Making global river ecosystem health assessments objective, quantitative and comparable

C Zhao; T Pan; T Dou; J Liu; C Liu; Y Ge; Y Zhang; X Yu; S Mitrovic; R Lim

doi:10.1016/j.scitotenv.2019.02.379

Making global river ecosystem health assessments objective, quantitative and comparable

Sci Total Environ. 2019 Jun 1:667:500-510. doi: 10.1016/j.scitotenv.2019.02.379. Epub 2019 Feb 27.

Authors

C Zhao¹, T Pan², T Dou³, J Liu⁴, C Liu⁵, Y Ge³, Y Zhang², X Yu², S Mitrovic⁶, R Lim⁷

Affiliations

¹ College of Water Sciences, Beijing Normal University, Beijing Key Laboratory of Urban Hydrological Cycle and Sponge City Technology, Beijing 100875, PR China; ICube, UdS, CNRS (UMR 7357), 300 Bld Sebastien Brant, CS 10413, 67412 Illkirch, France.
² School of Geography, Beijing Normal University, Beijing 100875, PR China.
³ Jinan Survey Bureau of Hydrology and Water Resources, Jinan 250013, PR China.
⁴ School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, PR China.
⁵ College of Water Sciences, Beijing Normal University, Beijing Key Laboratory of Urban Hydrological Cycle and Sponge City Technology, Beijing 100875, PR China. Electronic address: pacorrespondence@126.com.
⁶ School of Life Sciences, Faculty of Science, University of Technology, Sydney, NSW 2007, Australia.
⁷ School of the Environment, Faculty of Science, University of Technology, Sydney, NSW 2007, Australia.

PMID: 30833248
DOI: 10.1016/j.scitotenv.2019.02.379

Abstract

Assessing and comparing global river ecosystem health in an objective and quantitative way remains a major challenge. In this study the widely-used semi-quantitative methods Rapid Biological assessment Protocols (RBPs) was used to determine the health of rivers. The findings were then compared to the results derived from our new UAV (Unmanned aerial vehicles) orthophotographic imagery method. This method quantitatively and objectively assesses river ecosystem health. As a comparison, our method was used to quantitatively measure distance and areas of a range of hydrological and biological attributes thus improving the accuracy of distance- and area-related indices, consequently avoiding subjective errors in these estimations that is fraught in methods like the RBPs. To strengthen the objectivity of the assessment the weights of these indices were objectively determined using the entropy weighting method. This new method was then tested using 9551 UAV orthophotographs taken over six field campaigns. It performed satisfactorily, showing that in our study area the health status of mountain rivers was the best with the highest score of 0.94 out of 1.0. Temporally, the health of the river was better in summer (0.65) compared with that in autumn (0.40). Changes in river ecosystem health were driven by variations in biology and water quality. In contrast the outputs of RBPs, especially in relation to distance and area indices, had ~ 20% uncertainty due to visual errors and subjectivity in estimations by observers. The UAV orthophotographic imaging method proposed in this study can improve the ability to compare the health of rivers across different periods and regions throughout the globe.

Keywords: Biota; Habitat quality; Hydrology; River ecosystem health; Water quality.