Climate change is manifested by a modification in the frequency and intensity of extreme climatic phenomena that can cause significant damage to human activities and ecosystems. The objective of this study is to carry...Climate change is manifested by a modification in the frequency and intensity of extreme climatic phenomena that can cause significant damage to human activities and ecosystems. The objective of this study is to carry out a comparative analysis of the observed evolution of hydroclimatic extremes between the cities of Niamtougou (Togo) and Zinder (Niger) from 1980 to 2020. Daily data on rainfall and temperature (minimum and maximum) were used to calculate six (06) extreme rainfall indices and six (06) extreme temperature indices. Furthermore, the non-parametric Man-Kendhal test and Sen’s slope were applied to estimate trends in hydroclimatic extreme indices. The results indicate an increase in all extreme rainfall indices in both Niamtougou and Zinder. As for the indices relating to extreme temperatures, only the frequency of cool days and the frequency of cool nights show a negative trend in these two cities. These results are important for better management of climate risks in the study areas.展开更多
High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, ...High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, rapid socioeconomic development has increased the demand for water resources in the oases of the middle reaches of the Heihe River in northwestern China, and the lower reaches of the Heihe River have changed from a perennial river to an ephemeral stream with a decreased and degraded riparian zone. Tamarisk（Tamarix ramosissima） is the dominant shrub species of the desert riparian forest. In this study, the daily and seasonal patterns of tamarisk stem diameter growth, including the main period of tree ring formation, were examined. Observations concerning the driving forces of growth changes, along with implications for the ecology of the dendrohydrological area and management of desert riparian forests in similar arid regions, are also presented. The diurnal-seasonal activity of stem diameter and the dynamics of growth ring formation were studied using a point dendrometer and micro-coring methods during the 2012 growing season in shrub tamarisk in a desert riparian forest stand in the lower reaches of the Heihe River in Ejin Banner, Inner Mongolia of northwestern China. Generally, the variation in diurnal diameter of tamarisk was characterized by an unstable multi-peak pattern, with the cumulative stem diameter growth over the growing season following an S-shaped curve. The period from late May to early August was the main period of stem diameter growth and growth-ring formation. Among all of the hydroclimatic factors considered in this study, only groundwater depth was significantly correlated with stem diameter increment during this period. Therefore, for the dendrochronological study, the annual rings of the tamarisk can be used to reconstruct processes that determine the regional water regime, such as river runoff and fluctuations in groundwater depth. For the management of desert riparian forests, suitable groundwater depths must be maintained in the spring and summer to sustain tree health and a suitable stand structure.展开更多
In this paper, the tree cluster analysis and ISODATA of fuzzy cluster are made on the basis of the results(Chen et al, 1993) obtained by using the principal component analysis based on the hydroclimatic values over th...In this paper, the tree cluster analysis and ISODATA of fuzzy cluster are made on the basis of the results(Chen et al, 1993) obtained by using the principal component analysis based on the hydroclimatic values over the years of the China seas,where the climatic field may be divided into three climatic zones, 9 hydroclimatic regions and 1 climatic subregion Comparison of the distribution characteristics of hydrologic seasons with those of marine fauna and flora indicates that each climatic region possesses its inherent seasonal characteristics and biota distribution, and corresponds with each other. This fact proves that the division of the above-mentioned 10 climatic regions is reliable.展开更多
oceanographic data files on the China Seas prepared by the National Marine Data and Information Service, SOA, China and the '30-year (1953-1982) Reports of Sea Surface Monthly Mean Temperature in the East China Se...oceanographic data files on the China Seas prepared by the National Marine Data and Information Service, SOA, China and the '30-year (1953-1982) Reports of Sea Surface Monthly Mean Temperature in the East China Sea by the Meteorological Agency, Japan,' were used to calculate the digital characteristics of frequency distribution of sea and air temperature in 153 areas in the China Seas. Principal factor analysis and fuzzy cluster ISODATA were used to divide the China hydroclimatic area into three climatic zones including ten climatic regions. It is concluded that the characteristic values derived by this method may completely show the characteristics of frequency distribution of sea and air temperature in the studied area and the final division of hydroclimatic area is fully coincident with the author's former result [2].展开更多
On the basis of oceanographic data over years of the China seas,19 elements affecting the oceano are found with 91.06% of the accumulative ratio of their eigenvalue's variances to population variance,representing ...On the basis of oceanographic data over years of the China seas,19 elements affecting the oceano are found with 91.06% of the accumulative ratio of their eigenvalue's variances to population variance,representing fully the original information. In order to polarize the loading values of every principal factor tending to 1 or 0,vari max orthogonal rotation to the loading matrix of 6 principal factors is made.The results indicate that the oceanic thermoregime plays a leading role in the first principal factor F1 The second principal F2 is affected mainly by seafloor relief.The other principal factors F3, F4, F5 adn F6 are influenced by the occurring 10-d period of the lowest monthly mean sea temperature,the annual mean value and range of sea surface salinity,and the latitude respectively.The physical cause for these climatic characteristics is very clear.According to the scores of 6 principal factors of every station. the cluster diagram on each pair of factor axis planes is drawn and the climatic field over the China seas preliminarily divided into 6 regions, namely, temperate climatic region (Ⅰ1) in the Bobai Sea and the Huanghai Sea, transitional subtropical climatic region (Ⅱ1) in the East China Sea, subtropical climatic region (Ⅱ2) of Kuroshio,subtropical climatic region (Ⅱ3)in the eddy area on the right side of Kuroshio,tropical climatic region (Ⅲ1) in the central South China Sea and equatorial tropical climatic region(Ⅲ2). The climatological characteristics of every region are analyzed. Besides,the division of climatic area of the China seas is made by using Q-type principal com ponent analysis. The results of R- and Q-type methods are identical. It is thus proved that this preliminary division of climatic area is reliable and valid,and may be taken as a basis for further division.展开更多
The historicity of China's first state-level government(the Xia Dynasty),during which a Great Flood is claimed to have swept through the core of northern China,remains a well-known yet unresolved issue.Archaeologi...The historicity of China's first state-level government(the Xia Dynasty),during which a Great Flood is claimed to have swept through the core of northern China,remains a well-known yet unresolved issue.Archaeologists hypothesize a connection between the legendary events of the Xia Dynasty and archaeological discoveries in the Central China Plains cultural area,encompassing late Neolithic and Bronze Age cultures such as Henan's Longshan,Xinzhai,Erlitou,and Erligang.The authenticity of these speculations has been challenging to substantiate due to the lack of systematic evidence for the Great Flood in the middle to lower Yellow River(YR)Basin.In this paper,we present high-resolution hydrological environmental proxy data,sedimentological remains,and paleontological evidence from the central North China Plain.Our findings provide isochronous evidence of the termination of a hundred-year-long flood period dated to approximately 2080±216 BC,consistent with the observations from lower YR flood plain and marginal marine sediments.These findings both spatially and temporally overlap with the framework of the Great Flood described in the Chinese classics.The alignment between the geoscientific and archaeological evidence and the information in the Chinese classics provides robust confirmation that the Great Flood occurred in the middle to lower YR region during the late Longshan era.展开更多
The South-to-North Water Diversion Project in China aims to address the imbalanced distribution of water resources between the northern and southern regions,a critical safeguard for sustainable socio-economic and ecol...The South-to-North Water Diversion Project in China aims to address the imbalanced distribution of water resources between the northern and southern regions,a critical safeguard for sustainable socio-economic and ecological development.In this study,we investigated the hydroclimatic evolution of the water source area and its driving mechanisms using the inflow runoff data at Danjiangkou Reservoir from 1954 to 2013,along with multiple gridded hydroclimatic datasets.Based on the correlations between instrumental runoff data and gridded hydroclimatic variables,we used linear regression to extend the long-term runoff record to the period of 1902-2019.Our results indicate that climate changes,dominated by regional wet-dry cycles,have significant impacts on runoff variations,while the influence of human activities remains comparatively limited.Danjiangkou Reservoir can maintain a balanced base flow,even during the operation of the water diversion project.Preliminary synoptic climatology analyses reveal that runoff variations are mainly driven by the El Niño-Southern Oscillation(ENSO)and the Pacific Walker Circulation(PWC),which affect runoff by altering large-scale ocean-to-continent water vapor processes.This study advances the field by integrating multi-source data with analytical techniques,which enhances understanding of long-term runoff changes in the Danjiangkou Reservoir and their climatic drivers,ultimately supporting sustainable water resource management.展开更多
Hydroclimatic variations over the eastern Central Asia are highly sensitive to changes in hemispheric-scale atmospheric circulation systems. To fully understand the long-term variability and relationship between hydro...Hydroclimatic variations over the eastern Central Asia are highly sensitive to changes in hemispheric-scale atmospheric circulation systems. To fully understand the long-term variability and relationship between hydroclimate and atmospheric circulation system, we present a high-resolution lascustrine record of late Holocene hydroclimate from Lake Sayram, Central Tianshan Mountains, China, based on the total organic carbon, total nitrogen, and carbonate contents, carbon/nitrogen ratios, and grain size. Our results reveal four periods of substantially increased precipitation at the interval of 4000–3780, 3590–3210, 2800–2160, and 890–280 cal yr BP, and one period of slightly increased precipitation from 1700–1370 cal yr BP. These wetter periods broadly coincide with those identified in other records from the mid-latitude Westerlies-dominated eastern Central Asia, including the northern Tibetan Plateau. As such, a similar hydroclimatic pattern existed over this entire region during the late Holocene. Based on a close similarity of our record with reconstruction of North Atlantic Oscillation indices and solar irradiance, we propose that decreased solar irradiance and southern migration of the entire circum-North Atlantic circulation system, particularly the main pathway of the mid-latitude Westerlies, significantly influenced hydroclimate in eastern Central Asia during the late Holocene. Finally, the inferred precipitation at Lake Sayram has increased markedly over the past 100 years, although this potential future changes in hydroclimate in Central Asia need for further investigation.展开更多
Based on runoff, air temperature, and precipitation data from 1960 to 2010, the effects of climate change on water resources in the arid region of the northwestern China were investigated. The long-term trends of hydr...Based on runoff, air temperature, and precipitation data from 1960 to 2010, the effects of climate change on water resources in the arid region of the northwestern China were investigated. The long-term trends of hydroclimatic variables were studied by using both Mann-Kendall test and distributed-free cumulative sum （CUSUM） chart test. Results indicate that the mean annual air temperature increases significantly from 1960 to 2010. The annual precipitation exhibits an increasing trend, especially in the south slope of the Tianshan Mountains and the North Uygur Autonomous Region of Xinjiang in the study period. Step changes occur in 1988 in the mean annual air temperature time series and in 1991 in the precipitation time series. The runoff in different basins shows different trends, i.e., significantly increasing in the Kaidu River, the Aksu River and the Shule River, and decreasing in the Shiyang River. Correlation analy- sis reveals that the runoff in the North Xinjiang （i.e., the Weigan River, the Heihe River, and the Shiyang River） has a strong positive relationship with rainfall, while that in the south slope of the Tianshan Mountains, the middle section of the north slope of the Tianshan Mountains and the Shule River has a strong positive relationship with air temperature. The trends of rtmoff have strong negative correla- tions with glacier coverage and the proportion of glacier water in runoff. From the late 1980s, the climate has become warm and wet in the arid region of the northwestern China. The change in runoff is interacted with air temperature, precipitation and glacier coverage. The results show that streamflow in the arid region of the northwestern China is sensitive to climate change, which can be used as a reference for regional water resource assessment and management.展开更多
The present study concerns the lowlands of the Birnin Lokoyo watershed located in the Matankari Rural Commune (Southwestern borders of the large Iullemmeden basin in the Niger). Dominated by the Birnin Lokoyo pond, th...The present study concerns the lowlands of the Birnin Lokoyo watershed located in the Matankari Rural Commune (Southwestern borders of the large Iullemmeden basin in the Niger). Dominated by the Birnin Lokoyo pond, this watershed faced with the continuous silting up of the minor bed, dissipates further upstream in the east, so that it moves downstream to the west for the benefit of the populations of Matankari city. The main objective of this work is to analyze the representative elements of the new climatic and environmental situation as well as the various factors determining the surface conditions in the watershed. The methodological approach is based on documentary research, field observations, individual surveys and interviews with targeted groups. The results show that the silting up of the lowlands is the result of the concomitant degradation of the plant cover and the soils, which, as a result, triggered the development of crusting surfaces and area erosion on the slopes. The study underlined the importance of endogenous knowledge in the choice of remedies against the silting up of lowlands. In addition, rational land management practices on plateaus and structures (within the watershed) do not seem to be in phase with topographical factors and the tectonic framework. This work is part of the vision of better management of glacis on the banks, but also of sills subject to regressive erosion upstream and in order to guide the policies of resilience of the populations.展开更多
Accurate reconstructed series are crucial for studying the differences in regional hydroclimatic variations in Europe over the past millennium.Using hierarchical clustering analysis and stepwise regression methods,we ...Accurate reconstructed series are crucial for studying the differences in regional hydroclimatic variations in Europe over the past millennium.Using hierarchical clustering analysis and stepwise regression methods,we reconstructed yearly time series of the summer standardized precipitation evapotranspiration index(SPEl)for six European regions over the past millennium.Our analysis also revealed prominent regional hydroclimatic differences in multidecadal signals over the past 500 years.For instance,in the 1500s-1570s(from the beginning of the 1500s to the end of the 1570s),drying trends were observed in northern and southeastern Europe,whereas southwestern Europe experienced a wetting trend.Moreover,drying trends were observed in northern and central Europe in the 1640s-1670s.Additionally,wetting trends were observed in western and central Europe during the 1830s-1850s,with drying trends in northern and southeastern Europe.Notably,the hydroclimatic variations in most European regions showed drying trends in the 1920s-1950s,especially in southern Europe.By utilizing large amounts of tree-ring samples and directly comparing regional hydroclimatic variations,our reconstructions provide a consistent and comprehensive dataset for further analysis.The reconstructed dataset is available at https://doi.org/10.57760/sciencedb.07215.展开更多
文摘Climate change is manifested by a modification in the frequency and intensity of extreme climatic phenomena that can cause significant damage to human activities and ecosystems. The objective of this study is to carry out a comparative analysis of the observed evolution of hydroclimatic extremes between the cities of Niamtougou (Togo) and Zinder (Niger) from 1980 to 2020. Daily data on rainfall and temperature (minimum and maximum) were used to calculate six (06) extreme rainfall indices and six (06) extreme temperature indices. Furthermore, the non-parametric Man-Kendhal test and Sen’s slope were applied to estimate trends in hydroclimatic extreme indices. The results indicate an increase in all extreme rainfall indices in both Niamtougou and Zinder. As for the indices relating to extreme temperatures, only the frequency of cool days and the frequency of cool nights show a negative trend in these two cities. These results are important for better management of climate risks in the study areas.
基金funded by the National Natural Science Foundation of China (40971032, 91125026)
文摘High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, rapid socioeconomic development has increased the demand for water resources in the oases of the middle reaches of the Heihe River in northwestern China, and the lower reaches of the Heihe River have changed from a perennial river to an ephemeral stream with a decreased and degraded riparian zone. Tamarisk（Tamarix ramosissima） is the dominant shrub species of the desert riparian forest. In this study, the daily and seasonal patterns of tamarisk stem diameter growth, including the main period of tree ring formation, were examined. Observations concerning the driving forces of growth changes, along with implications for the ecology of the dendrohydrological area and management of desert riparian forests in similar arid regions, are also presented. The diurnal-seasonal activity of stem diameter and the dynamics of growth ring formation were studied using a point dendrometer and micro-coring methods during the 2012 growing season in shrub tamarisk in a desert riparian forest stand in the lower reaches of the Heihe River in Ejin Banner, Inner Mongolia of northwestern China. Generally, the variation in diurnal diameter of tamarisk was characterized by an unstable multi-peak pattern, with the cumulative stem diameter growth over the growing season following an S-shaped curve. The period from late May to early August was the main period of stem diameter growth and growth-ring formation. Among all of the hydroclimatic factors considered in this study, only groundwater depth was significantly correlated with stem diameter increment during this period. Therefore, for the dendrochronological study, the annual rings of the tamarisk can be used to reconstruct processes that determine the regional water regime, such as river runoff and fluctuations in groundwater depth. For the management of desert riparian forests, suitable groundwater depths must be maintained in the spring and summer to sustain tree health and a suitable stand structure.
文摘In this paper, the tree cluster analysis and ISODATA of fuzzy cluster are made on the basis of the results(Chen et al, 1993) obtained by using the principal component analysis based on the hydroclimatic values over the years of the China seas,where the climatic field may be divided into three climatic zones, 9 hydroclimatic regions and 1 climatic subregion Comparison of the distribution characteristics of hydrologic seasons with those of marine fauna and flora indicates that each climatic region possesses its inherent seasonal characteristics and biota distribution, and corresponds with each other. This fact proves that the division of the above-mentioned 10 climatic regions is reliable.
文摘oceanographic data files on the China Seas prepared by the National Marine Data and Information Service, SOA, China and the '30-year (1953-1982) Reports of Sea Surface Monthly Mean Temperature in the East China Sea by the Meteorological Agency, Japan,' were used to calculate the digital characteristics of frequency distribution of sea and air temperature in 153 areas in the China Seas. Principal factor analysis and fuzzy cluster ISODATA were used to divide the China hydroclimatic area into three climatic zones including ten climatic regions. It is concluded that the characteristic values derived by this method may completely show the characteristics of frequency distribution of sea and air temperature in the studied area and the final division of hydroclimatic area is fully coincident with the author's former result [2].
文摘On the basis of oceanographic data over years of the China seas,19 elements affecting the oceano are found with 91.06% of the accumulative ratio of their eigenvalue's variances to population variance,representing fully the original information. In order to polarize the loading values of every principal factor tending to 1 or 0,vari max orthogonal rotation to the loading matrix of 6 principal factors is made.The results indicate that the oceanic thermoregime plays a leading role in the first principal factor F1 The second principal F2 is affected mainly by seafloor relief.The other principal factors F3, F4, F5 adn F6 are influenced by the occurring 10-d period of the lowest monthly mean sea temperature,the annual mean value and range of sea surface salinity,and the latitude respectively.The physical cause for these climatic characteristics is very clear.According to the scores of 6 principal factors of every station. the cluster diagram on each pair of factor axis planes is drawn and the climatic field over the China seas preliminarily divided into 6 regions, namely, temperate climatic region (Ⅰ1) in the Bobai Sea and the Huanghai Sea, transitional subtropical climatic region (Ⅱ1) in the East China Sea, subtropical climatic region (Ⅱ2) of Kuroshio,subtropical climatic region (Ⅱ3)in the eddy area on the right side of Kuroshio,tropical climatic region (Ⅲ1) in the central South China Sea and equatorial tropical climatic region(Ⅲ2). The climatological characteristics of every region are analyzed. Besides,the division of climatic area of the China seas is made by using Q-type principal com ponent analysis. The results of R- and Q-type methods are identical. It is thus proved that this preliminary division of climatic area is reliable and valid,and may be taken as a basis for further division.
基金Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDB26000000National Natural Science Foundation of China,No.41888101,No.42072209Geological Survey Projects of China,No.DD20189629,No.DD20190370。
文摘The historicity of China's first state-level government(the Xia Dynasty),during which a Great Flood is claimed to have swept through the core of northern China,remains a well-known yet unresolved issue.Archaeologists hypothesize a connection between the legendary events of the Xia Dynasty and archaeological discoveries in the Central China Plains cultural area,encompassing late Neolithic and Bronze Age cultures such as Henan's Longshan,Xinzhai,Erlitou,and Erligang.The authenticity of these speculations has been challenging to substantiate due to the lack of systematic evidence for the Great Flood in the middle to lower Yellow River(YR)Basin.In this paper,we present high-resolution hydrological environmental proxy data,sedimentological remains,and paleontological evidence from the central North China Plain.Our findings provide isochronous evidence of the termination of a hundred-year-long flood period dated to approximately 2080±216 BC,consistent with the observations from lower YR flood plain and marginal marine sediments.These findings both spatially and temporally overlap with the framework of the Great Flood described in the Chinese classics.The alignment between the geoscientific and archaeological evidence and the information in the Chinese classics provides robust confirmation that the Great Flood occurred in the middle to lower YR region during the late Longshan era.
基金supported by the National Natural Science Foundation of China(NSFC Project No.32061123008)the Innovation Training Programme for Undergraduate Students of Yunnan University(Project No.202301051).
文摘The South-to-North Water Diversion Project in China aims to address the imbalanced distribution of water resources between the northern and southern regions,a critical safeguard for sustainable socio-economic and ecological development.In this study,we investigated the hydroclimatic evolution of the water source area and its driving mechanisms using the inflow runoff data at Danjiangkou Reservoir from 1954 to 2013,along with multiple gridded hydroclimatic datasets.Based on the correlations between instrumental runoff data and gridded hydroclimatic variables,we used linear regression to extend the long-term runoff record to the period of 1902-2019.Our results indicate that climate changes,dominated by regional wet-dry cycles,have significant impacts on runoff variations,while the influence of human activities remains comparatively limited.Danjiangkou Reservoir can maintain a balanced base flow,even during the operation of the water diversion project.Preliminary synoptic climatology analyses reveal that runoff variations are mainly driven by the El Niño-Southern Oscillation(ENSO)and the Pacific Walker Circulation(PWC),which affect runoff by altering large-scale ocean-to-continent water vapor processes.This study advances the field by integrating multi-source data with analytical techniques,which enhances understanding of long-term runoff changes in the Danjiangkou Reservoir and their climatic drivers,ultimately supporting sustainable water resource management.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41672169, 41473120 & 41502171)the Youth Innovation Promotion Association of Chinese Academy of Sciences (Grant No. 2012295)
文摘Hydroclimatic variations over the eastern Central Asia are highly sensitive to changes in hemispheric-scale atmospheric circulation systems. To fully understand the long-term variability and relationship between hydroclimate and atmospheric circulation system, we present a high-resolution lascustrine record of late Holocene hydroclimate from Lake Sayram, Central Tianshan Mountains, China, based on the total organic carbon, total nitrogen, and carbonate contents, carbon/nitrogen ratios, and grain size. Our results reveal four periods of substantially increased precipitation at the interval of 4000–3780, 3590–3210, 2800–2160, and 890–280 cal yr BP, and one period of slightly increased precipitation from 1700–1370 cal yr BP. These wetter periods broadly coincide with those identified in other records from the mid-latitude Westerlies-dominated eastern Central Asia, including the northern Tibetan Plateau. As such, a similar hydroclimatic pattern existed over this entire region during the late Holocene. Based on a close similarity of our record with reconstruction of North Atlantic Oscillation indices and solar irradiance, we propose that decreased solar irradiance and southern migration of the entire circum-North Atlantic circulation system, particularly the main pathway of the mid-latitude Westerlies, significantly influenced hydroclimate in eastern Central Asia during the late Holocene. Finally, the inferred precipitation at Lake Sayram has increased markedly over the past 100 years, although this potential future changes in hydroclimate in Central Asia need for further investigation.
基金Under the auspices of Major State Basic Research Development Program of China(No.2010CB951003)the National Climate Central,China Meteorological Administration,for providing the meteorological data for this study
文摘Based on runoff, air temperature, and precipitation data from 1960 to 2010, the effects of climate change on water resources in the arid region of the northwestern China were investigated. The long-term trends of hydroclimatic variables were studied by using both Mann-Kendall test and distributed-free cumulative sum （CUSUM） chart test. Results indicate that the mean annual air temperature increases significantly from 1960 to 2010. The annual precipitation exhibits an increasing trend, especially in the south slope of the Tianshan Mountains and the North Uygur Autonomous Region of Xinjiang in the study period. Step changes occur in 1988 in the mean annual air temperature time series and in 1991 in the precipitation time series. The runoff in different basins shows different trends, i.e., significantly increasing in the Kaidu River, the Aksu River and the Shule River, and decreasing in the Shiyang River. Correlation analy- sis reveals that the runoff in the North Xinjiang （i.e., the Weigan River, the Heihe River, and the Shiyang River） has a strong positive relationship with rainfall, while that in the south slope of the Tianshan Mountains, the middle section of the north slope of the Tianshan Mountains and the Shule River has a strong positive relationship with air temperature. The trends of rtmoff have strong negative correla- tions with glacier coverage and the proportion of glacier water in runoff. From the late 1980s, the climate has become warm and wet in the arid region of the northwestern China. The change in runoff is interacted with air temperature, precipitation and glacier coverage. The results show that streamflow in the arid region of the northwestern China is sensitive to climate change, which can be used as a reference for regional water resource assessment and management.
文摘The present study concerns the lowlands of the Birnin Lokoyo watershed located in the Matankari Rural Commune (Southwestern borders of the large Iullemmeden basin in the Niger). Dominated by the Birnin Lokoyo pond, this watershed faced with the continuous silting up of the minor bed, dissipates further upstream in the east, so that it moves downstream to the west for the benefit of the populations of Matankari city. The main objective of this work is to analyze the representative elements of the new climatic and environmental situation as well as the various factors determining the surface conditions in the watershed. The methodological approach is based on documentary research, field observations, individual surveys and interviews with targeted groups. The results show that the silting up of the lowlands is the result of the concomitant degradation of the plant cover and the soils, which, as a result, triggered the development of crusting surfaces and area erosion on the slopes. The study underlined the importance of endogenous knowledge in the choice of remedies against the silting up of lowlands. In addition, rational land management practices on plateaus and structures (within the watershed) do not seem to be in phase with topographical factors and the tectonic framework. This work is part of the vision of better management of glacis on the banks, but also of sills subject to regressive erosion upstream and in order to guide the policies of resilience of the populations.
基金supported by the National Natural Science Foundation(41831174)National Key Research and Development Program of China(2017YFA0603300)China Scholarship Council(CSC,202018006010083).
文摘Accurate reconstructed series are crucial for studying the differences in regional hydroclimatic variations in Europe over the past millennium.Using hierarchical clustering analysis and stepwise regression methods,we reconstructed yearly time series of the summer standardized precipitation evapotranspiration index(SPEl)for six European regions over the past millennium.Our analysis also revealed prominent regional hydroclimatic differences in multidecadal signals over the past 500 years.For instance,in the 1500s-1570s(from the beginning of the 1500s to the end of the 1570s),drying trends were observed in northern and southeastern Europe,whereas southwestern Europe experienced a wetting trend.Moreover,drying trends were observed in northern and central Europe in the 1640s-1670s.Additionally,wetting trends were observed in western and central Europe during the 1830s-1850s,with drying trends in northern and southeastern Europe.Notably,the hydroclimatic variations in most European regions showed drying trends in the 1920s-1950s,especially in southern Europe.By utilizing large amounts of tree-ring samples and directly comparing regional hydroclimatic variations,our reconstructions provide a consistent and comprehensive dataset for further analysis.The reconstructed dataset is available at https://doi.org/10.57760/sciencedb.07215.
