Friday’s announcement of an 85 percent California State Water Project allocation was, tentatively at least, good news for Lake Mead.

When the Metropolitan Water District of Southern California gets a small supply from up north via the State Water Project, it needs more Colorado River water. Conversely, with a big State Water Project supply coming out of Oroville Dam and down the Sacramento River to the big south-of-delta pumps, Met can back off on its Colorado River Aqueduct supplies.

The two river and plumbing systems are thus inextricably linked.

Until Oroville Dam’s problems, it looked like a huge State Water Project supply might allow Met to leave as much as 400,000 acre feet in Lake Mead this year. But with state officials managing Oroville conservatively, storing less water to leave more space as a safety buffer, there were fears that a low State Water Project allocation would cut Met’s leave-it-in-Lake-Mead number to as little as 200,000 acre feet.

With an 85 percent allocation, it now looks like that number could go back up to 400,000 acre feet of what is called in the lingo “intentionally created surplus” this year. That’s four feet of elevation in Mead, which is pretty important as we flirt with shortages.