Thank you, Faith. I was not aware of any of this. I presumed the lake was spring fed. Also, having spent many years living on a South Texas ranch, water was seasonal except for the artesian well. That is, when it rained, the tanks were full; when it didn't we filled outside bath tubs for the stock.
I guess I just find it a little startling that in a time when we all need to conserve (last month my SAWS bill was $31.00) we would even consider buying water for this purpose.