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Rivers have been under sampled to establish them as sinks or sources of the atmospheric carbon oxide (CO2). Such poor coverage is well known for tropical and sub-tropical, particularly monsoon driven rivers. An unprecedented high-temporal-resolution (daily) sampling during July 2008-August 2009 were conducted from the Longchuanjiang River of the upper Yangtze basin, a subtropical monsoon river in China to reveal the daily-to-seasonal dynamics of the partial pressure of CO2 (pCO2) and CO2 degassing flux from the river. The pCO2 levels were supersaturated in CO2 with respect to atmospheric equilibrium (380 µatm) during the entire survey period with obvious daily and seasonal variations, ranging from 450 to 63000 µatm with an average of 3900 µatm. pCO2 values in the surface water in the wet season were relatively low, except flooding period in November, due to a dilution effect by heavy rainfall. However, both daily and monthly minimal and maximal pCO2 also occurred in this period. In contrast, the pCO2 levels in the dry season were much higher, mainly resulted from lower pH by anthropogenic activities. Net CO2 flux and pCO2 were strongly correlated with pH, but weakly with water temperature, dissolved inorganic carbon and water discharge, and uncorrelated with particulate nutrients and biogenic elements. The estimated water-to-air CO2 degassing flux in the Longchuanjiang River was about 110 mol m-2 yr-1, with the upper limit of 460 mol m-2 yr-1. Our study also indicated that among the total organic carbon remobilized through soil erosion, around 17% (11 400tC yr-1) of was emitted to the atmosphere, 52% (35 000tC yr-1) deposited in the river-reservoirs system and 31 % (21 000tC yr-1) exported further downstream. High spatial and temporal resolution of estimates of CO2 emission from the world large rivers is required due to that catchment characteristics and anthropogenic activities are extremely heterogeneous in space and time. [ABSTRACT FROM AUTHOR]

Middle and eastern routes of the South-North Water Diversion Project (SNWDP) of China, which are approximately located within the area 28°-42°N and 110°-122°E, are being constructed. This paper investigates the past climatic variations on various time scales using instrumental and proxy data. It is found that annual mean surface air temperature has increased significantly during the past 50-100 years, and winter and spring temperatures in the northern part of the region have undergone the most significant changes. A much more significant increase occurs for annual mean minimum temperature and extreme low temperature than for annual mean maximum temperature and extreme high temperature. No significant trend in annual precipitation is found for the region as a whole for the last 50 and 100 years, although obvious decadal and spatial variation is detectable. A seesaw pattern of annual and summer precipitation variability between the north and the south of the region is evident. Over the last 100 years, the Haihe River basin has witnessed a significant negative trend of annual precipitation, but no similar trend is detected for the Yangtze and Huaihe River basins. Pan evaporation has significantly decreased since the mid-1960s in the region in spite of the fact that the trend appears to have ended in the early 1990s. The negative trend of pan evaporation is very significant in the plain area between the Yangtze and Yellow Rivers. There was a notable series of dry intervals lasting decades in the north of the region. The northern drought of the past 30 years is not the most severe in view of the past 500 years; however, the southern drought during the period from the 1960s to the 1980s may have been unprecedented. The dryness-wetness index (DWI) shows significant oscillations with periodicities of 9.5 and 20 years in the south and 10.5 and 25 years in the north. Longer periodicities in the DWI series include 160-170- and 70-80-yr oscillations in the north, and 100-150-yr oscillations in the south. The observed climate change could have implications for the construction and management of the SNWDP. The official approval and start of the hydro project was catalyzed by the severe multiyear drought of 1997-2003 in the north, and the operation and management of the project in the future will also be influenced by climate change-in particular by precipitation variability. This paper provides a preliminary discussion of the potential implications of observed climate change for the SNWDP. [ABSTRACT FROM AUTHOR]

The present paper provides a scientific assessment of the inter-decadal variability of the Asian summer monsoon and its significant effect on precipitation patterns in China. The paper consists of four parts. The first part shows the observed inter-decadal weakening of the Asian summer monsoon since the end of 1970s. The second part describes the impact of the weakening Asian summer monsoon on precipitation in China, which caused the major monsoon rainbelt to shift southward from North China to South China over about 30 years, with a 60-80 oscillation dominating. The third part projects the future change of the Asian summer monsoon in the warmer climate by using IPCC AR4 climate models. It has been found that major monsoon rainfall belts in East Asia will move northward in the 2040s, with summer precipitation in North China increasing considerably and stably. Finally, in the fourth part, the implication of the adaptation to the above climate change and related water management will be discussed including the water transport engineering project from the Yangtze River to the Yellow River and North China. [ABSTRACT FROM AUTHOR]

This study examines the making of local climate governance in the Chinese setting where central-local inter-governmental relations continue to play critical part in almost every policy domain. Through analysing the climate responses of the three provincial-level governments at the Yangtze River Delta (YRD), the paper argues that the process of “experimentation under hierarchy” is relevant to understanding the evolving of the subnational climate regime in the YRD region. We find the preponderance of the central authorities in initiating national climate strategies and galvanising responses at the local level. Meanwhile, provincial governments have been able to leverage climate plans and actions to achieve their own gains. These findings suggest that any optimism about subnational climate activism in a Chinese setting has to be mixed with caution. In fact, the shadow of hierarchical authority structure lingers and plays important part in the initiation of subnational response and spurring climate responses and innovations from below. [ABSTRACT FROM AUTHOR]

Water footprint of production can be used to identify pressure on national or regional water resources generated by production activities. Water stress is defined as the ratio of water use (the difference between a regional water footprint of production and a green water footprint) to renewable water resources available in a country or region. Water stress can be used to identify pressure on national or regional water resources generated by production activities. This paper estimates the water footprint of production and the water stress in China during the years 1985-2009. The result shows that China's water footprint of production increased from 781.58 × 109 m3 in 1985 to 1109.76 × 109 m3 in 2009. Mega-cities and regions with less agriculture production due to local climatic conditions (Tibet and Qinghai) had lower water footprint of production, while the provinces (Henan, Shandong) with higher agriculture production had higher footprint. Provinces with severe water stress increased from 6 in 1985 to 9 in 2009. High to severe water stress exists mainly in mega-cities and agricultural areas located in the downstream areas of the Yellow River and the Yangtze River in North and Central China. The outlook for water resources pressure in China is not optimistic, with areas of stress expanding from northern to southern of China. [ABSTRACT FROM AUTHOR]

The vast Dongting Lake in the middle Yangtze River basin, China, was occupied by Chinese Neolithic settlements starting 10 000 years ago, and rice cultivation there is probably the earliest in the world. The numerous Neolithic settlements identified by previous archaeological surveys represent the five major Neolithic cultural stages, i.e. the Pengtoushan (9000–7900 cal. yr BP), Zaoshixiaceng (7900–6800 cal. yr BP), Daxi (6800–5500 cal. yr BP), Qujialing (5500–5000 cal. yr BP), and Shijiahe (5000–4000 cal. yr BP). Using sedimentological and geoarchaeological approaches, this paper analyses the drivers of basin-scale settlement relocation in relation to lake-level fluctuations and monsoon climate variations in the Holocene. The relocation of Neolithic sites around the lake shoreline and on the adjacent floodplain, together with radiocarbon-dated stratigraphy, clearly indicates that the shape of the lake basin was an incised and elongated valley occupied by a lake in the early Holocene, which became a broader and shallower depression in the mid to late Holocene. The established lowest habitable base of the settlements positioned on the lake shore assists reconstruction of the change in lake level from 22 m at 9000 cal. yr BP to 26 m at 5500–4000 cal. yr BP, although higher and lower lake levels occurred during the intervening cultural stages. The pollen spectra reveal a warming trend throughout the Holocene with at least four major temperature cycles, driven by monsoon variations between temperate- and warm-humid conditions. In the early Holocene the climate changed from cool-dry to warm-humid, and this played a key role in developing the earliest Pengtoushan culture in the region. Subsequent climate fluctuations fit well with the advance and retreat of the lake shore, also coevally with Neolithic site movements in the lake region. In this study we show how geoarchaeological evidence can be used in environmental reconstruction during the Holocene. [ABSTRACT FROM AUTHOR]

This paper discusses projections of heavy rainfall events in China during the 21st century based on daily precipitation data from the Fourth Assessment Report's (AR4) Coupled General Circulation Models (CGCM). Results show that all three experimental scenarios (scenarios A2, A1B, and B1) project consistent changes in frequency and intensity of heavy rainfall at the end of 21st century. In the regions of Northeast China and North China, there are no significant changes in frequency but there are remarkable increases in intensity of heavy rainfall, indicating that enhanced intensity is the main contributor to increased ratios of heavy rainfall to total annual precipitation in these regions. In regions of the lower reaches of Yangtze River and South China, increases in the amount of heavy rainfall are closely associated with increased frequency and increased intensity. Projected frequencies of heavy rainfall at the end of 21st century increase by 30.9 ∼ 56.6% in the Yangtze River and 35.9 ∼ 50.2% in South China compared to the period of 1980-1999, and projected intensities increase by 1.0 ∼ 5.7% and 2.8 ∼ 6.3%, respectively. Additionally, the ratios of heavy rainfall to total annual precipitation increase by 2.3 ∼ 5.4% in the Yangtze River and 1.8 ∼ 3.8% in South China. The significant increases of heavy rainfall ratios indicate that as the climate warms, heavy rainfall events are expected to increase at rates that are much faster than increases in total precipitation amounts, indicating that China will experience increased amounts of flooding. These results are substantially consistent among the three IPCC (Intergovernmental Panel on Climate Change) scenarios. The increased probability of heavy rainfall events in China is closely connected with increased transportation of water vapour from the Arabian Sea and the South China Sea. Additionally, atmosphere stratification has become increasingly unstable, which has provided a favorable background for the initiation of heavy rainfall at the end of the 21st century. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

This paper reviews the land cover changes on the Tibetan Plateau during the last 50 years partly caused by natural climate change and, more importantly, influenced by human activities. Recent warming trends on the plateau directly influence the permafrost and snow melting and will impact on the local ecosystem greatly. Human activities increased rapidly on the plateau during the last half century and have significant impacts on land use. Significant land cover changes on the Tibetan Plateau include permafrost and grassland degradation, urbanization, deforestation and desertification. These changes not only impact on local climate and environment, but also have important hydrological implications for the rivers which originate from the plateau. The most noticeable disasters include the flooding at the upper reaches of Yangtze River and droughts along the middle and lower reaches of Yellow River. Future possible land cover changes under future global climate warming are important but hard to assess due to the deficits of global climate model in this topographically complex area. Integrated investigation of climate and ecosystems, including human-beings, are highly recommended for future studies. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the variability of daily temperature in the Yangtze River Delta (YRD) for the period 1958–2007 was investigated by selecting three typical temperature variables (daily minimum, mean and maximum temperatures) and the diurnal temperature range (DTR). Three variability patterns of daily mean temperature and two variability patterns of daily minimum and maximum temperatures were first classed, and then statistical properties of three temperature variables in 1958–1985 and 1986–2007 were analyzed. After that, temporal trends of three temperature variables and DTR were detected. Finally, the impacts of urbanization on the variability of daily temperature were investigated. Results indicate that: (1) daily mean temperature shows more complex variability than daily minimum and maximum temperatures; (2) in 1986–2007 three temperature variables have bigger mean values but smaller C v (coefficient of variance) values, and are more close to normal probability distribution; (3) three temperature variables show positive trends in 1986–2007, and the increase of daily mean temperature is more due to the increase of daily minimum temperature in the northern YRD but due to daily maximum temperature in the mid and southern YRD; (4) in the mid and southern YRD, daily maximum temperature has bigger increasing magnitude than daily minimum temperature in 1986–2007, causing positive trend of DTR; and (5) rapid urbanization causes normal distribution of three temperature variables, and notably increasing magnitude of daily temperature and DTR in 1986–2007 at the lower reaches of the Yangtze River and the Hangzhou Bay. [Copyright &y& Elsevier]

Abstract: Changes on water resources volume of 1960–2007 in the Upper Reaches of the Yangtze River are discussed in this paper. A time series (1960–2007) and its spatial patterns of actual evapotranspiration (ETa) estimation are analyzed based on Advection-Aridity model (A–A model) with selected parameters for 72 meteorological stations in the upper reaches of the Yangtze River Basin. The result indicates that average ETa of the basin changed in stages: slight increases in the first decade; a drop followed by fluctuations and lower increases in the next ten years; and then a dramatic decline in the latest decade, with three abrupt change years detected in the early 1970s, 1990s, and 2000s. ETa increases from mountainous northwest areas to plains in eastern areas, with significant decreases in plain regions and increases in the mountain region. ETa in the Sichuan Basin is found to decrease at the most rapid rate, and ETa in the sub-area to the south of the upland mountain region is increasing significantly. Such patterns of spatial trend in ETa result in reductions in regional variation, both annually and in all seasons. The change in ETa of this area is believed to be related to local water resource changes, and is impacted by the changes in climate factors. Temperature of this area has increased, and sunshine duration hours have shortened, leading to a reduction in net radiation. Relative humidity also has decreased. Comprehensively, reduction in both energy and moisture supply for evapotranspiration result in an increasing ETa. Moreover, a sharp drop of ETa occurred in the early 2000s, and meteorological factors including wind speed also show abrupt change to different extents. The impact of ETa on regional water balance at both inter-annual and intra-annual scales is also discussed in this study. [Copyright &y& Elsevier]

Abstract: This paper examines the spatial variation of sediment yield in the Yangtze basin in China, a large basin with complex geology, climate, land-use history, and extensive sediment monitoring. 287 stations with drainage area less than 10,000km2 were used to study the scale effects of sediment yield. In order to develop scale relations for regional sediment yield, the whole study area was divided into eight sub-basins. Relation between specific sediment yield and drainage basin area was built for each sub-basin. Regional scaling relation was analyzed based on landforms, geology, lithology and land-use of each sub-basin. Three regional trends were identified in relation to the drainage area: (1) a declining trend, due to soil erosion on heavily cultivated steep land and the storage of sediment in floodplains; (2) a flat trend, due to mass movement on the upper reach and heavy agricultural disturbance on the middle and lower reaches; and (3) an increasing trend, due to downstream recruitment of sediment from land downstream where slope farming and deforestation occurred. Using these developed relations, areally adjusted sediment yield maps were created over the entire Yangtze basin. [Copyright &y& Elsevier]

Abstract: With the increasing accumulation of data on early rice farming in the middle and lower reaches of the Yangtze River, this region has become one of the most important places to trace the origin and development of agriculture. This paper gives a general evaluation of some early rice sites, including the Hemudu, Majiabang, Kuahuqiao, and Shangshan cultures in the lower reaches of the Yangtze River; the Pengtoushan and Chengbeixi cultures, and the Xianrendong, Diaotonghuan and Yuchanyan sites in the middle reaches of the Yangtze River; and the Jiahu site in North China, and recognizes three main development stages of the prehistoric rice forming in China, i.e. initial stage (before 8000 BC, approximately equal to Mesolithic Age), developing stage (between 8000 BC and 5000 BC) and maturating stage (since 5000 BC). The initiation of agriculture is suggested to come with the establishment of more or less sedentary residences, which coexists with the occurrence of pottery making. Warming climate after the last glaciations is considered as a major factor that allowed the distribution of the wild rice northward. Food requirement and storage are another factor in initiating early rice farming, while the increasing population and the Holocene Maximum warm climate condition might greatly promote its development. Evidence from the middle and lower Yangtze River area exhibits the transitional process from a hunting and gathering society to an agriculture-oriented society. [ABSTRACT FROM AUTHOR]

Abstract: Frequently unknown climate change increases the risk of agriculture, more attention have been paid to agricultural system itself in the research field, but few has been attached to the perspective of social dimension. Based on the research on Yangtze River Basin of China, the paper has adopted vulnerability theory including the exposure of agricultural ecosystem, farmers’ sensitivity to exposure and adaptive capacity to climate risk, to explain farmer''s adaptation to climate risk. It concludes that climate change has increased climate risk in agriculture and the uncertainty of agricultural production. Confronting climate risk in agriculture, different farming bodies have shown different farm and off-farm/non-farm adaptations in pre-risk, during risk and post-risk, which has reduced their short-term vulnerability. Household life cycle, pressure, institution, available resources and technologies are the key influential factors. From the adaptation in long term, it still requires external support and more investment including agricultural insurance system, village-level information and technology dissemination mechanism. [Copyright &y& Elsevier]

A typhoon is one of the most dangerous natural disasters in the Yangtze River Delta of China. Based on an integrated assessment of the disaster risk elements, including hazard factor, exposure, and vulnerability, the risk level of a typhoon disaster for the Yangtze River Delta as a county-level unit was ultimately determined. The result shows that the risk levels of typhoon hazard factor are gradually weakened from the southeastern coastal areas to the northwest, and the highest-risk areas are located in the southeastern coastal regions. Due to many towns, dense population, a developed economy, and a huge disaster-bearing body in the north of the Yangtze River Delta, which is also located on the plain for a high susceptibility to a disaster-breeding environment, the exposure risk level in the northern areas is higher than in the south. The most vulnerable counties are Chun'an, Xianju, Tiantai, and Sanmen in Zhejiang Province, and Baoying and Xinghua in Jiangsu Province. The highest-risk areas for a typhoon disaster are primarily located in the southeastern coastal areas of Zhejiang Province, Hangzhou Bay, and Shanghai near the Yangtze River Estuary, while the lowest-risk areas are distributed in the western portion of Hangzhou and the northern area of the Yangtze River Delta. [ABSTRACT FROM AUTHOR]

The streamflow and water level complexity of the Poyang Lake basin has been investigated over multiple time-scales using daily observations of the water level and streamflow spanning from 1954 through 2013. The composite multiscale sample entropy was applied to measure the complexity and the Mann-Kendall algorithm was applied to detect the temporal changes in the complexity. The results show that the streamflow and water level complexity increases as the time-scale increases. The sample entropy of the streamflow increases when the time-scale increases from a daily to a seasonal scale, also the sample entropy of the water level increases when the time-scale increases from a daily to a monthly scale. The water outflows of Poyang Lake, which is impacted mainly by the inflow processes, lake regulation, and the streamflow processes of the Yangtze River, is more complex than the water inflows. The streamflow and water level complexity over most of the time-scales, between the daily and monthly scales, is dominated by the increasing trend. This indicates the enhanced randomness, disorderliness, and irregularity of the streamflows and water levels. This investigation can help provide a better understanding to the hydrological features of large freshwater lakes. Ongoing research will be made to analyze and understand the mechanisms of the streamflow and water level complexity changes within the context of climate change and anthropogenic activities. [ABSTRACT FROM AUTHOR]

The water-surface areas of the lakes in the mid-lower reaches of the Yangtze River, China, have undergone significant changes under the combined impacts of global climate change and local anthropogenic stress. As a typical lake in this region, the Honghu Lake features water-surface area variations that are documented in this study based on high-resolution remote sensing images from the 1990s to 2013. The impact of human activities is analyzed by a novel method based on land use data. The relative impacts of each driving force are further distinguished by the statistical analysis method. Results show that the water-surface area has significant inter-annual and seasonal variabilities, and the minimum of which generally occurs in spring. The degree to which climate factors and land use structure affect the water-surface area varies between different stages. In the April-May period, the sum of the water demands of paddies and aquaculture has a negative effect that is greater than the positive effect of the difference between the monthly precipitation and monthly evaporation. In the June-October period, the precipitation features a positive impact that is greater than the negative effect of the water demand of agriculture. Meanwhile, climate factors and human activities have no influence on the lake area in the November-March period. With the land use being altered when annual precipitations are close in value, paddy field areas decrease, ponds areas increase, and the water demand of agriculture rises in both flood and drought years. These findings provide scientific foundation for understanding the causes of water-surface area variations and for effectively maintaining the stability of the Honghu Lake area through adjustments in land use structure. [ABSTRACT FROM AUTHOR]

China's water source includes the headwaters of the Yangtze, Yellow, and Lantsang (the Mekong outside China) rivers and is located in the heart of the Tibet Plateau, which has an average altitude of 4,200 m. Due to the importance of the Water Tower to the ecological security and economic development of China and South Asia, desertification issues in this region have attracted the attention of the public, scholars, government officials, and international organizations. Combined satellite-derived vegetation indices, field surveys, and surface meteorological data to evaluate the effects of climate change, our analyzed results show that during the early part of the twenty-first century, no desertification occurred in these source areas. However, between 2000 and 2010, human activities may have had a negative effect on about 50 % of the region, although vegetation rehabilitation still occurred during this period. Although the Ecological Protection and Restoration Program was launched in China in 2005, the negative impacts of human activities such as agriculture have still increased in the water source. Vegetation rehabilitation in these source areas appears to be driven mainly by the effect of climate change, and it is possible that human activities do not play an important role in regional ecological and environmental evolution. Although at present we cannot determine whether it was rising temperatures or increasing precipitation that enhanced vegetation growth in the region, our results show that the dominant factors controlling vegetation rehabilitation in China's Water Tower are related to climate. [ABSTRACT FROM AUTHOR]

Under natural conditions, the evolution of lake trophic status is not only influenced by climatic and hydrological factors but also by the biological interactions and feedbacks occurring within the lake ecosystem. To envision long-term changes of lake trophic status in several shallow lakes from the Yangtze River basin, we focused on variations in nutrient level and attempted to use both hydrologic- and ecodynamic-based physical models. One was an equivalent-hydrology model with external driving forces from catchment climate and hydrology changes (Model 1), the other was a dynamic model with internal driving forces from the biological interactions within the lake ecosystem (Model 2). Two models were employed in order to distinguish the effects of climate change (by Model 1) from ecosystem feedbacks (by Model 2) on the long-term lake nutrients changes and to further determine which driver was the primary cause for the changes. Variations in lake producer biomass and total phosphorus (TP) were simulated for a historic 200-yr period (1640–1840 AD) in Lake Taihu and seven other similar lakes from the Yangtze River basin after calibration and validation of the control runs (1950–2000 AD). Results showed that (1) TP simulations by Model 1 and Model 2 were mostly consistent with the reconstructed nutrient records from lake sediment cores; (2) the long-term variations of lake nutrients were primarily affected by precipitation under the influence of climate change and the decreases in lake nutrients were more likely to respond to the dry climate; and (3) approximately 49% of the variability in nutrient concentrations were contributed by the feedback of biological interactions in the lake ecosystem. The study results provide a scientific basis for long-term control of nutrients in lakes along the middle–lower reaches of the Yangtze River. [ABSTRACT FROM AUTHOR]

The daily precipitation data of 740 stations in China (1958-2001) and the daily upper air data of European Centre for Medium-Range Weather Forecasts reanalysis dataset (1958-2001) are used to define an East Asian summer monsoon (EASM) index based on dynamic and thermal factors. The index is used to represent the front (or leading edge) of EASM to describe and characterize the advance and retreat of EASM objectively. During 1958-2001, the EASM movement underwent three interdecadal abrupt shifts in 1965, 1980 and 1994, respectively. During 1958-1964, the front primarily concentrated in South China and North China, while it stayed at the mid- and lower-Yangtze River for a short period. During 1965-1979, the front was located in South China and the lower reach of Yellow River for a long time. During 1980-1993, the time in which the front of EASM stayed at the mid- and lower-Yangtze River was much longer, but it settled in North China for just a short time. During 1994-2001, the front generally concentrated in the south of the mid- and lower-Yangtze River. The three interdecadal shifts of EASM directly resulted in rainfall anomalies, as well as frequent disasters of flood and drought in East China. [ABSTRACT FROM AUTHOR]

Variability of the climate in the headwater drainage basins of the Yangtze River and Yellow River during 1961-2010 was investigated by examining four typical climatic variables: daily minimum, mean, and maximum temperatures and daily precipitation. The results indicate that the temporal trends vary among the climatic variables and the time periods examined. The increase in daily minimum temperature began later than the daily mean and maximum temperatures, but the increase rate of the former was relatively greater after 1985. The abrupt increases in precipitation that occurred near 1978 were much clearer than the three temperature variables. Four dominant periodicities (3, 7, 11, and 18-20 yr) of temperature and precipitation were identified, and these variation patterns directly determined the periodic discharge variations in the two rivers. Under climate change impacts, periodic variations in temperature and precipitation at long temporal scales were intensified after the 1980s. Comparatively, climate change more severely impacts the minimum temperature and precipitation than the maximum and mean temperatures in the study area, and the variability of daily precipitation is more complex than the three temperature variables. Overall, the headwater drainage basin of the Yellow River is more susceptible to climate change compared with the other basin. After 2008, the increase rate of temperature (especially the daily mean and minimum temperatures) became greater, and precipitation showed a downward trend in the study areas. These trends are unfavorable for the safety of water resources and for eco-environmental safety in the two basins. [ABSTRACT FROM AUTHOR]

This study analyzed the interdecadal changes in the diurnal variability of summer (June-August) precipitation over eastern China during the period 1966-2005 using hourly station rain gauge data. The results revealed that rainfall diurnal variations experienced significant interdecadal changes. Over the area to the south of the Yangtze River, as well as the area between the Yangtze and Yellow Rivers, the percentages of morning rainfall (0000-1200 LST) to total rainfall in terms of amount, frequency and intensity, all exhibited increasing interdecadal trends. On the contrary, over North China, decreasing trends were found. As a result, diurnal rainfall peaks also presented pronounced interdecadal variations. Over the area between the Yangtze and Yellow Rivers, there were 16 out of 46 stations with afternoon (1200-0000 LST) frequency peaks in the first 20 years of the 40-year period of study, while only eight remained in the latter 20 years. In North China, seven stations experienced the opposite changes, which accounted for about 21% of the total number of stations. The possible causes for the interdecadal changes in diurnal features were discussed. As the rainfall in the active monsoon period presents morning diurnal peaks, with afternoon peaks in the break period, the decrease (increase) of rainfall in the active monsoon period over North China (the area south of the Yangtze River and the area between the Yangtze and Yellow Rivers) may contribute to interdecadal changes in diurnal rainfall variability. [ABSTRACT FROM AUTHOR]

Regional characteristics of extreme precipitation indices (EPI) of precipitation magnitude, intensity and persistence were analyzed based on a daily rainfall dataset of 135 stations during the period of 1961-2010 in the Yangtze River basin, China. The spatial distribution of temporal trends of the selected indices was regionally mapped and investigated by using non-parametric test method. Future projections of EPI changes derived from the output of general circulation model (HadCM3) under the SRES A2 and B2 emission scenarios were downscaled and analyzed. The results show that: (a) there is not a general significant increasing or decreasing trend in EPI for the Yangtze River basin based on historical recorded data; (b) the automated statistical downscaling method-based precipitation captures some spatial distribution of the EPI and the bias correction can improve the simulation results; (c) a mixed pattern of positive and negative changes is observed in most of the nine indices under both scenarios in the first half of twenty-first century, and they increase continuously in the second half of twenty-first century; and (d) the concurrent increase in the heavy rain and drought indices indicates the possibility of the sudden change from drought to water logging in the lower region of Yangtze River basin. [ABSTRACT FROM AUTHOR]

Pollen and charcoal records of a 150 cm long lake sediment core from Taibai Lake in the middle reach of the Yangtze River reveal seven major changes in regional vegetation over the last 1500 years. During the period c. ad 480–710, evergreen broadleaved forest dominated by Castanopsis/Lithocarpus and evergreen oaks occurred in the Taibai Lake catchment. From c. ad 710 to 1050, the vegetation shifted to a mixed conifer and broadleaved forest, with Pinus expanding at the expense of Castanopsis/Lithocarpus. Between c. ad 1050 and 1320, evergreen broadleaved forest reoccupied the studied area. From c. ad 1320 to 1650, the area of primary forest decreased markedly with synchronous reduction in broadleaved trees and Pinus. Between c. ad 1650 and 1740, the biomass declined rapidly, while secondary Pinus forest began to expand. During c. ad 1740–1950, forest extent increased slightly compared with the previous stage, but the landscape was still secondary forest with the minimum proportion of broadleaved trees. After c. ad 1950, the biomass in the surrounding area was very low, with vegetation types similar to that at present (secondary Pinus forest and mixed conifer and broadleaved forest). A detrended correspondence analysis (DCA) with 125 samples and 34 main pollen types is used to separate human and climatic impacts on vegetation. Then, the pollen assemblage, DCA, charcoal record, and magnetic susceptibility are combined to discuss the key factors inducing these vegetation changes. The vegetation changes were mainly controlled by the climatic changes, with the weak impacts of human activities before c. ad 1320. Since then, the intensity of human influences on vegetation increased gradually, entering a transitional period of main controlling factors of vegetation changes from nature to human activities. After c. ad 1740, the vegetation changes were chiefly controlled by human activities, and the climatic signal was weak. [ABSTRACT FROM AUTHOR]

The projected changes of precipitation and temperature in the Yangtze River Basin in the 20th Century from 20 models of the CMIP3 (phase 3 of the Coupled Model Inter-comparison Project) dataset are analyzed based on the observed precipitation and temperature data of 147 meteorological stations in the Yangtze River Basin. The results show that all models tend to underestimate the annual mean temperature over the Yangtze River Basin, and to overestimate the annual mean precipitation. The temporal changes of simulated annual mean precipitation and temperature are broadly comparable with the observations, but with large variability among the results of the models. Most of the models can reproduce maximum precipitation during the monsoon season, while all models tend to underestimate the mean temperature of each month over the Yangtze River Basin. The Taylor diagram shows that the differences between modeled and observed temperature are relatively smaller as compared to differences in precipitation. For a detailed investigation of regional characteristics of climate change in the Yangtze River Basin during 2011-2050, the multi-model ensembles produced by an upgraded REA method are carried out for more reliable projections. The projected precipitation and temperature show large spatial variability in the Yangtze River Basin. Mean precipitation will increase under the A1B and B1 scenarios and decrease under the A2 scenario, with linear trends ranging from −21 to 28.5 mm/decade. Increasing mean temperature can be found in all scenarios with linear trends ranging from 0.15 to 0.48°C/decade. Grids in the head region of the Jingshajiang catchment show distinct increasing trends for all scenarios. Some physical processes associated with precipitation are not well represented in the models. [ABSTRACT FROM AUTHOR]

Using generalised Pareto distribution (GPD) function, the regional characteristic of extreme monthly low temperatures (EMLT) distribution during 1960-2007 in China is studied, and the potential impact of climate warming on EMLT regions in China is analysed. The results show that EMLT space distribution has latitudinal difference in China. Higher-value EMLT events are likely to happen in northeastern and southwestern China, while EMLT variability and occurrence probability of high-value EMLT events are less in the Yangtze and Huaihe River basin and the coast of southern China. The study indicates that climate warming impacts EMLT, and EMLT distribution responds to the climate warming over most areas of China. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Many impact studies require climate change information at a finer resolution than that provided by general circulation models (GCMs). Therefore the outputs from GCMs have to be downscaled to obtain the finer resolution climate change scenarios. In this study, an automated statistical downscaling (ASD) regression-based approach is proposed for predicting the daily precipitation of 138 main meteorological stations in the Yangtze River basin for 2010-2099 by statistical downscaling of the outputs of general circulation model (HadCM3) under A2 and B2 scenarios. After that, the spatial-temporal changes of the amount and the extremes of predicted precipitation in the Yangtze River basin are investigated by Mann-Kendall trend test and spatial interpolation. The results showed that: (1) the amount and the change pattern of precipitation could be reasonably simulated by ASD; (2) the predicted annual precipitation will decrease in all sub-catchments during 2020s, while increase in all sub-catchments of the Yangtze River Basin during 2050s and during 2080s, respectively, under A2 scenario. However, they have mix-trend in each sub-catchment of Yangtze River basin during 2020s, but increase in all sub-catchments during 2050s and 2080s, except for Hanjiang River region during 2080s, as far as B2 scenario is concerned; and (3) the significant increasing trend of the precipitation intensity and maximum precipitation are mainly occurred in the northwest upper part and the middle part of the Yangtze River basin for the whole year and summer under both climate change scenarios and the middle of 2040-2060 can be regarded as the starting point for pattern change of precipitation maxima. [ABSTRACT FROM AUTHOR]

This review compares and contrasts the environmental changes that have influenced, or will influence, fishes and fisheries in the Yangtze and Mekong Rivers. These two rivers have been chosen because they differ markedly in the type and intensity of prevailing threats. The Mekong is relatively pristine, whereas the Three Gorges Dam on the Yangtze is the world's largest dam representing the apotheosis of environmental alteration of Asian rivers thus far. Moreover, it is situated at the foot of a planned cascade of at least 12 new dams on the upper Yangtze. Anthropogenic effects of dams and pollution of Yangtze fishes will be exacerbated by plans to divert water northwards along three transfer routes, in part to supplement the flow of the Yellow River. Adaptation to climate change will undoubtedly stimulate more dam construction and flow regulation, potentially causing perfect storm conditions for fishes in the Yangtze. China has already built dams along the upper course of the Mekong, and there are plans for as many as 11 mainstream dams in People's Democratic Republic (Laos) and Cambodia in the lower Mekong Basin. If built, they could have profound consequences for biodiversity, fisheries and human livelihoods, and such concerns have stalled dam construction. Potential effects of dams proposed for other rivers (such as Nujiang-Salween) are also cause for concern. Conservation or restoration measures to sustain some semblance of the rich fish biodiversity of Asian rivers can be identified, but their implementation may prove problematic in a context of increasing Anthropocene alteration of these ecosystems. [ABSTRACT FROM AUTHOR]

Quantitative evaluations of the impacts of climate change on water resources are primarily constrained by uncertainty in climate projections from GCMs. In this study we assess uncertainty in the impacts of climate change on river discharge in two catchments of the Yangtze and Yellow River Basins that feature contrasting climate regimes (humid and semi-arid). Specifically we quantify uncertainty associated with GCM structure from a subset of CMIP3 AR4 GCMs (HadCM3, HadGEM1, CCSM3.0, IPSL, ECHAM5, CSIRO, CGCM3.1), SRES emissions scenarios (A1B, A2, B1, B2) and prescribed increases in global mean air temperature (1 °C to 6 °C). Climate projections, applied to semi-distributed hydrological models (SWAT 2005) in both catchments, indicate trends toward warmer and wetter conditions. For prescribed warming scenarios of 1 C to 6 C, linear increases in mean annual river discharge, relative to baseline (1961-1990), for the River Xiangxi and River Huangfuchuan are +9% and 11% per +1 C respectively. Intra-annual changes include increases in flood (Q05) discharges for both rivers as well as a shift in the timing of flood discharges from summer to autumn and a rise (24 to 93%) in dry season (Q95) discharge for the River Xiangxi. Differences in projections of mean annual river discharge between SRES emission scenarios using HadCM3 are comparatively minor for the River Xiangxi (13 to 17% rise from baseline) but substantial (73 to 121%) for the River Huangfuchuan. With one minor exception of a slight (-2%) decrease in river discharge projected using HadGEM1 for the River Xiangxi, mean annual river discharge is projected to increase in both catchments under both the SRES A1B emission scenario and 2 rise in global mean air temperature using all AR4 GCMs on the CMIP3 subset. For the River Xiangxi, there is substantial uncertainty associated with GCM structure in the magnitude of the rise in flood (Q05) discharges (-1 to 41% under SRES A1B and -3 to 41% under 2 global warming) and dry season (Q95) discharges (2 to 55% under SRES A1B and 2 to 39% under 2° global warming). For the River Huangfuchuan, all GCMs project a rise in the Q05 flow but there is substantial uncertainty in the magnitude of this rise (7 to 70% under SRES A1B and 2 to 57% under 2 global warming). Differences in the projected hydrological changes are associated with GCM structure in both catchments exceed uncertainty in emission scenarios. Critically, estimated uncertainty in projections of mean annual flows is less than that calculated for extreme (Q05, Q95) flows. The common approach of reporting of climate change impacts on river in terms of mean annual flows masks the magnitude of uncertainty in flows that are of most importance to water management. [ABSTRACT FROM AUTHOR]

Two-year (June 2003–May 2005) precipitation samples were collected from three monitoring sites with similar economy development level in the Yangtze River Delta Region of China to investigate the spatial–temporal variation of inorganic N wet deposition. The results showed that the Yangtze River Delta Region had higher inorganic N wet deposition than the northwestern, northern, or southern China. There was spatial variation of inorganic N wet deposition. The positive relationship between inorganic N deposition and precipitation suggested that rainfall amount might be an important factor influencing the wet deposition of inorganic N. Deposition of inorganic N occurred mainly in the spring and summer season (March–August; 70% of the annual total), which was in accord with seasonal distribution of precipitation. However, a negative logarithmic relation between rainfall and inorganic N concentration in rainwater indicated the dilution effect of rainwater on inorganic N concentration. Distinguished variation of NH4 +/NO3 − ratio in wet deposition existed in the different time scale. NH4 +/NO3 − ratio evidently decreased from 6 in 1980s to 1.2 in 2003/2005 and greatly varied between 0.3 and 9.9 within a year. NH4 +/NO3 − ratio peaked in accordance with nitrogen-fertilizing time during crop growing season. Annual alternate appearance of the 15N-enriched and 15N-depleted periods coincided with the temporal variation of NH4 +/NO3 − ratio, which was closely related to the timing of fertilization and seasonal climate changes, suggesting the effect of NH4 + sources in the wet deposition. [ABSTRACT FROM AUTHOR]

In this study, the moisture source/sink and long-distance moisture transport associated with the summer precipitation in the mid-lower reaches of the Yangtze River Valley (YRV) over China have been investigated based on both data analysis and numerical simulations using the regional climate model RegCM3. The study focused on both a case of the 1998 summer flood events and the interannual variation of summer precipitation during 1961–2005 in the YRV. The results show that (1) the low latitudinal band from the Bay of Bengal, Indochina Peninsula, South China Sea to the Philippine Island is the major moisture source region for the summer precipitation in the YRV; (2) an eastward moisture transport from the Bay of Bengal and a westward moisture transport from the Philippines Sea meet at the South China Sea, where a main water vapor channel forms and advances north-northwestward and turns northeastward in the vicinity of the eastern Tibetan Plateau and South China to the YRV; and (3) the long-distance moisture transport from the eastern Indian Ocean-South China Sea to the YRV contributes to more than half of the summer precipitation in the YRV. Furthermore, it is shown that RegCM3 driven by the NCEP/NCAR reanalysis is able to reproduce the overall climatological water vapor transport in East Asia and the features of the water vapor flux for flooding and drought years in the YRV as well as simulate the YRV flood events in the summer of 1998 reasonably well. [ABSTRACT FROM AUTHOR]

In the source regions of the Yangtze and Yellow Rivers of China, glaciers, frozen ground, the hydrological system, and alpine vegetation have changed over the past decades years. Climatic causes of these variations have been analyzed using mean monthly air temperature and monthly precipitation between 1956 and 2000, and monthly evaporation from φ20 evaporation pans between 1961 and 1996. In the source region of the Yangtze River, lower temperature and plentiful precipitation during the 1960s and continuing into the early 1980s triggered a glacier advance that culminated in the early 1990s, while a robust temperature increase and precipitation decrease since 1986 has forced glaciers to retreat rapidly since 1995. Permafrost degradation is another consequence of the climatic warming. The variations in the hydrological system and alpine vegetation are controlled mainly by the climate during the warm season. Warmer and drier summer climate is the major cause of a degradation of the vegetation, desiccation of the high-cold marshland, a decrease in the areas and numbers of lakes and rivers in the middle and north source regions of the Yangtze and Yellow Rivers, and a reduction in surface runoff in the source region of the Yangtze River for the last 20 years. The causes of eco-environmental change in Dari area, near the outlet from the source area of the Yellow River, are different from those elsewhere in the study area. A noticeable reduction in runoff in the source region of the Yellow River and degradation of alpine vegetation in Dari area are closely related to the permafrost degradation resulting from climate warming. [ABSTRACT FROM AUTHOR]

The article offers information on the climactic teleconnections of summer monsoon streamflow to the Three Gorges Dam (TGD) at the Yangtze River Basin in China. From the period of 1882 to 2003, the summer monsoon inflow was analyzed at Yichang hydrological station (YHS). Statistical analysis was utilized to create a probative model for summer streamflow, followed by linear correlation maps using three-month ahead climate fields to determine the regions that exhibit climactic influences with streamflow at Yichang. The analysis shows regions in the eastern India and western Pacific oceans influences the YHS streamflow. It is inferred that an accurate climactic prediction can provide guidance for water management in the Yangtze River Basin.

Although satellite radar altimetry was developed and optimized for open oceans, it has been used to monitor variations in the level of inland water-bodies such as lakes and rivers. Here, for the first time, we have further used the altimetry-derived variation of water level for estimating the fluctuation of water storage as an addition to the present in situ water storage estimation systems to be used in remote areas and in emergency situation such as in the events flooding monitoring and for studying the effect of climate change. Lake Dongting, the second largest lake in China, influenced frequently by flooding, was, therefore, chosen to demonstrate the potential of the technique. By using the concept of an “assumed reference point”, we converted Topex/Poseidon satellite altimetry data on water level variations in Lake Dongting to “water level” data. The “water level” time-series data and in situ water storage were used to establish a rating curve. From the rating curve, we converted data on “water level” derived from seven years (1993–1999) of Topex/Poseidon data to actual water storage in Lake Dongting. The result reveals that the seasonal and annual fluctuations of water storage occurred during the 1990s with a more frequent flooding at the late 1990s' especially the flooding in whole catchment level in 1998 and 1999. The study supports the usefulness of satellite altimetry for dense and continuous monitoring of the temporal variations in water dynamic in moderate to large lakes. [ABSTRACT FROM AUTHOR]