Analysis the Runoff Variotion of Yangtze River in Yichang

The notion of'maintain a healthy Yangtze River and promote harmonious man-water relationships'is being actively practiced in China.The Three Gorges Project(TGP) achieved remarkable flood control and avoids peak discharge.Especially,in the flood period of 2010 when peak flow was close to that of 1998,the TGP effectively controlled upper Yangtze River flooding and reduced the amount of flooding in Jingjiang reach and Dongting Lake.It is now necessary to change contemporary ideas on water management,and explore a reasonable way to reach a harmonious man-water relationship for the Yangtze River basin.Here,hydrological data in Yichang,Cuntan and Wulong gauging stations were collected and analysed using Mann-Kendall tendency and mutation inspection,dbN Wavelet Analysis,concentration rates and concentrated periods of runoff.Our results indicate a decreasing trend in the flood season and increasing trend for dry season Yichang runoff.Annual runoff distribution within a year also changed in the last 60 years and this phenomenon's manifestation was most obvious in 2000-2010.There have mutations in February(minimum monthly runoff) and October(end of flood season) in Yichang runoff since 2000.The runoff sequence's break point happened during the second phase of the Three Gorges Reservoir(TGR) in 2006.Runoff variation in time and space confirmed that the operation of the TGP aggravated the decline in the flood season and increase in dry season runoff upstream of the Changjiang River.When the reservoir draws off water for power generation this augments the quantity of main stream runoff after the Three Gorges Dam(TGD) in the dry season,easing the lack of water downstream.The impounding of water at the end of flood season by the TGR decreased TGD downstream runoff and means the mid-lower reaches of the Changjiang River enter the dry season earlier.