What does this really mean though? In New England we have Walnut trees growing everywhere, and no one is watering them. If anything they're locking water into the soil that would otherwise just evaporate.
But most almonds and pistachios are grown in a desert, with water extracted from ground-water aquifers. Without the wells, the almonds would not grow.
Problems start when people grow walnuts in places that average 10" a year....
Also, those trees aren't locking water anywhere. They are probably releasing the same amount per tree to evaporation.
If you care about protecting our managed pollinators, giving up almonds is a good first step. I have also switched to peanuts.