Change silt charge of water in the rivers can negatively be reflected in throughput the rivers beds,stability of coast,change of river structures,disappearance of boggy places,etc.In work questions of variabilit...Change silt charge of water in the rivers can negatively be reflected in throughput the rivers beds,stability of coast,change of river structures,disappearance of boggy places,etc.In work questions of variability silt charge waters in the river Sluch in time and on length of the river are considered.It is revealed that in time average and maximal silt charge waters decrease.While on length of the river change silt charge waters is shown not precisely,similar on some increase silt charge waters to a mouth of the river.The researches led by the factorial analysis and graphic-analytical method on the basis of long-term materials of measurement of charges of water have shown that,on a part of posts average depth of water in the river grows,and on others-cyclically changes with the general tendency to reduction.Average speed in them,accordingly,falls and grows.Stratification of interrelations of a silt charge with other factors on years is observed.The reasons of reduction of a silt charge are:1)agrarian and forest meliorative actions on a catchments of the river,hydraulic engineering construction;2)grassy bed of the river;3)change of a climate that promotes growth of temperature of a surface of soils and grassy bed of the river.In developed natural-climatic conditions expediently application on reservoirs of the antierosion organization of territory of the land tenure including agrarian-forests-meliorative actions that will allow to adjust outflow of a moisture from reservoirs to lower warming up of a surface of the soils,to provide against a high water protection and it will favorably be reflected in manufacture of agricultural production.展开更多
The Amazon basin has experienced an extreme drought that started in the austral summer of 2022-23 and extends into 2024. This drought started earlier than other previous droughts. Although some rain fell during the au...The Amazon basin has experienced an extreme drought that started in the austral summer of 2022-23 and extends into 2024. This drought started earlier than other previous droughts. Although some rain fell during the austral summer, totals remained below average. Higher temperatures during austral winter and spring 2023, which affected most of Central South America, then aggravated drought conditions. This coincided with an intense El Niño and abnormally warm tropical North Atlantic Ocean temperatures since mid-2023. Decreased rainfall across the Amazon basin, negative anomalies in evapotranspiration (derived from latent heat) and soil moisture indicators, as well as increased temperatures during the dry-to-wet transition season, September-October-November (SON) 2023, combined to delay the onset of the wet season in the hydrological year 2023-24 by nearly two months and caused it to be uncharacteristically weak. SON 2023 registered a precipitation deficit of the order of 50 to 100 mm/month, and temperatures +3˚C higher than usual in Amazonia, leading to reduced evapotranspiration and soil moisture indicators. These processes, in turn, determined an exceptionally late onset and a lengthening of the dry season, affecting the 2023-2024 hydrological year. These changes were aggravated by a heat wave from June to December 2023. Drought-heat compound events and their consequences are the most critical natural threats to society. River levels reached record lows, or dried up completely, affecting Amazonian ecosystems. Increased risk of wildfires is another concern exacerbated by these conditions.展开更多
The decrease of runoff in the Luanhe river basin, which caused water crisis in Tian-jin for several times, was investigated using discharge data covering the period 1956-2002. The data from the differential integral c...The decrease of runoff in the Luanhe river basin, which caused water crisis in Tian-jin for several times, was investigated using discharge data covering the period 1956-2002. The data from the differential integral curves of the annual runoff indicate that the decreasing point began in 1979 in the six sub-basins. The decrease of runoff in the Luanhe river basin resulted from the combination of climate effects and human activities, in which the latter plays an important role. This can be illustrated by noting that after 1979 the runoff generated by similar precipitation decreased under the condition that the total precipitation did not decrease in the entire basin. As a result, the annual runoff of the Luanhe river basin after 1979 decreased by about 6.46×10^8 m^3 each year. To analyze the runoff characteristics, it is inadequate to seek the runoff trends only and the identification of cyclical component of the runoff as accurate as possible is necessary. From the natural annual runoff discharge time series, we can see the annual runoff fluctuates around the long-term average. Analyzed by VRL （Variable Record Length） method, the main periods of 3, 5-6, 7, 9, 16-20 and 37-39 years were found. The last decade causing water crisis was the driest period in the history, and this condition will last several years from trend analysis and power spectrum analysis. So finding new water sources is urgent to solve water crisis in Tianjin city, and the South-North Water Transfer is a feasible option.展开更多
By choosing a PVC slice to simulate flexible vegetation, we carried out experiments in an open channel with submerged flexible vegetation. A 3D acoustic Doppler velocimeter （micro ADV） was used to measure local flow...By choosing a PVC slice to simulate flexible vegetation, we carried out experiments in an open channel with submerged flexible vegetation. A 3D acoustic Doppler velocimeter （micro ADV） was used to measure local flow velocities and Reynolds stress. The results show that hydraulic characteristics in non-vegetation and vegetation layers are totally different. In a region above the vegetation, Reynolds stress distribution is linear, and the measured velocity profile is a classical logarithmic one. Based on the concept of new-riverbed, the river compression parameter representing the impact of vegetation on river is given, and a new assumption of mixing length expression is made. The formula for time-averaged velocity derived from the expression requires less parameters and simple calculation, and is useful in applications.展开更多
文摘Change silt charge of water in the rivers can negatively be reflected in throughput the rivers beds,stability of coast,change of river structures,disappearance of boggy places,etc.In work questions of variability silt charge waters in the river Sluch in time and on length of the river are considered.It is revealed that in time average and maximal silt charge waters decrease.While on length of the river change silt charge waters is shown not precisely,similar on some increase silt charge waters to a mouth of the river.The researches led by the factorial analysis and graphic-analytical method on the basis of long-term materials of measurement of charges of water have shown that,on a part of posts average depth of water in the river grows,and on others-cyclically changes with the general tendency to reduction.Average speed in them,accordingly,falls and grows.Stratification of interrelations of a silt charge with other factors on years is observed.The reasons of reduction of a silt charge are:1)agrarian and forest meliorative actions on a catchments of the river,hydraulic engineering construction;2)grassy bed of the river;3)change of a climate that promotes growth of temperature of a surface of soils and grassy bed of the river.In developed natural-climatic conditions expediently application on reservoirs of the antierosion organization of territory of the land tenure including agrarian-forests-meliorative actions that will allow to adjust outflow of a moisture from reservoirs to lower warming up of a surface of the soils,to provide against a high water protection and it will favorably be reflected in manufacture of agricultural production.
文摘The Amazon basin has experienced an extreme drought that started in the austral summer of 2022-23 and extends into 2024. This drought started earlier than other previous droughts. Although some rain fell during the austral summer, totals remained below average. Higher temperatures during austral winter and spring 2023, which affected most of Central South America, then aggravated drought conditions. This coincided with an intense El Niño and abnormally warm tropical North Atlantic Ocean temperatures since mid-2023. Decreased rainfall across the Amazon basin, negative anomalies in evapotranspiration (derived from latent heat) and soil moisture indicators, as well as increased temperatures during the dry-to-wet transition season, September-October-November (SON) 2023, combined to delay the onset of the wet season in the hydrological year 2023-24 by nearly two months and caused it to be uncharacteristically weak. SON 2023 registered a precipitation deficit of the order of 50 to 100 mm/month, and temperatures +3˚C higher than usual in Amazonia, leading to reduced evapotranspiration and soil moisture indicators. These processes, in turn, determined an exceptionally late onset and a lengthening of the dry season, affecting the 2023-2024 hydrological year. These changes were aggravated by a heat wave from June to December 2023. Drought-heat compound events and their consequences are the most critical natural threats to society. River levels reached record lows, or dried up completely, affecting Amazonian ecosystems. Increased risk of wildfires is another concern exacerbated by these conditions.
基金China Education Foundation National Natural Science Foundation of China, No.50579049
文摘The decrease of runoff in the Luanhe river basin, which caused water crisis in Tian-jin for several times, was investigated using discharge data covering the period 1956-2002. The data from the differential integral curves of the annual runoff indicate that the decreasing point began in 1979 in the six sub-basins. The decrease of runoff in the Luanhe river basin resulted from the combination of climate effects and human activities, in which the latter plays an important role. This can be illustrated by noting that after 1979 the runoff generated by similar precipitation decreased under the condition that the total precipitation did not decrease in the entire basin. As a result, the annual runoff of the Luanhe river basin after 1979 decreased by about 6.46×10^8 m^3 each year. To analyze the runoff characteristics, it is inadequate to seek the runoff trends only and the identification of cyclical component of the runoff as accurate as possible is necessary. From the natural annual runoff discharge time series, we can see the annual runoff fluctuates around the long-term average. Analyzed by VRL （Variable Record Length） method, the main periods of 3, 5-6, 7, 9, 16-20 and 37-39 years were found. The last decade causing water crisis was the driest period in the history, and this condition will last several years from trend analysis and power spectrum analysis. So finding new water sources is urgent to solve water crisis in Tianjin city, and the South-North Water Transfer is a feasible option.
基金supported by the National Natural Science Foundation of China (Nos. 50679061, 50709025,50749031)
文摘By choosing a PVC slice to simulate flexible vegetation, we carried out experiments in an open channel with submerged flexible vegetation. A 3D acoustic Doppler velocimeter （micro ADV） was used to measure local flow velocities and Reynolds stress. The results show that hydraulic characteristics in non-vegetation and vegetation layers are totally different. In a region above the vegetation, Reynolds stress distribution is linear, and the measured velocity profile is a classical logarithmic one. Based on the concept of new-riverbed, the river compression parameter representing the impact of vegetation on river is given, and a new assumption of mixing length expression is made. The formula for time-averaged velocity derived from the expression requires less parameters and simple calculation, and is useful in applications.
