Assessing Land-Cover Effects on Stream Water Quality in Metropolitan Areas Using the Water Quality Index

Taeho Kim,Yoonkyung Cha,Youngwoo Kim,Byeonggeon Go,Jihoon Shin

doi:10.3390/w12113294

Abstract

This study evaluated the influence of different land-cover types on the overall water quality of streams in urban areas. To ensure national applicability of the results, this study encompassed ten major metropolitan areas in South Korea. Using cluster analysis, watersheds were classified into three land-cover types: Urban-dominated (URB), agriculture-dominated (AGR), and forest-dominated (FOR). For each land-cover type, factor analysis (FA) was used to ensure simple and feasible parameter selection for developing the minimum water quality index (WQImin). The chemical oxygen demand, fecal coliform (total coliform for FOR), and total nitrogen (nitrate-nitrogen for URB) were selected as key parameters for all land-cover types. Our results suggest that WQImin can minimize bias in water quality assessment by reducing redundancy among correlated parameters, resulting in better differentiation of pollution levels. Furthermore, the dominant land-cover type of watersheds, not only affects the level and causes of pollution, but also influences temporal patterns, including the long-term trends and seasonality, of stream water quality in urban areas in South Korea.

Highlights

Global urbanization is an ongoing trend, with 55% to 68% of the world’s population projected to reside in urban areas by 2050 [1].Urbanization induces multiple stressors, especially land-use/land-cover changes such as deforestation and the growth of industrial and residential areas, resulting in increased impervious surfaces [2,3,4,5]
Our results suggest that Temp, pH, and dissolved oxygen (DO), whose patterns are substantially influenced by natural variations, may not successfully capture the total variance of stream water quality in urban areas, and may not be suitable for being included as key parameters
Our results indicate that the dominant land-cover affected the overall stream water quality in urban areas, with mean values of both WQIobj and WQImin decreasing in the order: FOR > AGR > URB

Summary

Introduction

Global urbanization is an ongoing trend, with 55% to 68% of the world’s population projected to reside in urban areas by 2050 [1].Urbanization induces multiple stressors, especially land-use/land-cover changes such as deforestation and the growth of industrial and residential areas, resulting in increased impervious surfaces [2,3,4,5]. Urbanization leads to a deterioration of water quality in streams through an increase in pollution sources and various hydromorphological changes [6,7,8] Despite their at-risk status, streams in urban areas are crucial water resources with a number of designated uses, such as drinking water supply, recreation, and wildlife conservation [9,10,11,12]. In recent years the advent of big data and the accumulation of monitored multivariate data has prompted a substantial increase in the application of WQI to environmental and ecological studies [18,19,20] In many of these studies, the developed WQI has been used to capture long-term trends [21,22], seasonal fluctuations [23,24], or spatial variations [25,26] in

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Discussion

Conclusion