三峡工程对库区水流水质影响预测

Prediction of the Impact of Three Gorges Project on Water Flow and Water Quality in the Reservoir

利用开发的三峡水库整体一维水流水质数学模型,对三峡水库建成前后的水流水质变化趋势进行预测分析.重点介绍三峡工程建成后,库区水流条件巨大变化对污染物输移转化特性和水质分布的影响.预测结果表明,三峡工程建成后,三斗坪水位175m条件下,回水区断面平均流速比建库前减小4倍左右,平均有机污染物自净降解速率和大气复氧速率比天然河道状况减小1倍.由于污染物在库区滞留时间成倍延长,有机污染物排入水库后的自净降解总量较天然河道状况增大,因而,建库后回水区内断面平均有机污染物浓度较天然河道状况明显下降,但是,断面平均溶解氧浓度与天然河道状况相比也明显降低,对于守恒类污染物,建库前后水质变化不大.因此,三峡工程对库区水质影响有利也有弊.

A one-dimensional water flow and water quality model of the Three Gorges Reservoir(TGR)has been developed and applied to predict the general change of water flow and water quality after and before the Three Gorges Project(TGP).In this paper,it is mainly introduced to the impact of the TGP on the water flow and water quality.The prediction results show that,at the normal storage level of175m in TGR,the average flow velocity will decrease down about 4times,and the decay rate of BOD 5 and atmospheric reaeration rate of DO will decrease about one time than that of in the natural river reach.But comparing to that of the natural river,due to the small ve-locity in the TGR,the pollutants will stay a longer time of period in the TGR and the self-degrading capacity will increase,so the average concentration of BOD 5 of TGR will decrease.The average concentration of DO will also decrease because of the increasing of demand oxy-genation of organic pollutant and the decreasing of atmospheric reaeration rate,and for the conservation pollutant ,the average concentra-tion will change little before and after TGR being built.