It's really worthwhile to install a rainwater tank on your property.
It'll save loads of $$$ off your water bill by utilising rainwater in your garden, to wash your car and even fill up your pool.
Water harvested by rainwater tanks is drinkable and some people even prefer the taste to standard tap water.
For smaller gardens, try bladder-type of Modtanks, they preserve space effectively.
Toroid tanks are built underground (but require minimal excavation) so you don't lose any of your garden space and you can actually connect the Toroid to other tanks for a larger water collection.