Creating surface area of water body by DTM and water level gauge

[RuedigerFuerll]

Hi folks,
do you know whether its possible to derrive/create surface area of a water body by applying only DTM and

water level gauge in GIS?

The attachment illustrates the DTM for the water reservoir , red lined the described aim, to create a surface ( or even polyline) by appying water gauge level.

Are further data required for that task?

Thanks for your comments.

surftrial

[DavidPike]

Just to be sure you mean surface area? If the DTM has hydrology removed you could count null cell values or whatever the common value for that water body is? That DTM may also have a large temporal resolution.

Better yet grab some multispectral imagery and run hydro detection band combos on it, turn to polygon then find Shape_Area.