  A first study of neutron tagging is conducted in Super--Kamiokande, a
50,000-ton water Cherenkov detector. The tagging efficiencies of thermal
neutrons are evaluated in a 0.2 % GdCl$_{3}$-water solution and pure water.
They are determined to be, respectively, 66.7 % for events above 3 MeV and 20 %
with corresponding background probabilities of 2 $\times$ 10$^{-4}$ and 3
$\times$ 10$^{-2}$. This newly developed technique may enable water Cherenkov
detectors to identify $\bar \nu_{e}$'s geological or astrophysical sources as
well as those produced by commercial reactors via the delayed coincidence
scheme.

High Energy Physics - Experiment