关键词: 生态水文, 水文变动指标, 变动范围法, 长江

Abstract:

The temporal variability of daily discharge from 1900 to 2004 in Yichang Gauge, which is located in the upper reaches of the Yangtze River with a catchment area over 1 million km2, has been analyzed in the present study. The MannKendall statistical test was applied to assess the significance of the trends. There is a decrease trend in annual and monthly discharge series, and the trend is significant at annual level and in February, August, October and November with the decrease significance exceeding 95% confidence. The MannWhitney statistical test was also applied to assess the jump of trends. A jump happened in 1969 with the confidence exceeding 99%, and the difference of mean discharge before 1970 and after 1970 is 937 m3/s (6.5%). The Range of Variability Approach (RVA), which contains thirtytwo ecohydrological parameters called Indicators of Hydrologic Alteration (IHA), was used to evaluate the flow conditions before and after 1970. 25th to 75th percentile values for each parameter before 1970 was set at the management target range. It is shown that light hydrological alternations are observed for most parameters, except five parameters including monthly discharge and rate/frequency of water condition changes parameters in January and November. The hydrological alternation is mainly due to the decrease in precipitation and the construction of dams in the upper Yangtze Basin.

Key words: eco hydrological alternation, IHA, RVA, the Yangtze River