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 .
Deluges during the atmospheric river give reservoirs a pleasant boost . But much more is needed after years of drought , NASA says in a new analysis . Satellites measure gravitational field and planet 's shape to find changes in water reserves . Water reserves have fallen so far , California is depleting its groundwater .