20年来中国河流水质变化特征及原因

Characteristics and Causes of Water Quality Change in Chinese Rivers during the Recent 20 Years

根据1997—2017年中国水资源公报所发布的全国降水量、污水排放量、地表径流量以及水质环境评价总河长、各类水质河长占比等信息,分析了我国江河水质演变态势及其变化原因。结果表明:20年来,我国污水排放量总体呈现增长趋势,但2011年之后逐年下降;降水量和地表径流量呈先减少后增加的趋势;2010年之前,不同级别水质河长占比并没有明显的规律性变化,但2011年之后,Ⅰ~Ⅲ类水质河长占比呈现稳定增长趋势,Ⅳ~Ⅴ类和劣Ⅴ类水质河长占比呈现减小趋势,说明我国江河水质总体趋于改善。地表径流增加以及近些年来污水排放量减小是河流水质改善的主要因素。

According to the information of the China′s national precipitation, sewage discharge, surface runoff, the total length of the investigated rivers for water quality assessment, and the ratios of river length with various water quality grades to the total investigated river length (RWG-TRL) released in the China Water Resources Bulletins published by Ministry of Water Resources from 1997 to 2017, the evolution trend of river water quality in China and the causes for the changes were analyzed. The results show that the sewage discharge in China has generally shown an increasing trend over the past 20 years, but it has decreased year by year after 2011. Precipitation and surface runoff have both shifted from a decreasing trend to an increasing trend in 2009. Before 2010, there was no obvious regular change in length percentage of the river with different water quality grade. But after 2011, the river length ratio of water quality in grade Ⅰ~Ⅲ showed a steady increasing trend while the river length ratio of water quality in grade Ⅳ~Ⅴ and inferior Ⅴ presented a decreasing trend, which shows that the water quality of rivers in China has been improved in general. The increase in surface runoff and the decrease in sewage discharge in recent years are the main factors for the improvement of river water quality.