Crop evapotranspiration estimation using remote sensing and the existing network of meteorological stations in Cyprus

摘要

Cyprus is frequently confronted with severe droughts andthe need for accurate and systematic data on crop evapotranspiration (ETc)is essential for decision making, regarding water irrigation management andscheduling. The aim of this paper is to highlight how data frommeteorological stations in Cyprus can be used for monitoring and determiningthe country's irrigation demands. This paper shows how daily ETc can beestimated using FAO Penman-Monteith method adapted to satellite data andauxiliary meteorological parameters. This method is widely used in manycountries for estimating crop evapotranspiration using auxiliarymeteorological data (maximum and minimum temperatures, relative humidity,wind speed) as inputs. Two case studies were selected in order to determineevapotranspiration using meteorological and low resolution satellite data(MODIS – TERRA) and to compare it with the results of the reference method(FAO-56) which estimates the reference evapotranspiration (ETo) by usingonly meteorological data. The first approach corresponds to the FAOPenman-Monteith method adapted for using both meteorological and remotelysensed data. Furthermore, main automatic meteorological stations in Cypruswere mapped using Geographical Information System (GIS). All theagricultural areas of the island were categorized according to the nearestmeteorological station which is considered as "representative" of thearea. Thiessen polygons methodology was used for this purpose. The intendedgoal was to illustrate what can happen to a crop, in terms of waterrequirements, if meteorological data are retrieved from other than therepresentative stations. The use of inaccurate data can result in low yieldsor excessive irrigation which both lead to profit reduction. The resultshave shown that if inappropriate meteorological data are utilized, thendeviations from correct ETc might be obtained, leading to water losses orcrop water stress.