If you do have a hill, you can use it for an orchard in the Israeli style.
Imagine a grid on it, now turn it 90^ so you have a diamond layout.
Run the drip line down one side of the diamond/V down as far as you are going to plant.
You will want the feed lines seperated by at least 15/20 ft, for the crown of your trees.
Go to the start of the next diamond/V and run the feed line down in parallel to the first. And again
You should Have parallel lines of hose running down the hill at a little less than 45^.
The top one will be a V soon, right now it will look \\\\
If you take a string and cross the \\\ with string /// , you can figure out where you are going to dig the hole for the tree at the bottom of the Vdiamond now. Then you can insert some feed lines from the main drip line, or screws into the feed line about a meter above the bottom of V, and at the bottom of the V . Now you can rake down parrallel to the string lines, and cover the drip feed lines. You want to protect them from the sun, but you are going to channel all the water down to the apex of the V, in every diamond area.
Start raking any dirt/rocks/ loose top soil down to the bottom 2 legs of the V, you want to create a catchment for any rain that falls in the V/diamond at the bottom. Now figure the crown width of your tree will be at maturity, and plant it half that distance up from the bottom join of the V.
If the crown will be 12ft, dig the hole about 6 ft up from the bottom point of the V. In very dry areas, i would keep it at 6ft anyway, so it has better water supply as a starter.
Dig your hole there at that 6ft point. Make sure the sides aren't smooth, as that will cause root binding in dry lands. Put a fish in the bottom (kidding) and plant your tree seedling with a small basin to the down hill side. Prob a crescent shape. Rake any extra dirt from hole down into your V, you want to make the point of the V taller than the sides to hold as much rain as possible.
That is the Israeli design. In china, and US irrigation style they would cover the bottom apex of the V with plastic to keep it from eroding when it does rain hard. Its not a bad idea at the very base of the V, as it will overflow and erode when it rains hard, then you wont have a catchment any more.
In SW US, They put flat rocks on the inside of the V berm, (and the outside/downhill of the V) and fill the bottom of the V with gravels and more flat rocks. The flat rocks allow the rain to flow off their sides, and capture moisture underneath. That reduces re-evaporation, and allows it to sink into the ground, and cuts down on weed growing area.
If you dump a bunch of organics or tree litter there, the water will just soak into the leaves and re-evaporate. Don't mulch with organics in drylands, unless you have drip lines underneath.
If you want to plant a ground cover on the arms of the V, to hold the dirt embankment steady, try looking for a Fuzzy Thyme. They are low water, bee friendly, and low growing. The whole thyme family also produces thymol, which is a topical anti-microbial.
You could also plant a rhizome freindly plant that matches your tree types, inoculating them for the long term.
I caught a case of skin MRSA from a gal who had been in India for a couple months. The thymol in a jar of marjorum oil was enough to kill it off, even after it had started to dig a crater in my skin. (pro tip) It burns for a while tho, don't put it on right out of the shower.
Thyme oil is crazy expensive, but the marjorum oil was cheap (online from India), cuz i think it is a cooking ingredient.
PS. marjourum makes a better pesto than basil too....
crude but the double angled lines are the embankment and the drip line, trees planted at base of diamonds.
