Stream networks are delineated from a digital elevation model (DEM) using the output from the Flow Accumulation tool by applying a threshold value to the results of the Flow Accumulation tool using either the Con or Set Null tools.

Input conditional raster : flowacc

Expression : "Value > 100"

Input true raster or constant value : 1

Input false raster or constant value : ""

Output raster : stream_net

But I need to calculate threshold value that can replace 100 in the expression: "value>100"

Thanks in advance