You know Battleship Mountain? That really long, big-ass slab of limestone about 5-6 miles in while hiking from First Water? Crescent Canyon is on the eastern slope of that. It's a huge, 100-foot tall canyon in a near-perfect crescent shape that runs into a beach and river. The river is about 3-4 feet deep in the February/March, but there are places in the canyon that are at least 10-12ft. Did some dives and cannonballs in there last year.
In general, springs are reliable from January-March, and anytime during the year within a few days after a decent rainfall. But other than that, you're gonna want to pack all your water. Unless you're going really far east, like high up near Reavis Ranch, in which case springs and creeks are reliable through May.