The 30 years continuous recorded
monthly data of rainfall, stream flow and
calculated ENSO indices during 1982 to 2011
are used in this study. For rainfall data, the
average rainfall data in Mae Rim watershed is
averaged from the 4 rainfall gauge stations
around the watershed. The rainfall data are
obtained from the Royal Irrigation
Department (RID), the Royal Project and the
Mae Tang Headwater Research Station. The
monthly rainfall data in June, July, August
and September is characterized to GMI
described in the next section. For stream flow
data, the data gauged from P21 station are
used. The stream flow data are obtained from
the RID. To select the appropriate ENSO
index with its associated impact in
UPRB, the comparison between the standard
ENSO indices