Looks to me that NGWA is pimping for it’s members, not unheard of when it comes to protecting/generating income for connected people. I have a son who was going to buy a foothill property. Previous buyers and builders in the neighborhood couldn’t find water in the area and resorted to hauling in water and storing in large supply tanks. My son hired a ‘witcher’ to check the property he intended to buy. The ‘witcher’ located a spot and suggested that a well be drilled. End of story- the well produced plenty of water even if the iron content was high.
The reason is that most drillers and all geologists know the facts about ground water: that it is almost everywhere. Non-scientists think water is in "underground streams" scattered here and there; that's false. When I was involved with drilling in limestone (the rock in the Texas story), the problem was not finding water; it was 1) finding clean water, because the large conduits are easily contaminated, and 2) avoiding creating sinkholes at the surface when the well is pumped.