"claude rogers" writes:

When you guys top off your ponds from evaporation, waterfall spillage and
"splashage" Water changes, etc.
How do you determine how much water by gallons I guess you are putting in.
Reason for asking is I always dump in some dechlor/chloramine stuff,
generally I just guestimate it, is this what everyone else does, oh, and do
you put in it before of after you top off the pond....Claude

You can calculate it by knowing your surface area and how many inches
of water you will be adding.

pond width in feet x pond length in feet x inches water added / 12 = cubic feet added

cubic feet water x 8 = gallons

/ 12 to convert inches water added to feet
x 8 because 8 gallons of water per cubic foot

Personally I wouldn't bother if the percentage changed is small,
say 5% but you should probably measure the chlorine to be sure.

HTH