Estimation of Spatial Evapotranspiration of Corn (Zea mays) Using the Sebal Algorithm at Callejón de Huaylas, Huaraz - Perú, During 2016

The objective of the research was to estimate the spatial evapotranspiration of corn with remote sensoring using the SEBAL algorithm for the conditions of the Callejón de Huaylas (Huaraz - Perú), during 2016. The study area has 5529 ha, 85% of which is corn cultivation. The algorithm was programmed using the ArcGis model builder program for 12 LANDSAT 8 satellite images from 14/MAY/2016 to 06/NOVEMBER/2016 with 15-day of temporal variability. At the same time, a 2 ha corn small farm was monitored by the Cañasbamba weather station, located at the Santiago Antúnez de Mayolo National University (UNASAM). The crop was sown field on 04/JUNE/2016 and lasted 112 days until harvest and its ET was recorded on a lysimeter. The SEBAL algorithm used has as its principle the energy balance, which considers the calculation of the net radiation (Rn), heat flow from the ground (G) and sensitive heat flow (H). The latter consisted of performing 20 iterations, which involved the choice of one hot pixel (area without culture) and one cold pixel (area with vegetation) per image. The meteorological data were obtained from the Cañasbamba and Tingua meteorological stations. The lysimeter results indicated a minimum ET of 2,68 mm/day on 13/SEPTEMBER/2016, an average ET of 3,93 mm/day and a maximum ET of 5,9 mm/day on 03/SEPTEMBER/2016. In addition, eleven maize monitoring points distributed in the study area were considered, since the beginning of planting depends on the owners of the agricultural land, varying by days or months. When comparing the observed and measured actual evapotranspiration, a relative error of 0,08, the root of the mean quadratic error of 0,3, a determination coefficient of 0,94 and a Nash-Sutcliffe efficiency of 0,91 were obtained, which indicate that the results obtained with the SEBAL algorithm are very satisfactory. In the study area located between Yungay and Carhuaz districts, average values ranging from 4,0 mm/day to 6,2 mm/day were found throughout the analysis period.