Application of Remote Sensing for Estimating the Evapotranspiration to Assess Grape Water Requirement in Marvast Plain using MODIS Terra Satellite Products

Today, due to water use and facing the world with problems such as water deficit and drought, short-term and long-term consumption management and planning is essential to achieve the goals set for water resources. The lack of data lysimeter measurements to estimate water requirements of plants is one of the biggest challenges that exist in the agricultural sector. On the other hand, using new methods to more accurately estimate the actual evapotranspiration and consequently, vegetation coefficient for different plants, especially the dominant cultivation in the plains of the country, can help better planning and management of water resources. In this study, using MODIS images and SEBAL algorithm, evapotranspiration for Marvast in Yazd province in four months (February, May, August ,November) 2017 was estimated. Maximum evapotranspiration the same time with the heating season is August and the plant occurred chlorophyll maximum amount of which is 582 mm. Then, with decreasing plant density, the evapotranspiration trend was reduced, which was the minimum evapotranspiration in February. Extraction of grapevine coefficient by FAO method showed that its amount was satisfied in May (1.23) and August (1.14). Due to the high rate of evapotranspiration and heat in these two months, the plant's need for water has been greater. Vegetation rates in the fall (November 0.25) and winter (February 29/09) were lower than during the growing season due to reduced leaf cover and reduced evaporation and transpiration. Then the values of evapotranspiration and water requirement of grapes were calculated with 5 other methods and were compared with the FAO method using statistical indicators of absolute error (MAE). The results showed that the experimental model of Hargreaves-Samani and Blaney-Criddle had a better performance in estimating the evapotranspiration of reference crop. In addition, results indicates the Hargreaves-Samani is the superior method and other methods are ranked in the next orders. Trajkovic and Bereti’s method did not show proper results, especially in the warm months.