Californians and Nevadans who watched Lake Tahoe’s water levels recede during the historic drought experienced in the states over the past few years are dealing with a completely different situation now, as the San Francisco Chronicle reports that a recent heat wave poured a staggering 12 billion gallons of runoff into the lake and brought it within a few inches of its max limit.

lake tahoe water level sierra runoff

Lake Tahoe, pictured above, is one of the deepest lakes in the world and is nearing its legal limit. Photo: Courtesy of Wilco737/Flickr

Now, per SnowBrains, water officials expect Lake Tahoe to fill to its limit by mid-July. To put that into perspective, SnowBrains reports that hasn’t happened since 1997. During the week-long heat wave last week which saw triple-digit temperatures, Lake Tahoe — which is over 1,600 feet deep at its deepest — saw its water level rise a full four inches.

While that huge influx of water melting off the snowpack from this year’s historic amounts of snowfall might seem like a good thing for states — particularly California — that have been gripped by drought, according to the Chronicle, it actually poses a real threat of flooding in the area.

Per the Sacramento Bee, a single dam in Tahoe City, California, regulates Lake Tahoe’s water levels and has been releasing billions of gallons into the Truckee River over the past four months to make sure the lake’s water levels don’t get to a dangerous level and exceed its legal limit.

lake tahoe water level sierra runoff

The dam in Tahoe City, seen above during the peak of California’s drought. Photo: Courtesy of AFP/Flickr

And on Friday, with the lake’s level sitting at 6,228.84 feet above sea level — its max legal limit is 6,229.1 feet — a water official with U.S. District Court told the San Francisco Chronicle the dam will continue dumping water into the Truckee River for the foreseeable future.

“It’s not typical to spill at all,” U.S. District Court water master Chad Blanchard told the Chronicle. “It’s only on the big years when you have to release water … We’re trying manage it to ensure that we fill, but we have to be able to adjust and compensate for variations in the actual runoff compared to the forecast. We could have filled it months ago, the inflow can be so much higher than your release capacity.”

Read more about the historic water season the Sierra has experienced

Northern Sierra has wettest ‘water year’ ever

California buried under the most snow it has seen in 22 years