三峡水库水质变化趋势研究

为全面研究三峡水库蓄水之前至175 m蓄水运行期库区水质变化趋势和因蓄水导致水文条件变化后悬浮物、高锰酸盐指数、总磷等主要污染因子变化及其相互关系,通过对2000~2015年三峡水库水体水质状况进行分析,得出如下结论:三峡水库干流水质较好,其受水期及水库蓄水调度影响明显但逐渐减弱。受蓄水导致的水流条件变化、上游来水、支流汇入及沿程点面源污染等因素影响,干流沿程各断面水质变化趋势不完全一致;除清溪场和沱口断面外,从库尾到库首水质评价结果优于Ⅲ类的比例总体呈上升趋势。受蓄水影响,御临河、小江、大宁河及香溪河河口断面水质均呈下降趋势。三峡水库上游来水悬浮物含量变化与水期存在较好相关性,但自2013年开始上游来水各水期悬浮物含量均下降,悬浮物通量较2013年之前平均降低约80%。水库库中、库首断面近年来悬浮物含量在丰水期和平水期下降,其后逐渐趋于稳定,枯水期变化不明显。蓄水后主要支流河口悬浮物含量大部分时段低于库区干流同期,上游支流河口断面悬浮物含量受水期影响较库区中下游支流河口明显。干支流各断面高锰酸盐指数和总磷在各水期变化趋势各异,上游断面丰水期变化较下游断面明显;随着蓄水进程,各断面高锰酸盐指数和总磷在平水期和枯水期之间、断面间差异越来越小。悬浮物含量与高锰酸盐指数、总磷等参数之间存在一定的相关性,但在较长时间范围,不能通过拟合等手段将水样一种状态的测定结果推出样品另一种状态近似检测结果。

TREND STUDY OF WATER QUALITY IN THE THREE GORGES RESERVOIR

Water quality of the Three Gorges Reservoir from 2000-2015 was analyzed,in order to investigate the trends of water quality parameters and the relationship between the key pollutants such as suspended substance(SS),potassium permanganate index (CODMn),and total phosphorus (TP) from the Three Gorges Reservoir storing up to 175 m.Results revealed a good water quality in the area of the mainstream of the Three Gorges Reservoir and a less pronounced influence by the reservoir scheduling.The observed trends differed among the monitoring sections along the mainstream owing to thechange of hydrologic character,upland water,branch inflow as well as non-point and point sources pollution resulted from the impoundment.The proportion of evaluation results of water quality that better than Class was increasing in the whole reservoir except the Qingxichang and Tuokou sections.Influenced by impoundment,water quality declining was found inYulinhekou,Xiaojianghekou,Daninghekou and Xiangxihekou sections.Although a good correlation between the SS concentration and the period was observed for the upland water of the Three Gorges Reservoir,SS concentration was reduced during each period since 2013,which resulted in a reduction about of 80％ for SS flux.SS concentration was decreased temporally during the high-flow period and normal-flow period in both the center and head region of the reservoir,but was stable during the low-flow period.After the impoundment,a lower value of SS was usually found in the main branches estuary compared with that in the mainstream of the reservoir at the same time.Meanwhile,the value of SS in the upper branches estuary was influenced by the flow period more obviously than that in the middle and lower branches of the reservoir.CODMn and TP differed significantly among different periods.During the high-flow period,the variation of CODMn and TP in the upstream sections was obviously than that in the downstream sections.After impoundment,CODMn and TP showed no significant differences among the periods and sections.Limited correlation was observed between SS,CODMn and TP,however,the results cannot be derived from the detect value of one sample in a long time.