Effects of Climate Change on the Irrigation Scheduling Parameters in Calabria (South Italy) during 1925-2013

Climate characteristics play an essential role in the crop evapotranspiration and therefore affect irrigation.Reference evapotranspiration (ET0) is a climatic parameter that can be computed from weather data and used to areliable variable for assessing long-term trends of the atmospheric evaporative demand. The study aims to evaluatethe effects of the climate change on ET0 and citrus and tomato irrigation scheduling parameters (irrigation depth,length of the irrigation season and number of irrigation) in Calabria, a Region of South Italy. The study covered 89years (1925-2013) and 9 of the most relevant irrigated areas in the Region. The software CROPWAT was used toestimate the irrigation scheduling parameters. The time series were analyzed at yearly and seasonal scale usingstandard trend analysis tests (Mann-Kendall and linear trend test). The results showed a slight decreasing trend formaximum temperature and both increasing and decreasing trends for minimum temperature. Due to the asymmetricbehavior of temperatures, impact on ET0 resulted in a decreasing tendency (-5.51 mm.decade-1). There was a slightdecrease in the seasonal irrigation depth for both citrus and tomato. The average annual magnitude of decreasesthroughout Calabria were 2.40 and 5.51 mm.decade-1 for citrus and tomato, respectively, corresponding to -7% and-11% of the mean irrigation depth of the period considered. This trend depended on both the decreased ET0 andprecipitation trend: precipitation decreased at yearly scale, but increased in summer, the season when irrigationrequirements are higher in the environment considered. The positive trend in summer precipitation also caused anadvance of the last watering, resulting in a slight decrease of the length of the irrigation season. The results, on thewhole, showed the importance of studies at regional scale considering the detection of trends even opposite withrespect to those founded in studies on other areas in the same Mediterranean region. The elaboration of more localstudies is useful in order to deepen knowledge on the problematic of each zone and to plan concrete actions.