[Objective] This study was conducted to explore the spatial distribution of carbon and nitrogen in the sediments of Xiangxi River, which was the biggest tribu- tary near the Three Gorges Dam. [Method] Sediment samples...[Objective] This study was conducted to explore the spatial distribution of carbon and nitrogen in the sediments of Xiangxi River, which was the biggest tribu- tary near the Three Gorges Dam. [Method] Sediment samples were collected using customized cylindrical samplers at three sites along Xiangxi River estuary in May, 2015 to measure the contents of total carbon, total nitrogen and an isotope of car- bon δ^13C. [Result] The total carbon content in the sediments varied from 1.74% to 3.52%, and the total nitrogen content varied from 0.1% to 0.3%. The average total carbon content in the sediments near the estuary was lower than in the upstream. The total carbon content in the sediments near the estuary gradually decreased with depth increasing. However, the variations in total nitrogen content in both horizontal direction （along the river from the estuary to the upstream） and vertical direction were not so obvious as in total carbon content. The isotopic analysis showed the δ^13C value increased with depth increasing. The overall δ^13C near the estuary was lower than that in the upstream. [Conclusioal The results will provide scientific refer- ences for the distribution of biogenic elements in sediments of Xiangxi River and the evolution process of aquatic ecosystem.展开更多
The phosphorus in water and sediment collected at different time from the Xiangxi River were analyzed. The results indicated that the phosphorus pollution have significant relations to human activities (especially the...The phosphorus in water and sediment collected at different time from the Xiangxi River were analyzed. The results indicated that the phosphorus pollution have significant relations to human activities (especially the phosphorus industry). The concentrations of total-phosphorus (TP), total dissolved phosphorus (TDP) and dissolved phosphorus (DP) in Dec.2004 were higher than those in Jul. 2005; the TP contents of sites 15 and 16 were much higher than others’, the TP content of the largest site 16 was 1946.29mg/kg in Dec. 2004 and 1756.11mg/kg in Jul. 2005, respectively, which was much higher than the average (1497.51mg/kg and 1369.38mg/kg, respectively). The TP content in the sediment of the Xiangxi River was from 1179.53mg/kg to 1851.20mg/kg. The TP contents of most sites except site 18, 19 and 20 were higher in Dec. 2004 than those in Jul. 2005. The aluminium-phosphorus (Al-P) content in the sediment was obviously higher in Jul. 2005 than that in Dec.2004, which indicated that the stability of Al-P has a significant relation to the change of season.展开更多
With the impoundment of the Three Gorges Reservoir, algal blooms have been found in some tributaries. In this study, according to the theoretical analysis of the eutrophication mechanism in a river-type reservoir trib...With the impoundment of the Three Gorges Reservoir, algal blooms have been found in some tributaries. In this study, according to the theoretical analysis of the eutrophication mechanism in a river-type reservoir tributary, a one-dimensional eutrophication model was developed for the Xiangxi River tributary of the Three Gorges Reservoir, and the influence of hydrodynamic conditions on the primary growth rate of algae was investigated. Furthermore, numerical predictions of hydraulic variables and eutrophication factors, such as the concentration distribution of TP, TN, and Chl-a in the spatial and temporal domains, were carried out. Comparison of computation results of TP, TN, and Chl-a concentrations along the river in the spring of 2005 with experimental data demonstrates the validity of the model. The agreement between the computation results and the experimental data of TP and TN concentrations is better than the agreement between those of Chl-a concentration. The simulated results also show that the Chl-a concentration downstream is much higher than that in the upstream tributary, which potentially indicates the outbreak of algae in this area. Therefore, this study provides a feasible method of accurately predicting the state of eutrophication in river-type reservoirs and their tributaries.展开更多
Due to the importance of riparian zone in maintaining and protecting regional biodiversity, increasingly more ecologists paid their attentions to riparian zone and had been aware of the important effects of riparian z...Due to the importance of riparian zone in maintaining and protecting regional biodiversity, increasingly more ecologists paid their attentions to riparian zone and had been aware of the important effects of riparian zone in basic study and practical management. In this study, 42 sampling belts (10 m?00 m) parallel to the bank of Xiangxi River at different elevations in Shennongjia Area were selected to investigate the riparian vegetation and rare plants. 14 species of rare plants were found distributing in riparian zone, accounting for 42.4% of the total rare plant species in Shennongjia Area. The main distribution range of the 14 rare plant species was the evergreen and deciduous mixed broadleaved forest at elevation of 1200-1800 m, where, species diversity of plant community was the maximum at the moderate elevation. The analysis of TWINSPAN divided the 14 rare species into 3 groups against the elevation, namely low elevation species group, moderate elevation species group, and high elevation species group. The analysis of DCA ordination showed similar results to that of TWINSPAN. In the paper, the authors discussed the reasons forming the distribution pattern of rare plant species, and pointed out that the important function of riparian zone on rare plant species protection.展开更多
Xiangxi River Basin, located in western Hubei Province in central China, is a karst ridge-trough area with an inhomogeneous and complicated distribution of water resources. This paper compares the characteristics of s...Xiangxi River Basin, located in western Hubei Province in central China, is a karst ridge-trough area with an inhomogeneous and complicated distribution of water resources. This paper compares the characteristics of surface and subsurface floods in this karst basin, utilizing a one-parameter Darcian model and the traditional exponential model. The observed hydrographs and inferred water components are strikingly similar for surface and subsurface floods. The Darcian model and the exponential model are based on different views of the flood generation process, with the former fitting the entire hydrograph with a single time constant, and the latter fitting only the recession limb with multiple time constants. Due to the anisotropy and heterogeneity of karst media, a combination of physical and chemical techniques including the use of 3S（remote sensing, geographical information system, global positioning system） method is proposed for an enhanced hydrological investigation to assess and characterize karst water resources in mountainous areas.展开更多
The Xiangxi River is one of the main tributaries in the Three Gorges reservoir, with the shortest distance to the Three Gorges Project Dam. Severe and frequent algal bloom events have occurred frequently in the Xiangx...The Xiangxi River is one of the main tributaries in the Three Gorges reservoir, with the shortest distance to the Three Gorges Project Dam. Severe and frequent algal bloom events have occurred frequently in the Xiangxi River in recent years. Therefore, the current study develops a three-dimensional unstructured-mesh model to investigate the dynamic process of algal bloom. The developed model comprises three modules, namely, hydrodynamics, nutrient cycles, and phytoplankton ecological dynamics. A number of factors, including hydrodynamic condition, nutrient concentration, temperature, and light illumination, that would affect the evolution of phytoplankton were considered. Moreover, the wave equation was used to solve the free surface fluctuations and vertical Z-coordinates with adjustable layered thicknesses. These values, in turn, are suitable for solving the algal bloom problems that occurred in the fiver style reservoir that has a complex boundary and dramatically changing hydrodynamic conditions. The comparisons between the modeling results and field data of years 2007 and 2008 indicate that the developed model is capable of simulating the algal bloom process in the Xiangxi River with reasonable accuracy. However, hydrodynamic force and external pollution loads affect the concentrations of nutrients, which, along with the underwater light intensity, could consequently affect phytoplankton evolution. Thus, flow velocity cannot be ignored in the analysis of fiver algal bloom. Based on the modeling results, building an impounding reservoir and increasing the releasing discharge at appropriate times are effective ways for controlling algal bloom.展开更多
Water release operation is crucial for water quality in large reservoirs such as Three Gorges Reservoir(TGR),because it determines the hydrodynamics and hence the self-purification capability.As algal blooms were ofte...Water release operation is crucial for water quality in large reservoirs such as Three Gorges Reservoir(TGR),because it determines the hydrodynamics and hence the self-purification capability.As algal blooms were often observed in some tributary bays of TGR during the release periods,high frequency field observations were carried out in a typical eutrophic tributary bay(Xiangxi River) from February 9 to May 10,2009.In this paper we assess the hydrodynamic behaviour,density stratification,and trophic status in this bay,respectively using a series of observations for flow,physical,chemical and biological parameters.Then,we analyze the effects of reservoir release operations on algal blooms using correlation analysis method.An empirical prognosis is concluded for the likelihood of algal bloom occurrence as a function of daily fluctuation of water level(DFWL) and water temperature.Our results indicate that during the release period,the algal bloom occurrences are closely tied to the DFWL in that if the ratio of DFWL to total water depth ranges from -10×10-4 to 0,the possibility of algal blooms may reach up to 70%,and if the ratio is less than -10×10-4,then that risk can be significantly reduced to less than 10%.This paper finally suggests that a wave-type water release operation should be beneficial in reducing bloom frequencies in the tributary water bodies,which is helpful for TGR water quality management,especially for the water release operation optimization.展开更多
基金Supported by Plan"948"of the Ministry of Water Resources(201408)
文摘[Objective] This study was conducted to explore the spatial distribution of carbon and nitrogen in the sediments of Xiangxi River, which was the biggest tribu- tary near the Three Gorges Dam. [Method] Sediment samples were collected using customized cylindrical samplers at three sites along Xiangxi River estuary in May, 2015 to measure the contents of total carbon, total nitrogen and an isotope of car- bon δ^13C. [Result] The total carbon content in the sediments varied from 1.74% to 3.52%, and the total nitrogen content varied from 0.1% to 0.3%. The average total carbon content in the sediments near the estuary was lower than in the upstream. The total carbon content in the sediments near the estuary gradually decreased with depth increasing. However, the variations in total nitrogen content in both horizontal direction （along the river from the estuary to the upstream） and vertical direction were not so obvious as in total carbon content. The isotopic analysis showed the δ^13C value increased with depth increasing. The overall δ^13C near the estuary was lower than that in the upstream. [Conclusioal The results will provide scientific refer- ences for the distribution of biogenic elements in sediments of Xiangxi River and the evolution process of aquatic ecosystem.
基金Key Project of the Chinese Academy of Sciences(KSCX2-SW-111) National Key Project for Basic Research(2002CB412304)
文摘The phosphorus in water and sediment collected at different time from the Xiangxi River were analyzed. The results indicated that the phosphorus pollution have significant relations to human activities (especially the phosphorus industry). The concentrations of total-phosphorus (TP), total dissolved phosphorus (TDP) and dissolved phosphorus (DP) in Dec.2004 were higher than those in Jul. 2005; the TP contents of sites 15 and 16 were much higher than others’, the TP content of the largest site 16 was 1946.29mg/kg in Dec. 2004 and 1756.11mg/kg in Jul. 2005, respectively, which was much higher than the average (1497.51mg/kg and 1369.38mg/kg, respectively). The TP content in the sediment of the Xiangxi River was from 1179.53mg/kg to 1851.20mg/kg. The TP contents of most sites except site 18, 19 and 20 were higher in Dec. 2004 than those in Jul. 2005. The aluminium-phosphorus (Al-P) content in the sediment was obviously higher in Jul. 2005 than that in Dec.2004, which indicated that the stability of Al-P has a significant relation to the change of season.
基金supported by the National Natural Science Foundation of China (Grant No. 50779028)the National Science and Technology Supporting Plan (Grant No. 2008BAB29B09)
文摘With the impoundment of the Three Gorges Reservoir, algal blooms have been found in some tributaries. In this study, according to the theoretical analysis of the eutrophication mechanism in a river-type reservoir tributary, a one-dimensional eutrophication model was developed for the Xiangxi River tributary of the Three Gorges Reservoir, and the influence of hydrodynamic conditions on the primary growth rate of algae was investigated. Furthermore, numerical predictions of hydraulic variables and eutrophication factors, such as the concentration distribution of TP, TN, and Chl-a in the spatial and temporal domains, were carried out. Comparison of computation results of TP, TN, and Chl-a concentrations along the river in the spring of 2005 with experimental data demonstrates the validity of the model. The agreement between the computation results and the experimental data of TP and TN concentrations is better than the agreement between those of Chl-a concentration. The simulated results also show that the Chl-a concentration downstream is much higher than that in the upstream tributary, which potentially indicates the outbreak of algae in this area. Therefore, this study provides a feasible method of accurately predicting the state of eutrophication in river-type reservoirs and their tributaries.
基金This project was supported by National Natural Science Foundation of China (NSFC39970123) Changbai Mountain Open Research Station, Chinese Acedamy of Science.
文摘Due to the importance of riparian zone in maintaining and protecting regional biodiversity, increasingly more ecologists paid their attentions to riparian zone and had been aware of the important effects of riparian zone in basic study and practical management. In this study, 42 sampling belts (10 m?00 m) parallel to the bank of Xiangxi River at different elevations in Shennongjia Area were selected to investigate the riparian vegetation and rare plants. 14 species of rare plants were found distributing in riparian zone, accounting for 42.4% of the total rare plant species in Shennongjia Area. The main distribution range of the 14 rare plant species was the evergreen and deciduous mixed broadleaved forest at elevation of 1200-1800 m, where, species diversity of plant community was the maximum at the moderate elevation. The analysis of TWINSPAN divided the 14 rare species into 3 groups against the elevation, namely low elevation species group, moderate elevation species group, and high elevation species group. The analysis of DCA ordination showed similar results to that of TWINSPAN. In the paper, the authors discussed the reasons forming the distribution pattern of rare plant species, and pointed out that the important function of riparian zone on rare plant species protection.
基金supported by the China Geological Survey (No. 12120113103800)
文摘Xiangxi River Basin, located in western Hubei Province in central China, is a karst ridge-trough area with an inhomogeneous and complicated distribution of water resources. This paper compares the characteristics of surface and subsurface floods in this karst basin, utilizing a one-parameter Darcian model and the traditional exponential model. The observed hydrographs and inferred water components are strikingly similar for surface and subsurface floods. The Darcian model and the exponential model are based on different views of the flood generation process, with the former fitting the entire hydrograph with a single time constant, and the latter fitting only the recession limb with multiple time constants. Due to the anisotropy and heterogeneity of karst media, a combination of physical and chemical techniques including the use of 3S（remote sensing, geographical information system, global positioning system） method is proposed for an enhanced hydrological investigation to assess and characterize karst water resources in mountainous areas.
基金supported by the National Natural Science Foundation of China (No. 50823005)
文摘The Xiangxi River is one of the main tributaries in the Three Gorges reservoir, with the shortest distance to the Three Gorges Project Dam. Severe and frequent algal bloom events have occurred frequently in the Xiangxi River in recent years. Therefore, the current study develops a three-dimensional unstructured-mesh model to investigate the dynamic process of algal bloom. The developed model comprises three modules, namely, hydrodynamics, nutrient cycles, and phytoplankton ecological dynamics. A number of factors, including hydrodynamic condition, nutrient concentration, temperature, and light illumination, that would affect the evolution of phytoplankton were considered. Moreover, the wave equation was used to solve the free surface fluctuations and vertical Z-coordinates with adjustable layered thicknesses. These values, in turn, are suitable for solving the algal bloom problems that occurred in the fiver style reservoir that has a complex boundary and dramatically changing hydrodynamic conditions. The comparisons between the modeling results and field data of years 2007 and 2008 indicate that the developed model is capable of simulating the algal bloom process in the Xiangxi River with reasonable accuracy. However, hydrodynamic force and external pollution loads affect the concentrations of nutrients, which, along with the underwater light intensity, could consequently affect phytoplankton evolution. Thus, flow velocity cannot be ignored in the analysis of fiver algal bloom. Based on the modeling results, building an impounding reservoir and increasing the releasing discharge at appropriate times are effective ways for controlling algal bloom.
基金supported by the National Natural Science Foundation of China (Grant Nos 50779028, 41001348)National Science Fund for Distinguished Young Scholars (Grant No 50925932)
文摘Water release operation is crucial for water quality in large reservoirs such as Three Gorges Reservoir(TGR),because it determines the hydrodynamics and hence the self-purification capability.As algal blooms were often observed in some tributary bays of TGR during the release periods,high frequency field observations were carried out in a typical eutrophic tributary bay(Xiangxi River) from February 9 to May 10,2009.In this paper we assess the hydrodynamic behaviour,density stratification,and trophic status in this bay,respectively using a series of observations for flow,physical,chemical and biological parameters.Then,we analyze the effects of reservoir release operations on algal blooms using correlation analysis method.An empirical prognosis is concluded for the likelihood of algal bloom occurrence as a function of daily fluctuation of water level(DFWL) and water temperature.Our results indicate that during the release period,the algal bloom occurrences are closely tied to the DFWL in that if the ratio of DFWL to total water depth ranges from -10×10-4 to 0,the possibility of algal blooms may reach up to 70%,and if the ratio is less than -10×10-4,then that risk can be significantly reduced to less than 10%.This paper finally suggests that a wave-type water release operation should be beneficial in reducing bloom frequencies in the tributary water bodies,which is helpful for TGR water quality management,especially for the water release operation optimization.
