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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]

Daily precipitation data of 148 measuring stations in the Yangtze River basin (P.R. China) for the period from 1961 to 2002 have been analyzed to detect quasi periodicities in the frequency of occurrence of extreme precipitation events. Extreme precipitation events of duration 1-day and 10-day were defined in terms of 90th percentile threshold exceedances for each station. The time series were standardized, averaged and detrended for each subbasin. Distinct temporal agglomerations of Gaussian peaks in the smoothed time series for all subbasins were detected for certain years. Quasi periodicities features in the time series were analyzed by means of spectrum analyses. Characteristic differences were found for the subbasins with typical significant quasi periodicities in the 2–3 and 3–4 year ranges. Wavelet analyses revealed that the stability of the observed quasi periodicities over time also varied between the subbasins. This results in various degrees of confidence that can be placed on the future extrapolation of Fourier emulations. Our extrapolations suggest occurrences of peaks in the frequencies of extreme precipitation events for most subbasins around the years 2012–2013 and 2017–2018 even though major differences between the subbasins are expected. [ABSTRACT FROM AUTHOR]