Spatial Analysis of Monthly and Annual Streamflow Trends In Huaihe Basin During The Past 50 Years

In the past 50 years, global climate change and increasingly extensive human activities have greatly altered the water cycle, inducing a series of environmental problems in Huaihe basin. The paper aims at examining the spatial and temporal variation characteristics of runoff, forecasting future trends and offering some meaningful and constructive suggestions for rational management and allocation of water resources in Huaihe basin. On the basis of the streamflow observed at 20 hydrological stations of the nine rivers belong to Huaihe basin for the period 1956-2008, the long-term monotonic trend and abrupt changes in climate change and human activities have been investigated. The Mann-Kendall statistic test is a rank-based, non-parametric approach and has been widely used to estimate the significance of long-term trends in the streamflow time series. So, the Mann-Kendall trend test and R/S method were applied to study changes in annual and seasonal streamflow. The linear regression was compared with the results obtained by using the Mann-Kendall trend test. The abrupt changes have been investigated in terms of a 5 year moving averaged annual series, using the moving t-test (MTT) method. Results suggested that the annual runoff showed a significantly decreasing trend, and more prominent at the lower reaches than that at the upper reaches over the past 50 years. The overall picture was that trends of decreased streamflow dominate annual values and the spring and autumn seasons, and trends identified in summer and winter flows were increasing. And then, the decreasing trend of runoff would be more significant in the future. The sharp points of runoff were found to be in the 1970s. The characteristics of annual runoff in the Huaihe basin were predominantly affected by the uncertainty of river volume in the headstream and increasingly extensive human activities at the headstream and mainstream as well as climate change. For the sake of sustainable social and economic development of the basin in the future, a comprehensive management of water resources should be implemented in the Hauihe Basin.