Sensitivity of Dar Es Salaam coastal aquifer to climate change with regard to seawater intrusion and groundwater availability

This paper presents the initial results of three years of investigation activities, carried on in the Dar es Salaam coastal plain (Tanzania) by the Adapting to Climate Change in Coastal Dar es Salaam (ACC-DAR) project, a cofounded research project, granted by the European Union, led by the Sapienza, University of Rome, in cooperation with Ardhi University of Dar es Salaam. The ACC-DAR project activities will enhance the capacities of Dar’s municipalities by increasing their understanding of adaptation practices, and by developing methodologies for integrating adaptation activities into strategies and plans for Urban Development and Environment Management (UDEM) in unplanned and unserviced coastal settlements. In order to provide a series of enhanced methodologies for improving municipal activities related to climate change (CC) issues in the water management sector, the specific environmental phenomenon of seawater intrusion was investigated. This phenomenon is already contributing, and will increasingly contribute as CC progresses, to the degradation of those natural resources on which a large part of Dar es Salaam’s peri-urban livelihoods depends. The target of this study was to investigate groundwater availability changes in Dar es Salaam’s coastal aquifer as a consequence of seawater intrusion and urbanization processes in the framework of CC effects, with the aim to set up an integrated approach to evaluate CC effects on groundwater resources in coastal plains affected by seawater intrusion, and to better manage these important natural resources. As such, geological and hydrogeological characterization of the area is part of the study, as lithological properties of outcropping geological formations and their main hydrogeological settings, as well as chemical groundwater characterization also depend on them, but they were not the target of the study

A tiered approach to natural background level (nbl) assessment in groundwater under a non hazardous waste land fill in Latium region (Italy)

This paper deals with the results of investigation and monitoring activity on groundwater flowing under an area of a non hazardous waste landfill, placed in the Agro Romano, in the South Rome town area, near to Colli Albani Volcanic region. The geological framework is mainly dominated by pyroclastic deposits of Colli Albani Volcanic Complex named pozzolanelle and tufo lionato. The purpose of the study has been the investigation of the origin of concentration values referred to Arsenic, Manganese, and Fluoride, exceeding the European law limit values. In order to identify whether the observed concentrations represent a naturally-occurring condition or they are due to an anthropogenic source, it was applied a tiered up approach. As a matter of fact in the aim of following a tiered approach, they were analyzed, different aspects like: the impacts coming from anthropogenic activities, regional and site specific geology knowledge, the mineralogic properties of the geological outcrops, site specific geochemistry, statistical approach. Carrying on a background analysis early may become an important guideline for statutory requirements in the site assessment based on legal fixed concentrations

Strontium Isotope as Tracers of Groundwater Contamination

Groundwater flowing under a municipal solid waste landfill has been studied to identify potential contamination phenomenon and to test strontium isotopic composition as a natural tracer of contamination. The study was carried on in June 2014 in central Italy. Five selected boreholes were selected and analysed according to their location related to the site. Samples taken from boreholes placed upward to the site were considered as uncontaminated groundwater. One borehole located downward from the site and with major contaminant values has been considered as potentially contaminated end-member. Sr isotope results show that samples located upward from the site present lower Sr concentration and highest Sr isotopic values, which reflects weathered bedrock, while borehole located downward from the site show lowest Sr values and 87Sr/86Sr ratio, probably due to pollution by landfill leachate. The mixing calculation highlights the possible mixing phenomenon for the other samples located downward from the site

Soil contamination evaluation by Enrichment Factor (EF) and Geoaccumulation Index (Igeo)

Heavy metals are natural constituents of soils and their concentration varies depending on parental materials. The soils were formed by. In the last years, the content of heavy metal in soils has increased due to human activities as: distribution of fertilizers, pesticides, industries, waste disposal and air pollution. Due to these activities the life capacity of soils decreased; especially where the natural background is already high because of natural parental material richness in heavy metal. As a matter of fact it is very important to distinguish between the natural background values and anthropogenic inputs, and to understand that the background values change from area to area and with the scale of the area investigated. To evaluate the soil contamination rate different indexes like Enrichment Factor (EF) and geoaccumulation index (Igeo) can be applied. These indexes are used to assess the presence and intensity of anthropogenic contaminant deposition on surface soil

Modellazione numerica dell'evoluzione dell'artesianismo nel sistema acquifero del sahara settentrionale // Numerical modeling to estimate the artesianism evolution in north-western sahara aquifer system

Nel presente lavoro vengono presentati i risultati ottenuti tramite l’applicazione di un modello numerico di circolazione idrica sotterranea al bacino artesiano del Sistema Acquifero del Sahara Settentrionale al fine ottenere delle realistiche simulazioni relative al trend di abbassamento piezometrico e relativa diminuzione dei fenomeni di artesianismo locale. L’esperienza effettuata negli ultimi anni nell’ambito di un progetto di cooperazione intergovernativa ha permesso di utilizzare un recente modello numerico regionale, elaborato dall’Osservatorio Sahara Sud, come base per la costruzione di un nuovo modello locale centrato sulla regione dei Chotts tunisini tramite il quale implementare differenti scenari plausibili di sfruttamento della risorsa idrica sotterranea. Il modello numerico locale si sviluppa su un’area di circa 30000 Km2, comprendente parte del territorio algerino accanto al confine con la Tunisia e l’intera regione del Chott el Djerid nel sud della Tunisia. L’attualizzazione del modello regionale servito come base per la modellazione locale ha richiesto l’utilizzo dei dati raccolti durati un’apposita campagna di misure svolta nel 2007 e incentrata sul monitoraggio piezometrico di alcuni pozzi artesiani e sull’esecuzione di numerose prove di portata. Le ipotesi fatte sulle possibili evoluzioni dei prelievi nell’area esaminata ha permesso di definire 16 diversi scenari di sfruttamento da implementare nel modello locale. Il risultato delle simulazioni ha mostrato previsioni di trend di abbassamento piezometrico variabili tra gli 0,8 e gli 1,2 m/a, con relative scomparsa dei fenomeni locali di artesianismo prevista tra il 2015 e il 2035

Vulnerability assessment of the karst aquifer feeding the Pertuso Spring (Central Italy): comparison between different applications of COP method

Karst aquifers vulnerability assessment and mapping are important tools for improved sustainable management and protection of karst groundwater resources. In this paper, in order to estimate the vulnerability degree of the karst aquifer feeding the Pertuso Spring in Central Italy, COP method has been applied starting from two different discretization approaches: using a polygonal layer and the Finite Square Elements (FSE). Therefore, the hydrogeological catchment basin has been divided into 72 polygons, related to the outcropping lithology and the karst features. COP method has been applied to a single layer composed by all these polygons. The results of this study highlight vulnerability degrees ranging from low to very high. The maximum vulnerability degree is due to karst features responsible of high recharge and high hydraulic conductivity. Comparing the vulnerability maps obtained by both methodologies it is possible to say that the traditional discretization approach seems to overestimate the vulnerability of the karst aquifer feeding the Pertuso Spring. Between the two different approaches of COP method, the proposed polygonal discretization of the hydrogeological basin seems to be more suitable to small areas, such as the Pertuso Spring hydrogeological basin, than the traditional grid mapping

Preliminary validation of an indirect method for discharge evaluation of Pertuso Spring (Central Italy)

This paper deals with the results of the first year of the Environmental Monitoring Plan, related to the catchment project of Pertuso Spring, which is going to be exploited to supply an important water network in the South part of Roma district. The study area is located in the Upper Valley of the Aniene River (Latium, Central Italy), in the outcrop of Triassic-Cenozoic carbonate rocks, and belong to an important karst aquifer. Pertuso Spring is the main outlet of this karst aquifer and is the one of the most important water resource in the southeast part of Latium Region, used for drinking, agriculture and hydroelectric supplies. Karst aquifer feeding Pertuso Spring is an open hydrogeological system aquifer characterized by complex interactions and exchanges between groundwater and surface water which influence the aquifer water budget. Thus, evaluation of groundwater discharge from this karst spring can be affected by difficulties in performing measurements because of the insufficient knowledge about water transfer processes in the hydrological cycle and geometry of drainage conduits. The aim of this paper is to assess the interactions between karst aquifer feeding Pertuso Spring and Aniene River based on stream discharge measurements and water geochemical tracer data in order to validate an indirect method for karst spring discharge evaluation. As a matter of fact, in this paper, there are presented the results of the application of Magnesium as a reliable tracer of karst spring discharge. This indirect method is based on the elaboration of surface water discharge measurements in relationship with Mg2+ concentration values, determined as for groundwater, coming from Pertuso Spring, as for surface water sample, collected upstream and downstream of Pertuso Spring, along Aniene River streamflow. The application of Magnesium as an environmental tracer provides a means to evaluate discharge of Pertuso Spring, as it came up to be a marker of the mixing of surface water and groundwater. On the other hand, the Magnesium ion concentration provides information for the identification of groundwater flow systems and the main hydrogeochemical processes affecting the composition of water within the karst aquifers

Pertuso Spring discharge assessment in the Upper Valley of Aniene River (Central Italy)

Sustainable management of karst aquifers is animportant tool for the protection of these strategic water resources. Assessing water balance in a karst aquifer can be very difficult,due to the complex interactions and exchanges between groundwater and surface water. Therefore, measurements of streamflow and spring discharges are useful to assess karst aquifers available budget. Water balance calculation requires the estimation of two main parameters: recharge (precipitation, agriculture water, surface runoff, etc.) and discharge (underground outflow) which are affected by the highly heterogeneous distribution of permeability due to conduits and voids developed by the dissolution of carbonate rocks. This paper deals with the preliminary results of Pertuso Spring groundwater discharge assessment, in the Upper Valley of Aniene River (Central Italy), where the complex hydrogeological characteristics, related to the high heterogeneity of hydraulic properties, make difficult to set up a reliable methodology of measurement. To achieve this objective, an integrated approach based on the streamflow measurements and geochemical modeling, applied to groundwater and surface water was carried out. Because no continuous discharge measurements of Pertuso Spring were available, different methods (velocity–area using current meter and geochemical assessment) were applied to evaluate the discharge of the spring and the stream flow during the monitoring period from July 2014 to May 2015. Aniene River streamflow measurements were carried out by using the conventional current-method and the salt dilution method. For the evaluation of the Pertuso Spring discharge, as a support for traditional discharge methodology, various groundwater and surface water monitoring campaigns have been made along the Aniene River, upstream and downstream the Pertuso Spring, for the acquisition of geochemical data. The aim of this study is to present the preliminary results of an indirect method for the estimation of the Pertuso Spring discharge, based on Magnesium concentration changes in groundwater and surface water

Isotope-Based Early-Warning Model for Monitoring Groundwater–Leachate Contamination Phenomena: First Quantitative Assessments

Groundwater contamination due to municipal solid waste landfills’ leachate is a serious environmental threat. Deuterium (2H) and oxygen (18O) isotopes have been successfully applied to identify groundwater contamination processes, due to interactions with municipal solid waste landfills’ leachate, including significant organic amounts. A parameter influencing the isotope content of deuterium and oxygen18 is the deuterium excess (d or d-excess). This paper presents a d-isotope-based model, defined early-warning model, depending on the assessment of the deuterium excess variations in groundwater samples. The isotopic results are corroborated with the trace elements’ concentrations (Fe, Mn, Ni, Co and Zn), suggesting that the methanogenic activity diminished under trace element limitation. This model provides the determination of an index, F, as the percentage variation of d-excess, which makes it possible to define an alert level system to assess and check groundwater contamination by leachate. The procedure shows that values of F index higher than 1.1 highlight possible contamination phenomena of groundwater due to leachate and, therefore, actions by the municipal solid waste landfill management are required. This early-warning model is presented by the application to a case study in Central Italy in order to evaluate innovative aspects and opportunities to optimize the model. The application of the procedure to the case study highlighted anomalous values of the F index for the samples AD16 (Fmax = 2.069) and AD13 (Fmax = 1.366) in January, April, July and October surveys as well as the boundary values (1 ≤ F ≤ 1.1) for samples AD73 (F = 1.229) and AD68 (F = 1.219) in the April survey. The proposed model can be a useful management tool for monitoring the potential contamination process of groundwater due to the presence of landfills with municipal solid waste, including a significant organic component

Application of 2H and 18O Isotopes for Tracing Municipal Solid Waste Landfill Contamination of Groundwater. Two Italian Case Histories

Groundwater contamination due to municipal solid waste landfills leachate is a serious environmental threat. During recent years, the use of stable isotopes as environmental tracers to identify groundwater contamination phenomena has found application to environmental engineering. Deuterium (2H) and oxygen (18O) isotopes have successfully used to identify groundwater contamination phenomena if submitted to interactions with municipal solid waste landfills leachate, with a significant organic amount. The paper shows two case studies, in central and southern Italy, where potential contamination phenomenon of groundwater under municipal solid waste landfills occurred. In both cases, isotope compositions referred to 2H and 18O highlight a δ2H enrichment for some groundwater samples taken in wells, located near leachate storage wells. The δ2H enrichment is probably caused by methanogenesis phenomena, during which the bacteria use preferentially the hydrogen “lighter” isotope (1H), and the remaining enriched the “heavier” isotope (2H). The study of the isotope composition variation, combined with the spatial trend of some analytes (Fe, Mn, Ni) concentrations, allowed to identify interaction phenomena between the municipal solid waste landfills leachate and groundwater in both case histories. Therefore, these results confirm the effectiveness of 2H isotopes application as environmental tracer of groundwater contamination phenomena due to mixing with municipal solid waste landfills leachate