Eric, I have done this in a seasonal spring, I obtained a 3000 gallon, new but defected septic tank, and buried it below the spring, this spring sits in the bottom of an annual creek. You have to cover the inlet with filter cloth, or landscape fabric, the best way is to wrap the fabric under the tank and bury it that way it wont slip off, the weight and pressure applied is enourmous. Without the fabric at the end of one season you end up with a silted in tank.
josh

Josh,

I thought about the silt problem. hmm

I also have a duck pond this stream / ditch fills. Why would I go through the expense of a tank and not just deepen the pond? Thinking out load

Eric

That would make more sense, and the water is pre-fertilized :0)
josh