So... if my annual rainfall is ~10", and each 1" per square foot is 0.5 gallons. I would need roughly 3,600 sqft of area to collect enough water to supply one person with the average 50 gallons/day a person uses. These are very generous estimates. My area actually gets 11.4" annually, and 1 sqft of cover will collect 0.63 gallons, but I believe this margin is realistic for calculating water requirements in this area. 10" annual rainfall × 0.5 gallons per sqft × 3,600 sqft = 18,000 gallons annually / 365 days =~ 49.3 gallons per day So, a 60' × 60' surface would be required to supply one person with enough water to last the year, given an average daily useage of approx 50 gallons per day in an area with an average of 10" of rainfall per year. I plan to build a small adobe style home in these conditions, roughly 2,400 sqft, so I need to add more roof surface to meet my water needs. A good excuse for a big covered porch. That does not include allowances for gardening, livestock, a family, etc... which could raise daily usage from 50 gallons/day to around 350 gallons/day, meaning roughly a bit more than 1/2 acre collection area to support one family living off-grid. That's a tremendous amount of cover.
So... if my annual rainfall is ~10", and each 1" per square foot is 0.5 gallons. I would need roughly 3,600 sqft of area to collect enough water to supply one person with the average 50 gallons/day a person uses.
These are very generous estimates. My area actually gets 11.4" annually, and 1 sqft of cover will collect 0.63 gallons, but I believe this margin is realistic for calculating water requirements in this area.
10" annual rainfall × 0.5 gallons per sqft × 3,600 sqft = 18,000 gallons annually / 365 days =~ 49.3 gallons per day
So, a 60' × 60' surface would be required to supply one person with enough water to last the year, given an average daily useage of approx 50 gallons per day in an area with an average of 10" of rainfall per year.
I plan to build a small adobe style home in these conditions, roughly 2,400 sqft, so I need to add more roof surface to meet my water needs. A good excuse for a big covered porch.
That does not include allowances for gardening, livestock, a family, etc... which could raise daily usage from 50 gallons/day to around 350 gallons/day, meaning roughly a bit more than 1/2 acre collection area to support one family living off-grid. That's a tremendous amount of cover.