The analysis of several data sets collected in Southern/Central Italy shows that an increase of the average annual temperature has occurred in this area over the last century. A large set of proxy data indicates that in the Italian Peninsula warmer periods have already alternated with cooler ones over the last 3000 years. The analysis of both instrumental and proxy data gives strong evidence that the warmer periods in this area have been drier than the cooler ones. A statistically significant negative relationship between average yearly temperature and rainfall has been observed in most of the analysed instrumental data sets, with gradients up to -130 mm/°C (according to the best linear fit). Following the analogous approach, a decrease in rainfall and groundwater recharge are to be expected if the present positive trend in temperature should continue: indeed, although just a few systems in Italy are suitable for being analysed in terms of climatic variations, due to the strong anthropic influence that most of them are subject to, the yields of some natural systems investigated show a clear negative trend for the last few decades. The extrapolation from the detected trends suggests a scenario of a 10-20 % decrease in water resources on average, for the next fifty years, but much more dramatic decreases are suggested for the less rainy areas, located in southern Italy and in the islands of Sardinia and Sicily. In the frame work of such general picture, the presentation focuses on the fact that the reaction of a specific hydrogeological system to the variation of the groundwater recharge is strictly dependant on the hydrogeological structure of the system (which determines the structure of flow paths) andon the way groundwater is collected. It is also pointed out that, in general, a variation of groundwater recharge is coupled to a variation of the water yield as well as to a variation of the recharge area of the hydrogeological systems; some examples are given.
Effects of climate changes on groundwater divides and flow paths
CAMBI, Costanza;DI MATTEO, Lucio;DRAGONI, Valter Ulderico;VALIGI, Daniela
2004
Abstract
The analysis of several data sets collected in Southern/Central Italy shows that an increase of the average annual temperature has occurred in this area over the last century. A large set of proxy data indicates that in the Italian Peninsula warmer periods have already alternated with cooler ones over the last 3000 years. The analysis of both instrumental and proxy data gives strong evidence that the warmer periods in this area have been drier than the cooler ones. A statistically significant negative relationship between average yearly temperature and rainfall has been observed in most of the analysed instrumental data sets, with gradients up to -130 mm/°C (according to the best linear fit). Following the analogous approach, a decrease in rainfall and groundwater recharge are to be expected if the present positive trend in temperature should continue: indeed, although just a few systems in Italy are suitable for being analysed in terms of climatic variations, due to the strong anthropic influence that most of them are subject to, the yields of some natural systems investigated show a clear negative trend for the last few decades. The extrapolation from the detected trends suggests a scenario of a 10-20 % decrease in water resources on average, for the next fifty years, but much more dramatic decreases are suggested for the less rainy areas, located in southern Italy and in the islands of Sardinia and Sicily. In the frame work of such general picture, the presentation focuses on the fact that the reaction of a specific hydrogeological system to the variation of the groundwater recharge is strictly dependant on the hydrogeological structure of the system (which determines the structure of flow paths) andon the way groundwater is collected. It is also pointed out that, in general, a variation of groundwater recharge is coupled to a variation of the water yield as well as to a variation of the recharge area of the hydrogeological systems; some examples are given.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
