Analysis of the most reliable meteorological datasets for Central Italy reveal that most of the series have trends. Their presence and intensity vary according to statistical technique, to quality of data and geographical location, but the general picture is quite clear: in practice, all stations showing significant trends report a decrease in rainfall and an increase in temperature. Temperature increase and rainfall decrease inevitably reduce the water yield of hydrological systems: indeed, analyses of discharge data series of some hydrogeological systems in Central Italy show negative trends. Although in some systems it is not easy to define in which proportions this trend is to be related to climatic variations or to exploitation or land use, there are some systems – particularly mountain catchments and springs - which can be considered as not influenced by human activity and which show a decrease in yield over the last 40-50 years. One of these systems is Bagnara Spring which has been studied in order to obtain some reasonable scenario about the discharges during the next 30 years, assuming that the climatic trend of the last decades will persist. Bagnara spring is fed by the Monte Pennino anticline, which is a typical Apenninic structure, an east-vergent asymmetric anticline, with a main thrust structure and some secondary thrusts on the eastern slope, and back thrusts structures on the western slope. The rocks outcropping in the area belong to the Umbria-Marche geological sequence, which is mainly made of limestone formations within which some marl formations occur. According to the geological setup, the potential recharge area of the spring is about 7.5 km2 wide. In spite of their poor quality, the analysis of the meteorological data in the area indicates that during the period 1982-2009 the water surplus (defined as the difference between rainfall and evapotranspiration) decreased of about 15 – 20 % compared to the 1954 – 1981 period. In order to have an idea about the future discharges of the spring, a set of lumped models of the rain-discharge process transformation was applied. All the models were on a monthly basis. Under the assumption that the present trend will continue and in spite of their different performance, the models indicate a decrease of the discharges higher than the decrease of the water surplus. This should be taken in account in the future water management plans. Sounder results and better modeling could be obtained if the meteorological data were more reliable: it is imperative that a reliable data net for the measurement of evaporation, piezometric heads, rain, snow and temperature is established
Impact of the present climatic trends on the discharge of Bagnara spring (Umbria - Marche Apennines, Italy)
CAMBI, Costanza;DRAGONI, Valter Ulderico;GIONTELLA, CECILIA;VALIGI, Daniela
2011
Abstract
Analysis of the most reliable meteorological datasets for Central Italy reveal that most of the series have trends. Their presence and intensity vary according to statistical technique, to quality of data and geographical location, but the general picture is quite clear: in practice, all stations showing significant trends report a decrease in rainfall and an increase in temperature. Temperature increase and rainfall decrease inevitably reduce the water yield of hydrological systems: indeed, analyses of discharge data series of some hydrogeological systems in Central Italy show negative trends. Although in some systems it is not easy to define in which proportions this trend is to be related to climatic variations or to exploitation or land use, there are some systems – particularly mountain catchments and springs - which can be considered as not influenced by human activity and which show a decrease in yield over the last 40-50 years. One of these systems is Bagnara Spring which has been studied in order to obtain some reasonable scenario about the discharges during the next 30 years, assuming that the climatic trend of the last decades will persist. Bagnara spring is fed by the Monte Pennino anticline, which is a typical Apenninic structure, an east-vergent asymmetric anticline, with a main thrust structure and some secondary thrusts on the eastern slope, and back thrusts structures on the western slope. The rocks outcropping in the area belong to the Umbria-Marche geological sequence, which is mainly made of limestone formations within which some marl formations occur. According to the geological setup, the potential recharge area of the spring is about 7.5 km2 wide. In spite of their poor quality, the analysis of the meteorological data in the area indicates that during the period 1982-2009 the water surplus (defined as the difference between rainfall and evapotranspiration) decreased of about 15 – 20 % compared to the 1954 – 1981 period. In order to have an idea about the future discharges of the spring, a set of lumped models of the rain-discharge process transformation was applied. All the models were on a monthly basis. Under the assumption that the present trend will continue and in spite of their different performance, the models indicate a decrease of the discharges higher than the decrease of the water surplus. This should be taken in account in the future water management plans. Sounder results and better modeling could be obtained if the meteorological data were more reliable: it is imperative that a reliable data net for the measurement of evaporation, piezometric heads, rain, snow and temperature is establishedI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
