Underground water in Shasta County, California mysteriously disappears

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Groningen, dinsdag 17 april 2012

CALIFORNIA - Stephen Wolf thinks something strange is happening underground in eastern Shasta County and it is draining water wells and maybe even causing sinkholes and subsiding pavement. A retired marine geologist with the U.S. Geological Survey, Wolf said he has seen what is happening in eastern Shasta County before. After the 1989 Loma Prieta earthquake, water well levels in the area of the quake fell significantly, he said. Following the 6.9 magnitude quake in the Santa Cruz Mountains, Wolf wrote a paper for the USGS about the effects the quake had on surface and groundwater. "The correlation is there. The behavior is identical," said Wolf, who has lived in the tiny eastern Shasta County community of Cassel since 2001. Back in October, 131 earthquakes hit the Lassen Peak area.

Most were less than 2.0 in magnitude. But since then the water table has fallen significantly, Wolf said. Pete Amos said his pump had been submerged 40 feet the entire 24 years he has lived in Cassel. But a couple months ago he ran out of water. When the pump company measured his water level, it had fallen to 54 feet, he said. "We've never had a water problem before. We never thought about the water table going down," Amos said. Terry Briggs, who owns Gallagher Pump in Fall River Mills, said what is going on in Cassel is unusual. He said the drop in the water table in eastern Shasta County is the most dramatic he has seen in the past 10 to 15 years. "It always moves up and down a little bit, but this was way more," Briggs said. Since January, he has had to help homeowners whose water tables have dropped below their pumps. Briggs said he isn't sure why the water level is dropping. Seismic activity may be affecting wells.

Rainfall levels also affect the water level, he said. And Cassel, like the rest of the north state, went through a dry winter. Wolf said the seismic activity further fractures the rocky, volcanic soil, allowing the water to flow deeper into the Earth. Every time a small quake rattles the area around Lassen Peak, his toilet fills with dirty, silted water, he said. That is the silt that is broken loose from the volcanic soil underground, he said. Officials at the USGS said they are hesitant to draw a correlation between the quakes and the drop in the water level in Cassel.

But Ingebritsen said the earthquakes were too far away to cause the water table to fall in the Cassel area. A magnitude 3.0 quake can affect water table levels in an area of about 6 miles; a magnitude 4.0 quake would affect groundwater up to about 18 miles away; and a 5.0 magnitude quake would affect wells in a 62-mile radius, Ingebritsen said. The swarm of quakes that hit the Lassen Peak area last fall were too small to be causing problems in the Cassel area, some 45 miles away, he said. Whatever caused the water table to drop, Wolf thinks homeowners in the area should learn a lesson from it and drill their water wells deeper to avoid the problems residents are seeing this year.

He thinks the seismic activity also may be related to other soil problems in the area, including a sinkhole that developed March 14 in the side of a holding pond Pacific Gas and Electric Co. uses in a Hat Creek Hydroelectric project in the Cassel area. -Redding.com

Bron: theextinctionprotocol