Collecting Rainwater

I find it necessary to harness the surface water for use at a later stage.
Why not use the natural resource that is given to us?!?
Many governments are willing to fund the installation of rain water collection systems.
The systems that are being marketed can vary from customizable barrels, cisterns and tanks. These systems may need dedicated piping that include filtration of debris and pumping to fixtures that you may choose to operate using stored water.
The start up cost are relatively inexpensive, and you conserve water used from a municipality. I view the only downside to a dual system is the uncertainty of the rainfall, at times there may not be enough water to use in your system. This is also why a "dual" system (still linked to a municipality) would be a good idea.
But why not save a little precious resource and green cash!?!