Rainwater for Commercial Buildings

Here in the Hill Country we are going back to the practice of harvesting rainwater.   On October 9, 2010 in Dripping Springs, Texas, there will be "a celebration of collection, conservation and common sense."  See details on facebook under The Rainwater Revival. 

Here next to West Hill Center we have two commercial buildings with rainwater as their water source and a third commercial metal building that will use rainwater is framed.  Builder James Bailey has two additional commerial buildings using rainwater.  It works!  Rainwater makes sense! Surface water from LCRA is used by the Deer Creek subdivison north of us and in fact we have a contract to bring LCRA water to our properties.  Why?  Isn't the water source Lake Travis rainwater?