# Calculating volume using polygon instead of contour line in ArcGIS Desktop?

What I'm attempting to do is calculate the volume of a lake using a polygon I created by classifying an image for water. I then extracted the polygon from the classification process. What I'm left with is a polygon showing the surface area of the water. I have a DEM of the lake. How do I determine the amount of water this lake contains? I don't want to use a contour line if I dont have to because the heights vary at the edges of the lake.

This is with ArcGIS Desktop.

• I think I may have found my solution. I converted the raster dem to a TIN and I'm trying to use the polygon volume tool. Except, I'm not sure what to put for the height field.... in_height_field The field in the polygon's attribute table that defines the height of the reference plane used in determining volumetric calculations. String May 14 '16 at 18:13
– PolyGeo
May 14 '16 at 20:57

I assume that what you call “DEM of the lake” is DEM of lake bottom and surrounding area.

If this a case, it is a few steps procedure main ones being calculation of lake bank altitude and average lake depth.

• Convert lake polygon to polyline, using feature to line tool
• Set environment settings snap raster to DEM, cell size = one for DEM and convert polyline to raster using any numeric field, output to raster “BANK”. Use raster calculator expression:

Con(~IsNull(”BANK”),”DEM”)

Output to raster “bankZ”.

• Right click on bankZ, SOURCE and scroll to see mean value. This is average altitude of lake bank (meanZ).
• Create numeric field in polygon and populate it by meanZ. Convert polygon to raster using that field, output “surfaceZ”.

• Use raster calculator to calculate lake depth accounting for imperfections in DEM and lake delineation.

Con(“surfaceZ”>”DEM”, “surfaceZ”-“DEM”,0)

Mean value of output is average lake depth. Now you can compute lake volume because lake area equal area of your polygon. Be careful with units