Harvest more rainwater with a living sponge than with a water tank
You can grow tanks (and living pumps), rather than buy them, and they’ll have a lot more water-harvesting capacity.
This video (filmed summer 2021) is about how living sponges (rain gardens) have far greater capacity than non-living manufactured water tanks, in that they utilize and infiltrate water during and immediately after rains to quickly make more room or capacity for the next rain – even if that rain comes just a few hours after the first rain.
Thus rain gardens (in this case, a water-harvesting, traffic-calming chicane or pull out) typically have much more potential for flood-control, groundwater-recharge, bioremediation (natural filtration of toxins), and heat-island abatement (due to the shading/cooling vegetation they grow and the cooling effect of the water transpiring through these “living pumps”).
This works in any climate, but the vegetation changes as you change bioregions. The easiest path to success is to use plants native or indigenous to your area and site’s microclimate. Go further, and select native plants that also produce food, medicine, craft/building materials, etc so you grow living pantries, pharmacies, craft suppliers, etc.
At minimum, make sure your tanks overflow to rain gardens, so that overflow is used as a resource. And place those rain gardens and their vegetation where you most need that vegetation, such as trees on the east and west sides of buildings to shade out the morning and afternoon summer sun for free, passive cooling.
The ideal, is that once this rain garden vegetation has become established the only irrigation water it will require is the freely harvested on-site water, so no importing/extracting of groundwater, municipal water, or other is needed. This way we can infiltrate more water into the living system than we take out – thereby enabling the recharge of groundwater, springs, and rivers; instead of their depletion and dehydration.