基于贝叶斯公式的不确定性水环境容量研究——以北运河为例

Uncertain water environmental capacity based on Bayesian formula—taking Beiyunhe river as example

针对水环境的随机不确定性,构建了基于贝叶斯公式的不确定性水环境容量核算方法,并以北运河为实证案例对所建立的核算方法进行验证:利用贝叶斯公式,通过对水环境容量核算涉及的流量、流速、背景浓度、污染物综合衰减系数这4个参数和水环境容量本身5个随机变量的分布特征进行分析,最后得到水环境容量的概率分布.结果表明:北运河流域10个河段的水环境容量都服从瘦尾偏态分布,并且河段流量与长度对其分布影响最大;与传统设计条件下的确定性水环境容量相比较,不确定性水环境容量分布不仅能够体现前者的信息,并且利用各参数的随机性以及实际监测数据进一步对前者进行了“修正”,能够更为全面准确的描述水环境.

Considering the uncertainty of water environment,an uncertain water environmental capacity calculating method based on Bayesian formula was demonstrated in this study,and it was applied to Beiyunhe river basin for its validation.With the knowledge of Bayesian formula,the probability distributions of 5 random variables which were involved in the calculation of water environmental capacity,including water flow,flow velocity,pollutant concentration,integrated attenuation coefficient of pollutants and water environmental capacity itself,were presented.The results showed that the probability distributions of the water environmental capacity of 10 river reaches in Beiyunhe river were all light tailed distribution.Water flow and length of the river reaches had the greatest impact on the distribution.Compared with the traditional calculating method of water environmental capacity,uncertain water environmental capacity calculating method generated the distribution of water environmental capacity,which not only presented the knowledge of the former,but also took the randomness of each parameter and observed data into account to further"correct"the former,so that we can understand water environment with a better comprehensive description.