwater is the main source of water supply for agriculture and domestic water. Shijiazhuang depression funnels due to the long-term exces...The Hutuo River alluvial-proluvial fan is located in North China Plain, and groundwater is the main source of water supply for agriculture and domestic water. Shijiazhuang depression funnels due to the long-term excessive exploitation are the bottleneck of the regional economic development. Analyzing the chemical characteristics of groundwater under the condition of strong human activities, can provide a scientific basis for further study of strong groundwater mining area environmental change. 143 groups of shallow groundwater samples are collected during the period of 2007-2008. In this paper, the hydrochemical characteristics of groundwater in the Hutuo River Plain area are analyzed systematically, using hydrogeochemical theory, combined with statistical methods and hydrochemical methods. Results are shown as follows: HCO_3^- and Ca^(2+) are major anion and cation. The variation coefficients of K^+, Ca^(2+), Mg^(2+) and HCO_3^- between 0.25 and 0.52, which means small and stable relatively. The variation coefficient of are Na^+, NO_3^-, Cl-, SO2-4 were large(0.89-1.01). They are sensitive and vulnerable to environmental change affect. Due to the impact of human activities, from the top to the edge of the alluvial-proluvial fan, the hydrochemical types of groundwater change from single to multiple, followed by HCO_3^-Ca·Mg, HCO_3·SO_4-Ca·Mg, HCO_3·SO_4·Cl-Ca·Mg, HCO_3·Cl-Ca·Mg and other types.展开更多
Based on the special hydrogeological conditions of the Dahei River Plain in the Inner Mongolia area, assessment of shallow groundwater vulnerability is conducted based on DRASTIC model. Each evaluation indicator weigh...Based on the special hydrogeological conditions of the Dahei River Plain in the Inner Mongolia area, assessment of shallow groundwater vulnerability is conducted based on DRASTIC model. Each evaluation indicator weight is determined by using analytic hierarchy process(AHP). The most important indicators are lithology in soil media and vadose zone. Assessment model of shallow groundwater vulnerability of the Dahei River plain is constructed. Distribution map of vulnerability index in this area is made with the spatial analysis function of ARCGIS. The results show that the particularly sensitive area is the piedmont of the Daqing Mountain, where the upstream place of the groundwater and the south-central place of the plain has the lowest vulnerability. The assessment results are more in accordance with the actual vulnerability conditions of this area by using analytic hierarchy process, and is helpful for groundwater protection.展开更多
A new hybrid model which combines wavelets and Artificial Neural Network (ANN) called wavelet neural network (WNN) model was proposed in the current study and applied for time series modeling of river flow. The time s...A new hybrid model which combines wavelets and Artificial Neural Network (ANN) called wavelet neural network (WNN) model was proposed in the current study and applied for time series modeling of river flow. The time series of daily river flow of the Malaprabha River basin (Karnataka state, India) were analyzed by the WNN model. The observed time series are decomposed into sub-series using discrete wavelet transform and then appropriate sub-series is used as inputs to the neural network for forecasting hydrological variables. The hybrid model (WNN) was compared with the standard ANN and AR models. The WNN model was able to provide a good fit with the observed data, especially the peak values during the testing period. The benchmark results from WNN model applications showed that the hybrid model produced better results in estimating the hydrograph properties than the latter models (ANN and AR).展开更多
As the leading urban agglomeration in China,the Yangtze River Delta(YRD)is experiencing a factor-driven to innovationdriven transition.However,the dynamics of regional innovation growth are not yet fully understood.Th...As the leading urban agglomeration in China,the Yangtze River Delta(YRD)is experiencing a factor-driven to innovationdriven transition.However,the dynamics of regional innovation growth are not yet fully understood.This paper combines the complex network methodology with spatial econometrics to disentangle the contributions of innovation endowments,innovation network flows,and innovation network positions to regional innovation growth,as well as their spatial spillover effects.The primary findings suggest that regional innovation growth results from the networked agglomeration economies,which is shaped by the interactions between agglomeration factors and network factors.Specifically,agglomeration factors play a fundamental role in regional innovation growth.In contrast,network factors,such as the network flows and network positions,may contribute to new path creation by promoting access to external innovation resources.Additionally,the institutional factors show multiplexity in fostering regional innovation patterns.Such findings indicate that the YRD region should shift the innovation growth pattern from competitive involution to mutually beneficial cooperation to reduce regional disparities.In this regard,the institutional capacity of organizing network flows and fostering reciprocal inter-city partnerships has become increasingly critical for promoting sustainable innovation and regional development.展开更多
The typical regions of the Taihu Lake Basin,China,were selected to analyze the variation characteristics of river-lake networks under intensive human activities.The characteristics of the fractal dimension of river ne...The typical regions of the Taihu Lake Basin,China,were selected to analyze the variation characteristics of river-lake networks under intensive human activities.The characteristics of the fractal dimension of river networks and lakes for different periods were investigated and the influences of river system evolution on water level changes were further explored through the comparison of their fractal characters.The results are as follows:1) River network development of the study area is becoming more monotonous and more simple;the number of lakes is reducing significantly,and the water surface ratio has dropped significantly since the 1980s.2) The box dimension of the river networks in all the cities of the study area decreased slowly from the 1960s to the 1980s,while the decrease was significant from the 1980s to the 2000s.The variations of lake correlation dimension are similar to those of the river network box dimensions.This is unfavorable for the storage capacity of the river networks and lakes.3) The Hurst exponents of water levels were all between 0.5 and 1.0 from the 1960s to the 1980s,while decreased in the 2000s,indicating the decline in persistence and increase in the complexity of water level series.The paper draws a conclusion that the relationship between the fractal dimension of river-lake networks and the Hurst exponents of the water level series can reveal the impacts of river system changes on flood disasters to some extent:the disappearance of river networks and lakes will increase the possibility of flood occurrence.展开更多
Complex water movement and insufficient observation stations are the unfavorable factors in improving the accuracy of flow calculation of river networks.A water level updating model for river networks was set up based...Complex water movement and insufficient observation stations are the unfavorable factors in improving the accuracy of flow calculation of river networks.A water level updating model for river networks was set up based on a three-step method at key nodes,and model correction values were collected from gauge stations.To improve the accuracy of water level and discharge forecasts for the entire network,the discrete coefficients of the Saint-Venant equations for river sections were regarded as the media carrying the correction values from observation locations to other cross-sections of the river network system.To examine the applicability,the updating model was applied to flow calculation of an ideal river network and the Chengtong section of the Yangtze River.Comparison of the forecast results with the observed data demonstrates that this updating model can improve the forecast accuracy in both ideal and real river networks.展开更多
In this paper, we reconsider the defining but often overlooked ‘hinge' function of megalopolises by analyzing how megalopolises have articulated national and international urban systems in the context of a global...In this paper, we reconsider the defining but often overlooked ‘hinge' function of megalopolises by analyzing how megalopolises have articulated national and international urban systems in the context of a globalizing knowledge economy. Taking the case of China's Yangtze River Delta(YRD) region, we particularly focus on knowledge circulation within and beyond the YRD region by analyzing the pattern and process of knowledge collaboration at different geographical scales during the 2004–2014 period. Results show that the structure of scientific knowledge collaboration as reflected by co-publications has been strongest at the national scale whereas that of technological knowledge collaboration as measured by co-patents has been strongest at the global scale. Despite this difference, the structure of both scientific and technological knowledge collaboration has been functionally polycentric at the megalopolitan scale but become less so at the national and global scales. The ‘globally connected but locally disconnected' pattern of Shanghai's external knowledge collaboration suggests that the gateway role of the YRD megalopolis in promoting knowledge collaboration at different geographical scales will take time before it is fully realized.展开更多
According to buried depth, the Yellow Rver’s Paleochannels can be divided into ground Paleochannels (buried depth 0-8m) and shallowburied Paleochannels theried depth 8-50m). Each of them can be roughly divided into t...According to buried depth, the Yellow Rver’s Paleochannels can be divided into ground Paleochannels (buried depth 0-8m) and shallowburied Paleochannels theried depth 8-50m). Each of them can be roughly divided into three major Paleochannel belts, stretching Parallel with each other from SW to NE. Sedimentary layers of the paleochannels were mainly made up by sand levee of meanders or natural leavee deposits, and the flooding sedments were found bebeen the layers. The paleochannels in North Shadong Plain were formed in three stags; stage I (buried depth 50-15m) in later period of late Pleistocene-early period of Holocene, stag II (20-8m) in earlymiddle period of HOlocene; and stag III (8-0m) in midddle-late period of Holocene.展开更多
基金supported by the Mega-projects of Science Research for Water Environment Improvement (No. 2012ZX07101)
文摘The great spatial and temporal variability in hydrological conditions and nitrogen(N)processing introduces large uncertainties to the identification of N sources and quantifying N cycles in plain river network regions. By combining isotopic data with chemical and hydrologic measurements, we determined the relative importance of N sources and biogeochemical N processes in the Taige River in the East Plain Region of China. The river was polluted more seriously by anthropogenic inputs in winter than in summer. Manure and urban sewage effluent were the main nitrate(NO-3) sources, with the nitrification of N-containing organic materials serving as another important source of NO-3. In the downstream, with minor variations in hydrological conditions, nitrification played a more important role than assimilation for the decreasing ammonium(NH+4-N) concentrations.The N isotopic enrichment factors(ε) during NH+4utilization ranged from- 13.88‰ in March to- 29.00‰ in July. The ratio of the increase in δ18O and δ15N of river NO-3in the downstream was 1.04 in January and 0.92 in March. This ratio indicated that NO-3assimilation by phytoplankton was responsible for the increasing δ15N and δ18O values of NO-3in winter. The relationships between δ15N of particulate organic nitrogen and isotopic compositions of dissolved inorganic nitrogen indicated that the phytoplankton in the Taige River probably utilized NH+4preferentially and mainly in summer, while in winter, NO-3assimilation by phytoplankton was dominant.
文摘The water distribution network is an important part of the plain water environment improvement system. To make efficient use of the regional water diversion source, scientifically distribute the water diversion flow and improve the water environment carrying capacity of Haishu Plain, the river network hydrodynamic model is used in this paper to simulate the water intake location, reasonable water quantity and influence range of water transfer in Haishu Plain. The simulation results have high accuracy, which can provide a scientific basis for the scale, water transfer mechanism and project layout of water transfer construction in Haishu Plain and show a strong reference value for the study of water diversion and distribution scheme of coastal plain river network.
基金Under the auspices of the Philosophy and Social Science Planning Project of Guizhou,China(No.21GZZD59)。
文摘China’s low-carbon development path will make significant contributions to achieving global sustainable development goals.Due to the diverse natural and economic conditions across different regions in China,there exists an imbalance in the distribution of car-bon emissions.Therefore,regional cooperation serves as an effective means to attain low-carbon development.This study examined the pattern of carbon emissions and proposed a potential joint emission reduction strategy by utilizing the industrial carbon emission intens-ity(ICEI)as a crucial factor.We utilized social network analysis and Local Indicators of Spatial Association(LISA)space-time trans-ition matrix to investigate the spatiotemporal connections and discrepancies of ICEI in the cities of the Pearl River Basin(PRB),China from 2010 to 2020.The primary drivers of the ICEI were determined through geographical detectors and multi-scale geographically weighted regression.The results were as follows:1)the overall ICEI in the Pearl River Basin is showing a downward trend,and there is a significant spatial imbalance.2)There are numerous network connections between cities regarding the ICEI,but the network structure is relatively fragile and unstable.3)Economically developed cities such as Guangzhou,Foshan,and Dongguan are in the center of the network while playing an intermediary role.4)Energy consumption,industrialization,per capita GDP,urbanization,science and techno-logy,and productivity are found to be the most influential variables in the spatial differentiation of ICEI,and their combination in-creased the explanatory power of the geographic variation of ICEI.Finally,through the analysis of differences and connections in urban carbon emissions under different economic levels and ICEI,the study suggests joint carbon reduction strategies,which are centered on carbon transfer,financial support,and technological assistance among cities.
基金supported by the Major Science and Technology Program for Water Pollution Control and Treatment in China (Grant No. 2008X07101-005)
文摘The land area in a river network is divided into certain-scale square cells for the sake of precision,and,based on the physical mechanisms of rainfall-runoff processes and runoff pollution,the non-point source pollution from cells is estimated using the export coefficients of different land use types.The non-point source pollution from a land cell should all go into the closest river reach,so it is distributed according to the terrain of the plain river network area and the positions of land cells and river network reaches.A relationship between a single land cell and its pollution-receiving reach can be determined using this system.In view of the above,a spatial distribution model of the rainfall runoff and non-point source pollution in reaches of a plain river network area was established.This model can provide technological support for further research on the dynamic effects of non-point source pollution on water quality.
基金National Natural Science Foundation of China(No.41671132,41771139)Natural Science Foundation of Jiangsu Province(No.BK20171516)
文摘This study examined the spatio-temporal trajectories of the international freight forwarding service(IFFS) in the Yangtze River Delta(YRD) and explored the driving mechanisms of the service. Based on a bipartite network projection from an IFFS firm-city data source, we mapped three IFFS networks in the YRD in 2005, 2010, and 2015. A range of statistical indicators were used to explore changes in the spatial patterns of the three networks. The underlying influence of marketization, globalization, decentralization, and integration was then explored. It was found that the connections between Shanghai and other nodal cities formed the backbones of these networks. The effects of a city's administrative level and provincial administrative borders were generally obvious. We found several specific spatial patterns associated with IFFS. For example, the four non-administrative centers of Ningbo, Suzhou, Lianyungang, and Nantong were the most connected cities and played the role of gateway cities. Furthermore, remarkable regional equalities were found regarding a city's IFFS network provision, with notable examples in the weakly connected areas of northern Jiangsu and southwestern Zhejiang. Finally, an analysis of the driving mechanisms demonstrated that IFFS network changes were highly sensitive to the influences of marketization and globalization, while regional integration played a lesser role in driving changes in IFFS networks.
文摘Four units and twenty-four zones of diatom have been discerned in the Borehole ZK5 in the estuarine plain of the Jiulong River, Fujian Province. Comprehensive analysis of these, together with microbiological assemblages and age determinations in some other boreholes, shows that during the Late Wurm Glacial, sea level of the study area rose and fell frequently, but had principally been in the environments of estuary-bay. This mainly resulted from the tectonic subouction. In this period 3 low sea levels occurred. at 18, 16 and 12 kaBP respectively. During Holocene, sea weter intruded massively and the sea level over the transgnaion maximum had been 5-10 m higher than that of the present.
基金supported by the Water Conservancy Science and Technology Project of Jiangsu Province(Grant No.2012041)the Jiangsu Province Ordinary University Graduate Student Research Innovation Project(Grant No.CXZZ13_0256)
文摘In this study, we simulated water flow in a water conservancy project consisting of various hydraulic structures, such as sluices, pumping stations, hydropower stations, ship locks, and culverts, and developed a multi-period and multi-variable joint optimization scheduling model for flood control, drainage, and irrigation. In this model, the number of sluice holes, pump units, and hydropower station units to be opened were used as decision variables, and different optimization objectives and constraints were considered. This model was solved with improved genetic algorithms and verified using the Huaian Water Conservancy Project as an example. The results show that the use of the joint optimization scheduling led to a 10% increase in the power generation capacity and a 15% reduction in the total energy consumption. The change in the water level was reduced by 0.25 m upstream of the Yundong Sluice, and by 50% downstream of pumping stations No. 1, No. 2, and No. 4. It is clear that the joint optimization scheduling proposed in this study can effectively improve power generation capacity of the project, minimize operating costs and energy consumption, and enable more stable operation of various hydraulic structures. The results may provide references for the management of water conservancy projects in complex river networks.
文摘Concern on alteration of sediment natural flow caused by developments of water resources system, has been addressed in many river basins around the world especially in developing and remote regions where sediment data are poorly gauged or ungauged. Since suspended sediment load (SSL) is predominant, the objectives of this research are to: 1) simulate monthly average SSL (SSLm) of four catchments using artificial neural network (ANN);2) assess the application of the calibrated ANN (Cal-ANN) models in three ungauged catchment representatives (UCR) before using them to predict SSLm of three actual ungauged catchments (AUC) in the Tonle Sap River Basin;and 3) estimate annual SSL (SSLA) of each AUC for the case of with and without dam-reservoirs. The model performance for total load (SSLT) prediction was also investigated because it is important for dam-reservoir management. For model simulation, ANN yielded very satisfactory results with determination coefficient (R2) ranging from 0.81 to 0.94 in calibration stage and 0.63 to 0.87 in validation stage. The Cal-ANN models also performed well in UCRs with R2 ranging from 0.59 to 0.64. From the result of this study, one can estimate SSLm and SSLT of ungauged catchments with an accuracy of 0.61 in term of R2 and 34.06% in term of absolute percentage bias, respectively. SSLA of the AUCs was found between 159,281 and 723,580 t/year. In combination with Brune’s method, the impact of dam-reservoirs could reduce SSLA between 47% and 68%. This result is key information for sustainable development of such infrastructures.
基金supported by Public Welfare Project of Ministry of Water Resources (201501008)Natural Science Foundation of Hebei Province (D2015504019)
文摘The Hutuo River alluvial-proluvial fan is located in North China Plain, and groundwater is the main source of water supply for agriculture and domestic water. Shijiazhuang depression funnels due to the long-term excessive exploitation are the bottleneck of the regional economic development. Analyzing the chemical characteristics of groundwater under the condition of strong human activities, can provide a scientific basis for further study of strong groundwater mining area environmental change. 143 groups of shallow groundwater samples are collected during the period of 2007-2008. In this paper, the hydrochemical characteristics of groundwater in the Hutuo River Plain area are analyzed systematically, using hydrogeochemical theory, combined with statistical methods and hydrochemical methods. Results are shown as follows: HCO_3^- and Ca^(2+) are major anion and cation. The variation coefficients of K^+, Ca^(2+), Mg^(2+) and HCO_3^- between 0.25 and 0.52, which means small and stable relatively. The variation coefficient of are Na^+, NO_3^-, Cl-, SO2-4 were large(0.89-1.01). They are sensitive and vulnerable to environmental change affect. Due to the impact of human activities, from the top to the edge of the alluvial-proluvial fan, the hydrochemical types of groundwater change from single to multiple, followed by HCO_3^-Ca·Mg, HCO_3·SO_4-Ca·Mg, HCO_3·SO_4·Cl-Ca·Mg, HCO_3·Cl-Ca·Mg and other types.
基金Basic Scientific Research Operating Expense Project of the Chinese Academy of Geological Sciences“Leaky System Numerical Modeling and Progressive Parameter Inversion Study”(YYWF201626)Geological survey project“1/50 000 Hydrogeological Survey of the Hutuo River-Fuyang River Basin Plain”(DD20160238)
文摘Based on the special hydrogeological conditions of the Dahei River Plain in the Inner Mongolia area, assessment of shallow groundwater vulnerability is conducted based on DRASTIC model. Each evaluation indicator weight is determined by using analytic hierarchy process(AHP). The most important indicators are lithology in soil media and vadose zone. Assessment model of shallow groundwater vulnerability of the Dahei River plain is constructed. Distribution map of vulnerability index in this area is made with the spatial analysis function of ARCGIS. The results show that the particularly sensitive area is the piedmont of the Daqing Mountain, where the upstream place of the groundwater and the south-central place of the plain has the lowest vulnerability. The assessment results are more in accordance with the actual vulnerability conditions of this area by using analytic hierarchy process, and is helpful for groundwater protection.
文摘A new hybrid model which combines wavelets and Artificial Neural Network (ANN) called wavelet neural network (WNN) model was proposed in the current study and applied for time series modeling of river flow. The time series of daily river flow of the Malaprabha River basin (Karnataka state, India) were analyzed by the WNN model. The observed time series are decomposed into sub-series using discrete wavelet transform and then appropriate sub-series is used as inputs to the neural network for forecasting hydrological variables. The hybrid model (WNN) was compared with the standard ANN and AR models. The WNN model was able to provide a good fit with the observed data, especially the peak values during the testing period. The benchmark results from WNN model applications showed that the hybrid model produced better results in estimating the hydrograph properties than the latter models (ANN and AR).
基金Under the auspices of National Natural Science Foundation of China(No.52078245)。
文摘As the leading urban agglomeration in China,the Yangtze River Delta(YRD)is experiencing a factor-driven to innovationdriven transition.However,the dynamics of regional innovation growth are not yet fully understood.This paper combines the complex network methodology with spatial econometrics to disentangle the contributions of innovation endowments,innovation network flows,and innovation network positions to regional innovation growth,as well as their spatial spillover effects.The primary findings suggest that regional innovation growth results from the networked agglomeration economies,which is shaped by the interactions between agglomeration factors and network factors.Specifically,agglomeration factors play a fundamental role in regional innovation growth.In contrast,network factors,such as the network flows and network positions,may contribute to new path creation by promoting access to external innovation resources.Additionally,the institutional factors show multiplexity in fostering regional innovation patterns.Such findings indicate that the YRD region should shift the innovation growth pattern from competitive involution to mutually beneficial cooperation to reduce regional disparities.In this regard,the institutional capacity of organizing network flows and fostering reciprocal inter-city partnerships has become increasingly critical for promoting sustainable innovation and regional development.
基金Under the auspices of Special Fund for Scientific Research in the Public Interestgranted by Ministry of Water Resources(No.2012010072,200701024)+3 种基金Key Program of National Natural Science Foundation of China(No.40730635)Open Foundation of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering(No.2011491111)Research Foundation of Nanjing University of Information Science and Technology(No.20100406)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘The typical regions of the Taihu Lake Basin,China,were selected to analyze the variation characteristics of river-lake networks under intensive human activities.The characteristics of the fractal dimension of river networks and lakes for different periods were investigated and the influences of river system evolution on water level changes were further explored through the comparison of their fractal characters.The results are as follows:1) River network development of the study area is becoming more monotonous and more simple;the number of lakes is reducing significantly,and the water surface ratio has dropped significantly since the 1980s.2) The box dimension of the river networks in all the cities of the study area decreased slowly from the 1960s to the 1980s,while the decrease was significant from the 1980s to the 2000s.The variations of lake correlation dimension are similar to those of the river network box dimensions.This is unfavorable for the storage capacity of the river networks and lakes.3) The Hurst exponents of water levels were all between 0.5 and 1.0 from the 1960s to the 1980s,while decreased in the 2000s,indicating the decline in persistence and increase in the complexity of water level series.The paper draws a conclusion that the relationship between the fractal dimension of river-lake networks and the Hurst exponents of the water level series can reveal the impacts of river system changes on flood disasters to some extent:the disappearance of river networks and lakes will increase the possibility of flood occurrence.
基金supported by the Major Program of the National Natural Science Foundation of China(Grant No.51190091)the National Natural Science Foundation of China(Grant No.51009045)the Open Research Fund Program of the State Key Laboratory of Water Resources and Hydropower Engineering Science of Wuhan University(Grant No.2012B094)
文摘Complex water movement and insufficient observation stations are the unfavorable factors in improving the accuracy of flow calculation of river networks.A water level updating model for river networks was set up based on a three-step method at key nodes,and model correction values were collected from gauge stations.To improve the accuracy of water level and discharge forecasts for the entire network,the discrete coefficients of the Saint-Venant equations for river sections were regarded as the media carrying the correction values from observation locations to other cross-sections of the river network system.To examine the applicability,the updating model was applied to flow calculation of an ideal river network and the Chengtong section of the Yangtze River.Comparison of the forecast results with the observed data demonstrates that this updating model can improve the forecast accuracy in both ideal and real river networks.
文摘In this paper, we reconsider the defining but often overlooked ‘hinge' function of megalopolises by analyzing how megalopolises have articulated national and international urban systems in the context of a globalizing knowledge economy. Taking the case of China's Yangtze River Delta(YRD) region, we particularly focus on knowledge circulation within and beyond the YRD region by analyzing the pattern and process of knowledge collaboration at different geographical scales during the 2004–2014 period. Results show that the structure of scientific knowledge collaboration as reflected by co-publications has been strongest at the national scale whereas that of technological knowledge collaboration as measured by co-patents has been strongest at the global scale. Despite this difference, the structure of both scientific and technological knowledge collaboration has been functionally polycentric at the megalopolitan scale but become less so at the national and global scales. The ‘globally connected but locally disconnected' pattern of Shanghai's external knowledge collaboration suggests that the gateway role of the YRD megalopolis in promoting knowledge collaboration at different geographical scales will take time before it is fully realized.
文摘According to buried depth, the Yellow Rver’s Paleochannels can be divided into ground Paleochannels (buried depth 0-8m) and shallowburied Paleochannels theried depth 8-50m). Each of them can be roughly divided into three major Paleochannel belts, stretching Parallel with each other from SW to NE. Sedimentary layers of the paleochannels were mainly made up by sand levee of meanders or natural leavee deposits, and the flooding sedments were found bebeen the layers. The paleochannels in North Shadong Plain were formed in three stags; stage I (buried depth 50-15m) in later period of late Pleistocene-early period of Holocene, stag II (20-8m) in earlymiddle period of HOlocene; and stag III (8-0m) in midddle-late period of Holocene.
