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The Taoer River, a representative ecologically sensitive area in Northeast China, has undergone great climate changes and rapid social developments since 1961. Subsequently, a substantial alteration of the streamflow regime was observed and severe eco-environmental problems were becoming prominent. To provide decision makers the scientific basis for effective resource management and sound future planning, it is crucial to understand and assess the impacts of the climate variability and human activities on streamflow in this region. In this study, we combined an observation-based statistical analysis and physical modeling experiments to address this broad question. The Mann-Kendall and Sen's slope were used to examine the trends and the moving t test was used to identify change points for the streamflow, precipitation, and potential evapotranspiration datasets. A statistically significant upward trend ( α = 5 %) was found for annual streamflow. An abrupt change point was identified in 1985 for the basin outlet station at Taonan. Accordingly, the streamflow was divided into baseline and changed period for attribution analysis. To investigate the impacts of climate change and human activities on annual streamflow, we applied a distributed hydrological model and six Budyko-type functions during the two periods. The results indicated that climate change and human activities accounted for about 45 and 55 % of the changes in streamflow, respectively. [ABSTRACT FROM AUTHOR]

Drought is one of the most costly natural disasters in the world. Understanding the drought characteristics in space and time will help deepen our apprehension of the drought formation and evolution mechanisms. It can also contribute to design monitoring system for drought warning and mitigation. In this study, we analyzed meteorological droughts, using the Standardized Precipitation Index, for Lancang River Basin, Southwest China. The 46-year (1960-2005) daily precipitation observations from 35 meteorological stations in the basin were used to derive the drought index. Spatial patterns and temporal patterns of the drought characteristics at multiple scales were investigated. The results utilizing the Principal Component Analysis and K-means clustering methods suggest that the study area can be divided into four sub-regions geographically with each sub-region having its own distinctive temporal evolution patterns of droughts. The temporal variability of droughts was investigated using the Empirical Mode Decomposition (EMD) analysis and the wavelet method. The EMD analysis showed that more than 60 % of the variance of the drought is associated with intra-decadal fluctuations in precipitation, except for one sub region, represented by the Changdu station. The wavelet transform showed an evolution of the main cycle near 3-7 years for most parts of the study area. [ABSTRACT FROM AUTHOR]