Sistema de estimativa da evapotranspiração - SEVAP.

Abstract

Most users of the irrigated areas in Brazil do not use any type of strategy and rational management of water in their irrigated projects. The automatic monitoring is still incipient. In this sense, a software called Evapotranspiration Estimate System - SEVAP was proposed in order to provide farmers and others with automatic estimations of the reference evapotranspiration. The methods of Penman-Monteith (FAO/56), Hargreaves, Jensen-Haise, Linacre, Makkink, Priestley & Taylor, Class A pan evaporation, and Thornthwaite were used in such a system. The SEVAP system was elaborated in Delphi computational language 5.0 version, and can be installed in a Pentium personnel computer with at least 150 MHz and 32 Mb RAM. It can run at Win 95 or higher and with Win NT. The efficiency of SEVAP system was evaluated with climatic data of Petrolina - PE, referring to 2002. Mean monthly data and daily data of maximum and minimum air temperature, relative humidity, insolation, wind velocity, Class A pan evaporation and solar radiation from March to August 2003 were used. Additionally, evapotranspiration assessments obtained by Penman-Monteith method accordingly with SEVAP and CROPWAT were compared and the determination coefficient obtained was equal to 0.96. The results show that the SEVAP system produce reliable and accurate evapotranspiration data in a monthly and daily scale. In the absence of insolation and wind velocity data the Penman-Monteith method can be substituted by with reasonable precision by Hargreaves' method.