I have hiked up in these mountains and seen some of the springs Arrowhead uses to get its water from. The ones I have seen are small pipes running from small springs, taking a small amount of the spring water. The San Bernardino mountains are next to LA. I am not an expert, but I don't think a large amount of water is used by anyone from these mountains. The US Forest Service probably just thinks it is an insignificant amount of the total water supply to pay tons of money to experts to come up with the required bureaucratic report. It really wasn't until the media starting referring to Arrowhead Mountain water company as "Nestle" that it started getting any coverage.
I'm curious how much water they actually take down the mountain (especially since I believe they have another well down the hill in San Bernardino... or "San Bernadino" as the article says half a dozen times). Even if it isn't much, it is seems silly since the communities up there have to import water from elsewhere, and a big part of the cost of doing that is pumping the water up to an elevation of ~1 mile.
That said, you're probably right that they're sending down a negligible amount of water, especially compared to what the water agencies up there pump locally or even compared to the declining water levels of the lakes in Arrowhead and Big Bear
