For a few months this year the rain water I collected during the Spring period provided enough moisture to keep everything alive. The water collected in the ´chacca´ or small swimming / plunge pool which was originally part of the agricultural water system on the farm which predates the house. The pool was renovated by us and seems pretty water tight now. I read advice on the Internet that water cress added to any standing water would help to avoid algae build up. The watercress helped for a couple of weeks but then the hot Spanish sun burned it up and the watercress joined other failures on the compost heap. If we get sufficient rain next year I will try the cress earlier in the season though I don´t think it will ever make the salad drawer in the refrigerator.