Simulation of irrigation demand hydrographs at sector level

An appropriate estimation of demand at turnouts supplying the distribution network of the sectors constituting an irrigation project is an essential tool to improve delivery scheduling in an upstream controlled irrigation system. This paper reports on studies developed at Sorraia irrigation system, Portugal, where main crops are paddy rice and furrow irrigated row crops. The project covers 15,000 ha and deserves near 2,000 farmers, the delivery being organized through near 20 sectors. Records of supply data by farmer and outlet are available for several years and have been utilized to calibrate the models. The model ISAREG has been adopted for the simulation of irrigation demand for row crops. This is an irrigation scheduling simulation model, with several options including the evaluation of delivery schedules. Adopting and calibrating theETa/ETm ratio as irrigation threshold, the model could be calibrated for the main crops. Aggregated results for several irrigation sectors closely follow the recorded ones. The model IRRICEP has been developed for simulating paddy rice irrigation. Continuous flow deliver is adopted and the model computes the flooding time and the corresponding irrigation units. The irrigation requirements are those required to keep the target water depths in the basins. The aggregated results also satisfactorily follow the recorded supplies. Models ISAREG and IRRICEP are coupled when both rice and row crops are planted in the same irrigation sector.