Page - 245 - in Book of Full Papers - Symposium Hydro Engineering

Fig. 1 Annual runoff variation in YiChang Station The monthly inflow is compared with the time line in 2003, when the TGP reservoir began to store water (Fig.2). According to the figure, it can be seen that the average monthly inflow in the TGP reservoir after 2003 is much less than that before 2003. As to the monthly distribution, it shows that it is slightly more than that before 2003s from January to April in recent years, while the inflow from June to December decreased in varying degrees, and mainly decreased from August to November, when the runoff decreased by 3638 m3/s and 6747 m3/s respectively. It is known that the formation of runoff in flood season and storage period is mostly derived from precipitation, except little runoff in storage period are affected by the discharge from reservoir group in upstream, which can be ignored compared with the influence of the precipitation in storage period. Fig. 2 Monthly runoff before and after 2003 in Yichang station In the background of runoff decreased, if the TGP reservoir is still operated in the flood limit water level in the flood season，the flood will be almost completely abandoned and unable to be effectively used. From the analysis above, the inflow in the water storage period is obviously decreasing, causing the water for storage is not enough. Therefore, if the reservoir still be operated by the original rule and doesn’t store water until October, it will be difficult to fill up the reservoir and the demand for water supply in the lower reaches in dry period will be hard to be guaranteed. y = -3.9575x + 12386 3000 3500 4000 4500 5000 5500 6000 6500 1963 1969 1975 1981 1987 1993 1999 2005 2011 2017 YearMeasured runoff .... linear intensity average value 0 2000 4000 6000 8000 10000 12000 1 2 3 4 5 6 7 8 9 10 11 12 MonthMonth-runoff before 2003 Month-runoff after 2003 245