While the number of wildfires on a nationwide basis has been way down this year near a record low, the one raging right now threatening Yosemite National Park in California is quite intense and still growing. This northern California wildfire called “The Rim Fire” has now devoured more than 149,000 acres which is about the size of the city of Chicago and, as of this morning, it is only about 15% contained. It has been growing eastward in recent hours and is close to a key part of the San Francisco water supply: the Hetch Hetchy Reservoir, which lies within Yosemite National Park. Ash from the fire has been falling on the reservoir, but so far hasn’t sunk far enough into the lake to reach the intake pumps. If ash eventually causes turbidity, the city of San Francisco will begin filtering supplies. San Francisco gets 85% of its water from Hetch Hetchy as well as power for many municipal buildings and the international airport. In addition to the water supply, the fire also threatens the area’s hydroelectric generators which provide much of San Francisco’s electricity. Because of the approaching flames officials have shut down the generators, and the city – more than 120 miles to the west – is temporarily getting power from elsewhere.
As far as Yosemite National Park is concerned, while the “Rim Fire” has consumed at least 12,000 acres in the northwest section of the park, it has had little or no direct impact on Yosemite Valley, a popular spot for tourists and home to many of the famous cliffs and waterfalls in the park. The fire does, however, pose a threat to the giant sequoias inside Yosemite National Park. In particular, the safety of two groves, Tuolumne Grove and the Merced Grove, are of particular concern. The massive trees in these areas are some of the largest living things on Earth and are believed to be more than 2,000 years old in some cases. Sequoia trees are naturally fire resistant due to their thick bark - must be in order to survive this long. Crews have used sprinklers and are lighting fires to clear brush as a protective measure, though the fire is still several miles from the massive trees. The vast majority of the national park remains open at this time.