Renmin Zhujiang (Jan 2020)
Water Quality Evaluation of the Middle and Lower Reaches of Hanjiang River Based on Comprehensive Water Quality Identification Index
Abstract
With the increase of water consumption for economic and social development in Hanjiang River Basin and the completion of middle route of South-to-North Water Diversion Project,the pressure of water ecological environment in the middle and lower reaches of Hanjiang River Basin is increased gradually.This paper selects five main water quality indexes, including ammonia nitrogen (NH3-N),permanganate index (CODMn),dissolved oxygen (DO),biochemical oxygen demand for five days (BOD5) and total phosphorus (TP) from five monitoring sections i.e.Shenwan,Yujiahu,Huangzhuang,Luohanzha and Shilou in the middle and lower reaches of Hanjiang River from 2001 to 2014,evaluates the water quality in the middle and lower reaches of Hanjiang River by single factor analysis,single factor index and comprehensive water quality identification index, and conducts quantitative analysis of the changing trend of comprehensive water quality in the middle and lower reaches of Hanjiang River with Spearman rank correlation coefficient. The results show that:At the middle and lower reaches of Hanjiang River,the relatively poorer indexes are TP and NH3-N,while the better index is BOD5. Moreover,NH3-N influences the water quality of Yujiahu section in the middle reaches greatly, and TP is the limiting factor for the comprehensive water quality of Luohanzha and Huangzhuang sections in the lower reaches.In terms of space, the water quality of Shenwan in the middle and lower reaches of Hanjiang River is the best,and that of Shilou is the worst.In terms of time,the overall water quality of the middle and lower reaches of Hanjiang River improved constantly from 2001 to 2014.The results can serve as theoretical basis for water pollution control in this basin.Although consistent results were obtained by all the evaluation methods,the comprehensive index method contains more information,which can fully present the number of over-standard items and the pollution degree of each section.Consequently,it is suggested to be widely popularized and applied.
