Human interference in the water discharge of the Changjiang (Yangtze River), China

This study analysed 130-year-long river flow and 58-year-long meteorological records, the volume capacity of reservoirs and water consumption records over the last 60 years of the Changjiang (Yangtze River) basin. The results show that there are strong periodicities in the river discharge at seasonal, and at 3-, 7-, 11- and 14.6-year cycles. The results also show that the river discharge has decreased noticeably, and the discrepancy between flood and dry-season flows has also decreased in the last 130 years. However, the basin-wide water discharge also showed spatial and temporal variability. In the 70-year period prior to 1949, the water discharge in the middle and lower reaches of the Changjiang did not show declining trends. Between 1949 and 2011, the water discharge in the upper and middle reaches of the river showed apparent decreasing trends. Yet, because of the modulation by large lakes in the middle reaches, the water discharge to the sea did not show any noticeable changes. The primary causes of the changes in water discharge in the Changjiang basin were basin-wide dam construction and water consumption. Therefore, a regulated index (RI) is proposed to quantify human activities in the river basin. Based on RI, the Changjiang basin was weakly regulated between 1950 and 1980, intermediately regulated between 1980 and 2010, and is highly regulated at present. This is expected to worsen by 2030.