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WATERMAN / Beach Water Quality Forecast

Beach water quality forecast and detailed information are provided for the following beaches only:

Please click a beach for details: Prediction results for 02/02/2022
Tuen MunTsuen WanIslands DistrictTai PoSai KungSouthern DistrictLower Cheung Sha BeachButterfly BeachPui O BeachCastle Peak BeachKadoorie BeachCafeteria New BeachGolden BeachSilver Mine Bay BeachMa Wan Tung Wan BeachDeep Water Bay BeachRepulse Bay BeachBig Wave Bay BeachShek O BeachSilverstrand BeachClear Water Bay Second BeachClear Water Bay First Beach

1. Big Wave Bay Beach    2. Butterfly Beach    3. Cafeteria New Beach   
4. Castle Peak Beach    5. Clear Water Bay First Beach    6. Clear Water Bay Second Beach    7. Deep Water Bay Beach    8. Golden Beach    9. Kadoorie Beach    10. Lower Cheung Sha Beach    11. Ma Wan Tung Wan Beach    12. Pui O Beach    13. Repulse Bay Beach    14. Shek O Beach    15. Silver Mine Bay Beach    16. Silverstrand Beach   

About this Pilot System

The Pilot Beach Water Quality Forecast System was first launched on March 22, 2010, in celebration of the International World Water Day 2010. The first launch provides daily forecast on 10 representative beaches to 200 registered users. With the success of the pilot testing in 2010, we are making the system accessible to the general public on August 8, 2011. The system covers 16 representative gazette beaches. The following sections give you a quick idea of what our forecast system is about. More details can be found from our Frequently Asked Questions.

What is Beach Water Quality Forecast?

Swimming in sewage-contaminated water may result in gastrointestinal and skin illnesses. Epidemiological studies of swimmers at Hong Kong beaches have demonstrated a strong relationship between the level of Escherichia coli (E. coli) and the incidence rate of swimming-associated illnesses.

To protect public health, Project WATERMAN has developed a beach water quality forecast system by predicting the concentration of the E. coli concentration at a beach. The forecast system is developed from an integrated approach based on statistical methods, hydrodynamic modeling and data-driven hydro-informatics tools. The model takes into account the most relevant environmental and hydro-meteorological parameters such as rainfall, solar radiation, onshore wind, tide level, to provide daily forecast of beach water quality.

What is Beach Water Quality Forecast Index?

The beach water quality forecast index is a four-level index system indicating the risk of contracting swimming associated gastro-intestinal and skin illnesses. An index of 1 to 4 is issued to the beach on a daily basis, which provides clearly defined categories associated with different health risks.

Beach Water Quality Forecast Index Predicted E. coli concentration
(counts / 100 mL)
Health risk *
≤ 24 Negligible
25 - 180 Low
181 - 610 Moderate
> 610 High
* Health risk: Risk in getting swimming associated gastro-intestinal and skin illnesses.

What is the difference between Beach Water Quality Forecast Index and Environmental Protection Department’s Weekly Beach Grading System?

The Beach Water Quality Forecast Index and the Environmental Protection Department (EPD)’s Weekly Beach Grading system are two different systems although they use similar grading scales. The EPD monitors the beach water quality regularly, and uses the most recent 5 sets of sampling results to grade the beach to reflect the recent water quality status. The EPD beach grading does not necessarily correspond to the WATERMAN daily forecast, due to the natural fluctuation of bacteriological indicator levels in the water bodies at different time and locations. The weekly beach grading is updated on a weekly basis, and is NOT intended to forecast beach water quality.

In recognition of the changing beach water quality, the Beach Water Quality Forecast Index predicts daily water quality status by applying the state-of-the-art mathematical model based on updated hydro-meteorological information. Nevertheless, inherent uncertainty is associated with any forecast, and the forecast results should be considered as supplementary information for reference by the beach users, and should not be confused with the weekly beach gradings of the EPD.

The current forecast considers the past 3 days’ meteorological information up to yesterday’s midnight. As beach water quality may have changed with reference to the weather for the immediately past few hours (e.g. water quality may improve under sunshine condition, or may deteriorate shortly after heavy downpours), beach-goers are advised to take note of the current weather together with the Beach Water Quality Forecast Index.

Evaluation of the Beach Water Quality Forecast System

The WATERMAN system is validated against the regular beach monitoring data of the EPD in the bathing season (March to October) in 2010. The system predicts compliances/exceedances with the beach water quality objectives with an overall accuracy 80% or above. Lower accuracy is obtained at beaches in Tsuen Wan district, where revolutionary improvements in water quality pattern have been observed in 2010 due to the implementation of disinfection facilities at the Stonecutters Island Sewage Treatment Works.

System validation will continue to further improve the capability and reliability of the forecast system, and to cope with the changing water quality and hydrological conditions of Hong Kong’s waters.



This Pilot Beach Water Quality Forecast System is purely for research purpose. While every effort is made to ensure that accurate information is disseminated through this medium, Project WATERMAN makes no representation about the content for any purpose, and assumes no responsibility for anyone’s use of the information.

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Quick links

Islands District
Sai Kung District
Southern District
Tai Po District
Tsuen Wan District
Tuen Mun District

About this Pilot System


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