Satellite data has confirmed that groundwater levels are declining rapidly in some parts of northwest India inhabited by 114 million people. Between 2002 and 2008, three Indian states lost a volume of groundwater equal to over twice the capacity of Lake Mead, the largest US reservoir. The depletion is mostly due to unsustainable pumping of groundwater for irrigation, which has tripled India's irrigated area since 1970. Without action to curb water usage, drinking water shortages and reduced crop production are likely to result.