How to Calculate Volume of Reservoir/Lake/any waterbody using GEE and ArcGIS

[@huihuiKing]

you can't leave the plane height blank. To determine the water surface elevation of the lake, calculate the average or other statistical values (such as the median) of the elevation values along the shoreline. This value can be used as the lake's water surface elevation.

[@ignaciogarcia3243]

In my opinion, the exercise is not well planned. This is because you cannot use a DEM as bathymetry. You are only calculating the volume of the lake "assuming" that the DEM shows said bathymetries, but strictly speaking this is not correct, since you do not have the real morphology of the lake and you are only entering the altitude at which the SRTM took the images.