改进WQI在川中丘陵地区典型流域水质评价中的应用-以琼江流域上游段为例

Application of improved WQI model in water quality assessment of typical watershed in the hilly area of central Sichuan Province:a case study in the upper reaches of Qiongjiang River Basin

水质指数(WQI)克服了传统水质评价方法无法同时满足定性评价与定量评价的缺点,但其所需指标较多,无法做到广泛运用。以琼江流域上游段为川中丘陵地区典型流域的代表,对其2018—2019年水质监测数据进行多元线性逐步回归分析,从25个水质指标中筛选出氨氮(NH_(3)-N)、化学需氧量(COD_(Cr))、生化需氧量(BOD_(5))、溶解氧(DO)4个指标建立改进WQI(WQI_(min))模型,该模型评价结果与WQI高度相关,并且具有较好的预测性能(R^(2)=0.81,PE=11.9%)。WQI_(min)评价结果表明:琼江流域上游段WQI_(min)均值为63.1±17.2,水质等级为好;干流WQI_(min)整体上呈沿程升高的趋势,流经安居区时,WQI_(min)明显降低,但能较快恢复至入城区前的水平;WQI_(min)由高至低依次为琼江干流>会龙河>玉丰河>蟠龙河>石洞河,主要支流水质均劣于干流,建议区域水污染治理的重点应逐步放到支流上。

Water quality index(WQI)overcomes the shortcomings of traditional water quality evaluation methods that cannot satisfy both qualitative and quantitative evaluation.However,WQI requires so many evaluation indexes that it cannot be widely used.Taking the upper reaches of Qiongjiang River Basin as the representative of the typical basin in the hilly area of central Sichuan Province,the monitoring data of water quality from 2018 to 2019 were analyzed through the multiple linear stepwise regression method.One improved model,the minimum water quality index(WQI_(min)) model,was established by choosing NH_(3)-N,COD_(Cr),BOD_(5) and DO from 25 water quality indexes.WQI_(min)model had better predictive performance,and its evaluation results were significantly correlated with WQI(R^(2)=0.81,PE=11.9%).According to the results of WQI_(min) model,the average WQI_(min) value in the upper reaches of Qiongjiang River Basin were 63.1±17.2,and the water quality grade was"good".On the whole,the WQI_(min) value of the mainstream increased along the flow direction.When it flowed through Anju District,WQI_(min) decreased significantly,but it could return to its pre-affected level before entering the city quickly.The WQI_(min) values from high to low were as follows:Qiongjiang River mainstream>Huilong River>Yufeng River>Panlong River>Shidong river,and the water quality in tributaries was worse than that of main streams.Therefore,the priority of water pollution control in this area should be gradually put on the tributaries.