维持黄河下游主槽不萎缩的塑槽需水量

Water demand for keeping main-channel from shrinkage in the Lower Yellow River

以滑动平均水量和滑动平均沙量为参数,建立了黄河下游汛期塑槽需水量的计算公式,包括上限需水量和下限需水量,构成塑槽需水量的变化区间。以平滩流量4000m3/s为例,在三黑小汛期来沙量8亿t时,汛期需水量区间为166～202亿m3。资料分析和公式计算均表明,汛期塑槽需水量与汛期来沙量及平滩流量均成正比关系,反映了来沙量对塑槽需水量的影响。考虑到平滩流量是连续4年汛期水沙条件累积作用的结果,对于给定平滩流量,不能只看当年汛期来水来沙量的大小,关键要看包括当年在内的前期连续4年滑动平均汛期水量的大小,允许个别年份的来水量小于平均值。

Using the moving average values of runoff and sediment load as primary parameters, formulas of water demand in the flood season for channel-forming in the Lower Yellow River are proposed. One formula is for determination of the upper bound and another is for the lower bound, thus forming the range of water demand for channel-forming. Taking the bankfull discharge of Qbf =4000m3/s as an example, the water demand in flood season is in the range from 16.6 billion m3 to 20.2 billion m3 corresponding to 0.8 billon tons of incoming sediment load. The water demand in the flood season for channel-forming is proportional to both incoming sediment load in flood season and the bankfull discharge. This indicates the effect of sediment load on water demand. Considering that the bankfull discharge is determined by the accumulated effects of flow discharge and sediment load in consecutive 4 years, for a given bankfull discharge, it is not enough to consider only the incoming sediment load and water inflow in flood season of the current year. The key point is to look at the accumulated effect of the previous consecutive 4 years＇ moving average value of water volumes in the flood season. The water inflow is allowed to be less than the average value of water demand in some individual years.