近期潼关水沙变化对河床冲淤的影响

1986年以来，潼关水量和沙量大幅减少，洪峰少，流量小，历时短，含沙量高。1986－1999年汛期平均水量120亿m^3，比前期减少40％－60％，日平均流量大于3000m^3/s的出现天数和水量均减少90％以上，沙量变化较小，含沙量成倍增加，致使潼关高程汛期平均下降幅度明显偏小，比非汛期上升偏小0．10m，比建库前汛期平均下降值偏小0．08m，若与控制运用初期相比，则偏小0．30m为了适应入库水和条件的不利变化，水库运用方式多次进行调整和改善，但河床淤积仍较1985年前严重，潼关高程逐上升，尤其1994年以来，入库水沙量在前期大幅减少的基础上又明显减少，潼闹程居高不下，长期变动在328．00－328．35m之间。

Effect of Water-sediment Changes on Erosion and Deposition of Bed at Tongguan in Recent Period

Since 1986，the incoming water and sediment at Tongguan section have decreased greatly with less discharge and flood peak，short duration and high sediment concentration。The average water volume with 12 billion m3 in 1986～1999's flood periods are 40%～60% less than that in previous periods。The average daily discharge of days with 3000m3/s larger and water volume reduced 90% above with smaller change of sediment amounts，the sediment concentration increased doubly 。The average lower margin in flood season of Tongguan elevation reduced obviously，it is 0.10m smaller than the raising value in non-flood season and 0.08m smaller than average lowering value at flood season before reservoir construction.It is 0.30m smaller comparing with initial period of operation。In order to suit the unfavorable conditions of reservoir's water-sediment ，the modes of reservoir operation are regulated and improved for several times，but the bed's deposition is more serious than that in 1985。Tongguan elevation was raised year by year。Since 1994 especially，the reservoir water-sediment reduced obviously based on the reduction by a big margin in previous period 。Tongguan elevation maintained at a high level with long-term variation between 328.00 and 328.35m.