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BatheWatch user guide

Publication date:  June 2013
Publication reference number:  ME 478

The BatheWatch user guide is for users of BatheWatch software. It was prepared for the Ministry for the Environment by the National Institute of Water & Atmospheric Research.

BatheWatch software

The BatheWatch software has been developed to assist in the assessment and monitoring of recreational areas bounded by water areas. Using BatheWatch, the user can perform either a marine or freshwater assessment. The software has been specifically designed to help councils determine the suitability for recreation grade (SFRG) or beach grade. 

If you have any questions about Bathewatch please send us an email,

Hazen percentile calculator

The Hazen percentile method is the percentile used in the Microbiological Water Quality Guidelines for Marine and Freshwater Recreational Areas and associated Bathewatch software. The Hazen percentile calculator is an Excel file that uses macros to calculate the percentile of a data set using the Hazen formula.

As there is no one correct way to calculate percentiles, the Hazen method is a "middle-of-the-road" option. Other percentile methods include Blom, Tukey, Weibull and Excel (the standard formula used to calculate percentiles in Excel). The methods vary in the minimum number of data they require, the formula used to calculate the percentile and the actual result. For example, the Excel percentile method always gives the lowest percentile result, while the Weibull method always gives the highest.

This Excel file calculator can calculate a Hazen percentile for up to 2000 data per site for multiple sites simultaneously and different percentiles eg, 5th percentile or 95th percentile.

Select ‘enable macros’ when opening the excel file.

Hazen Percentile Calculator - version 2 [EXCEL, 217 KB]

If you have any questions about the Hazen percentile calculator please send us an email,