Using flood water in Managed Aquifer Recharge schemes as a solution for groundwater management in the Cornia valley (Italy)

The lower Cornia valley aquifer system (Tuscany, Italy) provides the only source of water for drinking, irrigation, industrial purposes and it also contributes to the water needs of the nearby Elba island. Since 60 years, intensive exploitation of groundwater resulted in consistent head lowering and water balance deficit, causing subsidence, reduction of groundwater dependent ecosystems, and salinization of freshwater resources. Rebalancing the water budget of the hydrologic system is the main objective of the LIFE REWAT project (sustainable WATer management in the lower Cornia valley through demand REduction, aquifer Recharge and river REstoration; http://www.liferewat.eu). Here, five demonstration measures (river restoration; Managed Aquifer Recharge; reuse of treated wastewater for irrigation; high irrigation efficiency scheme; leakage management in water distribution systems) are set in place for promoting water resource management, along with capacity building and participatory actions. A pilot Managed Aquifer Recharge (MAR) infiltration basin for using flood-water was designed and set in operation in Suvereto, testing the new-issued Italian regulation on artificial recharge of aquifers (DM 100/2016). The infiltration basin is located at a pre-existing topographical low near the Cornia River. The river, having intermittent flow, provides the recharge water during high flow periods, including floods, and when discharge is above the minimum ecological flow. The infiltration basin is set in a groundwater recharge area where the aquifer is constituted by gravel and sands. A preliminary project and an executive one were prepared and discussed with the relevant authorities, following one-year long monthly monitoring of surface- and ground-water. The project was supported by a groundwater flow modelling-based approach using the FREEWAT platform (www.freewat.eu). The facility consists of the following elements: i) intake work on the River Cornia; ii) the inlet structure control system, managed by quality (mass spectrometer defining surface water spectral signature) and level probes, and allowing pumping into the facility at predefined head and chemical quality thresholds; iii) a sedimentation basin; iv) the infiltration area (less than 1 ha large); v) the operational monitoring system, based on a network of piezometers where both continuous data (head, T, EC, DO) are gathered and discrete measurements/sampling performed. The cost of construction of the plant is about 300000 C well below the cost of a surface water reservoir for a similar storage. Depending on the climatic conditions, the estimated volume of diverted surface water may vary between 300000 m3/year and 2 Mm3/year. Being the facility a pilot one, diverted water discharge ranges between 20 to 50 l/s. Minimal site development and modification was required, resulting in a no-impact water-work, while providing ecosystem benefits by reconnecting and inundating former abandoned riverbeds. The effectiveness of such pilot may demonstrate the potential for Flood-MAR schemes to increase water availability in scarcity prone areas

Potential shallow aquifers characterization through an integrated geophysical method: multivariate approach by means of k-means algorithms

The need to obtain a detailed hydrogeological characterization of the subsurface and its interpretation for the groundwater resources management, often requires to apply several and complementary geophysical methods. The goal of the approach in this paper is to provide a unique model of the aquifer by synthesizing and optimizing the information provided by several geophysical methods. This approach greatly reduces the degree of uncertainty and subjectivity of the interpretation by exploiting the different physical and mechanic characteristics of the aquifer. The studied area, into the municipality of Laterina (Arezzo, Italy), is a shallow basin filled by lacustrine and alluvial deposits (Pleistocene and Olocene epochs, Quaternary period), with alternated silt, sand with variable content of gravel and clay where the bottom is represented by arenaceous-pelitic rocks (Mt. Cervarola Unit, Tuscan Domain, Miocene epoch). This shallow basin constitutes the unconfined superficial aquifer to be exploited in the nearly future. To improve the geological model obtained from a detailed geological survey we performed electrical resistivity and P wave refraction tomographies along the same line in order to obtain different, independent and integrable data sets. For the seismic data also the reflected events have been processed, a remarkable contribution to draw the geologic setting. Through the k-means algorithm, we perform a cluster analysis for the bivariate data set to individuate relationships between the two sets of variables. This algorithm allows to individuate clusters with the aim of minimizing the dissimilarity within each cluster and maximizing it among different clusters of the bivariate data set. The optimal number of clusters "K", corresponding to the individuated geophysical facies, depends to the multivariate data set distribution and in this work is estimated with the Silhouettes. The result is an integrated tomography that shows a finite number of homogeneous geophysical facies, which therefore permits to distinguish and interpret the porous aquifer in a quantitative and objective way

When do global pipelines enhance the diffusion of knowledge in clusters?

Recent studies have stressed the role played by global pipelines in fostering the growth of clusters and innovativeness. In this article, we develop a formal model to investigate when global pipelines contribute to an increase in local knowledge, depending on various characteristics of clusters such as size, knowledge endowment, and the ease of transmission of internal knowledge. This model is an extension of Cowan and Jonard’s (2004) model in which we introduce the concept of cluster and a role for spatial proximity in the diffusion of knowledge. Our results reveal that there is a natural tendency of actors within global pipelines to act as external stars, rather than gatekeepers of knowledge. Global pipelines are beneficial for the accumulation of knowledge only if the cluster is either characterized by a high-quality local buzz or is small and weakly endowed in terms of knowledge

Reti sociali e diffusione della conoscenza nei cluster: un modello di simulazione

No abstract availabl

Evidence for age-structured depensation effect in fragmented plant populations: the case of the Mediterranean endemic <i>Anchusa sardoa</i> (Boraginaceae)

Depensation in a population growth rate, well-known as Allee effect, has dramatic implications for the dynamics and conservation of small or sparse populations, as it can drive low-density populations to extinction when their demographic size is below a critical threshold. Although rarely detected, depensation effects are believed to be common in nature. Here we present experimental evidence for Allee effect in one Mediterranean endemic plant: Anchusa sardoa. Depensation in the population growth rate is demonstrated through a density-based approach by showing the fingerprinting relationship which ties the population density to its per capita growth rate (pgr) during specific stages of the plant lifecycle. The pgr–density plots derived from observational data qualitatively compare with a general 2nd order polynomial function which features one of the peculiar trends underlying an Allee mechanism. We found strong evidence for depensation in the seedling and sapling classes, whereas no-depensation effect could be clearly observed in the adult classes. We also point out a characteristic demographic structure of A. sardoa (i.e. number of juveniles &lt; number of adults) which reflects a not common life strategy with respect to Mediterranean endemic plants. By combining dynamical and demographic information, the results of this study suggest a possible scenario by which A. sardoa population could go extinct, and are discussed in the context of the increasing mass tourism in Mediterranean coastal environments

Multivariate Analysis Applied to Aquifer Hydrogeochemical Evaluation: A Case Study in the Coastal Significant Subterranean Water Body between “Cecina River and San Vincenzo”, Tuscany (Italy)

The hydrogeochemical characteristics of the significant subterranean water body between “Cecina River and San Vincenzo” (Italy) was evaluated using multivariate statistical analysis methods, like principal component analysis and self-organizing maps (SOMs), with the objective to study the spatiotemporal relationships of the aquifer. The dataset used consisted of the chemical composition of groundwater samples collected between 2010 and 2018 at 16 wells distributed across the whole aquifer. For these wells, all major ions were determined. A self-organizing map of 4 × 8 was constructed to evaluate spatiotemporal changes in the water body. After SOM clustering, we obtained three clusters that successfully grouped all data with similar chemical characteristics. These clusters can be viewed to reflect the presence of three water types: (i) Cluster 1: low salinity/mixed waters; (ii) Cluster 2: high salinity waters; and (iii) Cluster 3: low salinity/fresh waters. Results showed that the major ions had the greater influence over the groundwater chemistry, and the difference in their concentrations allowed the definition of three clusters among the obtained SOM. Temporal changes in cluster assignment were only observed in two wells, located in areas more susceptible to changes in the water table levels, and therefore, hydrodynamic conditions. The result of the SOM clustering was also displayed using the classical hydrochemical approach of the Piper plot. It was observed that these changes were not as easily identified when the raw data were used. The spatial display of the clustering results, allowed the evaluation in a hydrogeological context in a quick and cost-effective way. Thus, our approach can be used to quickly analyze large datasets, suggest recharge areas, and recognize spatiotemporal patterns

Tectonic Setting of the Kenya Rift in the Nakuru Area, Based on Geophysical Prospecting

In this paper, we present results of tectonic and geophysical investigations in the Kenya Rift valley, in the Nakuru area. We compiled a detailed geological map of the area based on published earlier works, well data and satellite imagery. The map was then integrated with original fieldwork and cross sections were constructed. In key areas, we then performed geophysical survey using Electrical Resistivity Tomography (ERT), Hybrid Source Audio MagnetoTelluric (HSAMT), and single station passive seismic measurements (HVSR). In the study area, a volcano-sedimentary succession of the Neogene-Quaternary age characterized by basalts, trachytes, pyroclastic rocks, and tephra with intercalated lacustrine and fluvial deposits crops out. Faulting linked with rift development is evident and occurs throughout the area crosscutting all rock units. We show a rotation of the extension in this portion of the Kenya rift with the NE–SW extension direction of a Neogene-Middle Pleistocene age, followed by the E–W extension direction of an Upper Pleistocene-Present age. Geophysical investigations allowed to outline main lithostratigraphic units and tectonic features at depth and were also useful to infer main cataclasites and fractured rock bodies, the primary paths for water flow in rocks. These investigations are integrated in a larger EU H2020 Programme aimed to produce a geological and hydrogeological model of the area to develop a sustainable water management system

Ricostruzione probabilistica 3D dell’acquifero alluvionale della Val di Cornia (Provincia di Livorno)

The three-dimensional alluvial aquifer reconstruction through deterministic method from well stratigraphical data is a well-known problem. The purpose of this study concerns the realization of a geostatistical stochastic model based on 1d Markov chains with the use of T-PROGS codes of GMS Aquaveo. This method allows to obtain the vertical transition probability of the alluvial deposits and propagate them to x-y plane through the application of Walther law. The Val di Cornia valley and San Vincenzo coastal plain constitute a unique multilayered coastal aquifer, which extends over an area of 170 square kilometers, in the southern coast of Tuscany (Italy), and it is the results of the erosional and depositional processes of the Cornia river. The better understanding of this aquifer is a crucial issue, due to its regional importance and for managing the increasing saltwater intrusion, which affects the area during the last 50 years. The model realization was initially based on 300 stratigraphic data logs coming from a water well database implemented by local authorities, subsequently integrated with HVSR data acquired for this work. The stratigraphic data were digitized and simplified in order to permit a better reconstruction. The control of the quality of the input data allowed to eliminate the stratigraphic logs that could be inconsistent with the surrounding ones, in order to avoid interpretation problems of the conceptual geological model. This filtering operation led, finally, to the selection of only 140 stratigraphic logs. The processing of this data allowed the reconstruction of the bottom of the model (the bedrock) and the realization of n-equiprobable simulations of the sedimentary hetereogeneity. The obtained geological model will allow the realization of further groundwater flow model of the Cornia Valley to be implemented in the next months

Multidisciplinary geophysical surveys for 3D hydrogeological conceptual model reconstruction in areas contaminated by fluoride in Nakuru area, East African Rift System (Kenya)

An extensive geophysical fieldwork was performed in Nakuru county (Kenya), Autumn 2018, aiming to study the shallow structure of the rift valley, within the framework of FLOWERED activities, an H2020 European Commission project (www.floweredproject.org). The overall objective of the project is to contribute to the development of a sustainable water management system in East African Rift areas affected by natural fluoride contamination. The investigated area is located in South-western Kenya near Nakuru, in the central part of the Kenya Rift. The area is characterized by a thick volcano-sedimentary succession of Pleistocene-Quaternary age, with volcanic rocks as lavas (phonolites, basalts, and trachytes) and pyroclastic flows and fall deposits (tephra, tuffs and fall deposits), intercalated with alluvial gravel and sands. The geophysical fieldwork was designed to implement a local detailed three-dimensional hydrogeological model of Nakuru area. We performed resistivity surveys at two different scales by using electrical resistivity tomography (ERT) and Hybrid-Source Audio Magnetotelluric (HSAMT), integrated by single station passive seismic measurements (HVSR). Overall, the performed surveys were helpful to delineate: a) depth and thickness of aquifers, b) aquitards or confining units and c) locating preferential fluid migration paths such as fractures and fault zones (Ghiglieri et al., 2017)

Potential shallow aquifers characterization through an integrated geophysical method: multivariate approach by means of k-means algorithms

The need to obtain a detailed hydrogeological characterization of the subsurface and its interpretation for the groundwater resources management, often requires to apply several and complementary geophysical methods. The goal of the approach in this paper is to provide a unique model of the aquifer by synthesizing and optimizing the information provided by several geophysical methods. This approach greatly reduces the degree of uncertainty and subjectivity of the interpretation by exploiting the different physical and mechanic characteristics of the aquifer. The studied area, into the municipality of Laterina (Arezzo, Italy), is a shallow basin filled by lacustrine and alluvial deposits (Pleistocene and Olocene epochs, Quaternary period), with alternated silt, sand with variable content of gravel and clay where the bottom is represented by arenaceous-pelitic rocks (Mt. Cervarola Unit, Tuscan Domain, Miocene epoch). This shallow basin constitutes the unconfined superficial aquifer to be exploited in the nearly future. To improve the geological model obtained from a detailed geological survey we performed electrical resistivity and P wave refraction tomographies along the same line in order to obtain different, independent and integrable data sets. For the seismic data also the reflected events have been processed, a remarkable contribution to draw the geologic setting. Through the k-means algorithm, we perform a cluster analysis for the bivariate data set to individuate relationships between the two sets of variables. This algorithm allows to individuate clusters with the aim of minimizing the dissimilarity within each cluster and maximizing it among different clusters of the bivariate data set. The optimal number of clusters “K”, corresponding to the individuated geophysical facies, depends to the multivariate data set distribution and in this work is estimated with the Silhouettes. The result is an integrated tomography that shows a finite number of homogeneous geophysical facies, which therefore permits to distinguish and interpret the porous aquifer in a quantitative and objective way