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Abstract: The suspended sediment deposition (SSD) in the alluvial reach between the Qingtongxia station and the Toudaoguai station of the upper Yellow River has shown a dramatic variation since 1952. However, its spatial and temporal changing pattern and driving factors are still not clear. This paper examines the detailed spatial and temporal variations of the SSD based on the annual suspended sediment load at five gaging stations located in this alluvial reach in 1952–2007. The mean annual SSDs in four sub-reaches (Qingtongxia–Shizuishan, Shizuishan–Bayangaole, Bayangaole–Sanhuhekou, and Sanhuhekou–Toudaoguai) were calculated and analyzed for different periods. The mean annual kilometric SSDs in 1952–2007 were −0.228∗105, 0.97∗105, 0.165∗105 and 0.006∗105 ta−1 km−1 in the four sub-reaches, respectively, with the highest SSD occurred in the Shizuishan–Bayangaole sub-reach. Results also suggested that SSD was mainly accumulated in 1952–1959 before major reservoirs were constructed and in 1986–2007 after three major reservoirs (Qingtongxia, Liujiaxia and Longyangxia) were constructed in the main stream. During 1960–1985, all sub-reaches except the Shizuishan–Bayangaole sub-reach experienced channel erosion. Although climate change may play some roles, the changes in SSD were mainly influenced by human activities. In particular, the water and soil conservation actions, such as the construction of check dams from 1958 in upper stream tributaries, intercepted significant amount of suspended sediment and cause the net erosion of the main channel in the 1960s. The operation of the Qingtongxia reservoir reduced the SSD in this downstream reach in the 1970s and 1980s because upper stream suspended sediment was trapped by the reservoir and reservoir-released relative clear water scoured the downstream channel. Although the Liujiaxia and Longyangxia reservoirs trapped relatively small amount of suspended sediment, they stored a large amount of water during the flood season, reducing the discharge and the erosion capability of the downstream flow. Therefore, this operation mode may increase the SSD in this river reach. In addition, with the gradual loss of the Qingtongxia reservoir''s capacity in sediment storage, more suspended sediment was released to the downstream channel, causing strong SSD in this reach after 1990. [Copyright &y& Elsevier]

Abstract: This paper is to highlight the threatening of climate change on the water shortage problem in North China, a semi-arid and arid area. Observations show that the runoff of the major rivers is decreasing dramatically especially in the lower reaches where water ishighly demanded. Most noticeable are the dry-outs of the Yellow River, the so-called ‘mother river of China’.Water scarcity would be the most front challenge for the society and economy in China, especially the urban area with extremely high population density. The government already paid attention to the deepening of the underground water level at Beijing. Sustainable water resource management should the top priority for the local community to adapt to climate change. Studies show that human activities heavily impact on the local climate and environment in China and a dramatics amount of clean water is wasted or polluted. [Copyright &y& Elsevier]

Fluvial suspended sediment has multi-fold environmental implications and the study of the variation in suspended sediment load (SSL) of rivers is important both in environmental earth sciences and in river environmental management. Based on data collected for the upper Yellow River of China in the past 50-60 years, the purpose of this study is to elucidate the impact of human activity and climate change on SSL, thereby to provide some knowledge for the improvement of the drainage basin management. The results show that the SSL of the upper Yellow River exhibited a remarkable decreasing trend. A number of reservoirs trapped a considerable amount of sediment, resulting in a reduction in SSL at Toudaoguai station, the most downstream station of the upper Yellow River. The analyses based on Mann-Kendall'U and double-mass plot indicate some turning points, which were caused by the Liujiaxia and Longyangxia Reservoirs, two major reservoirs on the upper Yellow River. The implementation of soil and water conservation measures reduced the runoff coefficient, and therefore, the intensity of soil erosion. The climate change also played a role in reducing sediment yield. The increase in air temperature enhanced the evapo-transpiration and reduced the runoff, by which the SSL decreased. The decreased frequency of sand-dust storms reduced the amount of wind-blown, sand and dust to the river reaches located in desert, also reducing the SSL. Seven influencing variables are selected to describe the changing human activity and climate. As some of the influencing variables are strongly inter-correlated, the principle component regression was used to establish the relationship between SSL and the influencing variables. The squared multiple correlation coefficient is R = 0.823. Some further research is suggested with the minerals and pollutants related with the SSL. [ABSTRACT FROM AUTHOR]

The article discusses the possibility that the glaciers of the Tibetan plateau could be melted by global warming. This would lead to short-term floods and long-term drought for large sections of Asia, including China and India. Scientific studies are cited which indicate that glaciers around the world began to diminish in the 1950's, staged a modest comeback in the 1970's, and rapidly began shrinking again in the 1980's. Large and geopolitically important river systems such as the Yellow River and the Mekong are dependent on water from the glaciers of the Tibetan plateau.

The spatial and temporal variability of winter extreme low-temperature events and summer extreme high-temperature events was investigated using daily air temperature series (1960–2004) from 66 sites in the Yellow River basin, China, with the help of Mann–Kendall trend test method. In this study an extreme temperature event is defined by exceeding or falling below various threshold values of daily maximum and daily minimum air temperature: 90th percentile, 95th percentile for the high-temperature events; 10th percentile and 5th percentile for the low-temperature events. The analysis results indicate that: 1) significant upward trend of frequency and intensity of the high-temperature events is found in the stations in the west and north part of the Yellow River basin, but trends in most stations in the middle and lower Yellow River basin are not significant at >95% confidence level; 2) almost the whole Yellow River basin is dominated by the significant downward trend of frequency of the cold events. Stations featured by the increasing winter minimum temperature are also more than those featured by changing summer maximum temperature; and 3) annual warming trend in the Yellow River basin mainly results from the increase in winter minimum temperature. Significant warming in the upper reach of the Yellow River will be likely to threaten the availability of the water resource in the whole basin, which should draw certain concerns from local policy-makers and water resource management agency in the region. [ABSTRACT FROM AUTHOR]

Climatological features and variations of wet spells, especially their trends over China, are investigated using a dataset of 594 meteorological stations across China from 1951 to 2003. The results show that the lower the latitude is, the longer the annual duration of wet spells is. The mean annual precipitation from wet spells is higher in southeastern coastal areas and much lower in western and northern China. The longest wet spells are found in Southwest China and the eastern Tibetan Plateau. The maximum daily precipitation of wet spells decreases from the southeast to the northwest, with the highest in southeastern coastal areas and the lowest in western China. The trends of wet spells exhibit striking regional differences. In most areas of western China, the annual number of days in wet spells has slightly increased, but significantly decreased over North China, Central China and Southwest China. The annual precipitation amount from wet spells displays significant downward trends in North China, eastern Northeast China and the eastern part of Southwest China, but upward trends in the eastern Tibetan Plateau and some southeastern coastal areas. Two clearly-contrasting regions in climatic changes of wet spells are the mid-lower reaches of the Yellow River and the eastern Tibetan Plateau, characterized by a decrease of about 24 days and an increase of about 6 days in annual wet spell days from 1953 to 2003, respectively. [ABSTRACT FROM AUTHOR]

Based on monitoring data of 123 meteorological stations from 1960 to 2000 near or in the Yellow River Basin, the spatial and temporal distributions and their trends for pan evaporation (PE) are investigated in this study. The results indicate that, despite the annual mean air temperature over the Yellow River Basin has, on average, increased by 0.6° over the past 40 years, the rate of PE has steadily decreased, especially in summer and spring. Compared with the period of 1960s to 1970s, the rate of annual pan evaporation during 1980s to 1990s has decreased by 126mm or 7.0 percent Spatial distribution of the rate of change show that this kind of trend is general but not universal, PE has significantly decreased over the upper and lower reaches of the Yellow River, but increased to a small degree over the middle reaches. Further analyses show that the decrease of PE is mainly related to reductions in sunshine durations and solar irradiance, owing to more clouds and aerosols. [ABSTRACT FROM AUTHOR]