Optimization and verification are performance for a water Cherenkov
detector at high altitude of 4300 m a.s.l. by two simulation codes
of Cosmos and GEANT which use the Monte Carlo method.
The detector consists of a water pool with an area of 50m X 50m
and a depth of 1.5 m.
Photomultiplier tubes are arranged in the pool with a 17 X 17 matrix
pattern with a spacing of 3m, therefore, their total number are 289.
As a result, angular resolution of the detector is obtained to be about
0.7 degree for a primary energy of 1 TeV.
Trigger rate is expected to be larger than 15 kHz.
Significance for gamma sources is obtained to be about 30$B&R(B for
gamma-ray burst of GRB910503 and about 5$B&R(B for the Crab nebula
with an observation of 30 days.