Water storage does not begin with a tank. It begins with soil.
Healthy structure, roots, organic matter, vegetation and biological activity can all increase the ability of a landscape to intercept and retain rainfall. Our reservoirs and tanks remain extremely important, but so too are terraces, vegetation, mulch, compost, roots, ponds and functioning soil.
Each provides another opportunity to keep water within the landscape for longer. In a Mediterranean climate, winter rainfall is effectively a deposit into the landscape's water account. The challenge is keeping as much of that deposit available as possible for the months when rain disappears.