With only 15inch of rain, you are going to have to give your nuts 3x the normal spacing so that you effectively have 45inch of rain (15 X 3).
If you are able to pool the runoff by the plants even better (
swale on contour or 60ft basin/depression for each tree).
Areating the soil will make it easier for the plants, mineralizing/balancing the soil (rockdust/etc), making the mineral more bio-available by increasing the soil life (fungi-microbes) and also with
biochar.
As for which nut trees I would use, uzbek pistachios, almonds, chickapin chesnut, yellowhorn, sweet kernel apricot, (you can probably try some hazelnut), then there are stuff like monkey nut and pine nut, etc.
Iterations are fine, we don't have to be perfect
My 2nd Location:Florida HardinessZone:10 AHS:10 GDD:8500 Rainfall:2in/mth winter, 8in/mth summer, Soil:Sand pH8 Flat