You have been notified...

The sign reads, "These waters are entirely dedicated to livestock use from Jan. 1-Dec. 31 each year. NRS [Nevada Revised Statutes] makes any person who unlawfully diverts this livestock water guilty of a misdemeanor."
So, watch out! As I comment elsewhere, this area is in the vicinity of the Burning Man countercultural festival held in late summer every year, and there may have been problems with diversions by campers! The flat in the distance is Black Rock playa, where the festival is held a bit south (to the left) of here.