M. Polemio

Climate change, drought and groundwater availability in southern Italy

Abstract Data for the period 1821 to 2003 from 126 rain gauges, 41 temperature gauges, eight river discharge gauges and 239 wells, located in southern Italy, have been analysed to characterize the effect of recent climate change on availability of water resources, focusing on groundwater resources. Regular data are available from 1921 to 2001. Many analysis methods are used: principal component analysis, to divide the study area into homogenous portions; trend analysis, considering the Mann–Kendall, Student-t and Craddock tests, autocorrelation and cross-correlation analyses, and seasonal, annual and moving-average variables, applying the spatial analysis to each variable with a geographical information system approach. A widespread decreasing trend of annual rainfall is observed over 97% of the whole area. The decreasing trend of rainfall worsens or decreases as mean annual rainfall increases; the spatial mean of trend ranges from −0.8 mm/a in Apulia to −2.9 mm/a in Calabria. The decrease in rainfall is notable after 1980: the recent droughts of 1988–1992 and 1999–2001 appear to be exceptional. On a seasonal basis, the decreasing trend is concentrated in winter; a slight positive trend is observed in summer, the arid season in which the increase is useless as it is transformed into actual evapotranspiration. The temperature trend is not significant and homogeneous everywhere if the temperature increase seems to prevail, especially from about 1980. Net rainfall, calculated as a function of monthly rainfall and temperature, shows a huge and generalized negative trend. The trend of groundwater availability is so negative everywhere that the situation can be termed dramatic for water users, due not only to the natural drop in recharge but also to the increase of discharge by wells to compensate the non-availability of surface water tapped by dams, as a direct effect of droughts.

Evaluation and Selection of Indicators for Land Degradation and Desertification Monitoring: Methodological Approach

An approach to derive relationships for defining land degradation and desertification risk and developing appropriate tools for assessing the effectiveness of the various land management practices using indicators is presented in the present paper. In order to investigate which indicators are most effective in assessing the level of desertification risk, a total of 70 candidate indicators was selected providing information for the biophysical environment, socio-economic conditions, and land management characteristics. The indicators were defined in 1,672 field sites located in 17 study areas in the Mediterranean region, Eastern Europe, Latin America, Africa, and Asia. Based on an existing geo-referenced database, classes were designated for each indicator and a sensitivity score to desertification was assigned to each class based on existing research. The obtained data were analyzed for the various processes of land degradation at farm level. The derived methodology was assessed using independent indicators, such as the measured soil erosion rate, and the organic matter content of the soil. Based on regression analyses, the collected indicator set can be reduced to a number of effective indicators ranging from 8 to 17 in the various processes of land degradation. Among the most important indicators identified as affecting land degradation and desertification risk were rain seasonality, slope gradient, plant cover, rate of land abandonment, land-use intensity, and the level of policy implementation.

Carbonate Aquifers in Apulia and Seawater Intrusion

The predisposing factors and the determining factors of seawater intrusion in wide carbonate aquifers of Apulia (Southern Italy) are characterized. Main predisposing factors prove the sedimentation environment, the tectonic-karstic evolution, the geometry of the aquifers in relation to the coastline, the depth of the aquifers, the existence of underground outflows and their chemical nature. The effect of salinity pollution and its trend was characterized using data from a regional monitoring network, considering logs time series, and also from well loggings. The intensive and widespread use has led to a progressive deterioration in water quality, particularly in the Salento area, right where the aquifer is most susceptible to seawater intrusion. Key terms: Karstic aquifer, Seawater intrusion, Groundwater degradation

Evaluation and selection of indicators for land degradation and desertification monitoring: types of degradation, causes, and implications for management

Indicator-based approaches are often used to monitor land degradation and desertification from the global to the very local scale. However, there is still little agreement on which indicators may best reflect both status and trends of these phenomena. In this study, various processes of land degradation and desertification have been analyzed in 17 study sites around the world using a wide set of biophysical and socioeconomic indicators. The database described earlier in this issue by Kosmas and others (Environ Manage, 2013) for defining desertification risk was further analyzed to define the most important indicators related to the following degradation processes: water erosion in various land uses, tillage erosion, soil salinization, water stress, forest fires, and overgrazing. A correlation analysis was applied to the selected indicators in order to identify the most important variables contributing to each land degradation process. The analysis indicates that the most important indicators are: (i) rain seasonality affecting water erosion, water stress, and forest fires, (ii) slope gradient affecting water erosion, tillage erosion and water stress, and (iii) water scarcity soil salinization, water stress, and forest fires. Implementation of existing regulations or policies concerned with resources development and environmental sustainability was identified as the most important indicator of land protection.

Occurrence of landslide events and the role of climate in the twentieth century in Calabria, southern Italy

Abstract A methodological approach based on analysing landslides that occurred over a long period and climatic data characterizing that period is presented. The method investigates whether there are any effects of climate on landslide triggering. The approach has been tested in Calabria (Italy). Both landslide and climatic data have been obtained from available databases that have been expanded. Landslide data came from historical archives and newspapers, whereas the climatic analysis is based on daily and monthly series of rainfall and temperature. The method simplifies the comparative analysis of several time series by defining some indices (the monthly, bi-monthly … m-monthly indices of precipitation, temperature, wet days and precipitation, and the monthly landslide number) that can be used to study phenomena, such as landslides, that are characterized by spatial and temporal variability. For Calabria, the number of landslides is correlated to monthly precipitation, wet days and precipitation intensity. Thus, landslide occurrence could be roughly forecast using these climatic data. Despite the favourable climatic trend, landslides are not decreasing because the recent utilization of landslide-prone areas increases the vulnerability.

Modelling and management of a Mediterranean karstic coastal aquifer under the effects of seawater intrusion and climate change

The study and management of the groundwater resources of a large, deep, coastal, karstic aquifer represent a very complex hydrogeological problem. Here, this problem is successfully approached by using an equivalent porous continuous medium (EPCM) to represent a karstic Apulian aquifer (southern Italy). This aquifer, which is located on a peninsula and extends to hundreds of metres depth, is the sole local source of high-quality water resources. These resources are at risk due to overexploitation, climate change and seawater intrusion. The model was based on MODFLOW and SEAWAT codes. Piezometric and salinity variations from 1930 to 2060 were simulated under three past scenarios (up to 1999) and three future scenarios that consider climate change, different types of discharge, and changes in sea level and salinity. The model was validated using surveyed piezometric and salinity data. An evident piezometric drop was confirmed for the past period (until 1999); a similar dramatic drop appears to be likely in the future. The lateral intrusion and upconing effects of seawater intrusion were non-negligible in the past and will be considerable in the future. All phenomena considered here, including sea level and sea salinity, showed non-negligible effects on coastal groundwater.

Mechanics of a tectonized soil slope: influence of boundary conditions and rainfall

The Vadoncello landslide was mobilized in December 1993 and is still active. It involves highly tectonized soils and is the reactivation of a landslide dragged by a larger landslide at the toe of the slope soon after the 1980 Irpinia (Southern Italy) earthquake. Investigations and monitoring of the Vadoncello landslide were carried out, between 1994 and 1996, within an EC funded research project. The slope has been found to be formed of chaotic successions of soil and rock strata which have been grouped into soil complexes. The soil mechanical properties are shown to be very poor, the deep soils being prone to large plastic straining even due to relatively small loading changes. The soil displacements show that a shallow fast rotational sliding has occurred at the top of the slope and a shallow earthflow has developed downslope, both lying above deeper soils involved in a mechanism of slow and long-lasting irrecoverable movements. These slow deep movements are considered to be consequent to the plastic flow of the clayey soils. They can be activated by the effects of seasonal rainfall, of low-medium intensity seismic events and by the effects of the morphological changes resulting from the slow movements themselves. The landslide reactivation in 1993 is seen to have been the combination effect of a low return-period rainfall event and the slow movements active at depth in the slope.

The influence of climate variability and land use variations on the occurrence of landslide events (Subappennino Dauno, Southern Italy)

The aim of the paper is to describe the results of the application of a methodology based both on the use of time series analyses and of geospatial analyses of monthly climatic data (rainfall, wet days, rainfall intensity, and temperature), annual maximum of short-duration rainfall (from 1 hour to 5 days), and historical modification of land use in order to characterise the effects of these variables on the occurrence of landslide events. The methodology was applied in the Subappennino Dauno area, located on the eastern margin of the Southern Apennines thrust belt (southern Italy). Despite the decreasing trend of rainfall and rainfall intensity and the increasing trend of temperatures and wet days, there is an increasing trend of landslide occurrence, highlighting the negative effect of anthropogenic modifications and the mismanagement of landslide-prone areas. This hypothesis was confirmed by comparing the distribution of landslides with the land use variations data (especially urban areas and wooded areas) collected from 1930 to 2006.

Climate Variability and Landslide Occurrence in Apulia (Southern Italy)

This contribution is based on the analysis of different types of data recorded to provide monthly time series related to climate (rainfall, wet days, rainfall intensity and temperature) from 1877 to 2008, in order to verify the relationship between climate changes and landslide occurrence in Apulia region. Despite the decreasing trend of rainfall and rainfall intensity and the increasing trend of temperatures and wet days, there is an increasing trend of landslide occurrence, highlighting the negative effect of anthropogenic activities in landslide-prone areas.

Hydrogeological monitoring and image analysis of a mudslide in Southern Italy

Abstract This paper describes a methodological example of a data-integration procedure to improve the knowledge of landslide hazard related to a seismic area in the southern Apennine (Italy). Attention is focused on remote sensing data. The analysis is validated using detailed topographical, geophysical, geotechnical and hydrogeological data as ground truth. The investigated phenomenon, which started at the end of 1993, is an earthflow. The presented methodology recommends the combined use of DEM, multi-temporal panchromatic visible aerial photographs and thermal infrared images. The integration between these data and multidisciplinary monitoring data proved useful. The main hydrogeological pattern, the geological and geomorphological framework and the areas of latent instability can be clearly determined. Insight can be gained through the synoptic slope view in the relative short time needed to carry out the analysis. The proposed approach can be regarded as a useful contribution to the evaluation of landslide hazard, particularly during emergency periods.