River systems play an important role in the global carbon cycle. Rivers transport carbon to the ocean and also affect the carbon cycle in the coastal ocean. The flux from land to the ocean is thought to be a very impo...River systems play an important role in the global carbon cycle. Rivers transport carbon to the ocean and also affect the carbon cycle in the coastal ocean. The flux from land to the ocean is thought to be a very important part of the land carbon budget. To investigate the effect of dam-building on dissolved organic carbon(DOC)in rivers, three reservoirs of different trophic states in the Wujiang basin, Guizhou Province, were sampled twice per month between May 2011 and May 2012. Temporal and spatial distributions of DOC in the reservoirs and their released waters were studied. It was found that different factors controlled DOC in river water, reservoir water, and released water. DOC in the rivers tended to be affected by primary production. For reservoirs, the main controlling factors of DOC concentration varied by trophic state. For the mesotrophic Hongjiadu Reservoir, the effect of primary production on DOC concentration was obvious. For the eutrophic Dongfengdu Reservoir and the hypereutrophic Wujiangdu Reservoir, primary production was not significant and DOC came instead from soil and plant litter.展开更多
Surface runoff in the Wujiang River watershed was simulated by a GIS-based method using precipitation, hydrology data, and land-use data. The volume of surface runoff is chiefly controlled by climates, topographical c...Surface runoff in the Wujiang River watershed was simulated by a GIS-based method using precipitation, hydrology data, and land-use data. The volume of surface runoff is chiefly controlled by climates, topographical characteristics and types of land use at the watershed. Five subwatersheds that can represent the whole watershed were chosen and their average annual precipitation, average annual surface runoff and current land use were calculated respectively in the grid model of the Wujiang River watershed based on the climate and hydrology data from 1965 to 2000 and the land-use data acquired in the year of 2000. Surface runoff is assumed to be a function of precipitation and land use and the multiple regression tool is used to determine the relationship between surface runoff, precipitation and present land use. Thus, the rainfall-runoff model for each land-use type has been established. When calibrating these models, the results show that the percent errors are all below 7%, which indicates that the accuracy of this simulation is high.展开更多
The effects of optimized operation principles implemented at reservoirs on the Wujiang River in southwest China between September 2009 and April 2010 under drought conditions were analyzed based on operational data co...The effects of optimized operation principles implemented at reservoirs on the Wujiang River in southwest China between September 2009 and April 2010 under drought conditions were analyzed based on operational data collected from the Guizhou Wujiang Hydropower Development Co., Ltd. A set of linear regression equations was developed to identify the key factors impacting the electric power generation at reservoirs. A 59% reduction in the inflow discharge at the Hongjiadu Reservoir led to a decrease of only 38% in the total electric power generation at the Hongjiadu, Dongfeng, Suofengying, and Wujiangdu reservoirs on the Wujiang River, indicating that optimized operation can play an important role in drought management. The water level and the amount of other water inputs at the Hongjiadu Reservoir and the outflow discharge at all of the reservoirs except the Wujiangdu Reservoir were key factors affecting the total electric power generation at reservoirs on the Wujiang River under optimized operation.展开更多
The distribution of nutrients (N, P, Si, C) in the Wujiang River surface water was studied during the high-flow and low-flow periods in 2002. The results showed that nitrate nitrogen (NO-3-N) is the main form of disso...The distribution of nutrients (N, P, Si, C) in the Wujiang River surface water was studied during the high-flow and low-flow periods in 2002. The results showed that nitrate nitrogen (NO-3-N) is the main form of dissolved inorganic nitrogen (DIN) in the Wujiang River Basin. It accounts for about 90% of DIN. The average NO-3-N concentrations in the mainstream are {147.5} μM in the high-flow period and {158.0} μM in the low-flow period, respectively. The average concentrations of total phosphorus (TP) are {6.43} μM in the high-flow period and {4.18} μM in the low-flow period, respectively. Of the various forms of phosphorus, particulate phosphorus (PP) has the highest percentage ({62.9%}) of TP in the high-flow period. In the low-flow period, however, phosphate is the main form of phosphorus, which accounts for 49% of TP. With the Wujiangdu Reservoir as the boundary, the concentrations of DIN and phosphorus in the upper reaches are different from those in the lower reaches of the Wujiang River. As a whole, the concentrations of DIN and phosphorus are both higher in the low-flow period than in the high-flow period. The spatial and temporal variations of DIN and phosphorus concentrations suggested that DIN and phosphorus come from agricultural and domestic wastewaters and groundwaters and that the Wujiangdu Reservoir has an important impact on the concentrations and distribution of DIN and phosphorus in the Wujiang River. The distribution patterns of dissolved silica (DSi) and dissolved organic carbon (DOC) are similar. Both of them maintain no change in the whole course of the river and their concentrations (with the exception of the reservoir itself) are higher in the high-flow period than in the low-flow period. The average DSi and DOC concentrations in the mainstream are {85.4}, {84.6} μM in the high-flow period and {60.8}, {53.9} μM in the low-flow period, respectively. The concentrations of nutrients in most of the major tributaries are lower than in the mainstream. This suggested that the contributions of most tributaries are relatively small but importance should be attached to the influence of some individual tributaries such as the Qingshuijiang River and the Weng’an River on the mainstream.展开更多
In recent years, research on spatial scale and scale transformation of eroded sediment transport has become a forefront field in current soil erosion research, but there are very few studies on the scale effect proble...In recent years, research on spatial scale and scale transformation of eroded sediment transport has become a forefront field in current soil erosion research, but there are very few studies on the scale effect problem in Karst regions of China. Here we quantitatively extracted five main factors influencing soil erosion, namely rainfall erosivity, soil erodibility, vegetative cover and management, soil and water conservation, and slope length and steepness. Regression relations were built between these factors and also the sediment transport modulus and drainage area, so as to initially analyze and discuss scale effects on sediment transport in the Wujiang River Basin(WRB). The size and extent of soil erosion influencing factors in the WRB were gauged from: Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM), precipitation data, land use, soil type and Normalized Difference Vegetation Index(NDVI) data from Global Inventory Modeling and Mapping Studies(GIMMS) or Advanced Very High Resolution Radiometer(AVHRR), and observed data from hydrometric stations. We find that scaling effects exist between the sediment transport modulus and the drainage area. Scaling effects are expressed after logarithmic transformation by a quadratic function regression relationship where the sediment transport modulus increases before decreasing, alongside changes in the drainage area. Among the five factors influencing soil erosion, slope length and steepness increases first and then decreases, alongside changes in the drainage area, and are the main factors determining the relationship between sediment transport modulus and drainage area. To eliminate the influence of scale effects on our results, we mapped the sediment yield modulus of the entire WRB, adopting a 1 000 km^2 standard area with a smaller fitting error for all sub-basins, and using the common Kriging interpolation method.展开更多
With the development of hydropower in the karst area of Southwest China, a series of cascade canyon reservoirs have been formed through the construction of dams. Given that hydrodynamic conditions in canyon reservoirs...With the development of hydropower in the karst area of Southwest China, a series of cascade canyon reservoirs have been formed through the construction of dams. Given that hydrodynamic conditions in canyon reservoirs play a pivotal role in controlling the spatiotemporal distribution of physical and chemical properties of the stored water, hydrodynamic characteristics are of great importance in understanding biogeochemical cycles in those reservoirs. To further this understanding, a field campaign was conducted in the Wujiangdu Reservoir of Guizhou Province. It was found that from the reservoir inlet to the front of the dam, velocity(v) was negativelycorrelated and had a logarithmic relationship with distance along the ship track(s) under dry-season flow conditions[v =-0.104 ln(s) + 0.4756]. Analysis showed that dryseason flow velocity had no significant correlation with water temperature, p H, or dissolved oxygen(DO). However, when velocity decreased to 0.061 m/s, water depth increased abruptly. In addition, DO displayed a sudden drop and the trend in p H changed from increasing to decreasing, while water temperature showed an opposite trend, indicating the existence of a transition zone from the river to the reservoir.展开更多
Thirty-four sampling sites for surface water and twenty-seven sampling sites for ground water in areas of different land use were selected in the Wujiang River Basin, upstream section in Guizhou Province, China. Carbo...Thirty-four sampling sites for surface water and twenty-seven sampling sites for ground water in areas of different land use were selected in the Wujiang River Basin, upstream section in Guizhou Province, China. Carbonic anhydrase （CA） activity in surface and ground water was analyzed and compared. The results show that CA activity was detected in all surface and ground water samples. In general, average CA activity in surface and ground water was highest from samples in arbor lands, followed by shrub lands, shrub and grass lands, agricultural lands, and residential areas. The average CA activity in ground water from arbor lands, shrub lands, and shrub and grass lands was higher than that in surface water. Water CA activity was positively correlated with HCO3- concentration in surface water and ground water. These results imply that the contribution of CA in water to the karst carbon sink potential of river basins warrants further extensive and in-depth research.展开更多
TRACE element concentrations in river water are controlled by a number of factors, such as lithology,weathering processes or adsorption. Further investigations on trace elements, especially heavy andtransition metals,...TRACE element concentrations in river water are controlled by a number of factors, such as lithology,weathering processes or adsorption. Further investigations on trace elements, especially heavy andtransition metals, allow us to evaluate the impact on the environment by human activities. Chinese scholars focus their research on the geochemistry of river water of the Changjiang River and Huanghe River. A number of scholars have conducted research on the uranium geochemistry in river water in orderto know the variation of input of U from rivers to oceans, and to get better understanding of the geochemistry of uranium series in marine geochemistry. Moreover, the presence of uraninite in sediments has beenproposed as an indicator of atmospheric oxidation and reduction levels. Plamer and Edmond展开更多
GEOCHEMICAL studies of trace elements, especially heavy metal elements in river water will provide thegrounds for the assessment of the influence of human activities on the environment. At present, the stud- ies of wa...GEOCHEMICAL studies of trace elements, especially heavy metal elements in river water will provide thegrounds for the assessment of the influence of human activities on the environment. At present, the stud- ies of water bodies in karst areas are focussed on the analysis of chemical compositions of surface and underground water samples, and almost no systematic study has been done on trace elements. So theauthors have carried out systematic studies on the distribution of concentrations of the dissolved trace elements and their controlling factors, while some systematic studies are under way on the major compositionsof river water in the Wujiang drainage system in Guizhou Province. On the basis of the characteristics ofthe U-Ca-Sr system in river water and their geochemical indicating implications (Refer to the paper entitled "The hydrogeochemistry of the Wujiang River drainage system in Guizhou, China: I. The U-Ca-Srsystem in karst river water"), the paper is concerned mainly with the trace element composition of展开更多
蓝绿水评价可为流域水资源的全面管理提供科学参考,以地形复杂的乌江流域为例,基于SWAT(Soil and Water Assessment Tool)水文模型,通过年径流距平百分率法确定不同降水年型,利用曼-肯德尔M-K检验法(Mann-Kendall Trend Method)和线性...蓝绿水评价可为流域水资源的全面管理提供科学参考,以地形复杂的乌江流域为例,基于SWAT(Soil and Water Assessment Tool)水文模型,通过年径流距平百分率法确定不同降水年型,利用曼-肯德尔M-K检验法(Mann-Kendall Trend Method)和线性回归趋势分析法分析评估乌江流域1992-2019年蓝绿水资源量时空特征和不同降水年型蓝绿水年内分配和空间分布差异。结果表明:(1)SWAT模型模拟效果较好,可以准确描述乌江流域水循环过程;(2)流域多年平均降水量、蓝水资源量和绿水资源量分别为1126mm、549mm和589mm,降水量和蓝水资源量总体呈下降趋势,绿水资源量总体呈上升趋势;(3)丰水年、平水年和枯水年绿水系数分别为46%、52%和58%,绿水资源量有所变化,对生态系统维持起重要作用;(4)从流域上游到下游,降水量和蓝水资源量均呈现出先增加再减少的趋势,绿水资源量呈现出先增加再减少最后增加的趋势;(5)蓝水资源量时空分布差异主要受降水量变化影响,绿水资源量时空分布受到降水量、气温和土地利用覆被变化的影响。展开更多
To determine the impact of damming on the geochemical behavior of dissolved inorganic carbon(DIC)in the Wujiang River basin,field measurements and samples were collected semimonthly for a year.The surface waters of th...To determine the impact of damming on the geochemical behavior of dissolved inorganic carbon(DIC)in the Wujiang River basin,field measurements and samples were collected semimonthly for a year.The surface waters of the reservoirs contained concentrations of chlorophyll a up to 5.6 times higher than the upstream river.Compared with the entering waters,the contributions of HCO3-and dissolved CO2to DIC decreased,and the contribution of CO32-to DIC and the carbon isotopic composition of DIC(d13CDIC)increased in the surface waters of the reservoirs,while in the waters released,the DIC species showed reverse geochemical behaviors.The d13CDICranged from-10.2%to 2.5%,indicating that significant contributions were from carbonate weathering,photosynthesis,and respiration.After the damming of a river,the bioactivity of phytoplankton was enhanced,and this affected the geochemistry of DIC compared to an unimpacted river and d13CDICcan be used to discern these changes.High-frequency monitoring of river-reservoir systems is necessary to evaluate the efflux of CO2and provide a better understanding of the carbon sinks and sources in the impounded river.展开更多
基金financially supported by the National Key Research and Development Program of China(2016YFA0601001)the National Natural Science Foundation of China(Grant Nos.U1612441 and 41473082)
文摘River systems play an important role in the global carbon cycle. Rivers transport carbon to the ocean and also affect the carbon cycle in the coastal ocean. The flux from land to the ocean is thought to be a very important part of the land carbon budget. To investigate the effect of dam-building on dissolved organic carbon(DOC)in rivers, three reservoirs of different trophic states in the Wujiang basin, Guizhou Province, were sampled twice per month between May 2011 and May 2012. Temporal and spatial distributions of DOC in the reservoirs and their released waters were studied. It was found that different factors controlled DOC in river water, reservoir water, and released water. DOC in the rivers tended to be affected by primary production. For reservoirs, the main controlling factors of DOC concentration varied by trophic state. For the mesotrophic Hongjiadu Reservoir, the effect of primary production on DOC concentration was obvious. For the eutrophic Dongfengdu Reservoir and the hypereutrophic Wujiangdu Reservoir, primary production was not significant and DOC came instead from soil and plant litter.
文摘Surface runoff in the Wujiang River watershed was simulated by a GIS-based method using precipitation, hydrology data, and land-use data. The volume of surface runoff is chiefly controlled by climates, topographical characteristics and types of land use at the watershed. Five subwatersheds that can represent the whole watershed were chosen and their average annual precipitation, average annual surface runoff and current land use were calculated respectively in the grid model of the Wujiang River watershed based on the climate and hydrology data from 1965 to 2000 and the land-use data acquired in the year of 2000. Surface runoff is assumed to be a function of precipitation and land use and the multiple regression tool is used to determine the relationship between surface runoff, precipitation and present land use. Thus, the rainfall-runoff model for each land-use type has been established. When calibrating these models, the results show that the percent errors are all below 7%, which indicates that the accuracy of this simulation is high.
基金supported by the National Natural Science Foundation of China (Grant No. 51109229)
文摘The effects of optimized operation principles implemented at reservoirs on the Wujiang River in southwest China between September 2009 and April 2010 under drought conditions were analyzed based on operational data collected from the Guizhou Wujiang Hydropower Development Co., Ltd. A set of linear regression equations was developed to identify the key factors impacting the electric power generation at reservoirs. A 59% reduction in the inflow discharge at the Hongjiadu Reservoir led to a decrease of only 38% in the total electric power generation at the Hongjiadu, Dongfeng, Suofengying, and Wujiangdu reservoirs on the Wujiang River, indicating that optimized operation can play an important role in drought management. The water level and the amount of other water inputs at the Hongjiadu Reservoir and the outflow discharge at all of the reservoirs except the Wujiangdu Reservoir were key factors affecting the total electric power generation at reservoirs on the Wujiang River under optimized operation.
文摘The distribution of nutrients (N, P, Si, C) in the Wujiang River surface water was studied during the high-flow and low-flow periods in 2002. The results showed that nitrate nitrogen (NO-3-N) is the main form of dissolved inorganic nitrogen (DIN) in the Wujiang River Basin. It accounts for about 90% of DIN. The average NO-3-N concentrations in the mainstream are {147.5} μM in the high-flow period and {158.0} μM in the low-flow period, respectively. The average concentrations of total phosphorus (TP) are {6.43} μM in the high-flow period and {4.18} μM in the low-flow period, respectively. Of the various forms of phosphorus, particulate phosphorus (PP) has the highest percentage ({62.9%}) of TP in the high-flow period. In the low-flow period, however, phosphate is the main form of phosphorus, which accounts for 49% of TP. With the Wujiangdu Reservoir as the boundary, the concentrations of DIN and phosphorus in the upper reaches are different from those in the lower reaches of the Wujiang River. As a whole, the concentrations of DIN and phosphorus are both higher in the low-flow period than in the high-flow period. The spatial and temporal variations of DIN and phosphorus concentrations suggested that DIN and phosphorus come from agricultural and domestic wastewaters and groundwaters and that the Wujiangdu Reservoir has an important impact on the concentrations and distribution of DIN and phosphorus in the Wujiang River. The distribution patterns of dissolved silica (DSi) and dissolved organic carbon (DOC) are similar. Both of them maintain no change in the whole course of the river and their concentrations (with the exception of the reservoir itself) are higher in the high-flow period than in the low-flow period. The average DSi and DOC concentrations in the mainstream are {85.4}, {84.6} μM in the high-flow period and {60.8}, {53.9} μM in the low-flow period, respectively. The concentrations of nutrients in most of the major tributaries are lower than in the mainstream. This suggested that the contributions of most tributaries are relatively small but importance should be attached to the influence of some individual tributaries such as the Qingshuijiang River and the Weng’an River on the mainstream.
基金generously supported by Project of National Natural Science Foundation of China (41641011)National Geology and Mineral Resources Survey and Assessment Program (DDT0160087)
文摘In recent years, research on spatial scale and scale transformation of eroded sediment transport has become a forefront field in current soil erosion research, but there are very few studies on the scale effect problem in Karst regions of China. Here we quantitatively extracted five main factors influencing soil erosion, namely rainfall erosivity, soil erodibility, vegetative cover and management, soil and water conservation, and slope length and steepness. Regression relations were built between these factors and also the sediment transport modulus and drainage area, so as to initially analyze and discuss scale effects on sediment transport in the Wujiang River Basin(WRB). The size and extent of soil erosion influencing factors in the WRB were gauged from: Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM), precipitation data, land use, soil type and Normalized Difference Vegetation Index(NDVI) data from Global Inventory Modeling and Mapping Studies(GIMMS) or Advanced Very High Resolution Radiometer(AVHRR), and observed data from hydrometric stations. We find that scaling effects exist between the sediment transport modulus and the drainage area. Scaling effects are expressed after logarithmic transformation by a quadratic function regression relationship where the sediment transport modulus increases before decreasing, alongside changes in the drainage area. Among the five factors influencing soil erosion, slope length and steepness increases first and then decreases, alongside changes in the drainage area, and are the main factors determining the relationship between sediment transport modulus and drainage area. To eliminate the influence of scale effects on our results, we mapped the sediment yield modulus of the entire WRB, adopting a 1 000 km^2 standard area with a smaller fitting error for all sub-basins, and using the common Kriging interpolation method.
基金financially supported by the National Key Research and Development Programme of China(2016YFA0601001)the National Natural Science Foundation of China(Grant Nos.U1612441 and 41473082)CAS"Light of West China"Program
文摘With the development of hydropower in the karst area of Southwest China, a series of cascade canyon reservoirs have been formed through the construction of dams. Given that hydrodynamic conditions in canyon reservoirs play a pivotal role in controlling the spatiotemporal distribution of physical and chemical properties of the stored water, hydrodynamic characteristics are of great importance in understanding biogeochemical cycles in those reservoirs. To further this understanding, a field campaign was conducted in the Wujiangdu Reservoir of Guizhou Province. It was found that from the reservoir inlet to the front of the dam, velocity(v) was negativelycorrelated and had a logarithmic relationship with distance along the ship track(s) under dry-season flow conditions[v =-0.104 ln(s) + 0.4756]. Analysis showed that dryseason flow velocity had no significant correlation with water temperature, p H, or dissolved oxygen(DO). However, when velocity decreased to 0.061 m/s, water depth increased abruptly. In addition, DO displayed a sudden drop and the trend in p H changed from increasing to decreasing, while water temperature showed an opposite trend, indicating the existence of a transition zone from the river to the reservoir.
基金Sub-project of Geological Survey Work Item of China Geological Survey Bureau(Grant No.12120113005200)the Fundamental Research Funds for the Central Universities(Grant No.2015QN102)
文摘Thirty-four sampling sites for surface water and twenty-seven sampling sites for ground water in areas of different land use were selected in the Wujiang River Basin, upstream section in Guizhou Province, China. Carbonic anhydrase （CA） activity in surface and ground water was analyzed and compared. The results show that CA activity was detected in all surface and ground water samples. In general, average CA activity in surface and ground water was highest from samples in arbor lands, followed by shrub lands, shrub and grass lands, agricultural lands, and residential areas. The average CA activity in ground water from arbor lands, shrub lands, and shrub and grass lands was higher than that in surface water. Water CA activity was positively correlated with HCO3- concentration in surface water and ground water. These results imply that the contribution of CA in water to the karst carbon sink potential of river basins warrants further extensive and in-depth research.
文摘TRACE element concentrations in river water are controlled by a number of factors, such as lithology,weathering processes or adsorption. Further investigations on trace elements, especially heavy andtransition metals, allow us to evaluate the impact on the environment by human activities. Chinese scholars focus their research on the geochemistry of river water of the Changjiang River and Huanghe River. A number of scholars have conducted research on the uranium geochemistry in river water in orderto know the variation of input of U from rivers to oceans, and to get better understanding of the geochemistry of uranium series in marine geochemistry. Moreover, the presence of uraninite in sediments has beenproposed as an indicator of atmospheric oxidation and reduction levels. Plamer and Edmond
文摘GEOCHEMICAL studies of trace elements, especially heavy metal elements in river water will provide thegrounds for the assessment of the influence of human activities on the environment. At present, the stud- ies of water bodies in karst areas are focussed on the analysis of chemical compositions of surface and underground water samples, and almost no systematic study has been done on trace elements. So theauthors have carried out systematic studies on the distribution of concentrations of the dissolved trace elements and their controlling factors, while some systematic studies are under way on the major compositionsof river water in the Wujiang drainage system in Guizhou Province. On the basis of the characteristics ofthe U-Ca-Sr system in river water and their geochemical indicating implications (Refer to the paper entitled "The hydrogeochemistry of the Wujiang River drainage system in Guizhou, China: I. The U-Ca-Srsystem in karst river water"), the paper is concerned mainly with the trace element composition of
文摘蓝绿水评价可为流域水资源的全面管理提供科学参考,以地形复杂的乌江流域为例,基于SWAT(Soil and Water Assessment Tool)水文模型,通过年径流距平百分率法确定不同降水年型,利用曼-肯德尔M-K检验法(Mann-Kendall Trend Method)和线性回归趋势分析法分析评估乌江流域1992-2019年蓝绿水资源量时空特征和不同降水年型蓝绿水年内分配和空间分布差异。结果表明:(1)SWAT模型模拟效果较好,可以准确描述乌江流域水循环过程;(2)流域多年平均降水量、蓝水资源量和绿水资源量分别为1126mm、549mm和589mm,降水量和蓝水资源量总体呈下降趋势,绿水资源量总体呈上升趋势;(3)丰水年、平水年和枯水年绿水系数分别为46%、52%和58%,绿水资源量有所变化,对生态系统维持起重要作用;(4)从流域上游到下游,降水量和蓝水资源量均呈现出先增加再减少的趋势,绿水资源量呈现出先增加再减少最后增加的趋势;(5)蓝水资源量时空分布差异主要受降水量变化影响,绿水资源量时空分布受到降水量、气温和土地利用覆被变化的影响。
基金supported by the National Basic Research Program of China (2013CB956703)the National Natural Science Foundation of China (41021062)
文摘To determine the impact of damming on the geochemical behavior of dissolved inorganic carbon(DIC)in the Wujiang River basin,field measurements and samples were collected semimonthly for a year.The surface waters of the reservoirs contained concentrations of chlorophyll a up to 5.6 times higher than the upstream river.Compared with the entering waters,the contributions of HCO3-and dissolved CO2to DIC decreased,and the contribution of CO32-to DIC and the carbon isotopic composition of DIC(d13CDIC)increased in the surface waters of the reservoirs,while in the waters released,the DIC species showed reverse geochemical behaviors.The d13CDICranged from-10.2%to 2.5%,indicating that significant contributions were from carbonate weathering,photosynthesis,and respiration.After the damming of a river,the bioactivity of phytoplankton was enhanced,and this affected the geochemistry of DIC compared to an unimpacted river and d13CDICcan be used to discern these changes.High-frequency monitoring of river-reservoir systems is necessary to evaluate the efflux of CO2and provide a better understanding of the carbon sinks and sources in the impounded river.
