Daily Forecasting of Hong Kong Beach Water Quality by Multiple Linear Regression Models
Publication: Journal of Environmental Engineering
Volume 140, Issue 2
Abstract
A daily forecast system of marine beach water quality (WATERMAN) has been developed for Hong Kong. Individual multiple linear regression (MLR) models were developed to forecast daily water quality (lnEC concentration) at each of the 41 beaches. The forecast system was developed through data assimilation with the most recent water quality data, and supported by field studies and deterministic hydrological, hydrodynamic, and water quality models. Model input parameters included three rainfall variables (daily rainfall in the previous three days): the previous day’s solar radiation, onshore wind speed, and water temperature; tide level and predicted salinity at sampling time; and the geometric mean of the five most recent E. coli measurements. The forecasts were disseminated through the Internet and smart phone apps. The operational performance of the beach water quality forecast system during 2010–2011 is presented for 16 representative beaches. An overall accuracy of 78–100% in forecasting compliance or exceedance of the water quality objective (WQO) can be obtained, with correct positives (exceedances) of approximately 30–70%. A parameter analysis reveals beaches with different characteristics: (1) beaches dominated by nonpoint pollution sources; (2) beaches affected by nearby point source pollution; and (3) clean beaches that are relatively free of pollution. As compared with the current beach advisory based entirely on sparsely sampled data, the number of incorrect forecasts of WQO exceedances (beach incorrectly open) can be significantly reduced by 25% using the forecast system. The corresponding reduction of excess illnesses attributable to the incorrect open forecasts can be estimated to be approximately 30%. The forecast system is able to enhance protection of public health while allowing maximum beach access.
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Acknowledgments
This work is supported by the Hong Kong Jockey Club Charities Trust (Project WATERMAN) and in part by a grant from the University Grants Committee of the Hong Kong Special Administrative Region, China (Project No. AoE/P-04/04) to the Area of Excellence (AoE) in Marine Environment Research and Innovative Technology (MERIT). The assistance of the Hong Kong Environmental Protection Department, Drainage Services Department, Hong Kong Observatory, and the Leisure and Cultural Services Department in this project (2007–2011) is gratefully acknowledged. The authors would also like to thank the members of the Croucher Laboratory of Environmental Hydraulics of The University of Hong Kong for their kind assistance in conducting the field work and laboratory measurements.
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Information & Authors
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Published In
Journal of Environmental Engineering
Volume 140 • Issue 2 • February 2014
Copyright
© 2013 American Society of Civil Engineers.
History
Received: Jan 9, 2013
Accepted: Oct 16, 2013
Published online: Nov 18, 2013
Published in print: Feb 1, 2014
Discussion open until: Apr 18, 2014
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