San Francisco Chronicle - Online (August 23, 2014) - Geologists have long discredited the practice, saying successful dowsing is simply the result of water being hard to miss in many areas, according to the U.S. Geological Survey, an independent federal research agency in the Department of Interior that studies groundwater. The agency speculates there are thousands of dowsers practicing in the United States. "There is no scientific evidence that dowsing works," said Thomas Harter, a UC Davis professor who specializes in groundwater issues. "A lot of dowsers operate in areas where there is a lot of groundwater to begin with."