Estimation of Reference Evapotranspiration (ET0) for Gird Region of Madhya Pradesh

The reference evapotranspiration (ET0) for three district in Madhya Pradesh have been estimated using three evapotranspiration based methods like Hargreaves Samani, Caprio, trabert and Makkink-Hansen under local conditions. Comparison was also made between the estimated ET0 by using different evapotranspiration based method and the observed ET0 by using FAO-56PM Method. 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 travert method can be indicate the best result compression to other method and this method could be used for the estimation of ET0 values in all district in the gird region of Madhya Pradesh. Keyword: Reference Evapotranspiration by FAO-56 Penman Monteith, other ET0 methods and Gird region. Research Article Cite this article: Singh, Y. P., Mittal, H.K., Singh, P.K., & Bhakar, S.R. (2019). Estimation of Reference Evapotranspiration (ET0) for Gird Region of Madhya Pradesh, Ind. J. Pure App. Biosci. 7(5), 487-492. doi: http://dx.doi.org/10.18782/2320-7051.7765 Singh et al. Ind. J. Pure App. Biosci. (2019) 7(5), 487-492 ISSN: 2582 – 2845 Copyright © Sept.-Oct., 2019; IJPAB 488 The estimation of reference evapotranspiration (ET0) involves calculating the potential evapotranspiration (ET) or the actual evapotranspiration (ET), and then applying a suitable crop coefficient (Kc). 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). Numerous scientists and specialists worldwide was developed many methods for estimating of reference evapotranspiration (ET0) over the last 50 years. These methods were subject to rigorous local calibration and proved to have limited global validity (Smith et al., 1996). 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. Tanner (1967) emphasized that any empirical equation for estimating ET0 needs to be calibrated, particularly in sub-tropic and semi-arid regions, because of the increased ETc due to the adjective energy from dry surroundings. A few studies have been conducted to calculate ET0 for some selected areas in Madhya Pradesh (Saeed 1986; Al-Omran and Shalaby 1992; Mohammad and Abo-Ghobar 1994;). The previous studies have concentrated on the central and eastern regions and the literature lacks the estimation of ET0 in the gird region of Madhya Pradesh, which is considered to be some of the main agricultural regions in the country. Accordingly, the objective of this study was to determine ET0 for four major locations namely, Ashok Nagar, Shivpuri and Bhind (sub-tropic condition) in the gird region of Madhya Pradesh using four different ET0 based methods. In addition, estimated ET0 for the different locations were compared with that estimated and observed. MATERIALS AND METHODS In this study to carry out, mean monthly climatological data, 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, Ashok Nagar, Bhind and Shivpuri District of Madhya, for the duration of seven eleven (2004-2014). Other parameters like geographic locations, viz., latitude and longitude, as can be seen from Table 1. Table 1: Details of the selected stations in study area District Longitude (E) Latitude (N) Altitude (m) Ashok Nagar 77°43' E 24°34' N 499 Bhind 78°48' E 26°34' N 159 Shivpuri 77°39' E 25°25' N 457 Singh et al. Ind. J. Pure App. Biosci. (2019) 7(5), 487-492 ISSN: 2582 – 2845 Copyright © Sept.-Oct., 2019; IJPAB 489 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) Jensen-Haise (JH) method; (3) c a p r i o method (4) traver method (5) Hargreaves-samani (H-S) 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: 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: