AbstractStudy Region The Heihe River Basin (HRB) is the second largest inland river basin of China located in northwest China with a minor portion in Mongolia. Study Focus With increasing water demands from domestic, agricultural, and industrial sectors, the HRB has been increasingly undergoing water resources shortage and eco-environmental degradation, especially in the lower HRB. Discerning the trends and any abrupt changes in the streamflow over the river basin could help unravel the causes and effects of historical variations of the water resources. Statistical methods for detecting trends, abrupt and gradual changes were applied to the long-term streamflow, precipitation and temperature data over the HRB to analyze and understand annual and seasonal hydroclimatic variations over the past five decades. New Hydrological Insights for the Region The findings of this study indicated that although the streamflow coming from the upper reaches have risen, those flowing to the lower reaches have declined significantly. Analysis of the correlation between climatic factors and streamflow variations and the assessment of the development of socioeconomics revealed that: (1) rising temperature and precipitation are the main cause to explain the increases in streamflow in the upper HRB; and (2) human activities in the middle reaches of the HRB rather than climate changes were primarily responsible for the water shortage and ecological deterioration of the lower HRB.
