My conversation with a hard core Permie (HCP):
C: So our orchard design does not use swales
HCP: WTF? You don’t use swales are you crazy?
C: Probably, but I am an orcharding geologist and I have rationalised that with my soils swales are not very effective
HCP: Whoooaaa have you checked this off with David and Bill?
C: No didn’t figure I’d need to, thought they would appreciate independent thinking
HCP: Okay then independant fancy pants geo explain why swales are no good for you?
C: Well…. very purposefully we made sure our orcharding operation was on marine sediments deposited many millions of years ago when Victoria was the sea floor, these sediments created alternating layers of mudstone and sandstone which once weathered resulted is a very deep, friable and well drained soil.
HCP: Still can’t see how that means swales are of no use to you?
C: Well permies use swales to slow, spread and soak water into the landscape where it would otherwise runoff and be lost however my soils are so well drained that water very rarely runs off, it all soaks in anyway. Try building a dam in Stanley!
HCP: Okay I am starting to see your point, so does that mean that swales are useless in any free draining soil?
C: Pretty much however will depend on your slope and how your soil responds to summer dryness. Some soils that might drain well when moist can harden off under the summer sun meaning summer storms will runoff, in that case swales would be useful however I’d prefer to put swale making time and energy into building organic matter and improving soil structure which would reduce summer runoff and improve plant growth at the same time.
HCP: Do you use any keyline design then? You do know that P.A. Yeomans was well loved in the Kiewa Valley.
C: You know your history. Yep our orchard rows are designed using keyline principals meaning they help disperse water from wetter gullies to drier ridge lines. It took a lot of design work, time on the gps, GIS and laser level however well worth it. Our orchard is still irrigated though, there will be many years where we don’t have to irrigate however with our increasingly variable climate there will be many when we do.
HCP: Nice one Charlie, I need to get back to my mandala.
note: I have not gone all ad hominem on deep permies, this is essentially my internal dialogue between my inner deep and getting deeper permie and my inner deep and getting shallower industrial rationalist.