چكيده لاتين :
The objective of this study is to calibrate Priestley-Taylor (PT) model for estimating open water evaporation from an arid region reservoir called Chahnimeh. Chahnimeh Reservoir which is situated in the
Sistan area in the southeast of Iran is being affected by regional energy advection during May to October. Therefore, common models of open water evaporation estimation such as PT require calibration. PT method was calibrated for Chahnimeh Reservoir using a volume balance method. Results showed that PT coefficient, aPT,
as a constant over the year varies between 2.47±O.09 and 1.20±0.03 for two different hydrologic conditions of dry and wet. It means that there is also an intra-annular variation in aPT. Calibration of PT model also showed that aPT is a time dependant variable and varies monthly. In other word there is an inter-annular variation. Interannular variation of aPT showed that this coefficient varies from 1.56 to 3.16 against 0.67 to 1.95 for dry and wet conditions, respectively.
