感潮河道不同参数对水环境容量的影响分析

Impact analysis of different parameters on water environmental capacity for tidal rivers

作为水环境容量计算的重要组成部分,模型参数选值是否合理直接关系到模型计算结果的准确度和可靠性。本文以珠江三角洲西北江网河区的感潮河道为例,在考虑潮位、污染源概化方式、设计流量、综合衰减系数、本底水质浓度参数条件的基础上,利用感潮河网一维水动力和水质模型,分析和探究感潮河道不同参数对于水环境容量的影响,从而为感潮河道水环境容量计算的参数选值提供一个理论和经验参考。研究结果表明:感潮河道的水环境容量与潮位呈现十分显著的正相关关系,但在某些潮位变化时段,水环境容量的相对降低幅度会大于潮位的相对下降幅度,说明水环境容量会受到径流和潮流的共同作用。对于不同参数变化下的水环境容量,顶点排放远大于均匀和中间排放,而均匀和中间排放比较接近,这主要与不同污染源概化方式所引起的污染物稀释衰减程度有关。在不同的污染源概化方式下,设计流量、综合衰减系数和本底水质浓度的变化对于水环境容量的影响会不同,当COD综合衰减系数的取值≥0.28 d-1时,设计流量对于水环境容量的影响会变得很小;当COD本底水质浓度的取值在22 mg·L-1前后,设计流量和综合衰减系数对于水环境容量的影响会产生较大的差别。故在对感潮河道水环境容量的参数进行选值时,要注意参数变化对于计算结果的影响。

As an essential component of water environmental capacity calculation, rationality of model parameter value selection exerts a direct impact on the accuracy and reliability of the model results. Based on the parameter conditions of tidal level, generalization way of pollution source, design flow rate, comprehensive attenuation coefficient and background concentration of water quality, this paper took a river in the northwest river tidal network of Pearl River Delta as research object and applied one-dimensional hydrodynamic and water quality model for tidal river network to analyze and explore the impact of different parameters on water environmental capacity, which provides a theoretical and empirical reference for parameter value selection of water environmental capacity calculation in tidal rivers. The results show that： Water environmental capacity has a very significant positive correlation with tidal level, but at some tidal periods, the relative declining amplitude of water environmental capacity is greater than that of tidal level, which indicates that water environmental capacity is influenced by both runoff and tide of the river. For different parameter variations, the water environmental capacity of vertex emission is much greater than that of uniform emission and intermediate emission, which are close to each other. This is mainly due to the degree of pollutant dilution and attenuation caused by different generalization way of pollution source. The variations of design flow rate, comprehensive attenuation coefficient and background concentration of water quality have different effects on water environmental capacity under different generalization way of pollution source, when COD comprehensive attenuation coefficient〉0.28 dl, design flow rate has little impact on water environmental capacity, when COD background concentration of water quality is greater or less than 22 mgL-1, the effect of design flow rate and comprehensive attenuation coefficient on water environmental capacity is greatly different. So when conducting parameter value selection for water environmental capacity in tidal rivers, we should pay more attention to the influence of parameter variation on calculation results.