Study of Evapotranspiration in Context of Changing Climate

Abstract

It seems imperative to study evapotranspiration (ET) more broadly as a need of hour because in context of climate change as the average temperature is rising; certainly the evaporative demand is shooting up. The present study provides idea about likely change in evapotranspiration due to change in climatic parameters in context of changing climate. As different methods of estimating ET responses differently in specific meteorological parameters on ET demand. The change in temperature causes change in other parameters such as humidity, wind speed, and vapour pressure which ultimately changes ET. In the present study ten years (2002-2011) weather data taken from Ozone unit, Indian Meteorological Department, Banaras Hindu University (BHU), Varanasi, has been analysed for the change in temperature, wind speed and net radiation. It is found that an increase in 14.87% of total ETo demand with increase in temperature by 20 % for FAO 56 PM model, which is followed by net radiation (13.6%) and wind speed (4.16%) in comparison with temperature. While among the other ten temperature and radiation based methods taken up for same study Hargreaves & Samani temperature based method shows the highest change (21.87%) to temperature & solar radiation (Rs) based Irmak model evaluates least change (5.5%) for 20 % increase in temperature. Moreover, the details of the various combinations of changes in different parameters have been analysed. Further, it is found that approximately1oc increase in temperature could increase ETo by 30 m.m per year. It means it would require a huge amount of extra water to cater the need of several thousands of hectares of crops per year.