Response of land accretion of the Huanghe River Delta to global climate change and human activity

In the past 50 a, the East Asian summer monsoon intensity index has changed significantly, which has led to some response to the water cycle system of the Huanghe River Basin.The variation of the summer monsoon intensity index shows three stages: (1) from 1951 to 1963, the summer monsoon intensity index increased; (2) from 1963 to 1965, the summer monsoon intesity declined sharply, which may be regarded as an abrupt change; (3) from 1965 to 2000, the summer monsoon intensity index remained at low levels and showed a decreasing trend.The variation of annual precipitation is synchronic with that in the summer monsoon intensity index.From 1950 to 1970, annual air temperature showed slight decrease in large fluctuations.From 1970, a significant increasing trend can be seen.Climate change may result in a change in sediment flux into the sea, and therefore a change in the rate of land accretion of the delta.The annual rate of land accretion of delta and sediment flux into the sea tended to increase from 1952 to 1964, but decreased after 1964, its tendency was similar to the summer monsoon intensity index.Apart from the climate factor, human activity such as water and soil conservation measures and water division in the drainage basin also have some effect on land accretion of the Huanghe River Delta.A multiple regression analysis indicates that the rate of land accretion of the delta decreased with the decrease in the summer monsoon intensity index, the increase in annual temperature, the increase in the area of water and soil conservation measures and increase in water diversion.The contribution of the variations of the above influencing variables to the variation of the rate of land accretion of the delta was calculated as 34.94%, 3.80%, 53.82% and 7.44%, respectively.The cont ribution of the two climate factors sums 38.7%, indicating that the influence of global climate change on the variation in the land accretion of the Huanghe River Delta is significant.