Climate change and the performance of pressurized irrigation water distributionnetworks under mediterranean conditions: Impacts and adaptations

摘要

Numerous previous studies have modelled the impact of climate change on cropwater requirements and hence future water resource needs for irrigatedagriculture. Fewer have considered the impacts on the performance of irrigationsystems and the required engineering and managerial adaptations. This studyconsiders the impacts and adaptations for a typical pressurized pipe irrigationsystem. The dry years of the baseline period (1970-90) in the southern part ofItaly are expected to become the average or even wet year by the 2050s,according to HadCM3 projections. Under these conditions, the large waterdistribution systems designed to satisfy the baseline dry years will fail unlessappropriate engineering or managerial adaptations are made. The resilience ofDistrict 8 of the Sinistra Ofanto to the possible future increase in irrigationdemand has been assessed. A stochastic weather generator was used to generatefuture weather under the IPCC A1 and B1 emissions scenarios, taking intoconsideration the outputs of the HadCM3 model. A daily water balance model wasused to quantify the actual and future peak water demand of the district. Thereliability of each hydrant under baseline and future demand was calculatedusing a stochastic hydraulic model and the failure zones identified. Under thecurrent design, the system can tolerate a peak demand discharge up to 1,500 l.s(-1), which is below the 2050s' average (1,720 l.s(-1)). Above that value, theperformance of the system will fall drastically as the number of unreliablehydrants will increase. In the future, assuming the same cropping pattern, thethreshold discharge (1,500 l.s(-1)) will be exceeded 80% of the time and, as anaverage, 20% of the system's hydrants will be failing during the peak demandperiods. The adaptation options available to farmers and system managers inresponse to the increasing demand are discussed.