A Methodology for Conducting Diagnostic Analyses and Operational Simulation in Large-scale Pressurized Irrigation Systems

摘要

This paper describes a methodology, which is currently being tested, aimed at generating flow hydrographs and the operational simulation of existing pressurized irrigation delivery networks in southern Italy. The approach involves a combined use of high-resolution remote sensing and of a simplified agro-hydrological model to simulate the soil water balance at the level of each delivery node of the irrigation network. High resolution multispectral satellite imagery was acquired on a single date overpass for an existing irrigation district located in southern Italy. The use of high-resolution imagery enables mapping the land use, identifying the specific extent of different cropped areas, and accounting for the spatial variability of parameters related to crop evapotranspiration over the irrigated areas. In the rationale of the proposed methodology, the agro-hydrological model uses spatially-distributed inputs derived from the high-resolution multispectral image and, by maintaining a soil-water balance in the cropped fields downstream from the delivery hydrants, would allow generating disaggregated information on soil water deficits and thus on timing and volumes of irrigation demand for the area served by the distribution network. The aggregation of hydrant hydrographs would allow generating the flow hydrographs at the upstream end of the irrigation network. Results from simulations will then be compared with historical datasets of irrigation events that will be obtained by downloading data records from multiuser electronically-fed hydrants equipped with the AcquaCARD* technology. These comparisons will allow investigating any deviation of actual water deliveries to farm fields from the simulation results, accounting for various uncertainties, including the ones related to farmers' water management strategy. The overall objective of the study being conducted is validating the reliability of the proposed methodology for modernization of large-scale irrigation systems.