Calculating Surface Area

Easy! Length times width, right?

Question is, my (soon to be) pond will have about 104 square feet of surface
area. There is a waterfall, with a series of smaller 8" deep pools that
cascade into the pond. The waterfalls and their pools comprise about 34
square feet of surface area.

When sizing things up, and using the rules of thumb for plants, fish, etc.,
does the surface area of the falls count [do I consider it to be 104 sq ft,
or 138 sq ft]?

Thanks!