Water Quality Evaluation of the Yangtze River in China Using Machine Learning Techniques and Data Monitoring on Different Time Scales

Zhenzhen Di,Peikun Guo,Miao Chang

doi:10.3390/w11020339

Abstract

Unlike developed countries, China has a nationally unified water environment standard and a specific watershed protection bureau to perform water quality evaluation. It is a major challenge to assess the water quality of a large watershed at a wide spatial scale and to make decisions in a scientific way. In 2016, weekly and real-time data for four monitoring indicators (pH, dissolved oxygen, permanganate index, and ammonia nitrogen) were collected at 21 surface water sections (sites) of the Yangtze River Basin, China. Results showed that one site had a relatively low Site Water Quality Index and was polluted for 12 weeks meanwhile. By using expectation-maximization clustering and hierarchical clustering algorithms, the 21 sites were classified. Variable spatiotemporal distribution characteristics for water quality and pollutants were found; some sites exhibited similar water quality variations on the weekly scale, but had different yearly grades. The results revealed polluted water quality for short periods and abrupt anomalies, which imply potential pollution sources and negative effects on water ecosystems. Potential spatio-temporal water quality characteristics, explored by machine learning methods and evidenced by time series and statistical models, could be applied in environmental decision support systems to make watershed management more objective, reliable, and powerful.

Highlights

Water quality evaluation is commonly based on water environment standards (WESs).In developed countries such as the United States, member states of the European Union, Australia, and Japan, the local WESs in specific states or territories are based on a national unified Water QualityCriteria (WQC)
In developed countries, water quality assessment is enforced by local government in specific states or territories [1,3], while, in China, water quality evaluation is performed by a specific watershed protection bureau [4,5]
Surface water usually has supersaturation of dissolved oxygen and a pH that fluctuates over a normal range

Summary

Introduction

Water quality evaluation is commonly based on water environment standards (WESs).In developed countries such as the United States, member states of the European Union, Australia, and Japan, the local WESs in specific states or territories are based on a national unified Water QualityCriteria (WQC). Water quality evaluation is commonly based on water environment standards (WESs). In developed countries such as the United States, member states of the European Union, Australia, and Japan, the local WESs in specific states or territories are based on a national unified Water Quality. China has a nationally unified WES, but without WQC [1,2]. In developed countries, water quality assessment is enforced by local government in specific states or territories [1,3], while, in China, water quality evaluation is performed by a specific watershed protection bureau [4,5]. Due to the way water quality management is organized in China, it is a difficult challenge for the central government of China to assess the water quality on a large spatial scale and to make decisions in a scientific manner

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Conclusion