We just finished building a 4 acre lake at my place in South Texas. The tank portion by the damn is 20 foot deep. We had a waterwell drilled and have a 2 inch pipe running to lake. Before we started the well, we got a real good rain. It filled the tank up by about 4 foot of water. The water went down about 1 foot in the last two weeks. Here is my question, how do i know if my tank is going to leak or if this is just normal for a new lake (this is what the guy who built it said). I haven't turned on the water well because if i need to add bentonite i want to do.

Should i wait another couple of weeks to see if it keeps draining?

Any recommendatios are appreciated.