Where, di, G is the Euclidean distance between optimum point G and water sample i, and di, B
is the Euclidean distance between worst point B and water sample i. Ei is the osculating value
of i sample. The min {di, G} and max {di, B} are the minimum and maximum of optimum and
worst point distances.
(5) Water quality assessment
All samples and standard ranks are ordered from small to big according to the calculated
osculating value Ei, and water quality is determined by the osculating value. For example, the
water sample locate before rank 1 is classified into excellent quality water, and the water
sample locates between rank 1 and rank 2 is good quality water.