Crop irrigation, especially in irrigation networks, often consumes larger quantities of irrigation water than necessary since most of the times irrigation is carried out empirically and not based on actual crop requirements. The aim of this work is the management of irrigation water though the use of meteorological data. This approach was utilized for the first time in Greece and applied in a pilot area of about 6,000 ha at the Local Organization of Land Reclamation in Nigrita. The method is based on accurate calculation of daily evapotranspiration of the common cultivations at the area (maize, cotton, alfalfa), using meteorological data. Thus irrigation is organized based on actual water consumption of the crops ensuring the qualitative and quantitative characteristics of their products.