Design and implementation of a hybrid model based on two-layer decomposition method coupled with extreme learning machines to support real-time environmental monitoring of water quality parameters

Elham Fijani; Rahim Barzegar; Ravinesh Deo; Evangelos Tziritis; Konstantinos Skordas

doi:10.1016/j.scitotenv.2018.08.221

Design and implementation of a hybrid model based on two-layer decomposition method coupled with extreme learning machines to support real-time environmental monitoring of water quality parameters

Sci Total Environ. 2019 Jan 15:648:839-853. doi: 10.1016/j.scitotenv.2018.08.221. Epub 2018 Aug 18.

Authors

Elham Fijani¹, Rahim Barzegar², Ravinesh Deo³, Evangelos Tziritis⁴, Konstantinos Skordas⁵

Affiliations

¹ School of Geology, College of Science, University of Tehran, Tehran, Iran. Electronic address: efijani@ut.ac.ir.
² Department of Earth Sciences, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran; Department of Bioresource Engineering, McGill University, 21111 Lakeshore, Ste Anne de Bellevue, Quebec H9X3V9, Canada. Electronic address: rm.barzegar@tabrizu.ac.ir.
³ School of Agricultural Computational and Environmental Sciences, International Centre for Applied Climate Sciences, Institute of Agriculture and Environment, University of Southern Queensland, Springfield, Australia. Electronic address: ravinesh.Deo@usq.edu.au.
⁴ Hellenic Agricultural Organization, Soil and Water Resources Institute, 57400 Sindos, Greece. Electronic address: dir.lri@nagref.gr.
⁵ Department of Ichthyology and Aquatic Environment, School of Agricultural Sciences, University of Thessaly, Fitokou street, 38446 Volos, Greece. Electronic address: kskord@apae.uth.gr.

PMID: 30138884
DOI: 10.1016/j.scitotenv.2018.08.221

Abstract

Accurate prediction of water quality parameters plays a crucial and decisive role in environmental monitoring, ecological systems sustainability, human health, aquaculture and improved agricultural practices. In this study a new hybrid two-layer decomposition model based on the complete ensemble empirical mode decomposition algorithm with adaptive noise (CEEMDAN) and the variational mode decomposition (VMD) algorithm coupled with extreme learning machines (ELM) and also least square support vector machine (LSSVM) was designed to support real-time environmental monitoring of water quality parameters, i.e. chlorophyll-a (Chl-a) and dissolved oxygen (DO) in a Lake reservoir. Daily measurements of Chl-a and DO for June 2012-May 2013 were employed where the partial autocorrelation function was applied to screen the relevant inputs for the model construction. The variables were then split into training, validation and testing subsets where the first stage of the model testing captured the superiority of the ELM over the LSSVM algorithm. To improve these standalone predictive models, a second stage implemented a two-layer decomposition with the model inputs decomposed in the form of high and low frequency oscillations, represented by the intrinsic mode function (IMF) through the CEEMDAN algorithm. The highest frequency component, IMF1 was further decomposed with the VMD algorithm to segregate key model input features, leading to a two-layer hybrid VMD-CEEMDAN model. The VMD-CEEMDAN-ELM model was able to reduce the root mean square and the mean absolute error by about 14.04% and 7.12% for the Chl-a estimation and about 5.33% and 4.30% for the DO estimation, respectively, compared with the standalone counterparts. Overall, the developed methodology demonstrates the robustness of the two-phase VMD-CEEMDAN-ELM model in identifying and analyzing critical water quality parameters with a limited set of model construction data over daily horizons, and thus, to actively support environmental monitoring tasks, especially in case of high-frequency, and relatively complex, real-time datasets.

Keywords: Complementary ensemble empirical mode decomposition with adaptive noise; Environmental monitoring; Extreme machine learning; Small Prespa Lake; Variational mode decomposition; Water quality modelling.