China has implemented large-scale hydraulic engineering projects in arid regions where water resources are severely scarce to efficiently maximize limited water resources for production and domestic needs.The processe...China has implemented large-scale hydraulic engineering projects in arid regions where water resources are severely scarce to efficiently maximize limited water resources for production and domestic needs.The processes and consequences of how the change of hydrological factors affects vegetation distribution remain unclear.This study employed multi-source remote sensing data to investigate the impact of hydrological factors on vegetation distribution in the Shiyang River Basin(SRB)in the arid region in Northwestern China.The results indicate that:(1)The NDVI values in the SRB showed a fluctuating upward trend of(0.0014/yr),with vegetation increase occurring in 62.71%of the area while vegetation degradation was observed in only 6.44%of the area.(2)The Surface Water Storage Anomaly(SWSA)shows an increasing trend of(0.112 mm/month),while Terrestrial Water Storage Anomaly(TWSA)and Groundwater Storage Anomaly(GWSA)exhibit significant declines at rates of-0.124 mm/month and-0.236 mm/month,respectively.(3)Vegetation growth on agricultural land and in planted forests has shown significant growth,in contrast to the general degradation of natural vegetation that is dependent on groundwater.In addition,surface water inputs directly catalyze vegetation growth dynamics.However,the complex mechanisms linking vegetation increase and decreasing terrestrial water reserves in arid regions still need to be studied in depth.The potential negative ecological impacts that may result from the continuous decline of terrestrial and groundwater reserves should not be taken lightly.展开更多
The fluctuation pattern of China’s civilization can be ascribed to climate change and historical geopolitical variations. The ancient Silk Road served as the most prosperous route connecting East Asia and Europe duri...The fluctuation pattern of China’s civilization can be ascribed to climate change and historical geopolitical variations. The ancient Silk Road served as the most prosperous route connecting East Asia and Europe during Han Dynasty(206 BC–220 AD) and Sui-Tang Dynasties(581–907 AD), but was deserted in Wei, Jin, Northern and Southern dynasties(220–580 AD), of which the Tarim Basin was a key area. However, our understanding about the decline of the route during this period remains limited. Here, we present an ~7-year resolution record based on optically stimulated luminescence(OSL) age-depth model(ca. 120 BC–750 AD) from Luntai(LT) profile, about 5 km from the modern Tarim River, which fed the ancient oases, to assess the potential causes on the documented decline of the ancient Silk Road between Late Han and Sui dynasties. In this study, five episodes of hydrological change were identified by combining grain size, magnetic susceptibility, geochemistry and TOC/TN contents. Our reconstruction reveals that cold and wet climate dominated at 120 BC–50 AD and 550–750 AD, respectively, indicated by strong hydrodynamic conditions. Relatively warm and humid climate occurred at 120–550 AD, between Eastern Han and Sui-Tang dynasties, indicating a better and more suitable local environment. A comparison between the studied region and other areas of China demonstrates that the paleoclimatic variations in eastern and western China exhibit rough discrepancies, and the hydrological conditions in arid region is inconsistent with the decline of ancient Silk Road in the northern Tarim Basin. We suggest that political and societal factors are the key issues that caused the interruption of Silk Road during Wei, Jin, Northern and Southern dynasties, such as the co-occurrence of societal crises, turmoil and division in eastern China, rather than the deteriorating climatic condition in the northern Tarim basin.展开更多
The hydrologic changes and the impact of these changes constitute a fundamental global-warmingrelated concern. Faced with threats to human life and natural ecosystems, such as droughts, floods, and soil erosion, water...The hydrologic changes and the impact of these changes constitute a fundamental global-warmingrelated concern. Faced with threats to human life and natural ecosystems, such as droughts, floods, and soil erosion, water resource planners must increasingly make future risk assessments. Though hydrological predictions associated with the global climate change are already being performed, mainly through the use of GCMs, coarse spatial resolutions and uncertain physical processes limit the representation of terrestrial water/energy interactions and the variability in such systems as the Asian monsoon. Despite numerous studies, the regional responses of hydrologic changes resulting from climate change remains inconclusive. In this paper, an attempt at dynamical downsealing of future hydrologic projection under global climate change in Asia is addressed. The authors conducted present and future Asian regional climate simulations which were nested in the results of Atmospheric General Circulation Model （AGCM） experiments. The regional climate model could capture the general simulated features of the AGCM. Also, some regional phenomena such as orographic precipitation, which did not appear in the outcome of the AGCM simulation, were successfully produced. Under global warming, the increase of water vapor associated with the warmed air temperature was projected. It was projected to bring more abundant water vapor to the southern portions of India and the Bay of Bengal, and to enhance precipitation especially over the mountainous regions, the western part of India and the southern edge of the Tibetan Plateau. As a result of the changes in the synoptic flow patterns and precipitation under global warming, the increases of annual mean precipitation and surface runoff were projected in many regions of Asia. However, both the positive and negative changes of seasonal surface runoff were projected in some regions which will increase the flood risk and cause a mismatch between water demand and water availability in the agricultural season.展开更多
Intense human activities have greatly changed the flood generation conditions in most areas of the world, and have destroyed the consistency in the annual flood peak and volume series. For design flood estimation, coa...Intense human activities have greatly changed the flood generation conditions in most areas of the world, and have destroyed the consistency in the annual flood peak and volume series. For design flood estimation, coaxial correlation diagram and conceptual hydrological model are two frequently used tools to adjust and reconstruct the flood series under human disturbance. This study took a typical mountain catchment of the Haihe River Basin as an example to investigate the effects of human activities on flood regime and to compare and assess the two adjustment methods. The main purpose is to construct a conceptual hydrological model which can incorporate the effects of human activities. The results show that the coaxial correlation diagram is simple and widely-used, but can only adjust the time series of total flood volumes. Therefore, it is only applicable under certain conditions(e.g. There is a strong link between the flood peaks and volumes and the link is not significantly affected by human activities). The conceptual model is a powerful tool to adjust the time series of both flood peak flows and flood volumes over different durations provided that it is closely related to the catchment hydrological characteristics, specifically accounting for the effects of human activities, and incorporating expert knowledge when estimating or calibrating parameters. It is suggested that the two methods should be used together to cross check each other.展开更多
The relationship between climate change and water resources in the Tarim River was analyzed by combining the temperature,precipitation and streamflow data from 1957 to 2007 from the four headstreams of the Tarim River...The relationship between climate change and water resources in the Tarim River was analyzed by combining the temperature,precipitation and streamflow data from 1957 to 2007 from the four headstreams of the Tarim River （Aksu,Hotan,Yarkant and Kaidu rivers） in the study area.The long-term trend of the hydrological time series including temperature,precipitation and streamflow were studied using correlation analysis and partial correlations analysis.Holt double exponential smoothing was used to fit the trends between streamflow and the two climatic factors of Aksu River,Hotan River and Yarkant River.The streamflow of the main stream was forecasted by Autoregressive Integrated Moving Average Model （ARIMA） modeling by the method of time series analysis.The results show that the temperature experienced a trend of monotonic rising.The precipitation and runoff of the four headstreams of the Tarim River increased,while the inflow to the headstreams increased and the inflow into the Tarim River decreased.Changes of temperature and precipitation had a significant impact on runoff into the four headstreams of the Tarim River： the precipitation had a positive impact on water flow in the Aksu River,Hotan River and Kaidu River,while the temperature had a positive impact on water flow in the Yarkant River.The results of Holt double exponential smoothing showed that the correlation between the independent variable and dependent variable was relatively close after the model was fitted to the headstreams,of which only the runoff and temperature values of Hotan River showed a significant negative correlation.The forecasts by the ARIMA model for 50 years of annual runoff at the Allar station followed the pattern of the measured data for the same years.The short-term forecasts beyond the observed series adequately captured the pattern in the data and showed a decreasing tendency in the Tarim River flow of 3.07% every ten years.The results showed that global warming accelerated the water recharge process of the headstreams.The special hydrological characteristics of the arid area determined the significant association between streamflow and the two climatic factors studied.Strong glacier retreat is likely to bring a series of flood disasters within the study area.展开更多
Based on the comprehensive analyses of 18 core profiles’sedimentary sequences and lithological characteristics in Jianghan-Dongting Basin of the middle reaches of the Yangtze River and the spatial-temporal distributi...Based on the comprehensive analyses of 18 core profiles’sedimentary sequences and lithological characteristics in Jianghan-Dongting Basin of the middle reaches of the Yangtze River and the spatial-temporal distribution of archeological sites in this area,we reconstructed the Holocene hydro-environmental evolution,and its relationship with human occupation.The comparison reveals:11.5–5.5 ka BP,the water level of rivers and lakes in the middle Yangtze River appeared a rising trend,concurrently,under the development of Neolithic culture and rice agricultural activities,human occupation extended from piedmont plain to inner basin plain in the study area.The water level fell in 5.5–4.0 ka BP,meanwhile,the number of human settlements of Qujialing-Shijiahe culture rapidly increased,especially in the inner basin plain.The water level rose again around 4.0 ka BP,floods spread massively in this period,which led to the decline of Shijiahe culture.The main causes for hydro-environmental evolution in the study area are the fluctuation of sea level and the aggradation of fluvio-lacustrine sediments.展开更多
Changes in the elements of the Earth system are closely related.Finding the key factors linked with hydrological changes is significant for in-depth analysis of hydrological changes.This study chooses polar motion,whi...Changes in the elements of the Earth system are closely related.Finding the key factors linked with hydrological changes is significant for in-depth analysis of hydrological changes.This study chooses polar motion,which is the movement of the Earth’s rotational axis relative to its crust,as a key factor in the investigation of the physical processes of its interaction with several hydrological elements.First,the statistical relationships between polar motion and multi-hydrological elements(i.e.,precipitation,evaporation,runoff,and terrestrial water storage)are investigated,using trend analysis,mutation analysis,cycle analysis,and correlation analysis methods,from basinal to global and from intra-annual to inter-annual scales.Second,their interactions are explored.The study quantifies the effect of hydrological changes on polar motion using the excitation function.It explores the effect of polar motion on hydrological changes based on the theory of equilibrium tides and atmospheric dynamics.The results show that they are significantly correlated and abruptly changed at a similar time.First,regional to global hydrological changes can significantly excite polar motion.From April 2002 to June 2020,the global terrestrial water storage decreased significantly(by approximately−4.68 mm yr^(−1)),which significantly drove polar motion towards the direction of the Greenwich Meridian(by approximately 4.32 mas yr^(−1)).Changes in regional terrestrial water storage also contributed significantly to directional changes in polar motion around 2005 and 2012.Second,polar motion can perturb the Earth’s centrifugal force system and generate equilibrium tides,and thus further cause changes in sea-level pressure,wind,and water vapor transport.Results show that polar motion-induced water vapor flux divergences correlate significantly with actual precipitation and terrestrial water storage changes in the Yangtze River and the Pearl River basins.Their correlations are also significant when trends are removed,and the polar motion-induced changes are 4 to 14 months earlier.This study further demonstrates the relationship between polar motion and hydrological changes and helps to understand the related factors of hydrological changes in other Earth systems.展开更多
The latest Coupled Model Intercomparison Project Phase 6(CMIP6)proposes new shared pathways(SSPs)that incorporate socioeconomic development with more comprehensive and scientific experimental designs;however,few studi...The latest Coupled Model Intercomparison Project Phase 6(CMIP6)proposes new shared pathways(SSPs)that incorporate socioeconomic development with more comprehensive and scientific experimental designs;however,few studies have been performed on the projection of future multibasin hydrological changes in China based on CMIP6 models.In this paper,we use the Equidistant Cumulative Distribution Function method(EDCDFm)to perform downscaling and bias correction in daily precipitation,daily maximum temperature,and daily minimum temperature for six CMIP6 models based on the historical gridded data from the high-resolution China Meteorological Forcing Dataset(CMFD).We use the bias-corrected precipitation,temperature,and daily mean wind speed to drive the variable infiltration capacity(VIC)hydrological model,and study the changes in multiyear average annual precipitation,annual evapotranspiration and total annual runoff depth relative to the historical baseline period(1985–2014)for the Chinese mainland,basins and grid scales in the 21st century future under the SSP2-4.5 and SSP5-8.5 scenarios.The study shows that the VIC model accurately simulates runoff in major Chinese basins;the model data accuracy improves substantially after downscaling bias correction;and the future multimodel-mean multiyear average annual precipitation,annual evapotranspiration,and total annual runoff depth for the Chinese mainland and each basin increase relative to the historical period in near future(2020–2049)and far future(2070–2099)under the SSP2-4.5 and SSP5-8.5scenarios.The new CMIP6-based results of this paper can provide a strong reference for extreme event prevention,water resource utilization and management in China in the 21st century.展开更多
Combining the temperature and precipitation data from 77 climatological stations and the climatic and hydrological change data from three headstreams of the Tarim River:Hotan,Yarkant,and Aksu in the study area,the pla...Combining the temperature and precipitation data from 77 climatological stations and the climatic and hydrological change data from three headstreams of the Tarim River:Hotan,Yarkant,and Aksu in the study area,the plausible association between climate change and the variability of water resources in the Tarim River Basin in recent years was investigated,the long-term trend of the hydrological time series including temperature,precipitation,and streamflow was detected,and the possible association between the El Ni(n)o/Southern Oscillation(ENSO)and these three kinds of time series was tested.The results obtained in this study show that during the past years,the temperature experienced a significant monotonic increase at the speed of 5%,nearly 1℃rise;the precipitation showed a significant decrease in the 1970s,and a significant increase in the1980s and 1990s,the average annual precipitation was increased with the magnitude of 6.8 mm per decade.A step change occurred in both temperature and precipitation time series around 1986,which may be influenced by the global climate change.Climate change resulted in the increase of the streamflow at the headwater of the Tarim River,but the anthropogenic activities such as over-depletion of the surface water resulted in the decrease of the streamflow at the lower reaches of the Tarim River.The study result also showed that there is no significant association between the ENSO and the temperature,precipitation and streamflow.展开更多
The Tianshan Mountains is a high and huge mountain body lying across the central part of Xinjiang,China,and is also the main area where the runoff forms in Xinjiang.In this paper,a set of RS-based study methods is put...The Tianshan Mountains is a high and huge mountain body lying across the central part of Xinjiang,China,and is also the main area where the runoff forms in Xinjiang.In this paper,a set of RS-based study methods is put forward for deriving the information about the natural change of the ecology in arid areas,and the relationship between the climate change trend and the corresponding ecological response on the northern slope of the Tianshan Mountains since recent 40 years is analyzed from the scales of the land cover ecosystems and landscapes based on the observed data of climate,hydrology,modern glaciers and lakes on the northern slopes of the Tianshan Mountains since recent 40 years and the satellite RS data since recent 10 years by using the RS and GIS technologies.The results are as follows:(1)The overall trend of climate change on the northern slope of the Tianshan Mountains since recent 40 years is that both air temperature and precipitation are increased,especially the increase amplitudes of air tempera-ture,precipitation and annual runoff volume are high since the decade of the 1990s;(2)the in-tegrated indexes of the vegetation in all the geographical divisions on the northern slope of the Tianshan Mountains are obviously increased since recent 10 years,especially in the artificial oases and the foothill belts,such a change trend is advantageous for improving the vegetation ecology;and(3)the vegetation ecology in the arid areas is extremely sensitive to the climate change,the vegetation coverage and the biomass on the northern slope of the Tianshan Moun-tains are continuously increased because of the climate change since recent 10 years,their in-crease amplitudes in the plains and during the late stage are obviously higher than that in the mountainous regions and during the early stage.展开更多
Hydrological changes under climate warming drive the biogeomorphic succession of wetlands and may trigger substantial carbon loss from the carbon-rich ecosystems.Although many studies have explored the responses of we...Hydrological changes under climate warming drive the biogeomorphic succession of wetlands and may trigger substantial carbon loss from the carbon-rich ecosystems.Although many studies have explored the responses of wetland carbon emissions to short-term hydrological change,it remains poorly understood how the carbon cycle evolves with hydrology-driven wetland succession.Here,we used a space-for-time approach across hydrological gradients on the Tibetan Plateau to examine the dynamics of ecosystem carbon fluxes(carbon dioxide(CO_(2))and methane(CH4))and soil organic carbon pools during alpine wetland succession.We found that the succession from mesic meadow to fen changed the seasonality of both CO_(2)and CH4 fluxes,which was related to the shift in plant community composition,enhanced regulation of soil hydrology and increasing contribution of spring-thaw emission.The paludification caused a switch from net uptake of gaseous carbon to net release on an annual timescale but produced a large accumulation of soil organic carbon.We attempted to attribute the paradox between evidence from the carbon fluxes and pools to the lateral carbon input and the systematic changes of historical climate,given that the wetlands are spatially low-lying with strong temporal climate-carbon cycle interactions.These findings demonstrate a systematic change in the carbon cycle with succession and suggest that biogeomorphic succession and lateral carbon flows are both important for understanding the long-term dynamics of wetland carbon footprints.展开更多
Climatic state under greenhouse effect is a currently hot point. Whether greenhouse climate in geological history, especially in Cretaceous, was equable or not has aroused extensive discussion. By analysis on depositi...Climatic state under greenhouse effect is a currently hot point. Whether greenhouse climate in geological history, especially in Cretaceous, was equable or not has aroused extensive discussion. By analysis on depositional cyclcity, wind direction change and hydrologic cycle variation of Cretaceous desert in the Ordos Basin of China, the unequability of Cretaceous cli-mate is dealt. It is shown that Cretaceous climate was extremely cyclic, not only having long and mid term but also having strong seasonal even instantaneous changes. Therefore, it is sug-gested that Cretaceous climate was not equable.展开更多
基金financially supported by the National Natural Science Foundation of China(42371040,41971036)Key Natural Science Foundation of Gansu Province(23JRRA698)+2 种基金Key Research and Development Program of Gansu Province(22YF7NA122)Cultivation Program of Major key projects of Northwest Normal University(NWNU-LKZD-202302)Oasis Scientific Research achievements Breakthrough Action Plan Project of Northwest normal University(NWNU-LZKX-202303).
文摘China has implemented large-scale hydraulic engineering projects in arid regions where water resources are severely scarce to efficiently maximize limited water resources for production and domestic needs.The processes and consequences of how the change of hydrological factors affects vegetation distribution remain unclear.This study employed multi-source remote sensing data to investigate the impact of hydrological factors on vegetation distribution in the Shiyang River Basin(SRB)in the arid region in Northwestern China.The results indicate that:(1)The NDVI values in the SRB showed a fluctuating upward trend of(0.0014/yr),with vegetation increase occurring in 62.71%of the area while vegetation degradation was observed in only 6.44%of the area.(2)The Surface Water Storage Anomaly(SWSA)shows an increasing trend of(0.112 mm/month),while Terrestrial Water Storage Anomaly(TWSA)and Groundwater Storage Anomaly(GWSA)exhibit significant declines at rates of-0.124 mm/month and-0.236 mm/month,respectively.(3)Vegetation growth on agricultural land and in planted forests has shown significant growth,in contrast to the general degradation of natural vegetation that is dependent on groundwater.In addition,surface water inputs directly catalyze vegetation growth dynamics.However,the complex mechanisms linking vegetation increase and decreasing terrestrial water reserves in arid regions still need to be studied in depth.The potential negative ecological impacts that may result from the continuous decline of terrestrial and groundwater reserves should not be taken lightly.
基金This research was supported by the States Key Program of National Natural Science of China (grants No. 40830420)the Special Funds Projects for Basic Scientific Research Business Expenses of Mineral Resources, Research Institutes in Chinese Academy of Geological Sciences (No. KK1924)the National Key R&D Program of China (grants No. 2018YFA0606401)
文摘The fluctuation pattern of China’s civilization can be ascribed to climate change and historical geopolitical variations. The ancient Silk Road served as the most prosperous route connecting East Asia and Europe during Han Dynasty(206 BC–220 AD) and Sui-Tang Dynasties(581–907 AD), but was deserted in Wei, Jin, Northern and Southern dynasties(220–580 AD), of which the Tarim Basin was a key area. However, our understanding about the decline of the route during this period remains limited. Here, we present an ~7-year resolution record based on optically stimulated luminescence(OSL) age-depth model(ca. 120 BC–750 AD) from Luntai(LT) profile, about 5 km from the modern Tarim River, which fed the ancient oases, to assess the potential causes on the documented decline of the ancient Silk Road between Late Han and Sui dynasties. In this study, five episodes of hydrological change were identified by combining grain size, magnetic susceptibility, geochemistry and TOC/TN contents. Our reconstruction reveals that cold and wet climate dominated at 120 BC–50 AD and 550–750 AD, respectively, indicated by strong hydrodynamic conditions. Relatively warm and humid climate occurred at 120–550 AD, between Eastern Han and Sui-Tang dynasties, indicating a better and more suitable local environment. A comparison between the studied region and other areas of China demonstrates that the paleoclimatic variations in eastern and western China exhibit rough discrepancies, and the hydrological conditions in arid region is inconsistent with the decline of ancient Silk Road in the northern Tarim Basin. We suggest that political and societal factors are the key issues that caused the interruption of Silk Road during Wei, Jin, Northern and Southern dynasties, such as the co-occurrence of societal crises, turmoil and division in eastern China, rather than the deteriorating climatic condition in the northern Tarim basin.
基金the Global Environment Research Fund of Japan's Ministry of the En- vironment (S-5-3)The data used in this study were acquired as part of the Tropical Rainfall Measuring Mission (TRMM)+1 种基金The algorithms were developed by the TRMM Science TeamThe data were processed by the TRMM Science Data and Information System (TSDIS) and the TRMM Offce.
文摘The hydrologic changes and the impact of these changes constitute a fundamental global-warmingrelated concern. Faced with threats to human life and natural ecosystems, such as droughts, floods, and soil erosion, water resource planners must increasingly make future risk assessments. Though hydrological predictions associated with the global climate change are already being performed, mainly through the use of GCMs, coarse spatial resolutions and uncertain physical processes limit the representation of terrestrial water/energy interactions and the variability in such systems as the Asian monsoon. Despite numerous studies, the regional responses of hydrologic changes resulting from climate change remains inconclusive. In this paper, an attempt at dynamical downsealing of future hydrologic projection under global climate change in Asia is addressed. The authors conducted present and future Asian regional climate simulations which were nested in the results of Atmospheric General Circulation Model （AGCM） experiments. The regional climate model could capture the general simulated features of the AGCM. Also, some regional phenomena such as orographic precipitation, which did not appear in the outcome of the AGCM simulation, were successfully produced. Under global warming, the increase of water vapor associated with the warmed air temperature was projected. It was projected to bring more abundant water vapor to the southern portions of India and the Bay of Bengal, and to enhance precipitation especially over the mountainous regions, the western part of India and the southern edge of the Tibetan Plateau. As a result of the changes in the synoptic flow patterns and precipitation under global warming, the increases of annual mean precipitation and surface runoff were projected in many regions of Asia. However, both the positive and negative changes of seasonal surface runoff were projected in some regions which will increase the flood risk and cause a mismatch between water demand and water availability in the agricultural season.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41130639, 51179045, 41201028)the Nonprofit Industry Financial Program of MWR of China (201501022)
文摘Intense human activities have greatly changed the flood generation conditions in most areas of the world, and have destroyed the consistency in the annual flood peak and volume series. For design flood estimation, coaxial correlation diagram and conceptual hydrological model are two frequently used tools to adjust and reconstruct the flood series under human disturbance. This study took a typical mountain catchment of the Haihe River Basin as an example to investigate the effects of human activities on flood regime and to compare and assess the two adjustment methods. The main purpose is to construct a conceptual hydrological model which can incorporate the effects of human activities. The results show that the coaxial correlation diagram is simple and widely-used, but can only adjust the time series of total flood volumes. Therefore, it is only applicable under certain conditions(e.g. There is a strong link between the flood peaks and volumes and the link is not significantly affected by human activities). The conceptual model is a powerful tool to adjust the time series of both flood peak flows and flood volumes over different durations provided that it is closely related to the catchment hydrological characteristics, specifically accounting for the effects of human activities, and incorporating expert knowledge when estimating or calibrating parameters. It is suggested that the two methods should be used together to cross check each other.
基金supported by the National Basic Research Program of China (2010CB951003)
文摘The relationship between climate change and water resources in the Tarim River was analyzed by combining the temperature,precipitation and streamflow data from 1957 to 2007 from the four headstreams of the Tarim River （Aksu,Hotan,Yarkant and Kaidu rivers） in the study area.The long-term trend of the hydrological time series including temperature,precipitation and streamflow were studied using correlation analysis and partial correlations analysis.Holt double exponential smoothing was used to fit the trends between streamflow and the two climatic factors of Aksu River,Hotan River and Yarkant River.The streamflow of the main stream was forecasted by Autoregressive Integrated Moving Average Model （ARIMA） modeling by the method of time series analysis.The results show that the temperature experienced a trend of monotonic rising.The precipitation and runoff of the four headstreams of the Tarim River increased,while the inflow to the headstreams increased and the inflow into the Tarim River decreased.Changes of temperature and precipitation had a significant impact on runoff into the four headstreams of the Tarim River： the precipitation had a positive impact on water flow in the Aksu River,Hotan River and Kaidu River,while the temperature had a positive impact on water flow in the Yarkant River.The results of Holt double exponential smoothing showed that the correlation between the independent variable and dependent variable was relatively close after the model was fitted to the headstreams,of which only the runoff and temperature values of Hotan River showed a significant negative correlation.The forecasts by the ARIMA model for 50 years of annual runoff at the Allar station followed the pattern of the measured data for the same years.The short-term forecasts beyond the observed series adequately captured the pattern in the data and showed a decreasing tendency in the Tarim River flow of 3.07% every ten years.The results showed that global warming accelerated the water recharge process of the headstreams.The special hydrological characteristics of the arid area determined the significant association between streamflow and the two climatic factors studied.Strong glacier retreat is likely to bring a series of flood disasters within the study area.
基金The Major Program of the National Social Science Foundation of China,No.11&ZD183Foundation for Distinguished Professors of Henan Province+2 种基金Zhengzhou Research Council for the Origins of Chinese CivilizationNational Key Project of Scientific and Technical Supporting Program of China,No.2013BAK08B02National Natural Science Foundation of China,No.41701220。
文摘Based on the comprehensive analyses of 18 core profiles’sedimentary sequences and lithological characteristics in Jianghan-Dongting Basin of the middle reaches of the Yangtze River and the spatial-temporal distribution of archeological sites in this area,we reconstructed the Holocene hydro-environmental evolution,and its relationship with human occupation.The comparison reveals:11.5–5.5 ka BP,the water level of rivers and lakes in the middle Yangtze River appeared a rising trend,concurrently,under the development of Neolithic culture and rice agricultural activities,human occupation extended from piedmont plain to inner basin plain in the study area.The water level fell in 5.5–4.0 ka BP,meanwhile,the number of human settlements of Qujialing-Shijiahe culture rapidly increased,especially in the inner basin plain.The water level rose again around 4.0 ka BP,floods spread massively in this period,which led to the decline of Shijiahe culture.The main causes for hydro-environmental evolution in the study area are the fluctuation of sea level and the aggradation of fluvio-lacustrine sediments.
基金supported by the National Key Research and Development Program of China (Grant No. 2018YFE0106500 & 2017YFA0603702)the National Program on Key Basic Research Project of China (Grant No. 2012CB957802)+1 种基金the Danida Fellowship Centre EOFor China project (Grant No. 18-M01-DTU)the China Water Sense project (Grant No. 8087-00002B)
文摘Changes in the elements of the Earth system are closely related.Finding the key factors linked with hydrological changes is significant for in-depth analysis of hydrological changes.This study chooses polar motion,which is the movement of the Earth’s rotational axis relative to its crust,as a key factor in the investigation of the physical processes of its interaction with several hydrological elements.First,the statistical relationships between polar motion and multi-hydrological elements(i.e.,precipitation,evaporation,runoff,and terrestrial water storage)are investigated,using trend analysis,mutation analysis,cycle analysis,and correlation analysis methods,from basinal to global and from intra-annual to inter-annual scales.Second,their interactions are explored.The study quantifies the effect of hydrological changes on polar motion using the excitation function.It explores the effect of polar motion on hydrological changes based on the theory of equilibrium tides and atmospheric dynamics.The results show that they are significantly correlated and abruptly changed at a similar time.First,regional to global hydrological changes can significantly excite polar motion.From April 2002 to June 2020,the global terrestrial water storage decreased significantly(by approximately−4.68 mm yr^(−1)),which significantly drove polar motion towards the direction of the Greenwich Meridian(by approximately 4.32 mas yr^(−1)).Changes in regional terrestrial water storage also contributed significantly to directional changes in polar motion around 2005 and 2012.Second,polar motion can perturb the Earth’s centrifugal force system and generate equilibrium tides,and thus further cause changes in sea-level pressure,wind,and water vapor transport.Results show that polar motion-induced water vapor flux divergences correlate significantly with actual precipitation and terrestrial water storage changes in the Yangtze River and the Pearl River basins.Their correlations are also significant when trends are removed,and the polar motion-induced changes are 4 to 14 months earlier.This study further demonstrates the relationship between polar motion and hydrological changes and helps to understand the related factors of hydrological changes in other Earth systems.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0206)the National Key Research and Development Program of China(Grant No.2017YFA0603703)+1 种基金the National Natural Science Foundation of China(Grant No.4200011953)the fundamental scientific research fund of China Institute of Water Resources and Hydropower Research(Grant No.JZ110145B0052021)。
文摘The latest Coupled Model Intercomparison Project Phase 6(CMIP6)proposes new shared pathways(SSPs)that incorporate socioeconomic development with more comprehensive and scientific experimental designs;however,few studies have been performed on the projection of future multibasin hydrological changes in China based on CMIP6 models.In this paper,we use the Equidistant Cumulative Distribution Function method(EDCDFm)to perform downscaling and bias correction in daily precipitation,daily maximum temperature,and daily minimum temperature for six CMIP6 models based on the historical gridded data from the high-resolution China Meteorological Forcing Dataset(CMFD).We use the bias-corrected precipitation,temperature,and daily mean wind speed to drive the variable infiltration capacity(VIC)hydrological model,and study the changes in multiyear average annual precipitation,annual evapotranspiration and total annual runoff depth relative to the historical baseline period(1985–2014)for the Chinese mainland,basins and grid scales in the 21st century future under the SSP2-4.5 and SSP5-8.5 scenarios.The study shows that the VIC model accurately simulates runoff in major Chinese basins;the model data accuracy improves substantially after downscaling bias correction;and the future multimodel-mean multiyear average annual precipitation,annual evapotranspiration,and total annual runoff depth for the Chinese mainland and each basin increase relative to the historical period in near future(2020–2049)and far future(2070–2099)under the SSP2-4.5 and SSP5-8.5scenarios.The new CMIP6-based results of this paper can provide a strong reference for extreme event prevention,water resource utilization and management in China in the 21st century.
基金This study was supported by the State Key Basic Research and Development Plant of China(Grant No.2004CB720200)the National Natural Science Foundation of China(Grant No.90102007)the Knowledge Innovation Project of the Chinese Academy of Sciences(Grant No.KZCX1-08-03).
文摘Combining the temperature and precipitation data from 77 climatological stations and the climatic and hydrological change data from three headstreams of the Tarim River:Hotan,Yarkant,and Aksu in the study area,the plausible association between climate change and the variability of water resources in the Tarim River Basin in recent years was investigated,the long-term trend of the hydrological time series including temperature,precipitation,and streamflow was detected,and the possible association between the El Ni(n)o/Southern Oscillation(ENSO)and these three kinds of time series was tested.The results obtained in this study show that during the past years,the temperature experienced a significant monotonic increase at the speed of 5%,nearly 1℃rise;the precipitation showed a significant decrease in the 1970s,and a significant increase in the1980s and 1990s,the average annual precipitation was increased with the magnitude of 6.8 mm per decade.A step change occurred in both temperature and precipitation time series around 1986,which may be influenced by the global climate change.Climate change resulted in the increase of the streamflow at the headwater of the Tarim River,but the anthropogenic activities such as over-depletion of the surface water resulted in the decrease of the streamflow at the lower reaches of the Tarim River.The study result also showed that there is no significant association between the ENSO and the temperature,precipitation and streamflow.
基金the important orientation program of the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KZCX3-SW-327).
文摘The Tianshan Mountains is a high and huge mountain body lying across the central part of Xinjiang,China,and is also the main area where the runoff forms in Xinjiang.In this paper,a set of RS-based study methods is put forward for deriving the information about the natural change of the ecology in arid areas,and the relationship between the climate change trend and the corresponding ecological response on the northern slope of the Tianshan Mountains since recent 40 years is analyzed from the scales of the land cover ecosystems and landscapes based on the observed data of climate,hydrology,modern glaciers and lakes on the northern slopes of the Tianshan Mountains since recent 40 years and the satellite RS data since recent 10 years by using the RS and GIS technologies.The results are as follows:(1)The overall trend of climate change on the northern slope of the Tianshan Mountains since recent 40 years is that both air temperature and precipitation are increased,especially the increase amplitudes of air tempera-ture,precipitation and annual runoff volume are high since the decade of the 1990s;(2)the in-tegrated indexes of the vegetation in all the geographical divisions on the northern slope of the Tianshan Mountains are obviously increased since recent 10 years,especially in the artificial oases and the foothill belts,such a change trend is advantageous for improving the vegetation ecology;and(3)the vegetation ecology in the arid areas is extremely sensitive to the climate change,the vegetation coverage and the biomass on the northern slope of the Tianshan Moun-tains are continuously increased because of the climate change since recent 10 years,their in-crease amplitudes in the plains and during the late stage are obviously higher than that in the mountainous regions and during the early stage.
基金supported by the National Natural Science Foundation of China(32130065,31901145,32111530062)the Discipline Construction Fund of Peking University and the Academy of Finland(341294).
文摘Hydrological changes under climate warming drive the biogeomorphic succession of wetlands and may trigger substantial carbon loss from the carbon-rich ecosystems.Although many studies have explored the responses of wetland carbon emissions to short-term hydrological change,it remains poorly understood how the carbon cycle evolves with hydrology-driven wetland succession.Here,we used a space-for-time approach across hydrological gradients on the Tibetan Plateau to examine the dynamics of ecosystem carbon fluxes(carbon dioxide(CO_(2))and methane(CH4))and soil organic carbon pools during alpine wetland succession.We found that the succession from mesic meadow to fen changed the seasonality of both CO_(2)and CH4 fluxes,which was related to the shift in plant community composition,enhanced regulation of soil hydrology and increasing contribution of spring-thaw emission.The paludification caused a switch from net uptake of gaseous carbon to net release on an annual timescale but produced a large accumulation of soil organic carbon.We attempted to attribute the paradox between evidence from the carbon fluxes and pools to the lateral carbon input and the systematic changes of historical climate,given that the wetlands are spatially low-lying with strong temporal climate-carbon cycle interactions.These findings demonstrate a systematic change in the carbon cycle with succession and suggest that biogeomorphic succession and lateral carbon flows are both important for understanding the long-term dynamics of wetland carbon footprints.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.49572113 and 40372064)the Tenth Five-Year Plan Major Geological Exploration Project of The underground water exploration in Ordos Basin.
文摘Climatic state under greenhouse effect is a currently hot point. Whether greenhouse climate in geological history, especially in Cretaceous, was equable or not has aroused extensive discussion. By analysis on depositional cyclcity, wind direction change and hydrologic cycle variation of Cretaceous desert in the Ordos Basin of China, the unequability of Cretaceous cli-mate is dealt. It is shown that Cretaceous climate was extremely cyclic, not only having long and mid term but also having strong seasonal even instantaneous changes. Therefore, it is sug-gested that Cretaceous climate was not equable.
