台湾集集堰沉沙池泥沙浓度与浊度率定关系研究

Rating relations between suspended sediment concentration and turbidity in Ji-Ji Weir settling tank

水体浊度观测为水环境及水资源领域中之例常观测项目,泥沙浓度则为水资源及水利工程中重要之水文观测数据。浊度数据对于水生态环境、水资源利用评估及公共用水营运,为极重要判别指标;泥沙浓度数据则为集水区保育及河道稳定评估规划所需之重要基本数据。现行浊度观测方式及仪器,相对于传统泥沙浓度之观测,其仪器自动化程度高、价格较低,且设站较为简易方便且普遍。虽河川中悬移泥沙浓度与浊度之物理定义不同,但在工程实务应用上仍有许多泥沙浓度数据以浊度数据来替代表示。本文研究特定水沙条件下之浊度与浓度率定关系,并以集集拦河堰为案例,探讨试样水体浊度、浓度观测数值在不同含沙量条件下之对应及量化关系规律,并依ISO标准规范,进行不确定度分析及误差分析。研究成果显示,浊度观测方式之重现性及精度良好,且浊度与浓度测值间对应率定关系明确,但此率定关系与泥沙类别、泥沙粒径及分布组成条件密切相关。参照本研究所提出之泥沙浊度与浓度观测之率定关系规律,可以利用现已普遍设站之水质观测站之浊度观测数据,建立推估特定流域河道之水、沙特性关系。

Turbidity is a commonly monitored parameter in environmental and water resources investigations, whereas sediment concentration is one of the primary field data needed in water resources and hydrological engineering. The turbidity data is an essential indicator for assessing the quality of aquatic habitat or the utilization of water resource or management of water use. Sediment concentration, on the other hand, is the basic information to watershed protection and stream channel stabilization. The purpose of engineered settling tanks is to abridge the turbidity and sediment concentration. However, the method and apparatus used for monitoring turbidity, compared to those of sediment concentration, have many advantages, such as being highly automatic, capable of instant recording and data transmitting, low cost, and flexible setup at observation stations. In addition, continuous turbidity measurements can be done for periods of years, accumulating considerable amount of data. Despite of having different physical definitions, turbidity has been used as a surrogate of suspended sediment concentration in some engineering applications. This paper is to study the rating relations between .turbidity and suspended sediment concentration under given water-sediment combinations. Using the Ji-Ji Weir as case study, the authors investigated and quantified the rating relations between turbidity and suspended sediment concentration samples collected under different field conditions. Based on the ISO standard, uncertainty analysis and error analysis are conducted. The results indicate that the turbidity monitoring method demonstrates good repetitiveness and precision, and a distinct relation between the sampled turbidity and concentration. The rating relation is closely related to sediment size and sediment particle size distribution. The turbidity and suspended sedment concentration rating curve resulting from this study can be used together with the actual turbidity measurements that are available on the websites of streamflow gauging stations to predict suspended sediment quantities, and to further study the water-sediment characteristics in the site-specific watershed.