Mathematical analysis for comparing water transparency measurements with two different Secchi disks

Abstract

The Secchi disk is a simple device easy to use. It measures the transparency of water. The different diameters and colors of the disks did not allow easy comparisons. Following the international norm edition (ISO 7027-(2000)), we have compared the measures we made during six years with disks we already have. To match former data with the international norm, we have used two statistical methods: the Lin concordance coefficient and the Bland and Atlman method. Thanks to methods, the quality of the regression between the measures of disks was checked and a correction formula can be suggested. The transformed data can be used for further studies of the water quality of alpine lakes.