Elisabetta Preziosi

Vulnerability to Drought of a Complex Water Supply System. The Upper Tiber Basin Case Study (Central Italy)

The importance of simulation models to assess the impacts of droughts and the effects of mitigation options on water supply systems is well known. However a common procedure about the exploitation of model results is not established yet. Vulnerability is used to characterize the performance of the system, and it can be a helpful indicator in the evaluation of the most likely failures. In this paper a water allocation model is applied to the water supply system of the upper Tiber Basin (Central Italy) in which both surface waters (rivers, reservoirs) and ground waters (wells, springs) are exploited to feed mainly irrigation and civil users. Drought vulnerability indices are calculated to analyze the performance of the supply system under different climate and management conditions. Water shortage scenarios are simulated as a progressive reduction of mean precipitation, an increase in its standard deviation or a combination of both. The model shows that the safety of the water supply system mainly relies on the reservoirs and that the foreseen increased exploitation of the springs to replace contaminated wells, could be seriously limited by discharge decrease during fall. The vulnerability reduction obtained by a hypothetical augmentation of the storage capacity through additional small reservoirs was positively tested by the model. In conclusion vulnerability indices and synoptic risk maps demonstrated to be useful tools to analyze the model outputs. They provide easy-to-read scenarios to be used in a decision making framework considering negotiating among the main users.

Combining natural background levels (NBLs) assessment with indicator kriging analysis to improve groundwater quality data interpretation and management.

The natural background level (NBL) concept is revisited and combined with indicator kriging method to analyze the spatial distribution of groundwater quality within a groundwater body (GWB). The aim is to provide a methodology to easily identify areas with the same probability of exceeding a given threshold (which may be a groundwater quality criteria, standards, or recommended limits for selected properties and constituents). Three case studies with different hydrogeological settings and located in two countries (Portugal and Italy) are used to derive NBL using the preselection method and validate the proposed methodology illustrating its main advantages over conventional statistical water quality analysis. Indicator kriging analysis was used to create probability maps of the three potential groundwater contaminants. The results clearly indicate the areas within a groundwater body that are potentially contaminated because the concentrations exceed the drinking water standards or even the local NBL, and cannot be justified by geogenic origin. The combined methodology developed facilitates the management of groundwater quality because it allows for the spatial interpretation of NBL values.

Integration of local and scientific knowledge to support drought impact monitoring: some hints from an Italian case study

According to the Hyogo Framework for Action, increasing resilience to drought requires the development of a people-centered monitoring and early warning system, or in other words, a system capable of providing useful and understandable information to the community at risk. To achieve this objective, it is crucial to negotiate a credible and legitimate knowledge system, which should include both expert and local knowledge. Although several benefits can be obtained, the integration of local and scientific knowledge to support drought monitoring is still far from being the standard in drought monitoring and early warning. This is due to many reasons, that is, the reciprocal skepticism of local communities and decision makers, and the limits in the capacity to understand and assess the complex web of drought impacts. This work describes a methodology based on the sequential implementation of Cognitive Mapping and Bayesian Belief Networks to collect, structure and analyze stakeholders’ perceptions of drought impacts. The methodology was applied to analyze drought impacts at Lake Trasimeno (central Italy). A set of drought indicators was developed based on stakeholders’ perceptions. A validation phase was carried out comparing the perceived indicators of drought and the physical indicators (i.e., Standard Precipitation Index and the level of the lake). Some preliminary conclusions were drawn concerning the reliability of local knowledge to support drought monitoring and early warning.

Robust Method to Quantify the Risk of Shortage for Water Supply Systems

AbstractConditions 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 convent...

A Gis Tool for the Fast Identification of Drinking Water Abstraction Points Possibly Reached by a Contamination Event

In the framework of collaboration between the Water Research Institute and the National Civil Protection Department, in order to improve response capability at both national and local level, a procedure for the emergency management of accidental pollution of groundwater exploited for human consumption is being developed.

Groundwater chemical status assessment considering geochemical background: an example from Northern Latium (Central Italy)

The evaluation of the chemical status of groundwater bodies, pursuant to the European Groundwater Directive 2006/118/EC, requires the assessment of the natural background levels when concentration exceeds the national standards. In large part of Italy, including the case-study region Latium, the presence of substances of natural origin has long been recognized. Nonetheless, a systematic assessment of background levels is still missing. Guidelines have been published both at the European and Italian level, but there are still unanswered questions, including the appropriate geographical scale, the time and spatial variation. In this paper, the evaluation of the groundwater chemical status at the groundwater body scale for the Latium region for the above-mentioned elements is presented. We used the preselection method, choosing the 95th percentile of the preselected datasets for various groundwater bodies. Results show that the natural background levels differ at the groundwater body scale reflecting the complexity of the geological asset. At a smaller scale, the variation of the background even at short distances may be dramatic, and this should be considered especially when dealing with site scale assessment. Conversely, the time variation of the considered parameters seems to be modest. In the case-study region, the chemical status assessment considering the background levels would result “good” as for the exceedances of arsenic and fluoride, solving the problem of erroneous classification of water bodies characterized by contamination of natural origin.