Runoff of the Jinsha River: Characteristics and Its Response to Climate Change

The Jinsha River,one of the largest rivers in the Southwest China,has the characteristics that its runoff variation plays an important role to the temporal and spatial water resources variation in most areas of China.However,only few studies focus on the features of runoff in the Jinsha River basin up to present.In this paper,the annual,decadal variations of runoff and the effect of climate factors(such as precipitation and mean air temperature) on runoff from 1960 to 2004 in the Jinsha River basin are investigated.It is found that: 1) the runoff has gradually increased in the past 40 years and the Yalong River(a main tributary) basin is the main runoff producing area.There were evident decadal variation in flood and dry season both in mainstream and tributary stream.Namely,runoff was rich in the 1960s and the 1990s but poor in the 1970s.Runoff yield from mainstream is somewhat larger than that from tributary streams during the summer half year,while that from the latter is obviously larger than that from the former during winter half year.Besides,M-K test reveals that notable abrupt change of annual runoff took place somewhere in 1966 and 1997.In addition,the Jinsha River basin was dry and rainless in the 1970s but rainy in other period.Air temperature was quite low in the 1960s and the 1970s,but pretty high after the 1980s,with an evident increase in precipitation and air temperature after 2000.2) Annual precipitation,especially the precipitation of upper reaches of the river,greatly affects the variation of annul runoff yield.Runoff in spring is not only influenced by precipitation and temperature(negative relation) in the corresponding period,but is also positively dependent on the temperature of the prior period,while runoff in summer mostly depends on precipitation.Runoff in autumn is jointly influenced by the precipitation in the corresponding period and the precipitation and air temperature in the prior period.Runoff in winter is influenced by temperature(positive relation) in the corresponding period and precipitation in the prior period.