My first thought is at the bottom and to put a swale before the HK. The 1 reason you might not want to put it at the lowest point on your property would be if you are worried about frost settling at the lowest point -but maybe the plants on top of the HK would be above a frost pocket. The other reason is you may want to capture water higher up. Depend what else is growing and how hard does it get hit by drought.
My project thread Agriculture collects solar energy two-dimensionally; but silviculture collects it three dimensionally.
you dont want a hegel (hill), you want a trough. and you want 2 , one at the base of each grade.
put one at top of property, at head of grade. work back the distance of width of canopy of desired trees. you want to build long term for trees, even if planting crops now. nature always builds to trees, and you dont want to fight it because it gives you windbreak, shade, and leaves for mulch and compost.
dig a trench across, on level, or slightly eyebrowed swale. dig down at least 3 ft. dump in dead wood, or if not fully decomposed, char it a bit, but dont burn bark all the way off. if you burn a bit in the deep pit , you are ok, but dont burn in shallow, cuz you will kill all soil bacteria.
fill pit with wood and brush. let it rain on it a bit. sprinkle in some fertilizer, or sea water salt (full spectrum fert, see agri-grow) to prime the pump, and hasten the day it will supply instead of demand. backfill at least 2 1/2 feet. it will sink later quite a bit. hill up left over dirt just below to trap water to percolate down to wood.
you can just spray lightly with seawater too, but then you are adding mostly calcium chloride, the bitter, salt building part of saltwater.
If you have some high quality, moist compost, is good to sneak some in, in spots about a foot down. save some small brush to dig in with it, for it to decompose.
otherwise , you are prob going to have to add innoculant to get a dirt community of fungi going.
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