The U.S. Geological Survey released a study today showing that large groundwater withdrawals are causing land in California’s Central Valley to sink. A 1,200 square mile area is sinking up to a foot a year in some places. The situation has become so serious that it’s threatening flood control and water deliveries. The proposed high speed rail system will also have deal with the changing terrain. But Amy Quinton reports from Sacramento, finding a solution won’t be easy.