Maybe someone can shed some light on how to solve this problem. My garden is very fast draining sandy loam on a hillside, we have a healthy mole population, so the soil is super aerated.
I've made an investment into an extensive drip system, but after getting $1200 water bills and seing my trees drought stressed despite the watering, I tried switching to above ground micro-irrigation. But that has turned out to be even worse.
Finally, this year, I just decided to shut off the entire irrigation system because it's pointless. Instead, I've manually created swales and once a week, I just flood the swales with a hose and I also make sure to close up any mole created burrows. The test is to watch for standing water, as long as the water stands for a few minutes, then i know it's not draining off into mole tunnels. The plants are doing incredibly well and the water bill has dropped to a reasonable $200.
However, this is requiring that I spend a considerable amount of time irrigating manually. I've been trying to see what would actually work in terms of automated systems, but so far, no such luck. For example, I took a round lawn irrigation sprayer, and after 4 hours of watering the hillside, the soil was 100% bone dry, I mean not ONE once of moisture. It was as if there was no watering whatsoever.
I am at a complete loss as to how to create an automated watering system that would work.