Trend analysis of reference evapo-transpiration and governing meteorological parameters in an arid saline region of Haryana

Abstract

Long-term changes in reference evapo-traspiration (ETo) can have profound implications on water balance, salinity development and agricultural production in any region. Temporal trends of ETo values, estimated by Penmen Monteith approach utilizing historical weather data, were investigated for an arid region (Hisar) of Haryana. Thirty years (1981-2010) meteorological data of Hisar was statistically analyzed for estimating the trends in ETo and governing climate parameters. Statistical significance trends in annual and seasonal (monsoon, post monsoon, winter, summer) ETo, maximum and minimum temperature, bright sunshine hours (BSS), morning and afternoon relative humidity and wind speed was evaluated using nonparametric Mann-Kendall (MK) tests at the 10% significant level. In order to identify the dominant weather variables influencing ET0, backward stepwise regression method was adopted. During the last 30 years, ETo has been found to decrease significantly at annual and seasonal time scales at Hisar. Of the governing weather parameters, temperature (both maximum and minimum) showed no clear trend at annual or seasonal scales, while significant decreasing trends have been observed in BSS hours and wind speed on annual and all seasons except during monsoon. The contribution of the temperature on ETo seems to be offset by steady reduction in wind speed and BSS hours, also reflected by strong correlation of BSS and wind speed with ET0 evaluated through regression analysis at almost all the time scales. The nature and magnitude of trends of ETo and other weather parameters can be purposefully utilized to derive rational climate change scenarios and evaluate their impact through controlled crop physiological and modelling studies on soil, water, salinity and crop production in arid regions of Haryana.