Effetti della realizzazione degli invasi sul clima delle zone circostanti

The Capitanata area Reclamation Consortium created a dam halfway up the valley of the river Fortore, at Occhito, in the municipality of Carlantino (Foggia province), in order to create a reservoir for the numerous agricultural irrigation districts on the Tavoliere plain, covering a total area of 140 x 103 ha. Work began in 1957 and was completed in 1966. The dam was built in earth and rock with a waterproof concrete core. At its summit it is 432 m long, 60 m high and has a volume of 3 x 106 m3 . The overall capacity of the reservoir, which collects surface water in a catchment basin covering an area of 103 km2, is 300 x 106 m3, of which 250 x 106 m3 are useful: when the reser-voir is full, its surface area is 13 km2. As is well known, the quality of the waters is determined by the efficacy (itself due to the efficiency) of the vegetation present in the basin in protecting the water regime and the soil. In this study case, since the 1950s great attention has been paid by the authorities to im-prove the natural woodlands and to create new stands using Mediterranean conifer species on the slopes of the rivers which flow into Lake Occhito. The formation of such a large body of water in a relatively short time has led to substan-tial variations in the climate along the whole midcourse of the river: these variations have been noticed by the local resident population, starting with their consequences on agricultural land. This study investigated the variations in the main climate parameters before and after 1975, the year the reservoir first filled up: the variations were measured by processing rainfall and temperature data from the Hydrological Service’s equipment installed in the study area. We studied the monthly, seasonal and annual variations in the main parameters, i.e. air temperature and rainfall. The results made it possible to determine what variations have taken place locally in the rainfall regime and in the bioclimate. The annual variations were then correlated with the quantity of water collected each year by the reservoir. These results will be used to start up a research program into the best methods for con-serving the local natural forests and artificial stands, which have respectively undergone regen-eration and naturalisation.