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Runoffs in the Yellow River and Yangtze River basins, China, have been changing constantly during the last half century. In this paper, data from eight river gauging stations and 529 meteorological stations, inside and adjacent to the study basins, were analyzed and compared to quantify the hydrological processes involved, and to evaluate the role of human activities in changing river discharges. The Inverse Distance Weighted (IDW) interpolation method was used to obtain climatic data coverage from station observations. According to the runoff coefficient equation, the effect of human activities and climate can be expressed by changes in runoff coefficients and changes in precipitation, respectively. Annual runoff coefficients were calculated for the period 1950-2008, according to the correlation between respective hydrological series and regional precipitation. Annual precipitation showed no obvious trend in the upper reaches of the Yellow River but a marked downward trend in the middle and downstream reaches, with declines of 8.8 and 9.8 mm/10 a, respectively. All annual runoff series for the Yellow River basin showed a significant downward trend. Runoff declined by about 7.8 mm/10 a at Sanmenxia and 10.8 mm/10 a at Lijin. The series results indicated that an abrupt change occurred in the late 1980s to early 1990s. The trend of correlations between annual runoff and precipitation decreased significantly at the Yellow River stations, with rates ranging from 0.013/10 a to 0.019/10 a. For the hydrologic series, all precipitation series showed a downward trend in the Yangtze River basin with declines ranging from about 24.7 mm/10 a at Cuntan to 18.2 mm/10 a at Datong. Annual runoff series for the upper reaches of the Yangtze River decreased significantly, at rates ranging from 9.9 to 7.2 mm/10 a. In the middle and lower reaches, the runoff series showed no significant trend, with rates of change ranging from 2.1 to 2.9 mm/10 a. Human activities had the greatest influence on changes in the hydrological series of runoff, regardless of whether the effect was negative or positive. During 1970-2008, human activities contributed to 83% of the reduction in runoff in the Yellow River basin, and to 71% of the increase in runoff in the Yangtze River basin. Moreover, the impacts of human activities across the entire basin increased over time. In the 2000s, the impact of human activities exceeded that of climate change and was responsible for 84% of the decrease and 73% of the increase in runoff in the Yellow River and Yangtze River basins, respectively. The average annual runoff from 1980 to 2008 fell by about 97%, 83%, 83%, and 91%, compared with 1951-1969, at the Yellow River stations Lanzhou, Sanmenxia, Huayuankou and Lijin, respectively. Most of the reduction in runoff was caused by human activities. Changes in precipitation also caused reductions in runoff of about 3%, 17%, 17%, and 9% at these four stations, respectively. Falling precipitation rates were the main explanation for runoff changes at the Yangtze River stations Cuntan, Yichang, Hankou, and Datong, causing reductions in runoff of 89%, 74%, 43%, and 35%, respectively. Underlying surface changes caused decreases in runoff in the Yellow River basin and increases in runoff in the Yangtze River basin. Runoff decreased in arid areas as a result of increased water usage, but increased in humid and sub-humid areas as a result of land reclamation and mass urbanization leading to decreases in evaporation and infiltration. [ABSTRACT FROM AUTHOR]

Summary: In this paper, the trends of the annual streamflow and precipitation and cross correlations between them were analyzed in nine large river basins of China during 1956–2005. The results indicate that: (1) the annual mean streamflow decreases in arid and semi-arid regions of north China; however, increasing trends occur in south and Southwest China; (2) the annual streamflow and precipitation exhibit reasonable correlation in nine large river basins except those located in inland areas. The annual streamflow over most areas of China is fed by precipitation; however, the decline in streamflow is faster than the decreases of precipitation since 1970s in the arid and semi-arid regions of north China. The relationship between the annual precipitation and streamflow presents a non-stationary state in north China. This non-stationary relationship is strongly influenced by both human activities and precipitation changes; (3) a significant increase of water use might be the major factor responsible for the steeper decline in streamflow than in precipitation in Haihe River, Yellow River and Songliao River basins in north China. In inland river areas, increase of water use and actual evapotranspiration might result in decline in streamflow although precipitation has an increase tendency. This paper sheds light on the non-stationary relationship between annual precipitation and streamflow and possible underlying causes, which will be helpful for a better understanding of the changes of precipitation and streamflow in China at large scale and in other regions of the world. [Copyright &y& Elsevier]

With global warming, climate change has tremendously changed the hydrological processes. To discover the non-linear trend of the natural runoff and its response to precipitation and temperature in the Yellow River Basin, the non-linear relationships among the runoff, precipitation and temperature are analyzed by the wavelet decomposition and reconstruction methods, partial correlation analysis and multiple linear regression analysis. The main findings of this study are: (1) The annual natural runoff, precipitation and temperature have the similar periods (27-year, 12-year), which indicates that the periodicity of the natural annual runoff has closely relationship with the regional climate change. (2) The annual runoff, precipitation and temperature exhibit five patterns non-linear variations at five time scales (1, 2, 4, 8, 16 years), that is to say, their non-linear trends are scale-dependent with time. (3) The annual natural runoff has a significant positive correlation with the precipitation and has a negative correlation with temperature. In addition, the runoff variation is more sensitive to change in precipitation than the change in temperature at all the five time scales. (4) Although the runoff and the climate change factors have non-linear trends at different time scales, the runoff has linear correlation with the temperature and the precipitation, especially at a large time scale. [ABSTRACT FROM AUTHOR]

Abstract: Long-term changes to the Yellow River delta in China have received considerable attention not only because of the growing economic importance of the delta region but also because they provide a clear example of the dominant role played by anthropogenic effects upon a large dynamic river delta. This paper presents a detailed study on the morphological consequences of reduction in river sediment load and influence of human activities based on sediment load data at three gauging stations in the upper, middle and lower reaches of the Yellow River basin from 1950 to 2007. The results indicate that sediment loads at all three gauging stations display a gradually decreasing trend over the past 58years. The primary reason for this decrease is shown to be due to various human activities, including the construction of Longyangxia and Liujiaxia reservoirs in the upper reaches, water–soil conservation practices and the commissioning of Sanmenxia and Xiaolangdi reservoirs in the middle reaches. It is estimated that water–soil conservation practices which are a major factor to the decrease of sediment load at Huayuankou gauging station account for 40% of the total amount of reduction, sediment trapping by Sanmenxia and Xiaolangdi reservoirs account for 30% of the total amount of reduction and the 10% decrease is caused by human activities in the upper reaches. The remaining 20% decrease is attributed to precipitation decrease. The reduction of sediment load has directly impacted on the lower Yellow River and the delta region, causing alternate changes between siltation and scouring in the lower river channel along with an increased rate of erosion over the whole Yellow River delta. [Copyright &y& Elsevier]

Abstract: The purpose of the paper is to extract and make the best use of rainfall information contained in the Chinese historical archives of Qing Dynasty, and reconstruct the precipitation series during 1736–1911. The study followed the Yu-Fen-Cun (rainfall infiltration depth) observation method in Qing Dynasty, to conduct soil infiltration experiment under the natural rainfall conditions during 2004–2006. The related parameters, such as precipitation, intensity, initial soil moisture content and infiltration depth have been measured at 10 stations (east of 105°E, 30°–40°N) with representative climatic conditions and soil physical texture in the middle and lower reaches of the Yellow River and Yangtze-Huaihe River Valley. The statistical results indicate that precipitation is the primary influencing factor to infiltration depth and is positively correlated with the infiltration depth. Additionally, the effects of every factor on infiltration depth are significantly different between the middle and lower reaches of the Yellow River and Yangtze-Huaihe River Valley. Finally, the relationship equations of precipitation and infiltration depth are established for each site, most of which can pass over 60% of the variance explanations and provide quantitative models to reconstruct the precipitation series using Yu-Fen-Cun records in Qing Dynasty. [Copyright &y& Elsevier]

The article presents a study on the long-term monotonic trend and abrupt changes for major climate variables at 23 meteorological stations in the headwater catchment of the Yellow River basin in China from 1960 to 2001 on the basis of mean air temperature, precipitation, sunshine duration and pan evaporation. It states that the abrupt changes have been examined in terms of a five-year moving averaged annual series using the moving t-test (MTT) method, Yamamoto method and Mann-Kendall method. The results indicated that the annual air temperature has increased by 0.80 degrees Celsius in the headwater catchment of the Yellow River basin during the past 42 years.