Water management in low permeability catchments and in times of climatic change: the case of the Nestore River (western central Italy)

The analysis of the historical data series for rainfall and temperature in Central Italy indicates that a slight increase in temperature is occurring in this area, accompanied by a decrease of up to 3–4 mm/year in rainfall, rather significant when compared to the local average of 600–800 mm/year of rain. The causes of these trends are still not clear so that the persistency and intensity of these climatic variations in the future cannot be defined with any certainty. Nonetheless, when considering plans for water management, it is necessary to bear in mind that the duration of warm periods in the past and the increase in greenhouse gases suggest that these trends will persist. This situation is particularly worrying in an area where the Mediterranean climate––with hot and dry summers––causes the summer discharge of rivers to be very low or even nil, especially in the catchments––very common in Central Italy––made up of low permeability flysch-type rocks, with no significant aquifers. As an exemplification of the difficulties involved in water management and of the way to try to solve them, the authors present here the case of an artificial lake used to store water for the cooling of a thermo-electric power plant. The water from the Nestore River, located in an area with low-permeability, flysch-type rocks, fills the lake. A specially set up model was calibrated to simulate the lake level changes under different climatic conditions. The model indicated that a certain portion of the basin is enough for the needs of the power plant, even with severely limiting restrictions regarding the releasing of the minimum acceptable flow into the natural channel, and in the most pessimistic hypotheses of climatic variations.