Evapotranspiration (ETo) is a major component of hydrological cycle. Its estimation is important for water resource management purposes and for understanding soil water balance at a place. ETo is known to be dependent upon climatic factors and hence climate change is having an effect on evapotranspiration. In this study, the effect of climate change on evapotranspiration has been studied in Jaipur district of Rajasthan using long term weather data. The data for various meteorological factors, temperature, wind speed, relative humidity for the period (1955–2006) was collected from India Meteorological Department. Using the data, evapotranspiration was estimated using the internationally accepted FAO version of Penman-Monteith equation. The data was analyzed monthly, seasonally and annually. Trend analysis was done for all the factors affecting evapotranspiration. PET was found to show a decreasing trend for January, February, March, June; remains more or less constant for April, May, December; and increases for July, August, September, October, and November. Seasonal analysis showed that temperature and PET are closely correlated during the monsoons and wind speed is correlated to PET during summers. Khariff and Rabi seasons were analyzed separately. The water demand during the Khariff season was found to twice as much as during Rabi season. Regression equations, which give values close to P-M ETo have also been given for the three different seasons. Similarly, regression equations are also given for all the months except April, October and December as R2 values were found to be too low for these months. An attempt has also been made to provide local adjustment factors for the Hargreaves equation and Blaney-Criddle equation wherever feasible, to help in easy estimation of evapotranspiration using only temperature data.
