Assessing Crop Water Demand by Remote Sensing and GIS for the Pontina Plain, Central Italy

An estimation of the crop water requirements for the Pontina Plain, Central Italy, was carried out through the use of remote sensing land classification and application of a simple water balance scheme in a GIS environment. The overall crop water demand for the 700 km2 area was estimated at about 70 Mm3 year?1, i.e. 100 Mm3 year?1 irrigation requirements when considering an average irrigation application efficiency of 70%. The simplest and least demanding available methodology, in terms of data and resources, was chosen. The methodology, based on remote sensing and GIS, employed only 4 Landsat ETM+ images and a few meteorological and geographical vectorial layers. The procedure allowed the elaboration of monthly maps of crop evapotranspiration. The application of a spatially distributed simple water balance model, lead to the estimation of temporal and spatial variation of crop water requirements in the study area. This study contributes to fill a gap in the knowledge on agricultural use of water resources in the area, which is essential for the implementation of a sustainable and sound water policy as required in the region for the application of the EU Water Framework Directive.