  SuperKamiokande (SK) doped with gadolinium has the capability to efficiently
identify electron-antineutrinos through inverse beta-decay. Given the size of
SK and the number of nuclear reactors in its vicinity, we argue that SK can
observe the oscillations of reactor antineutrinos driven by the so-called solar
mass-squared difference $\Delta m^2_{21}$. After only one year of data taking,
we estimate that SK can measure $\Delta m^2_{21}$ with enough precision to help
inform the current small tension between existing results from KamLAND and
solar neutrino experiments.
