Calculation of Reference Evapotranspiration (ET0) for Chhattisgarh Plains

The evapotranspiration (ET) for Balaghat district was estimated using different evapotranspiration based methods like Meyer, Hargreaves and Valiantzas under local conditions. Comparison was also made between the observed ET0 by Penman Monteith (FAO-56) and the estimated ET0 by different other model. Regression analysis revealed that estimated ET0 values were highly correlated with observed ET0 values. In addition, linear regression relationships between ET0 values estimated by the Penman monteith method and other methods were determined. The result of this study shows that the valaintzas method can be indicate the best result compression to other method and this method could be used for the estimation of ET0 values in Balaghat district in the Chhattisgarh plane of Madhya Pradesh. Keyword: Chhattisgarh Plains, evapotranspiration by FAO-56 Penman Monteith, other ET0 methods. Research Article Cite this article: Singh, Y.P., Paradkar, V.D. , Sharma, V. , & Kour, M. (2019). Calculation of Reference Evapotranspiration (ET0) for Chhattisgarh Plains, Ind. J. Pure App. Biosci. 7(4), 401-405. doi: http://dx.doi. org/10.18782/2320-7051.7633 Singh et al. Ind. J. Pure App. Biosci. (2019) 7(4), 401-405 ISSN: 2582 – 2845 Copyright © July-Aug., 2019; IJPAB 402 Potential ET is defined as the rate at which water would be removed from wet soil and plant surfaces expressed as the rate of latent heat transfer per unit area, or as a depth of water per unit time. ET0 is defined as the rate at which water would be removed from the soil and plant surfaces expressed as the rate of latent heat transfer per unit area, or as a depth of water per unit time evaporated and transpired from a reference crop. The use of ET0 for a specified crop surface has largely replaced the use of the more general potential crop ET. This is because of the ambiguities involved in the interpretation of potential ET. Also, the use of a reference crop ET permits a physically realistic characterization of the effect of the microclimate of a field on the evaporative transfer of water from the soilplant system to the atmospheric air layers overlying the field (Uright, 1996). (Allen et al., 1996 & Smith et al., 1996) specialists worldwide was developed many methods for estimating of reference evapotranspiration (ET0) over the last 60 years. These methods were subject to rigorous local calibration and proved to have limited global validity. Doorenbos & Pruitt (1977) adopted the concept ETc and adjusted several existing methods to yield identical ET0 estimates varying from complex energy balance techniques requiring detailed climatological data to simpler methods with limited data requirements. The accuracy of ET0 estimates depends primarily on the ability of the methods being used to describe the physical laws governing the processes and the accuracy of the meteorological and cropping data (Jensen et al., 1990). Since the existing methods of estimating ETc from meteorological data involve empirical relationships, some local or regional verification or calibration is advisable with any selected method. According to Tanner (1967) emphasized that any empirical equation for estimating ET0 needs to be calibrated, particularly in sub-tropic and semiarid regions, because of the increased ETc due to the adjective energy from dry surroundings. The different studies were conducted to estimated ET0 for some selected areas in Chhattisgarh Plains (Saeed 1986, Al-Omran & Shalaby 1992, Mohammad & Abo-Ghobar 1994). The previous studies have concentrated on the central and eastern regions and the literature lacks the estimation of ET0 in the Chhattisgarh Plains of Madhya Pradesh, which is considered to be some of the main agricultural regions. Accordingly, the objective of this study was to determine ET0 for single major locations for Balaghat (sub-tropic condition) in the Chhatisgarh Plains of Madhya Pradesh using different ET0 based methods. In addition, estimated ET0 for the particular location was compared with that estimated and observed. MATERIALS AND METHODS The weather average monthly data used in this stud , viz., maximum temperature (Tmax), minimum temperature (Tmin), mean relative humidity (RHmean), solar radiation (Sr) and wind speed (WS) were collected from global weather data site at balaghat District located on Chhattisgarh Plains of Madhya, for the period of twenty years eleven (1993-2013). The site is an elevation of 279 m above mean see level and lies at a longitude of 80°31' E and a latitude of 21°69' N. the annual rainfall range between 1200 to 1600mm. The availability of meteorological data is a major consideration in the selection of a method for calculating ET0. Selection of the appropriate method for a specific location is a difficult task because unique guidelines are not available for defining the method of application most likely to give the best estimates. The methods considered in this study include those ranging from temperature, radiation and mass transfer-based methods to the more data-intensive combination methods. The methods are (1) FAO-56 Penman monteith method; (2) Hargreaves method; (3) M e y e r method (4) Valiantzas method for gird region climatic conditions. These methods were chosen for this study to estimate the ET0 for each district and also to make a comparison among them in order to select the most suitable method for each area. The following methods are given below: Singh et al. Ind. J. Pure App. Biosci. (2019) 7(4), 401-405 ISSN: 2582 – 2845 Copyright © July-Aug., 2019; IJPAB 403 FAO-56 Penman Monteith method According to Allen et al. (1998), recommended form of FAO56-PM model consisting of aerodynamic and surface resistance terms is: