The combined effect of periodic water impoundment and seasonal natural flood events has created a 30 m high water-level fluctuation zone(WLFZ) around the Three Gorges Reservoir(TGR), China, forming a unique eco-landsc...The combined effect of periodic water impoundment and seasonal natural flood events has created a 30 m high water-level fluctuation zone(WLFZ) around the Three Gorges Reservoir(TGR), China, forming a unique eco-landscape. Siltation, eutrophication, enrichment of heavy metals, and methane emissions in the WLFZ have been widely associated with sediment and soil particles generated from the upstream catchment or upland slopes. However, little attention has been paid to the complexity of sediment particle-size distributions in the WLFZ. In the present study, core samples(from a 345 cm thick sediment core from the base of the WLFZ), slope transect surface samples(across/up a WLFZ slope), and along-river/longitudinal surface samples(from the reservoir reaches) were collected. Laser granulometry and a volume-based fractal model were used to reveal the characteristics of sediment particle-size distributions. Results indicate that the alternation of coarse and fine particles in the sedimentary core profile is represented as a fluctuation of low and high values of fractal dimension(D), ranging from 2.59 to 2.77. On the WLFZ slope transect, surface sediment particles coarsen with increasing elevation, sand content increases from 3.3% to 78.5%, and D decreases from 2.76 to 2.53. Longitudinally, surface sediments demonstrate a downstream-fining trend, and D increases gradually downstream. D is significantly positively correlated with the fine particle content. We conclude that D is a useful measure for evaluating sediment particle-size distribution.展开更多
Based on the 2016 airgun experimental data of the Fujian Nanyi reservoir,we adopted the frequency domain water-level deconvolution method and cross-correlation time delay detection technique to study the influence of ...Based on the 2016 airgun experimental data of the Fujian Nanyi reservoir,we adopted the frequency domain water-level deconvolution method and cross-correlation time delay detection technique to study the influence of level scaling factor and the background noise level of the station on deconvolution calculation results, and analyze the effect of deconvolution on eliminating the influence of the source caused by different air-gun pressures. The results show that:( 1) When the level scaling factor is smaller,the signal to noise ratio of the waveform after the deconvolution is smaller,and when the level scaling factor is over smaller,the identification error of travel time is greater.( 2) When the SNR of the station record is higher,the recognition accuracy of travel time is higher,the influence of SNR on the reference station record is far greater than the far station,when the SNR of the far station record is more than 10,the error of travel time is within6 ms,but when the SNR of the reference station record is 30,the travel time error may reach to 20 ms.( 3) When the airgun source difference is big,the frequency domain waterlevel deconvolution method has better effect on eliminating the source influence,but the method error may be introduced when the source difference is small.展开更多
Urmia Lake in northwest of Iran, through the recent years has been extremely faced with the water crisis. Climate variations and anthropogenic impacts could be two main affiliated factors in this regard. We considered...Urmia Lake in northwest of Iran, through the recent years has been extremely faced with the water crisis. Climate variations and anthropogenic impacts could be two main affiliated factors in this regard. We considered the long term data series of precipitation, temperature and evaporation in monthly and yearly scales in order to compare to water-level values of Urmia Lake. The statistics approaches such as: standard deviation, trend analysis, T test, Pearson and Spearman correlations, liner regression are used to analyze all variables. The results released that the water-level of Urmia Lake along with the precipitation and temperature of the lake’s basin have experienced the periodic changes through 1961 to 2010, as there are some gradual dryness trends on the study area according to precipitation and temperature variations. Urmia Lake periodic water-level fluctuations show more significant correlation to temperature than the precipitation. Whiles, the water-level’s decreasing behavior especially through 1998 to 2010 is more harsh and different than the rate that is considered for precipitation’s decrease and temperature’s increase. Thus, there could be some anthropogenic factors in the basin which produced some supplementary causes to shrink Urmia Lake. Extracting the double precipitation over the basin through introducing and categorizing of atmospheric synoptic systems in order to cloud seeding operation could be one of urgent and innovative solutions to mitigate water crisis in the basin.展开更多
[ Objective] The research aimed to study influence of the repeated flooding on growth and development of A. calamus in water-level-fluc- tuation zone of the Three Gorges Reservoir. [ Method] A. calamus plants were exp...[ Objective] The research aimed to study influence of the repeated flooding on growth and development of A. calamus in water-level-fluc- tuation zone of the Three Gorges Reservoir. [ Method] A. calamus plants were exposed to water under the dark conditions respectively in Septem- ber 2009 and September 2010. Then, they were taken away from the water, and grew in natural conditions in the following March and April respec- tively ( marked as S1, S2, S1 and S2). The plant number was conducted statistics respectively. On May 7, the leaf number was made statistics. Length, width and rapid light responding curve of the leaf were determined. [ Result] Repeated flooding restrained significantly plant germination un- der the dark condition. Plant number in S1 and S2 groups decreased by 38.9% and 33.3% respectively compared with the control. It also reduced survival rate of the plant. Plant number in S2 group decreased by 16.7% (P 〈 0.05) compared with that of S2 group when they were taken away from the water. Both of flooding promoted elongation of the leaves, restrained leaves to grow wider, and also restrained leaf formation of the plants except for S1 and S1 groups. Total leaf length of a plant decreased markedly after the second flooding which in S1 and S2 groups were 50.6% and 36.9% respectively less than that after the first flooding. Total leaf number of the plant in S1and S2 groups reduced significantly, and they were only 63.1% and 38.5% respectively of the control. Compared with the first flooding, total leaf length of a plant in the control increased signifi- cantly and decreased remarkably in S2 group after the second flooding. Furthermore, light response ability of the relative electronic transfer rate (rETR) in S1 group wasn't significantly different from the control, and rETRmax, in S2 group was significantly less than the control. Moreover, non- photochemical quenching (NPQ) decreased remarkably in S1 and S2 groups. It indicated that A. calamus had good restore ability of the light re- sponse, but restoring of its heat dissipation capacity was slower. [ Conclusion] Repeated flooding inhibited plant growth and population recovery of A. calamus under the dark condition.展开更多
Inundation of the Three Gorges Reservoir has created a 30-m water-level fluctuation zone with seasonal hydrological alternations of submergence and exposure, which may greatly affect soil properties and bank stability...Inundation of the Three Gorges Reservoir has created a 30-m water-level fluctuation zone with seasonal hydrological alternations of submergence and exposure, which may greatly affect soil properties and bank stability. The aim of this study was to investigate the response of soil pore structure to seasonal water-level fluctuation in the reservoir, and particularly, the hydrological change of wetting and drying cycles. Soil pore structure was visualized with industrial X-ray computed tomography and digital image analysis techniques. The results showed that soil total porosity(? 100 ?m), total pore number, total throat number, and mean throat surface area increased significantly under wetting and drying cycles. Soil porosity, pore number and throat numberwithin each size class increased in the course of wetting and drying cycles. The coordination number, degree of anisotropy and fractal dimension were indicating an increase. In contrast, the mean shape factor, pore-throat ratio, and Euler-Poincaré number decreased due to wetting and drying cycles. These illustrated that the wetting and drying cycles made soil pore structure become more porous, continuous, heterogeneous and complex. It can thus be deduced that the water-level fluctuation would modify soil porosity, pore size distribution, and pore morphology in the Three Gorges Reservoir, which may have profound implications for soil processes, soil functions, and bank stability.展开更多
In order to understand the monitoring efficiency status of the well-water-level observation network in China after the completion of the 10 th "Five-year Plan " digital network project,and to provide a basis...In order to understand the monitoring efficiency status of the well-water-level observation network in China after the completion of the 10 th "Five-year Plan " digital network project,and to provide a basis for the future network optimization and equipment updating, the monitoring efficiency of the well-water-level observation network was evaluated. On the whole,61. 8% observing stations have good monitoring effectiveness,the observation environment of 73. 5% of observing stations meets the monitoring requirements of well-water-level. The operation status of the network is as a whole getting better,operation rates of 75% observing instruments are above 95%. Most well water levels can monitor crustal stress changes and seismic activities. However,some observation stations,due to inherent deficiency in wells,environmental disturbance,instrument aging,and low-level operation and maintenance,need to improve the monitoring efficiency level by taking measures such as observation environment improvement,equipment updating,and management training. About 6. 5% of the stations need to stop observation due to the unqualified observational environment.展开更多
Rule curves dictating target water levels for management have been implemented in several water bodies in North America over the last 70 years or more. Anthropogenic alterations of water levels are known to affect sev...Rule curves dictating target water levels for management have been implemented in several water bodies in North America over the last 70 years or more. Anthropogenic alterations of water levels are known to affect several components of wetland ecosystems. Evaluating the influence of rule curves on biological components with simple performance indicators could help harmonize water level management with wetland integrity. We assessed the potential of using the probability of common loon nest viability as a performance indicator of long-term impacts of rule curves on nesting wetland birds. We analyzed the outcome of rule curves on the probability of loon nest viability in Rainy Lake and Namakan Reservoir, 2 regulated water bodies located along the Ontario-Minnesota border. The analysis was focused on 4 hydrological time series between 1950 and 2013: 2 sets of time series simulating rule curves used to manage the water bodies in the past decades (referred to as the 1970RC and 2000RC), one of the historical measured water levels, and one of computed natural water levels. The probability of loon nest viability under the 1970RC was 2× higher than under natural conditions in both water bodies. The probability was also 2× higher under the 2000RC than under the 1970RC in the Namakan Reservoir but not in Rainy Lake. The rule curves generally improved conditions for nesting loons in both water bodies. The presented performance indicator can be used to evaluate future rule curves before they are implemented in the Rainy-Namakan or other similar systems.展开更多
基金funded by the National Natural Science Foundation of China (Grant nos. 41771320, 41771321, and 41571278)the Opening Project of Chongqing Key Laboratory of Earth Surface Processes and Environmental Remote Sensing in the Three Gorges Reservoir Area (Grant no. DBGC201801)the Sichuan Science and Technology Program (Grant no. 2018SZ0132)
文摘The combined effect of periodic water impoundment and seasonal natural flood events has created a 30 m high water-level fluctuation zone(WLFZ) around the Three Gorges Reservoir(TGR), China, forming a unique eco-landscape. Siltation, eutrophication, enrichment of heavy metals, and methane emissions in the WLFZ have been widely associated with sediment and soil particles generated from the upstream catchment or upland slopes. However, little attention has been paid to the complexity of sediment particle-size distributions in the WLFZ. In the present study, core samples(from a 345 cm thick sediment core from the base of the WLFZ), slope transect surface samples(across/up a WLFZ slope), and along-river/longitudinal surface samples(from the reservoir reaches) were collected. Laser granulometry and a volume-based fractal model were used to reveal the characteristics of sediment particle-size distributions. Results indicate that the alternation of coarse and fine particles in the sedimentary core profile is represented as a fluctuation of low and high values of fractal dimension(D), ranging from 2.59 to 2.77. On the WLFZ slope transect, surface sediment particles coarsen with increasing elevation, sand content increases from 3.3% to 78.5%, and D decreases from 2.76 to 2.53. Longitudinally, surface sediments demonstrate a downstream-fining trend, and D increases gradually downstream. D is significantly positively correlated with the fine particle content. We conclude that D is a useful measure for evaluating sediment particle-size distribution.
基金“Analysis of Accuracyof Airgun Source in Monitoring Crustal Media Change and Its Influence Factors”,the National Natural Science Foundation of China(41774068)and Special Fund for Science and Technology,Fujian Earthquake Agency(SF201709)
文摘Based on the 2016 airgun experimental data of the Fujian Nanyi reservoir,we adopted the frequency domain water-level deconvolution method and cross-correlation time delay detection technique to study the influence of level scaling factor and the background noise level of the station on deconvolution calculation results, and analyze the effect of deconvolution on eliminating the influence of the source caused by different air-gun pressures. The results show that:( 1) When the level scaling factor is smaller,the signal to noise ratio of the waveform after the deconvolution is smaller,and when the level scaling factor is over smaller,the identification error of travel time is greater.( 2) When the SNR of the station record is higher,the recognition accuracy of travel time is higher,the influence of SNR on the reference station record is far greater than the far station,when the SNR of the far station record is more than 10,the error of travel time is within6 ms,but when the SNR of the reference station record is 30,the travel time error may reach to 20 ms.( 3) When the airgun source difference is big,the frequency domain waterlevel deconvolution method has better effect on eliminating the source influence,but the method error may be introduced when the source difference is small.
文摘Urmia Lake in northwest of Iran, through the recent years has been extremely faced with the water crisis. Climate variations and anthropogenic impacts could be two main affiliated factors in this regard. We considered the long term data series of precipitation, temperature and evaporation in monthly and yearly scales in order to compare to water-level values of Urmia Lake. The statistics approaches such as: standard deviation, trend analysis, T test, Pearson and Spearman correlations, liner regression are used to analyze all variables. The results released that the water-level of Urmia Lake along with the precipitation and temperature of the lake’s basin have experienced the periodic changes through 1961 to 2010, as there are some gradual dryness trends on the study area according to precipitation and temperature variations. Urmia Lake periodic water-level fluctuations show more significant correlation to temperature than the precipitation. Whiles, the water-level’s decreasing behavior especially through 1998 to 2010 is more harsh and different than the rate that is considered for precipitation’s decrease and temperature’s increase. Thus, there could be some anthropogenic factors in the basin which produced some supplementary causes to shrink Urmia Lake. Extracting the double precipitation over the basin through introducing and categorizing of atmospheric synoptic systems in order to cloud seeding operation could be one of urgent and innovative solutions to mitigate water crisis in the basin.
基金Supported by Natural Science Foundation Project,Chongqing Science and Technology Commission(CSTC) ,China(2009BB7255)Talent Start-up Foundation Project ,Chongqing University of Arts and Science,ChinaScience Research Project,Chongqing University of Arts and Science(XZ031)
文摘[ Objective] The research aimed to study influence of the repeated flooding on growth and development of A. calamus in water-level-fluc- tuation zone of the Three Gorges Reservoir. [ Method] A. calamus plants were exposed to water under the dark conditions respectively in Septem- ber 2009 and September 2010. Then, they were taken away from the water, and grew in natural conditions in the following March and April respec- tively ( marked as S1, S2, S1 and S2). The plant number was conducted statistics respectively. On May 7, the leaf number was made statistics. Length, width and rapid light responding curve of the leaf were determined. [ Result] Repeated flooding restrained significantly plant germination un- der the dark condition. Plant number in S1 and S2 groups decreased by 38.9% and 33.3% respectively compared with the control. It also reduced survival rate of the plant. Plant number in S2 group decreased by 16.7% (P 〈 0.05) compared with that of S2 group when they were taken away from the water. Both of flooding promoted elongation of the leaves, restrained leaves to grow wider, and also restrained leaf formation of the plants except for S1 and S1 groups. Total leaf length of a plant decreased markedly after the second flooding which in S1 and S2 groups were 50.6% and 36.9% respectively less than that after the first flooding. Total leaf number of the plant in S1and S2 groups reduced significantly, and they were only 63.1% and 38.5% respectively of the control. Compared with the first flooding, total leaf length of a plant in the control increased signifi- cantly and decreased remarkably in S2 group after the second flooding. Furthermore, light response ability of the relative electronic transfer rate (rETR) in S1 group wasn't significantly different from the control, and rETRmax, in S2 group was significantly less than the control. Moreover, non- photochemical quenching (NPQ) decreased remarkably in S1 and S2 groups. It indicated that A. calamus had good restore ability of the light re- sponse, but restoring of its heat dissipation capacity was slower. [ Conclusion] Repeated flooding inhibited plant growth and population recovery of A. calamus under the dark condition.
基金funded by the National Natural Science Foundation of China(Grant No.41771321,41771320 and 41571278)Sichuan Science and Technology Program(Grant No.2018SZ0132)
文摘Inundation of the Three Gorges Reservoir has created a 30-m water-level fluctuation zone with seasonal hydrological alternations of submergence and exposure, which may greatly affect soil properties and bank stability. The aim of this study was to investigate the response of soil pore structure to seasonal water-level fluctuation in the reservoir, and particularly, the hydrological change of wetting and drying cycles. Soil pore structure was visualized with industrial X-ray computed tomography and digital image analysis techniques. The results showed that soil total porosity(? 100 ?m), total pore number, total throat number, and mean throat surface area increased significantly under wetting and drying cycles. Soil porosity, pore number and throat numberwithin each size class increased in the course of wetting and drying cycles. The coordination number, degree of anisotropy and fractal dimension were indicating an increase. In contrast, the mean shape factor, pore-throat ratio, and Euler-Poincaré number decreased due to wetting and drying cycles. These illustrated that the wetting and drying cycles made soil pore structure become more porous, continuous, heterogeneous and complex. It can thus be deduced that the water-level fluctuation would modify soil porosity, pore size distribution, and pore morphology in the Three Gorges Reservoir, which may have profound implications for soil processes, soil functions, and bank stability.
基金Thanks the financial support from National Natural Science Foundation of China (#40561006), National Natural Science Foundation of China (06XYJ017), and Key Foundation of Chongqing Normal University (08XLZ13).
基金funded by the National Key Basic Research Program of China(Grant No.2013CB733205)
文摘In order to understand the monitoring efficiency status of the well-water-level observation network in China after the completion of the 10 th "Five-year Plan " digital network project,and to provide a basis for the future network optimization and equipment updating, the monitoring efficiency of the well-water-level observation network was evaluated. On the whole,61. 8% observing stations have good monitoring effectiveness,the observation environment of 73. 5% of observing stations meets the monitoring requirements of well-water-level. The operation status of the network is as a whole getting better,operation rates of 75% observing instruments are above 95%. Most well water levels can monitor crustal stress changes and seismic activities. However,some observation stations,due to inherent deficiency in wells,environmental disturbance,instrument aging,and low-level operation and maintenance,need to improve the monitoring efficiency level by taking measures such as observation environment improvement,equipment updating,and management training. About 6. 5% of the stations need to stop observation due to the unqualified observational environment.
文摘Rule curves dictating target water levels for management have been implemented in several water bodies in North America over the last 70 years or more. Anthropogenic alterations of water levels are known to affect several components of wetland ecosystems. Evaluating the influence of rule curves on biological components with simple performance indicators could help harmonize water level management with wetland integrity. We assessed the potential of using the probability of common loon nest viability as a performance indicator of long-term impacts of rule curves on nesting wetland birds. We analyzed the outcome of rule curves on the probability of loon nest viability in Rainy Lake and Namakan Reservoir, 2 regulated water bodies located along the Ontario-Minnesota border. The analysis was focused on 4 hydrological time series between 1950 and 2013: 2 sets of time series simulating rule curves used to manage the water bodies in the past decades (referred to as the 1970RC and 2000RC), one of the historical measured water levels, and one of computed natural water levels. The probability of loon nest viability under the 1970RC was 2× higher than under natural conditions in both water bodies. The probability was also 2× higher under the 2000RC than under the 1970RC in the Namakan Reservoir but not in Rainy Lake. The rule curves generally improved conditions for nesting loons in both water bodies. The presented performance indicator can be used to evaluate future rule curves before they are implemented in the Rainy-Namakan or other similar systems.