Determine the width of individual sections

Hello, maybe it is a really simple question but I’m new to ParaView.
In the picture you can see a simulation of the water depth on a street section with a tilt along and across. Now i want to know how big the areas with different water depth are. I know how do to it with calculator and histogram and excel to get the percentage but for such easy cases like shown in the picture with constant tilt it is to laborious.
Is there an easy way to get the width of every area? (width 1, 2 and 3 in the picture)

Thanks for your help in advance!
Best regards Raphael

A Ruler source would be a quick way to get the info