Emanuele Romano | Consiglio Nazionale delle Ricerche (CNR) (original) (raw)

Papers by Emanuele Romano

This paper focuses on a multidisciplinary study carried out in an urban area affected by subsiden... more This paper focuses on a multidisciplinary study carried out in an urban area affected by subsidence and related structural damages. The study area is located about 20 km east of Rome (Italy) and is characterised by relevant groundwater exploitation for various purposes as well as by the presence of compressible soils immediately below the ground level. Extensive processing at different scales of SAR satellite images (ERS and ENVISAT provided by ESA in the frame of a CAT-1 project) by means of A-DInSAR technique was performed. The time histories of ground displacements, have been analysed in combination with a detailed geological setting of the study area and with the hydrogeological changes occurred in the last decades (as the response to the anthropic stress) based on a large piezometric dataset. This comprehensive dataset allowed us to describe the space and time distributions of the subsidence process. The spatial pattern and deformation rate change is attributed to the following causes: i) the changes in the groundwater levels due to the intensification of mine exploitation (requiring dewatering operations) and ii) the distribution and thickness of recent compressible deposits. Specifically, it is derived that the groundwater level variations drive the timing of subsidence triggering over the area, whereas the local geological conditions control the magnitude of the deformation process.

Studies on recent climate trends from the Hi-malayan range are limited, and even completely absen... more Studies on recent climate trends from the Hi-malayan range are limited, and even completely absent at high elevation (> 5000 m a.s.l.). This study specifically explores the southern slopes of Mt. Everest, analyzing the time series of temperature and precipitation reconstructed from seven stations located between 2660 and 5600 m a.s.l. during 1994–2013, complemented with the data from all existing ground weather stations located on both sides of the mountain range (Koshi Basin) over the same period. Overall we find that the main and most significant increase in temperature is concentrated outside of the monsoon period. Above 5000 m a.s.l. the increasing trend in the time series of minimum temperature (+0.072 • C yr −1) is much stronger than of maximum temperature (+0.009 • C yr −1), while the mean temperature increased by +0.044 • C yr −1. Moreover, we note a substantial liquid precipitation weakening (−9.3 mm yr −1) during the monsoon season. The annual rate of decrease in precipitation at higher elevations is similar to the one at lower elevations on the southern side of the Koshi Basin, but the drier conditions of this remote environment make the fractional loss much more consistent (−47 % during the monsoon period). Our results challenge the assumptions on whether temperature or precipitation is the main driver of recent glacier mass changes in the region. The main implications are the following: (1) the negative mass balances of glaciers observed in this region can be more ascribed to a decrease in accumulation (snowfall) than to an increase in surface melting; (2) the melting has only been favoured during winter and spring months and close to the glaciers terminus; (3) a decrease in the probability of snowfall (−10 %) has made a significant impact only at glacier ablation zone, but the magnitude of this decrease is distinctly lower than the observed decrease in precipitation; (4) the decrease in accumulation could have caused the observed decrease in glacier flow velocity and the current stagnation of glacier termini, which in turn could have produced more melting under the debris glacier cover, leading to the formation of numerous supraglacial and proglacial lakes that have characterized the region in the last decades.

The assessment of the impact of long-term climate variability onwater supply systems depends not ... more The assessment of the impact of long-term climate variability onwater supply systems depends not only on possible variations of the resources availability, but also on the variation of the demand. In this framework, a robust estimation of direct (climate induced) and indirect (anthropogenically induced) effects of climate change ismandatory to design mitigation measures, especially in those regions of the planet where the groundwater equilibrium is strongly perturbed by exploitations for irrigation purposes. The main goal of this contribution is to propose a comprehensive model that integrates distributed crop water requirements with surface and groundwater mass balance, able to considermanagement rules of thewater supply system. The proposed overallmodel, implemented, calibrated and validated for the case study of the Fortore water supply system (Apulia region, South Italy), permits to simulate the conjunctive use of the water from a surface artificial reservoir and from groundwater. The relative contributions of groundwater recharges and withdrawals to the aquifer stress have been evaluated under different climate perturbations, with emphasis on irrigation practices. Results point out that irrigated agriculture primarily affects groundwater discharge, indicating that ecosystem services connected to river base flow are particularly exposed to climate variation in irrigated areas. Moreover, findings show that the recharge both to surface and to groundwater is mainly affected by drier climate conditions, while hotter conditions have a major impact on the water demand. The non-linearity arising from combined drier and hotter conditions may exacerbate the aquifer stress by exposing it to massive sea-water intrusion.

Macroscopic properties of flow through porous media can be directly computed by solving the Navie... more Macroscopic properties of flow through porous media can be directly computed by solving the Navier– Stokes equations at the scales related to the actual flow processes, while considering the porous structures in an explicit way. The aim of this paper is to investigate the effects of the pore-scale spatial distribution on seepage velocity through numerical simulations of 3D fluid flow performed by the lattice Boltzmann method. To this end, we generate multiple random Gaussian fields whose spatial correlation follows an assigned semi-variogram function. The Exponential and Gaussian semi-variograms are chosen as extreme-cases of correlation for short distances and statistical properties of the resulting porous media (indicator field) are described using the Matèrn covariance model, with characteristic lengths of spatial autocorrelation (pore size) varying from 2% to 13% of the linear domain. To consider the sensitivity of the modeling results to the geostatistical representativeness of the domain as well as to the adopted resolution, porous media have been generated repetitively with re-initialized random seeds and three different resolutions have been tested for each resulting realization. The main difference among results is observed between the two adopted semi-variograms, indicating that the roughness (short distances autocorrelation) is the property mainly affecting the flux. However, computed seepage velocities show additionally a wide variability (about three orders of magnitude) for each semi-variogram model in relation to the assigned correlation length, corresponding to pore sizes. The spatial resolution affects more the results for short correlation lengths (i.e., small pore sizes), resulting in an increasing underestimation of the seepage velocity with the decreasing correlation length. On the other hand, results show an increasing uncertainty as the correlation length approaches the domain size.

Among different uses of freshwater, irrigation is the most impacting groundwater resource, leadin... more Among different uses of freshwater, irrigation is the most impacting groundwater resource, leading to water table depletion and possible seawater intrusion. The unbalance between the availability of water resources and demand is currently exacerbated and could become worse in the near future in accordance with climate change observations and scenarios provided by Intergovernmental Panel on Climate Change (IPCC). In this context, Increasing Maximum Capacity of the surface reservoir (IMC) and Managed Aquifer Recharge (MAR) are adaptation measures that have the potential to enhance water supply systems resiliency. In this paper, a multiple-users and multiple-resources-Water Supply System (WSS) model is implemented to evaluate the effectiveness of these two adaptation strategies in a context of overexploited groundwater under the RCP 4.5 and the RCP 8.5 IPCC scenarios. The presented a case study that is located in the Puglia, a semi-arid region of South Italy characterized by a conspicuous water demand for irrigation. We observed that, although no significant long-term trend affects the proposed precipitation scenarios, the expected temperature increase highly impacts the WSS resources due to the associated increase of water demand for irrigation purposes. Under the RCP 4.5 the MAR scenario results are more effective than the IMC during long term wet periods (typically 5 years) and successfully compensates the impact on the groundwater resources. Differently, under RCP 8.5, due to more persistent dry periods, both adaptation scenarios fail and groundwater resource become exposed to massive sea water intrusion during the second half of the century. We conclude that the MAR scenario is a suitable adaptation strategy to face the expected future changes in climate, although mitigation actions to reduce greenhouse gases are strongly required.

Conditions of shortage in a water supply system (WSS) occur when the available water resources ar... more Conditions of shortage in a water supply system (WSS) occur when the available water resources are unable to satisfy the related demand (failure). The definition of risk of shortage conventionally relies on three indexes that capture the characteristics of possible failures in terms of probability of occurrence (reliability), duration (resiliency), and intensity (vulnerability). Although the conceptual bases for these definitions are largely acknowledged, the operative way to define them can largely affect the final value of the risk of shortage, making it difficult to compare among different WSSs when different formulations are applied. In this paper, a robust method to quantify the risk of shortage for WSSs that rely on surface water is proposed. The major novelties are to consider the extreme events in the risk analysis and to overcome the issue of the representativeness of the observed time series with respect to the characteristic return periods of drought events. To this aim, a stochastic approach based on a zero mean autoregressive (AR) model of standardized precipitation indexes (SPIs) is combined with a multilinear regressive model learning from observed SPI and associated inflow anomalies. This approach has been applied to the case study of the Ridracoli Reservoir in Central Italy, taking into account several climate scenarios, as well as several configurations of the WSS. Results show the ability of the proposed procedure to obtain convergence in the risk indexes and to distinguish among different levels of shortage risk, giving additional information for drought episodes with longer return periods. In particular, the standardized indexes focusing also on extreme events led to a quantification of the risk able to capture, at least in the proposed case study, the benefit of management options aiming to reduce the vulnerability (i.e., not fully meeting the demand in anticipation of a dry period), while those considering only the average features do not.

The present communication describes several regional-scale modelling experiences involving the ca... more The present communication describes several regional-scale modelling experiences involving the carbonatic aquifer of Mt Coscerno and the alluvial aquifer of Petrignano d'Assisi. The aim is to highlight the principal differences and similarities in the applica-tion of mathematical models to carbonatic aquifers in mountain areas and to alluvial type aquifers resulting principally from the different availability of data. In the first case the hydrogeological balance, determined by field measurements, is usually known while direct observation of the piezometric surface is difficult owing to its extreme depth; in the second case, the piezometric surface is deter-mined by measurement of piezometric level in wells although the aquifer balance is generally known only through indirect estimates of the effective infiltration and any other ancillary contributions (exchanges with watercourses, infiltration from boundaries, etc). The determination of the hydrodynamic parameters, wherever thi...

The aim of this study was the estimate of aquifer recharge by means of a finitedifference model, ... more The aim of this study was the estimate of aquifer recharge by means of a finitedifference model, which solves the non-linear 1-D Richards equation in transient conditions: the water flow rate through the ground surface, which is the upper boundary condition for the model, was evaluated from standard meteorological data, taking into account the limitation to the evaporation/infiltration given by the soil retention features. A field campaign was carried out for 16 months in the suburban area of the Lambro Park to evaluate the local recharge due to the rainfall infiltration through the unsaturated zone. Meteorological data (atmospheric pressure, rainfall, humidity, wind velocity and air temperature) were collected to evaluate potential evaporation using a based-temperature equation (Hamon method); the real evaporation was assessed as a fraction of the potential one, on the basis of the actual soil water content. Simultaneously, the soil water content and the capillary pressure head at different depths (down to 76 cm) were measured with TDR probes and tensiometers, respectively. Characteristic retention curves were estimated in laboratory using Richards apparatus and compared with data collected in situ. The model allowed us to well reproduce soil moisture experimental data both during dry periods and wet periods, taking into account as input only standard meteorological data and the retention features of the soil.

Conditions of scarcity for a water supply system occur when the available resource are not able t... more Conditions of scarcity for a water supply system occur when the available resource are not able to satisfy the related demands. The definition of risk of scarcity usually relies on three quantities: the reliability, that is a measure of the probability of the system to perform in a satisfactory way during a given operation period, the resiliency, aiming to capture the ability of the system to recover after a period of deficit, and the vulnerability, whose goal is to measure the severity of possible deficits. Then, the three different quantities can be merged in a single risk index by a simple weighted average. Although the basis for such a definition are clear, the operative way to define the risk index can much affect the final value and, as a consequence, the assessment of the effective risk of scarcity for a water supply system. This work aims at getting more insight on the following issues: 1) the most commonly accepted definitions of reliability, resiliency and vulnerability are based on the probability of occurrence of failure and the related persistence and intensity; however, defining such a probability is quite hard due to the fact that for most of the water supply systems the available time series of recharge, demand and number of failures are not sufficient to process them statistically. 2) Resiliency is usually defined as the mean duration of failures, whatever its probability of occurrence. However, in many cases water managers are more troubled by few persistent episodes (although less probable), than by several short episodes of water scarcity. 3) Analogously, vulnerability is usually defined as the mean deficit during failure periods, neglecting the maximum possible deficit which is sometimes more useful for management purposes. Along these lines, a new method to evaluate the risk of failure for water supply systems is proposed. The new definition of risk takes into account also the extreme events, both positive and negative. Reliability, resiliency and vulnerability are estimated using synthetic time series generated on the ground of the observed standardized precipitation indices, long enough to get a statistically significant number of different hydrological conditions. Results from a case study concerning a drinking water supply system in Central Italy (Ridracoli) are presented and discussed.

Climate changes are expected to decrease the water availability in the Mediterranean area especia... more Climate changes are expected to decrease the water availability in the Mediterranean area especially during summer, due to the concurrence of a generalized negative trend in the precipitation and an increased frequency of droughts. The use of groundwater can mitigate droughts, because many aquifers have a large storage capacity and are potentially less sensitive to climate change than surface water bodies, which often rely on groundwater discharge to maintain their baseflow. However, the real effects of precipitation decline on water availability must also account for human impacts, which conversely tend to increase, partly as a result of climate change. Especially, the so called secondary impacts of climate change, resulting from human intervention in water systems, are expected to have the largest short-term effects on groundwater resources. Typical examples of secondary impacts on groundwater are the increased abstractions particularly for irrigation. For these reasons, groundwater heads are hardly directly usable as indicators of climate change effects. On the other hand, large springs in mountain aquifers, which are very little or not affected by well pumping, could be helpful to evaluate the primary impacts of climate changes on groundwaters, although the paucity of long-term historical data often limits an effective assessment of the direct consequences of climatic forcing.

In the real world, environmental decision-making takes place in a highly interconnected environme... more In the real world, environmental decision-making takes place in a highly interconnected environment, in which neither the decisional ramifications of a management action, nor the complexity of its impact, can be neglected. This contribution focuses on drought management. Due to the high complexity of drought impacts and the ambiguity in drought perceptions, different and often conflicting drought management strategies could be implemented by different actors. This, in turn, could have a strong negative impact on the effectiveness of drought mitigation strategies. Therefore, a deep conflict analysis and the definition of effective negotiation strategies could be really useful. In this work, a method based on the integration between Cognitive Map and Bayesian Belief Network is proposed to support the elicitation and the analysis of stakeholders perceptions of drought, and the conflicts analysis. The method was applied to support drought management in Trasimeno Lake (Umbria Region).

Journal of Hydrology, 2009

Journal of Hydrologic Engineering, 2007

The aquifer system, which is the resource of water for the city of Milano ͑Italy͒, is a multilaye... more The aquifer system, which is the resource of water for the city of Milano ͑Italy͒, is a multilayered aquifer, characterized by sandy and sandy-gravel units, connected by discontinuous aquitards. The recharge area of the phreatic aquifer is close to the prealpine area, some tens of kilometers north of the city; nevertheless the local recharge given by rain infiltration through the soil is not negligible and contributes to the mass balance of the aquifer. A field campaign was carried out for 16 months in the suburban area of the Lambro Park to evaluate the local recharge due to the rainfall infiltration through the unsaturated zone; the water table in this area lies about 15 m below the ground surface. Standard meteorological data ͑atmospheric pressure, rainfall, humidity, wind velocity and air temperature͒ were collected, along with incident and net radiation, to evaluate potential and actual evaporation from the bare soil using three methods ͑Bowen ratio, Penman, and Hamon equations͒. Simultaneously, the volumetric soil water content at different depths ͑down to 76 cm͒ was measured with time domain reflectrometry probes. A finite-difference model, which solves the one-dimensional Richards equation in transient conditions, was developed to simulate the flow through the unsaturated zone, to evaluate the characteristic time of recharge and the mass balance. The water flow rate through the ground surface was assigned as the upper boundary condition and was evaluated from the mass and energy balance at the atmosphere-soil interface with different approaches based on the meteorological data and the actual soil water content. The lower boundary condition is given by the saturation condition at the water table. Characteristic retention curves were estimated in laboratory using Richards apparatus. In order to calibrate the model, the numerical results were compared with experimental data for two different periods: A dry period ͑July 2001͒ and a wet period ͑October 2001͒. Finally, the calibrated model was used to simulate the infiltration and the flow through the unsaturated zone for a 15-year-long period ͑1988-2003͒ and to estimate the total phreatic aquifer recharge. Moreover, the time lag between a variation of the infiltration/exfiltration rate and the corresponding variation of the recharge rate was evaluated; the values of the delay time of recharge are longer than those computed with models that approximate the transmission zone as a unique cell.

This paper focuses on a multidisciplinary study carried out in an urban area affected by subsiden... more This paper focuses on a multidisciplinary study carried out in an urban area affected by subsidence and related structural damages. The study area is located about 20 km east of Rome (Italy) and is characterised by relevant groundwater exploitation for various purposes as well as by the presence of compressible soils immediately below the ground level. Extensive processing at different scales of SAR satellite images (ERS and ENVISAT provided by ESA in the frame of a CAT-1 project) by means of A-DInSAR technique was performed. The time histories of ground displacements, have been analysed in combination with a detailed geological setting of the study area and with the hydrogeological changes occurred in the last decades (as the response to the anthropic stress) based on a large piezometric dataset. This comprehensive dataset allowed us to describe the space and time distributions of the subsidence process. The spatial pattern and deformation rate change is attributed to the following causes: i) the changes in the groundwater levels due to the intensification of mine exploitation (requiring dewatering operations) and ii) the distribution and thickness of recent compressible deposits. Specifically, it is derived that the groundwater level variations drive the timing of subsidence triggering over the area, whereas the local geological conditions control the magnitude of the deformation process.

Studies on recent climate trends from the Hi-malayan range are limited, and even completely absen... more Studies on recent climate trends from the Hi-malayan range are limited, and even completely absent at high elevation (> 5000 m a.s.l.). This study specifically explores the southern slopes of Mt. Everest, analyzing the time series of temperature and precipitation reconstructed from seven stations located between 2660 and 5600 m a.s.l. during 1994–2013, complemented with the data from all existing ground weather stations located on both sides of the mountain range (Koshi Basin) over the same period. Overall we find that the main and most significant increase in temperature is concentrated outside of the monsoon period. Above 5000 m a.s.l. the increasing trend in the time series of minimum temperature (+0.072 • C yr −1) is much stronger than of maximum temperature (+0.009 • C yr −1), while the mean temperature increased by +0.044 • C yr −1. Moreover, we note a substantial liquid precipitation weakening (−9.3 mm yr −1) during the monsoon season. The annual rate of decrease in precipitation at higher elevations is similar to the one at lower elevations on the southern side of the Koshi Basin, but the drier conditions of this remote environment make the fractional loss much more consistent (−47 % during the monsoon period). Our results challenge the assumptions on whether temperature or precipitation is the main driver of recent glacier mass changes in the region. The main implications are the following: (1) the negative mass balances of glaciers observed in this region can be more ascribed to a decrease in accumulation (snowfall) than to an increase in surface melting; (2) the melting has only been favoured during winter and spring months and close to the glaciers terminus; (3) a decrease in the probability of snowfall (−10 %) has made a significant impact only at glacier ablation zone, but the magnitude of this decrease is distinctly lower than the observed decrease in precipitation; (4) the decrease in accumulation could have caused the observed decrease in glacier flow velocity and the current stagnation of glacier termini, which in turn could have produced more melting under the debris glacier cover, leading to the formation of numerous supraglacial and proglacial lakes that have characterized the region in the last decades.

The assessment of the impact of long-term climate variability onwater supply systems depends not ... more The assessment of the impact of long-term climate variability onwater supply systems depends not only on possible variations of the resources availability, but also on the variation of the demand. In this framework, a robust estimation of direct (climate induced) and indirect (anthropogenically induced) effects of climate change ismandatory to design mitigation measures, especially in those regions of the planet where the groundwater equilibrium is strongly perturbed by exploitations for irrigation purposes. The main goal of this contribution is to propose a comprehensive model that integrates distributed crop water requirements with surface and groundwater mass balance, able to considermanagement rules of thewater supply system. The proposed overallmodel, implemented, calibrated and validated for the case study of the Fortore water supply system (Apulia region, South Italy), permits to simulate the conjunctive use of the water from a surface artificial reservoir and from groundwater. The relative contributions of groundwater recharges and withdrawals to the aquifer stress have been evaluated under different climate perturbations, with emphasis on irrigation practices. Results point out that irrigated agriculture primarily affects groundwater discharge, indicating that ecosystem services connected to river base flow are particularly exposed to climate variation in irrigated areas. Moreover, findings show that the recharge both to surface and to groundwater is mainly affected by drier climate conditions, while hotter conditions have a major impact on the water demand. The non-linearity arising from combined drier and hotter conditions may exacerbate the aquifer stress by exposing it to massive sea-water intrusion.

Macroscopic properties of flow through porous media can be directly computed by solving the Navie... more Macroscopic properties of flow through porous media can be directly computed by solving the Navier– Stokes equations at the scales related to the actual flow processes, while considering the porous structures in an explicit way. The aim of this paper is to investigate the effects of the pore-scale spatial distribution on seepage velocity through numerical simulations of 3D fluid flow performed by the lattice Boltzmann method. To this end, we generate multiple random Gaussian fields whose spatial correlation follows an assigned semi-variogram function. The Exponential and Gaussian semi-variograms are chosen as extreme-cases of correlation for short distances and statistical properties of the resulting porous media (indicator field) are described using the Matèrn covariance model, with characteristic lengths of spatial autocorrelation (pore size) varying from 2% to 13% of the linear domain. To consider the sensitivity of the modeling results to the geostatistical representativeness of the domain as well as to the adopted resolution, porous media have been generated repetitively with re-initialized random seeds and three different resolutions have been tested for each resulting realization. The main difference among results is observed between the two adopted semi-variograms, indicating that the roughness (short distances autocorrelation) is the property mainly affecting the flux. However, computed seepage velocities show additionally a wide variability (about three orders of magnitude) for each semi-variogram model in relation to the assigned correlation length, corresponding to pore sizes. The spatial resolution affects more the results for short correlation lengths (i.e., small pore sizes), resulting in an increasing underestimation of the seepage velocity with the decreasing correlation length. On the other hand, results show an increasing uncertainty as the correlation length approaches the domain size.

Among different uses of freshwater, irrigation is the most impacting groundwater resource, leadin... more Among different uses of freshwater, irrigation is the most impacting groundwater resource, leading to water table depletion and possible seawater intrusion. The unbalance between the availability of water resources and demand is currently exacerbated and could become worse in the near future in accordance with climate change observations and scenarios provided by Intergovernmental Panel on Climate Change (IPCC). In this context, Increasing Maximum Capacity of the surface reservoir (IMC) and Managed Aquifer Recharge (MAR) are adaptation measures that have the potential to enhance water supply systems resiliency. In this paper, a multiple-users and multiple-resources-Water Supply System (WSS) model is implemented to evaluate the effectiveness of these two adaptation strategies in a context of overexploited groundwater under the RCP 4.5 and the RCP 8.5 IPCC scenarios. The presented a case study that is located in the Puglia, a semi-arid region of South Italy characterized by a conspicuous water demand for irrigation. We observed that, although no significant long-term trend affects the proposed precipitation scenarios, the expected temperature increase highly impacts the WSS resources due to the associated increase of water demand for irrigation purposes. Under the RCP 4.5 the MAR scenario results are more effective than the IMC during long term wet periods (typically 5 years) and successfully compensates the impact on the groundwater resources. Differently, under RCP 8.5, due to more persistent dry periods, both adaptation scenarios fail and groundwater resource become exposed to massive sea water intrusion during the second half of the century. We conclude that the MAR scenario is a suitable adaptation strategy to face the expected future changes in climate, although mitigation actions to reduce greenhouse gases are strongly required.

Conditions of shortage in a water supply system (WSS) occur when the available water resources ar... more Conditions of shortage in a water supply system (WSS) occur when the available water resources are unable to satisfy the related demand (failure). The definition of risk of shortage conventionally relies on three indexes that capture the characteristics of possible failures in terms of probability of occurrence (reliability), duration (resiliency), and intensity (vulnerability). Although the conceptual bases for these definitions are largely acknowledged, the operative way to define them can largely affect the final value of the risk of shortage, making it difficult to compare among different WSSs when different formulations are applied. In this paper, a robust method to quantify the risk of shortage for WSSs that rely on surface water is proposed. The major novelties are to consider the extreme events in the risk analysis and to overcome the issue of the representativeness of the observed time series with respect to the characteristic return periods of drought events. To this aim, a stochastic approach based on a zero mean autoregressive (AR) model of standardized precipitation indexes (SPIs) is combined with a multilinear regressive model learning from observed SPI and associated inflow anomalies. This approach has been applied to the case study of the Ridracoli Reservoir in Central Italy, taking into account several climate scenarios, as well as several configurations of the WSS. Results show the ability of the proposed procedure to obtain convergence in the risk indexes and to distinguish among different levels of shortage risk, giving additional information for drought episodes with longer return periods. In particular, the standardized indexes focusing also on extreme events led to a quantification of the risk able to capture, at least in the proposed case study, the benefit of management options aiming to reduce the vulnerability (i.e., not fully meeting the demand in anticipation of a dry period), while those considering only the average features do not.

The present communication describes several regional-scale modelling experiences involving the ca... more The present communication describes several regional-scale modelling experiences involving the carbonatic aquifer of Mt Coscerno and the alluvial aquifer of Petrignano d'Assisi. The aim is to highlight the principal differences and similarities in the applica-tion of mathematical models to carbonatic aquifers in mountain areas and to alluvial type aquifers resulting principally from the different availability of data. In the first case the hydrogeological balance, determined by field measurements, is usually known while direct observation of the piezometric surface is difficult owing to its extreme depth; in the second case, the piezometric surface is deter-mined by measurement of piezometric level in wells although the aquifer balance is generally known only through indirect estimates of the effective infiltration and any other ancillary contributions (exchanges with watercourses, infiltration from boundaries, etc). The determination of the hydrodynamic parameters, wherever thi...

The aim of this study was the estimate of aquifer recharge by means of a finitedifference model, ... more The aim of this study was the estimate of aquifer recharge by means of a finitedifference model, which solves the non-linear 1-D Richards equation in transient conditions: the water flow rate through the ground surface, which is the upper boundary condition for the model, was evaluated from standard meteorological data, taking into account the limitation to the evaporation/infiltration given by the soil retention features. A field campaign was carried out for 16 months in the suburban area of the Lambro Park to evaluate the local recharge due to the rainfall infiltration through the unsaturated zone. Meteorological data (atmospheric pressure, rainfall, humidity, wind velocity and air temperature) were collected to evaluate potential evaporation using a based-temperature equation (Hamon method); the real evaporation was assessed as a fraction of the potential one, on the basis of the actual soil water content. Simultaneously, the soil water content and the capillary pressure head at different depths (down to 76 cm) were measured with TDR probes and tensiometers, respectively. Characteristic retention curves were estimated in laboratory using Richards apparatus and compared with data collected in situ. The model allowed us to well reproduce soil moisture experimental data both during dry periods and wet periods, taking into account as input only standard meteorological data and the retention features of the soil.

Conditions of scarcity for a water supply system occur when the available resource are not able t... more Conditions of scarcity for a water supply system occur when the available resource are not able to satisfy the related demands. The definition of risk of scarcity usually relies on three quantities: the reliability, that is a measure of the probability of the system to perform in a satisfactory way during a given operation period, the resiliency, aiming to capture the ability of the system to recover after a period of deficit, and the vulnerability, whose goal is to measure the severity of possible deficits. Then, the three different quantities can be merged in a single risk index by a simple weighted average. Although the basis for such a definition are clear, the operative way to define the risk index can much affect the final value and, as a consequence, the assessment of the effective risk of scarcity for a water supply system. This work aims at getting more insight on the following issues: 1) the most commonly accepted definitions of reliability, resiliency and vulnerability are based on the probability of occurrence of failure and the related persistence and intensity; however, defining such a probability is quite hard due to the fact that for most of the water supply systems the available time series of recharge, demand and number of failures are not sufficient to process them statistically. 2) Resiliency is usually defined as the mean duration of failures, whatever its probability of occurrence. However, in many cases water managers are more troubled by few persistent episodes (although less probable), than by several short episodes of water scarcity. 3) Analogously, vulnerability is usually defined as the mean deficit during failure periods, neglecting the maximum possible deficit which is sometimes more useful for management purposes. Along these lines, a new method to evaluate the risk of failure for water supply systems is proposed. The new definition of risk takes into account also the extreme events, both positive and negative. Reliability, resiliency and vulnerability are estimated using synthetic time series generated on the ground of the observed standardized precipitation indices, long enough to get a statistically significant number of different hydrological conditions. Results from a case study concerning a drinking water supply system in Central Italy (Ridracoli) are presented and discussed.

Climate changes are expected to decrease the water availability in the Mediterranean area especia... more Climate changes are expected to decrease the water availability in the Mediterranean area especially during summer, due to the concurrence of a generalized negative trend in the precipitation and an increased frequency of droughts. The use of groundwater can mitigate droughts, because many aquifers have a large storage capacity and are potentially less sensitive to climate change than surface water bodies, which often rely on groundwater discharge to maintain their baseflow. However, the real effects of precipitation decline on water availability must also account for human impacts, which conversely tend to increase, partly as a result of climate change. Especially, the so called secondary impacts of climate change, resulting from human intervention in water systems, are expected to have the largest short-term effects on groundwater resources. Typical examples of secondary impacts on groundwater are the increased abstractions particularly for irrigation. For these reasons, groundwater heads are hardly directly usable as indicators of climate change effects. On the other hand, large springs in mountain aquifers, which are very little or not affected by well pumping, could be helpful to evaluate the primary impacts of climate changes on groundwaters, although the paucity of long-term historical data often limits an effective assessment of the direct consequences of climatic forcing.

In the real world, environmental decision-making takes place in a highly interconnected environme... more In the real world, environmental decision-making takes place in a highly interconnected environment, in which neither the decisional ramifications of a management action, nor the complexity of its impact, can be neglected. This contribution focuses on drought management. Due to the high complexity of drought impacts and the ambiguity in drought perceptions, different and often conflicting drought management strategies could be implemented by different actors. This, in turn, could have a strong negative impact on the effectiveness of drought mitigation strategies. Therefore, a deep conflict analysis and the definition of effective negotiation strategies could be really useful. In this work, a method based on the integration between Cognitive Map and Bayesian Belief Network is proposed to support the elicitation and the analysis of stakeholders perceptions of drought, and the conflicts analysis. The method was applied to support drought management in Trasimeno Lake (Umbria Region).

Journal of Hydrology, 2009

Journal of Hydrologic Engineering, 2007

The aquifer system, which is the resource of water for the city of Milano ͑Italy͒, is a multilaye... more The aquifer system, which is the resource of water for the city of Milano ͑Italy͒, is a multilayered aquifer, characterized by sandy and sandy-gravel units, connected by discontinuous aquitards. The recharge area of the phreatic aquifer is close to the prealpine area, some tens of kilometers north of the city; nevertheless the local recharge given by rain infiltration through the soil is not negligible and contributes to the mass balance of the aquifer. A field campaign was carried out for 16 months in the suburban area of the Lambro Park to evaluate the local recharge due to the rainfall infiltration through the unsaturated zone; the water table in this area lies about 15 m below the ground surface. Standard meteorological data ͑atmospheric pressure, rainfall, humidity, wind velocity and air temperature͒ were collected, along with incident and net radiation, to evaluate potential and actual evaporation from the bare soil using three methods ͑Bowen ratio, Penman, and Hamon equations͒. Simultaneously, the volumetric soil water content at different depths ͑down to 76 cm͒ was measured with time domain reflectrometry probes. A finite-difference model, which solves the one-dimensional Richards equation in transient conditions, was developed to simulate the flow through the unsaturated zone, to evaluate the characteristic time of recharge and the mass balance. The water flow rate through the ground surface was assigned as the upper boundary condition and was evaluated from the mass and energy balance at the atmosphere-soil interface with different approaches based on the meteorological data and the actual soil water content. The lower boundary condition is given by the saturation condition at the water table. Characteristic retention curves were estimated in laboratory using Richards apparatus. In order to calibrate the model, the numerical results were compared with experimental data for two different periods: A dry period ͑July 2001͒ and a wet period ͑October 2001͒. Finally, the calibrated model was used to simulate the infiltration and the flow through the unsaturated zone for a 15-year-long period ͑1988-2003͒ and to estimate the total phreatic aquifer recharge. Moreover, the time lag between a variation of the infiltration/exfiltration rate and the corresponding variation of the recharge rate was evaluated; the values of the delay time of recharge are longer than those computed with models that approximate the transmission zone as a unique cell.