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Drought is a major natural hazard that can have devastating impacts on regional agriculture, water supply, ecological environment and social economy. Extreme events, including droughts, are expected to be severer and more frequent because of climate warming. This paper presents an analysis of observed changes and future projections of meteorological drought in the Daqing River Basin (DRB), North China, based on the modified Standardized Precipitation Index (SPImod). Observed changes of meteorological drought are analyzed based on the precipitation series of 26 meteorological stations from 1971 to 2011, and future projections are made under two representative concentration pathways (RCPs 4.5 and 8.5) from 2021 to 2050. The result shows a change from wet to dry detected in most areas of the DRB in summer, winter and annual series. The drought risk is higher under the condition of "OR" and "AND" return period during the observation period, and the high-risk regions cover a large area. The drought risk from 2021 to 2050 will increase across the basin under RCP 4.5 and RCP 8.5, compared with which in the base period from 1971 to 2000. Most regions will be at a higher drought risk under the condition of "OR" return period, and the area with high-risk under RCP 4.5 is slightly larger than that under RCP 8.5. Under the condition of "AND" return period, the high-risk regions will cover the area from the northwest to the northeast, while the area of high-risk regions under RCP 8.5 will be larger than that under RCP 4.5. The result of this paper will be helpful for performing an efficient water resource management in the DRB under the impacts of global warming and climate change. [ABSTRACT FROM AUTHOR]

Previous studies attempting to quantify the contributions of climate change and human activities to runoff variations in a changing environment have widely focused on an annual scale, while seasonal scales are rarely involved. China is the largest socialist country in the world, and its economic development is affected by its Five-year Plan policy. To this end, the upper Han River Basin, the largest tributary of the Yangtze River Basin, was selected as a case study. A seasonal-scale Budyko framework was extended based on the monthly abcd model in this study for quantifying the effects of climate and human activities changes on seasonal runoff variations, especially exploring the effect of China's Five-year Plan policy. Results disclose that: (1) the change point in the annual runoff series is 1990, and the monthly abcd model achieves good performance in the prechange and postchange period; (2) the relative contribution of climate change to runoff variations is 62.99%, 70.20%, 87.54%, and 90.30% in spring, summer, autumn, and winter, respectively, indicating that climate change is the dominant factor controlling runoff variations in every season; (3) the contributions of climate change and human activities show obvious dynamic and seasonal characteristics, which are strongly impacted by the implementation of the Five-year Plan policy. Generally, the findings of this study provide valuable references for local reasonable water resource planning and management to make timely and appropriate use of the water supply. [ABSTRACT FROM AUTHOR]