1) Find the key point of the land . This is where the slope of the land changes from convex to concave. The key point in a valley is the ideal place to site a dam, if the subsoil is clay. A dam here would be able to water crops in the valley floor.
2) To the right and to the left of the key point, mark out the contour line. For this you would need a laser level, dumpy level, Bunyip water level, or 3 pieces of wood made into a sturdy A frame with a spirit level taped to the horizontal member
3) This contour line which passes through the key point is known as the Key Line and is permanently marked by a line of trees, a road , a fence line or such like.
4) Your plough is pulled parallel to the key line , above and below it. The plough lines fill with water when it rains and prevent water run off. The shoe of each tyne creates a space underground, and only a slight bump with a slit cut into the surface of the soil. Rain water enters through the slot and sits in the air chamber, safe from evaporation. During a rain event water percolates slowly into the soil surrounding the air chamber. A warm and humid atmosphere in the chamber creates a good habitat for soil biota. When the soil reaches saturation point , any excess water is collected in the dam at the keypoint. Its all laid out in PA Yeoman's classic book "Water for Every Farm",
I have never read the book because I have not managed a large farm with clay soil . We have sandy soil, which doesn't respond so well to the Yeoman's plough. The response of farms on the Eastern states with their
summer rainy season and heavier soils is phenomenal, and of course there is plenty of farms in WA which would totally regenerate with this treatment.
P.A. Yeoman's son Allan Yeomans lives in Surfers Paradise and has done amazing work on floating parabolic solar thermal power stations, as well as improving on the design of keyline ploughs. http://www.yeomansplow.com.au/10.htm
Allan was talking publically about carbon sequestration to avoid climate change back in the 80's! He has this to say ( on his website) about his plough and soils: "Creating fertile soil is easy. Rich top soil is just dead subsoil plus a lot of reasonably stable humus plus a heap of active fungi, a mass of air breathing microbes and lots of earth worms, all with masses of dead plant root material to eat, air to breathe, water to drink and space to live in. If your soil is like that you know you don't have a problem growing anything.
For nature to create space, unassisted, it had to wait for a tree to grow to maturity, then wait for it to die and then eventually fall over so finally the tree's roots could loosen up the deep, hard, subsoil.
Or nature can do the job with grasses. That works, but it can take centuries for grasses to battle their way into dense compacted subsoil and loosen the stuff. It took centuries to create the deep, rich prairies and savannas of the world.
In an instant you can create the space needed to allow soil life to do its thing, to massively proliferate. One deep pass with a subsoil plow that produces minimum disturbance of soil layers and the perfect microbe and earthworm housing estate is created. The soil fertility creation process can thus be speeded up....What took centuries can be done in two or three seasons.
Pouring expensive chemicals, year in and year out to just produce saleable crops is invariably more expensive than turning poor soils, dead soils and “worn out” soils, into rich and permanent and hugely productive soils.
The end products of all this soil [microbial] activity are stable humic and fulvic acid molecules. Really the difference between the two is academic. They are both mainly made of carbon atoms. And technically, that mixture is what “humus” is. The individual molecules are enormous. They contain hundreds of carbon atoms."
The large humus molecules are negatively charged, so they attract and loosely hold the soluble soil minerals which would otherwise be washed away every time it rains. To quote Allan's website again,( and it is a rich source of information re the Key Line system) "Storm rains go straight into the deep worked soil. Storm erosion vanishes. There is just no wash. And with all that water and air, and provided the microbes and fungi have some dead root material to eat, then soil life will just explodes.... creating fertility..."