Deluges during the seasonal river give California a pleasant boost . But much more is needed after years of drought , NASA says in a new report . Scientists study gravitational field and Earth 's shape to find changes in water reserves . It has done this throughout the Southwest , where groundwater levels are at their absolute lowest levels in the last 65 years , said NASA 's Jet Propulsion Laboratory in Pasadena . Water reserves have fallen so far , California is depleting its groundwater .
Deluges during the seasonal river give California a pleasant boost . But much more is needed after years of drought , NASA says in a new report . Scientists study gravitational field and Earth 's shape to find changes in water reserves . Water reserves have fallen so far , California is depleting its groundwater .