Good Luck cm,
Some folks like the idea of siphons, some dont.
The link above is a good example to use, IMO.
(added) The size of pipe plus other factors will determine how much water the system will move (additionally - something to think about) larger pipe equals higher cost. The size of pond, watershed, average rainfall and other factors will determine what size pipe you should use. (Maybe) your NRCS person can help with that?
Here is an interesting link on pipe flow rates too:
http://www.sahra.arizona.edu/programs/water_cons/resources/pipeToFlow.htm happy reading!