Stand pipe capacity calculations

[10Gallen]

Good morning all,
Can anyone provide advice as to calculating the capacity of a vertical standpipe acting as overflow relief in a pond? The only formulae I have that approximate the situation are for weir flow, but I'm not sure if it is applicable. I'm particularly interested in the performance as the water level rises.
Thanks for your attention,
Glenn Allen

 

[RWF7437]

Flow will transition from weir flow at low heads to orifice flow at high heads. Using this, you might be able to develop a rating curve recognizing that flows in the transition range are difficult to predict accurately.