As the drought in California continues and the wells are sputtering it’s time to take a more serious look at domestic rain water collection.
With the rising temperatures, the snowpack in the Sierras is decreasing and the melting freshwater, we rely on for irrigation drys up too quickly. If we however can harvest the rain and store the water in cisterns and reservoirs, we should have a sustainable water source.
Up until this point I have ignored these systems due to the relative high cost of a large capacity (10,000 gal) system. This is the minimum size I would need to sustain irrigation over the dry/hot summer months.
Why bother – my well is producing just fine – Right?
Not so sure anymore – it’s time to start thinking about how we can use the well water only for domestic use and calculate the capacity, configuration and cost of a rainwater harvesting system for irrigation.
At a glance a 10,000 gal system would cost me about $10,000 I figure. $6k for the collection tank and probably another $4k for pipes, pumps and installation. Ugh – more pumps for my off-grid system (read: https://modern-off-grid.com/2015/04/23/pumps-are-bad-news-for-off-gris-systems-here-is-how-i-solved-it/)
I’ll update this post as the project progresses – but so far I’ve made a few initial calculations:
If I redirect the drain pipes for the gutters on one side of the house (too hard to use both sides since the drain pipers are buried deep in the ground) I still end up with roughly 50′ x 30′ = 1,500 sq. ft. surface area. 1 foot of rain (12″) will then produce 1,500 cu ft. ~ 11,250 gal of water!
We have rain-year-to-date (since October 1st) received 10″ of rain up here on the hill – with a yearly avg. of. 40″. BTW we need about 100″ this year to make up for the previous drought years.
I can reasonably expect another 30″ of rain this year – or 3x the water I need to collect. So the math works out now it’s just a matter of the practical implementation.
This is the basic system design (thank you http://www.watercache.com/education/rainwater-how/)