Rainwater systems
Article written here based on below links forthcoming.
Introduction
Municipal water networks are vulnerable to disaster events like earthquakes, flooding, pollutants and water shortages caused by drought or poor management. With a rainwater system a home or community can capture and collect water suitable for drinking, cooking and gardening even during periods where there is insufficient rainfall to satisfy the public water network. Other benefits cited by the collection of rainwater include reducing expense (in regions where water supply is not free), lowers local demand on freshwater resources, reduces risk of flooding in low-lying areas and slows erosion in dry environments[1]. Water is typically captured from a sloped roof, but it can also be captured from a structure deliberately built for the purpose.
Linkdump
Great overview of home-scale rainwater systems, with some handy calculations (Imperial) to help think through needs and supply
https://www.treehugger.com/beginners-guide-to-rainwater-harvesting-5089884
Another 101 guide, possible commercially affiliated. Good overview, same good quality diagrams as seen in above article
https://cleanwatergear.com/rainwater-harvesting-systems/
And another 101/overview, with a functioning roof surface catchment calculator
https://www.watercache.com/education/rainwater-harvesting-101
Article on care and cleaning of rainwater tanks
https://rainwaterharvesting.org.au/care-maintenance-of-rainwater-tanks/
Great collection of helpful images on rainwater harvesting
https://www.pinterest.ch/ServiceHomeTholen/rainwater-systems-regenwater-systemen/
Interesting article of a very low cost solution using multiple steel barrels
https://survivalblog.com/2017/04/19/rainwater-harvesting-an-easy-and-efficient-build-by-l-r/
The same low cost 'rain barrel' system outlined here, fed by downspout. This looks ideal for water infrastructure disruption fallback, to tie a household over for a week or so. They cite USD150 total cost:
https://www.treehugger.com/make-rain-barrel-system-at-home-5194982