Not sure for what purpose ...
Published by Martin P. Pelle, Water Technology Advisor, Engineering & Built Project Utility Team EMEA at Cargill
Not sure for what purpose you are asking this: city applications or rural applications, developed areas or developing areas to help them become self-reliant.
We did several fruitful projects in rural areas of Sri Lanka with internationally known foundation http://lankarainwater.org/wp/?page_id=364. Check out their website for links, ways to calculate how large your catchment area should be versus climatic data (dry/wet season) versus size of the (cheap) tank and efficient first flush to prevent dirt coming into the (above or underground) tank AND prevent mosquitos to infest the water (Dengue/malaria). AS another application of the water you could consider gardening high added value crops.
Sri Lanka has a more than 3000 years (also Royal) history of the early Kings to invest in catchment of rainwater, and using that for agriculture. SO they do know one or two things.
Good luck