WATER BALANCE OPTIMIZATION: CASE STUDY BY THE FAO PENMAN-MONTEITH MODEL IN APPLE TREE CULTIVATION (MALUS DOMESTICA BORKH) SUPPORTED BY WEB, BIO-BIO, CHILE Marcos Lévano 1 , Camilo Friz 2 and Billy Peralta 3 1 Computer Engineering Department, Catholic University of Temuco Ave. Manuel Montt 56, Mailbox 15-D, Temuco, Chile 2 Software Development Consultant, Los Angeles, Chile 3 Departamento de Ciencias de la Ingeniería, Universidad Andres Bello Antonio Varas 880, piso 6, Providencia, Región Metropolitana, Chile ABSTRACT This paper proposes a framework for water resource optimization by balanced use, where a case study by the FAO Penman-Monteith model is presented in the cultivation of apple fruit (Malus Doméstica Borkh) in a region of Chile called “Bio-Bio”. A technological support by Web is proposed for water balance in calculating the evapotranspiration (evaporation and transpiration) as an important variable in an abundant irrigation activity. The results generate recommendations to Chilean authorities in agriculture about how to care for water in these times of water shortages for rational use. KEYWORDS Water Optimization, Productivity Increasing, Web Technology, Apple Fruit 1. INTRODUCTION The amount of water that a crop needs through its different stages of vegetative development, a term that is expressed as use-consumption or evapotranspiration (Sanjay & Lakshman, 2020), is a fundamental antecedent in the determination of irrigation rates, in the irrigation planning both at property and regional level, in the design of method and structures of irrigation, distribution of water, etc. However, use-consumption values determined in one place have a limited extrapolation area because this factor is strongly influenced by the place climatic characteristics for a specific crop (Tosso, 1976). On the other hand, the use-consumption measurements require several years of experimentation so that they are representative, requiring, in addition, equipment and specialized personnel. According to Xiaojie (Xiaojie et al., 2019) and (Sanjay & Lakshman, 2020), it is possible to make estimates of evapotranspiration knowing the relationship between both parameters (use-consumption and evaporation) in the different stages of the crop vegetative development. This relationship is known as evapotranspiration K coefficient. In this paper the water resource balance for the apple tree (Malus Doméstica Borkh) was made, the evapotranspiration was estimated manually and with support of computational program by Web technology through the Penman-Monteith model (Penman, 1948; Monteith, 1965; Sanjay & Lakshman, 2020). Drought, desertification and degraded soil, 76% of the country's surface is affected by drought, desertification and degraded soil. This is 57.5 million hectares. There live 11.6 million inhabitants: 65% of the national population. 22% of the country's surface shows desertification signs to some degree, 80% show soil degradation signs and 72% of drought effects. That is the diagnosis with which Chile is updating its strategy and 2016-2030 national plan before the UN Convention to combat Desertification and Drought. The combined action of the three problems affects 76% of the national territory: 57.5 million hectares where 11.6 million people live (65% of the national population) (Schneider et al., 2007; BM, 2011; CONAMA, 2010). 13th IADIS International Conference Information Systems 2020 45