Estimating crop water requirements by the combined use of advanced numerical models and remote sensing satellite data [irrigation; Campania]
2004
Somma, G. (Naples Univ., Portici (Italy). Dipartimento di Ingegneria Agraria e Agronomia del Territorio) | D'Urso, G. (Naples Univ., Portici (Italy). Dipartimento di Ingegneria Agraria e Agronomia del Territorio)
Soil water balance models are acknowledged as valuable tools to support water resources management in irrigated agriculture. However, their application over large areas is hampered by strong limitations due to input data availability as well as high spatial and temporal variability of relevant variables in relation to the described processes, the environmental and climatic conditions. To overcome such limitations, satellite remote sensing data have proved to be able to support the application of water balance models both in input and output validation phase. In the present study, the results obtained from the comparison of two different methods developed for the assessment of crop water requirements based on the use of high resolution remote sensing optical data are presented. In the first case, radiometric measurements in the visible and near infrared ranges are used to define the upper boundary conditions, necessary for the numeric solution of the Richards equation describing unsaturated soil water flow and root water uptake. Potential soil evaporation, canopy transpiration and net precipitation are the terms defining the upper boundary conditions, which basically depend on canopy cover and status of vegetation. Conversely, the other methodology is based on the solution of the surface energy balance equation, which uses, beside the mentioned data, also thermal infrared acquisitions. The evaporative demand, estimated on the basis of the calculation of the heat and moisture fluxes in the soil-plant-atmosphere system, can be used to validate the results of the soil water flow model. The results of the application of the two approaches to a case study in Italy are compared, both at field scale (using soil water content and Bowen ratio measurements) and at the scale of irrigation district (using Landsat-5 TM satellite data). Results indicate that most reliable estimates of crop water requirements for irrigation planning can be obtained by a synergistic approach
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