Hi, I'm quite new at this so would appreciate some advice. I'm living in Portugal and have begun to incorporate permaculture methods into an already existing orchard. It's olives and mixed fruit, built on a semi-steep slope- with a heavy clay soil. Given the water situation here, I'd like to put swales in - but wondered if...(a) this is a good idea for trees such as olives, built not to need much water? And (b) how to put these in. My idea is to dig them between the rows of trees across the hill, fitting to contour of course. But once i've dug the swale, do I put stone or loam in the bottom? Do I cover them over?