Invention Journal of Research Technology in Engineering & Management (IJRTEM) ISSN: 2455-3689 www.Ijrtem. com Volume 3 Issue 5 ǁ July –August 2019 ǁ PP 06-12
Estimation of Evapotranspiration using CROPWAT 8.0 Model for Taung-Nyo Dam Cultivated Area, Myanmar Mi Yin San1, May Thinzar2 1
(Civil Department, West Yangon Technological University, Myanmar) 2 (Civil Department, Pyay Technological University, Myanmar)
ABSTRACT : The estimate of actual evapotranspiration is very important not only in the study of climate changes and evaluation of water resources but also in crop water requirement scheduling etc. This study was conducted to estimate the evapotranspiration using CROPWAT 8.0 Model for Taung-Nyo dam cultivated area. It was collected the long term daily meteorological data including maximum temperature, minimum temperature, relative humidity, wind speed and sunshine hours from the Meteorological and Hydrological Department to calculate the reference evapotranspiration, ETO. Crop coefficient, KC was multiplied with ETO which is a measure of evaporative demand to get actual evapotranspiration, ET. The major crops in this cultivated area are Monsoon season crops which are paddy, sesame and maize and dry season crops which are green gram, bean, sugarcane and groundnut. The study observed that the maximum actual ET are 170.6 mm and 186.8 mm in the month of April for the average period and for each year, respectively due to high temperature and the minimum are 89.093 mm and 85.513 mm in December. So, it can be concluded from the observation that as the temperature increases, the ET increases and as the temperature decreases, it also decreases.
KEYWORDS: reference evapotranspiration, actual evapotranspiration, CROPWAT, crop coefficients, meteorological parameter
I.
INTRODUCTION
Actual evapotranspiration is defined as the rate of evapotranspiration by particular crop in a given period under prevailing soil water and atmosphere condition. The CROPWAT is an irrigation management and planning model simulating the complex relationships of on-farm parameters, the climate, soil and crop.In arid regions, agricultural development strongly depends on the irrigation because of low rainfall conditions and high evaporation. The transfer of water from the soil surface (evaporation) and plants (transpiration) to the atmosphere is referred to evapotranspiration. From the irrigation point of view, the ET estimates the amount of water to be applied through the artificial means. Using the ET, the sizes of canals and pumps are determined. Many different methods are used to find the ETO. These methods are Blaney-Criddle method, Radiation method, Pan evaporation method, Penman method or Modified Penman method and FAO Penman-Monteith method, etc. Hashem et al., (2016) made an attempt to compare the reference evapotranspiration computed using a mathematical model with ETO estimated using CROPWAT software program. Vivekanand Singh et al., (2006) calculated ETO by using seven different methods and as a standard Penman-Monteith method was used and compared with the other six methods. It is found to be good correlation between them. In this study, the ETO is calculated using the CROPWAT 8.0 model and its value is multiplied with crop coefficient to get the actual evapotranspiration. In the fields of irrigation and water management, estimates of reference ET are used to make irrigation recommendations for growers. Thus, the current study conducted at Taung-Nyo cultivated area can be used as a reference for calculating ET in other area having the same conditions. This study provides the necessary information on water requirements for growing different crops in different season.
II.
MATERIALS AND METHODS
Study Area : Taung-Nyo dam is situated near Magyibin village, Nattlin Township in Bago division. It is located at north latitude: 18.5167º, east Longitude: 95.60 ° and its altitude is 82 m above mean sea level. Taug-Nyo dam project is proposed to irrigate 50000 acres in project area. The study area comprises of Zigon Township and Nattlin Township. The location of the project area is shown in Fig 1.
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