Water Technology (3rd edition)
Chapter 9. Water Quality Assessment
It is not always appropriate to simply take the mean value of ions without taking the volume into account, especially when more
detailed estimates of loadings are required. With episodic events such as rainfall then associated ions may only be deposited in
large amounts on a small number of occasions. In these cases the normal mean would be highly screwed. It is very simple to
calculate, especially using EXCEL . See methodology.