Make sure to have anti-seep collars on any pipes going thru the dam. We lost 7' of water in our pond in only one day due to a leak cause by a faulty collar! Try to have the pond's outlet at the end were the prevailing winds blow towards. This helps greatly to get rid of floating agae blooms and pollen on the water's surface when you get a good water flow from rain storms. You also might want to have a overflow pipe that has adjustable elevations in order to control your water levels at various times of the year. Some people do a winter draw down level in order to control underwater weeds.
