Irrigation water recovery

[Leucadian]

Southern California is heaven for growing orchids, but the water situation is not good. Our water is relatively salty and alkaline, forcing many of the commercial growers here on the coast to use reverse osmosis water.

I have been collecting rainwater for the last 2 years, and the plants look terrific, with no leaf tip burn. But it hardly rained last year, and I have nearly exhausted my supply, maybe a couple of weeks left.

I am considering an inexpensive consumer RO system, with the idea of saving the good water for the orchids, and using the rest for landscaping. At the same time, I am planning a greenhouse of about 500 square feet, and I'd like to capture the runoff to send to the fruit trees. I can let the RO system run during the day, powered by solar cells.

My first idea was a cement floor draining into a sump of some sort. The other day someone suggested a plastic sheet (technically a GeoMembrane as used for ponds and catchment basins) with a topping of gravel (and a layer of sand maybe) for the walking surface. That would provide humidity as well, I expect. A third alternative would be a trough system of corrugated fiberglass sheets under the benches, draining into a gutter/tubing system to convey with water for disposition. This would probably be the cheapest but the least elegant solution. I'm leaning toward the GeoMembrane, but don't have a cost yet.

Thoughts?