February 14, 2017

• Water, Water, Everywhere

  No photos this time -- but some comments about Oroville.  Oroville is a small (16,000 people) farming community on the Feather River, about 100 miles north of Sacramento, CA.  About 50 years ago, an earthen dam was built on the Feather River, across the street from downtown Oroville.  At 795 feet, this is the tallest dam in the country.  This dam is the source of about 1/3 of the water used in Southern California.  Next to the dam there are two spillways, which allow for the release of water if the dam fills and to keep water from simply spilling over the top of the dam.  The main spillway is concrete lined -- a chute down which water rushes when the dam is full and the gates are open.  The second, commonly known as the emergency spillway, is simply a gate for water to flow out to raw hillside.  Downstream from Oroville, there are major agricultural cities (Yuba City and Marysville) and many smaller ones.  The Feather River feeds into the Sacramento River, which then merges with the American River just outside of Sacramento, and the combined rivers flow to San Francisco Bay.   The lake, which three months ago was the most widely publicized example of a low lake level (the one with the houseboats), is now full and over the weekend they opened the spillway gates on the main spillway.

  Northern California has received a great deal of rain and snow this winter, and there is more to come this weekend -- not enough to break the state's drought going forward, but more than one year's average rainfall.  They are calling the rainfall part of an "atmospheric river."  On the radar, it looks like water flowing from a hose from south of Hawaii towards California.

  Over the weekend, the lake was full, and the gates were opened to the main spillway to allow some of the water to flow down to the Feather River and to make room for more water running off from previous storms and from the current storm and snowmelt in a month or two.  Very quickly, workers noticed a sinkhole developing under the concrete lining -- this sinkhole has now grown to the size of a football field.  So that they could inspect the hole, they opened the gates to the emergency spillway for the first time in the history of the dam.  This allowed water simply to flow downhill to the river, taking with it whatever was in the way (trees, mud, rocks, etc.  Very quickly they saw erosion developing that threatened the integrity of the emergency spillway gates.  With both spillways in trouble, there was a serious threat of major flooding, and 180,000 people were ordered to leave immediately.

  The emergency gates were closed, and the main spillway flow increased.  They are working on a fix for the emergency spillway, dumping 1000 truckloads of boulders every 24 hours into the eroded hole, along with slurry to anchor the rocks and create a smooth surface for the water to flow over.  As of this evening, the risk is reduced sufficiently that the evacuees are being allowed to go home, but with warnings that they may need to evacuate again as conditions change -- weather conditions, dam and spillway integrity, snow melt, river flow, and so on.

  Some 20 years ago I lived in Sacramento -- I think that if I lived anywhere downstream from the Oroville Dam, I would go home and pack all my valuables to be ready to leave again.  If the dam or any spillway should break, they are saying that it would send a 30-foot wall of water downstream -- that could reach all the way to Sacramento, and the rivers are already in flood-control condition through Sacramento.  Furthering the dangers, there is Folsom Dam, on the American River, which merges into the Sacramento just outside of town and which is already full.  There is an extensive area which is used for free overflow of the two rivers -- the Yolo Causeway.  When the rivers are high, the gates to the Yolo Causeway are opened and the water flows freely over agricultural land, and down to the San Francisco Bay, about 100 miles away..  Much of Sacramento is below the level of the levees that protect it -- in a worst case scenario, Sacramento could be lost to a break of the Oroville Dam!

  All of this is happening about 600 miles north of where I live -- although I am not directly affected by any of it, a break would affect the availability of water in Southern California.  Another 1/3 of the water used in the Los Angeles area comes from Lake Mead -- that lake is precariously low due to the drought, and we are likely to see the allocation reduced in the near future.  Los Angeles has massive water storage capacity, and has been filling the tanks with this winter's rainfall.  Santa Barbara's Lake Cachuma lies in a rain shadow, and has currently reached only about 20% of capacity.  Should Oroville Dam or its spillways have further problems of catastrophic proportions, it would create major problems here in "the Southland."

  As Samuel Taylor Coleridge said in his famous poem,

  Water, water, everywhere, Nor any drop to drink.

  • 9:38 pm
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