  The novel idea of water Cherenkov calorimeter made of water tanks as the next
generation neutrino detector for nu factories and nu beams is investigated. A
water tank prototype with a dimension of 1*1*13m^3 is constructed, its
performance is studied and compared with a GEANT4 based Monte Carlo simulation.
By using measured parameters of the water tank, including the light collection
efficiency, attenuation length, angular dependent response etc, a detailed
Monte Carlo simulation demonstrates that the detector performance is excellent
for identifying neutrino charged current events while rejecting neutral current
and wrong-flavor backgrounds.
