Estimation of Evapotranspiration Rate Due to Climate Change in the Urmia Lake Basin

Evapotranspiration is a major component of the hydrological cycle which shows the amount of water loss. Since the amount of evapotranspiration is directly associated with climate variables and is related with the amount of changes in climate parameters, particularly temperature plays a key role in this regard. Therefore, in this study, possible impacts of climate change on evapotranspiration rate are estimated in the Lake Urmia Basin as a wet basin in the country. The basin nowadays is faced with drought and reduction of water level. Predictions of the changes in the lake, were examined Under scenarios A1B, A2, B1 and B2 using LARS-WG and SDSM Statistical Downscaling models and HadCM3 general circulation model output in the next three periods (2030-2011, 2065-2046 and 2099-2080) . Using the predicted climate parameters changes, Evapotranspiration rates in the basin in monthly and seasonal periods, was calculated using Hargreaves Samani and Priestley Taylor. The results showed an increase in long-term average minimum temperature in the basin between 0.2 to 3.4 degrees and a maximum temperature increase of between 0.9 to 2.9 degrees in future periods compared to the base period (1990-1961). The estimate of evaporation rate shows an increase in monthly and seasonal time series in future affected by the temperature. The increase would be between 2.4 to 15 percent on long-term average in the basin. The results can be used in the management of groundwater and surface water resources, irrigation and drainage projects, estimating crop water requirements, irrigation scheduling and environmental studies and watershed plans.