Hi, I finally managed to create DEM from bathymetry points and calculate the volume, but the output does not make sense. I guess I need to modify the units or coordinates. I don't know how. Here is the output (My input surface is the elevations of the bed in meters above sea level (m asl) in GCS_WGS_1984 and decimal degrees and my Plane Height is the reservoir full supply level (FSL) which is 556.87 m asl:
Plane_Height, Reference, Z_Factor, Area_2D, Area_3D, Volume
556.87, BELOW, 1.00, 0.053866900608273, 126.88623569244, 1.3850421777189