Runoff diverted from the Jingjiang reach to the Dongting Lake and the effect of Three Gorges Reservoir

As the water and sediment of the Yangtze River are diverted at the three outlets into the Dongting Lake, the relationship of rivers and lakes in the middle Yangtze River is mainly determined by the changes of the flow diversion ratio at the three outlets (FDRTO). To reveal the variation characteristics of FDRTO, average daily discharge of hydrometric stations both in the Jingjiang reach and the diversion channels in recent 60 years are employed. Abnormal hydrological conditions and major human activities have been proved as the main factors induced the FDRTO changes. Besides, Reduction calculation of runoff at Yichang station considering without TGR water was conducted based on balance approach, by compared with the field data, the influence of TGR on the diversion flow can be estimated. The studies show that (1) catastrophic flood and major human activities cause a 4 to 5-year trend-adjustment period of the FDRTO, the flow diversion ratio was continuously decreased during such period, and then became stable in the following balance-adjustment period; (2) From 2003 to 2014, the runoff diverted from Jingjiang reach increased by 0.800 0 billion cubic meter every year under the low compensation operation of TGR in dry season, but decreased by 2.900 billion cubic meter every year effected by impounding water of TGR after the flood season. The comprehensive influence of TGR on the diversion flow of the three outlets is about 2.100 billion cubic meter every year, accounted for 4.29% of its total annual runoff. © 2016, Editorial Board of Advances in Water Science. All right reserved.