Costanza Cambi

Climatic characterization and response of water resources to climate change in limestone areas: some considerations on the importance of geological setting

AbstractThis work analyzes the response of springs fed by karst/fractured limestone aquifers, which extensively outcrop in central Italy, to climatic variations. In the central Italy area, climatic variations are represented by a general decrease in annual and winter precipitation. It is shown how groundwater regime, the discharge of springs, and their response to climate change depend to a great extent on the geologic and structural setting of the system. Some mountain springs of central Italy are local systems representing the overflow of a deeper regional flow feeding larger base springs, often of poor quality. A dynamic groundwater divide separates the recharge areas of base springs from those of local springs: if, due to low recharge, the piezometric surface lowers, the watershed moves toward systems located at higher altitudes, reducing their recharge areas. Therefore, local springs connected to a base flow are more vulnerable to climate change than those which are not. The Bagnara and Lupa springs,...

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

Abstract 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.

Reliability of water content estimation by profile probe and its effect on slope stability

Shallow landslide failures are distributed worldwide and cause economic losses and fatalities. A proper evaluation of the possible occurrence of shallow landslides requires reliable characterization of water content. Volumetric water content (θ) is commonly estimated using dielectric sensors, which use manufacturers’ calibration curves developed for specific soil types. In this study, we present the experimental results achieved during a laboratory calibration of a capacitance probe (PR2/6 probe), tested on two sandy soils widely outcropping in Central Italy. The proposed equations demonstrate a more reliable estimation of θ with respect to the generalized soil equation provided by the manufacturer, which overestimates θ by up to 10 percentage points. Such overestimation could affect the evaluation of suction stress in partially saturated shallow soils affecting the slope stability analysis. Although the use of θ from correct calibration equations provides less precautionary factor of safety values, a reliable evaluation of the soil moisture condition is fundamental when mapping and predicting the spatial and temporal occurrence of shallow landslides. The use of the PR2/6 probe with the appropriate soil calibration equations in early warning monitoring systems will provide a more reliable forecast, minimizing the number of false alarms.

Use of the Methylene Blue Stain Test to Evaluate the Efficiency of Lime Treatment on Selected Clayey Soils

AbstractThe methylene blue (MB) stain test was used to determine the efficiency of lime modification of clay soils and to define the percentage of lime required to reach the stabilization field. Montmorillonite and kaolinite, mixed in variable proportions with quartz sand, were treated with differing percentages of lime, and the MB test was performed on both untreated and treated soils. Results show that the test can determine whether a soil is prone to efficient modification, follows the evolution of clay minerals in the lime modification field, and it also determines the quantity of lime necessary to enter the stabilization field. X-ray powder diffraction, thermal analyses, and electron microscopy observations of the montmorillonite-richer sample showed its crystal chemical evolution in the modification field. Mineralogical results match the outcome of the MB test, defining the same lime percentage for best modification (4%) and confirming that the test can be used for preliminary and ongoing analyses o...