Groundwater resources in Brazil: a review of possible impacts caused by climate change

Groundwater has a strategic role in times of climate change mainly because aquifers can provide water for long periods, even during very long and severe drought. The reduction and/or changes on the precipitation pattern can diminish the recharge mainly in unconfined aquifer, causing available groundwater restriction. The expected impact of long-term climate changes on the Brazilian aquifers for 2050 will lead to a severe reduction in 70% of recharge in the Northeast region aquifers (comparing to 2010 values), varying from 30% to 70% in the North region. Data referring to the South and Southeast regions are more favorable, with an increase in the relative recharge values from 30% to 100%. Another expected impact is the increase in demand and the decrease in the surface water availability that will make the population turn to aquifers as its main source of water for public or private uses in many regions of the country. Thus, an integrated use of surface and groundwater must therefore be considered in the water use planning. The solution of water scarcity is based on three factors: society growth awareness, better knowledge on the characteristics of hydraulic and chemical aquifers and effective management actions.

Small-scale landfills: impacts on groundwater and soil

In Brazil, the large quantities of solid waste produced are out of step with public policies, technological developments, and government budgets for the division. In small municipalities, the common lack of technological knowledge and financial conditions for suitable waste disposal has resulted in a large number of illegal dumps. Therefore, small sanitary landfill facilities are working with simplified operations focusing on cost reduction and meeting the economic and technological standards of the city without endangering the environment or public health. Currently, this activity is regulated at a federal level although there is some uncertainty regarding the risk of soil and aquifer contamination as theses facilities do not employ liners. Thus, this work evaluates a small landfill to identify changes in soil and groundwater using geotechnical parameters, monitoring wells, and geophysical tests performed by electrical profiling. It is verified that based on current conditions, no contaminants have migrated via underground water aquifers, and overall no significant changes have occurred in the soil. It is concluded that, despite its simplicity, the method investigated is a viable alternative for the final disposal of municipal solid waste from small cities, especially in developing countries.

Origin of the groundwater salinization in La Aldea coastal aquifer (Gran Canaria, Canary Islands)

[EN] Groundwater chemistry in La Aldea aquifer (Gran Canaria, Canary Islands) shows high contents of chloride and nitrate ions. The salinization process has been modelled using the geochemical data, taking into account the results of a previous flow model. The results allow to identify the salinity of the recharge from the rainfall under aridity conditions and the irrigation returns like the main causes of the groundwater salinization.

Speciation of Pu(III) in the environmental system humic substances-groundwater-kaolinite

For the safety assessments of nuclear waste repositories, the possible migration of the radiotoxic waste into environment must be considered. Since plutonium is the major contribution at the radiotoxicity of spent nuclear waste, it requires special care with respect to its mobilization into the groundwater. Plutonium has one of the most complicated chemistry of all elements. It can coexist in 4 oxidation states parallel in one solution. In this work is shown that in the presence of humic substances it is reduced to the Pu(III) and Pu(IV). This work has the focus on the interaction of Pu(III) with natural occurring compounds (humic substances and clay minerals bzw. Kaolinite), while Pu(IV) was studied in a parallel doctoral work by Banik (in preparation). As plutonium is expected under extreme low concentrations in the environment, very sensitive methods are needed to monitor its presence and for its speciation. Resonance ionization mass spectrometry (RIMS), was used for determining the concentration of Pu in environmental samples, with a detection limit of 106- 107 atoms. For the speciation of plutonium CE-ICP-MS was routinely used to monitor the behaviour of Pu in the presence of humic substances. In order to reduce the detection limits of the speciation methods, the coupling of CE to RIMS was proposed. The first steps have shown that this can be a powerful tool for studies of pu under environmental conditions. Further, the first steps in the coupling of two parallel working detectors (DAD and ICP_MS ) to CE was performed, for the enabling a precise study of the complexation constants of plutonium with humic substances. The redox stabilization of Pu(III) was studied and it was determined that NH2OHHCl can maintain Pu(III) in the reduced form up to pH 5.5 – 6. The complexation constants of Pu(III) with Aldrich humic acid (AHA) were determined at pH 3 and 4. the logß = 6.2 – 6.8 found for these experiments was comparable with the literature. The sorption of Pu(III) onto kaolinite was studied in batch experiments and it was determine dthat the pH edge was at pH ~ 5.5. The speciation of plutonium on the surface of kaolinite was studied by EXAFS/XANES. It was determined that the sorbed species was Pu(IV). The influence of AHA on the sorption of Pu(III) onto kaolinite was also investigated. It was determined that at pH < 5 the adsorption is enhanced by the presence of AHA (25 mg/L), while at pH > 6 the adsorption is strongly impaired (depending also on the adding sequence of the components), leading to a mobilization of plutonium in solution.

Groundwater recharge estimation in a data sparse arid catchment of westbank. Stima della ricarica delle falde acquifere in bacini aridi e carenti di osservazioni idrometriche: il Darga in Cisgiordania.

Il seguente elaborato è frutto del lavoro di ricerca, della durata di cinque mesi, svolto presso il Department of Catchment Hydrology del centro di ricerca UFZ (Helmholtz-Zentrum für Umweltforschung) con sede in Halle an der Saale, Germania. L’obiettivo della Tesi è la stima della ricarica della falda acquifera in un bacino idrografico sprovvisto di serie di osservazioni idrometriche di lunghezza significativa e caratterizzato da clima arido. Il lavoro di Tesi è stato svolto utilizzando un modello afflussi-deflussi concettualmente basato e spazialmente distribuito. La modellistica idrologica in regioni aride è un tema a cui la comunità scientifica sta dedicando numerosi sforzi di ricerca, presentando infatti ancora numerosi problemi aperti dal punto di vista tecnico-scientifico, ed è di primaria importanza per il sostentamento delle popolazioni che vi abitano. Le condizioni climatiche in queste regioni fanno sì che la falda acquifera superficiale sia la principale fonte di approvvigionamento; una stima affidabile della sua ricarica, nel tempo e nello spazio, permette un corretta gestione delle risorse idriche, senza la quale il fabbisogno idrico di queste popolazioni non potrebbe essere soddisfatto. L’area oggetto di studio è il bacino idrografico Darga, una striscia di terra di circa 74 km2, situata in Cisgiordania, la cui sezione di chiusura si trova a circa 4 kilometri dalla costa del Mar Morto, mentre lo spartiacque a monte, ubicato a Nord-ovest, dista circa 3 kilometri dalla città di Gerusalemme.

Model reduction of stochastic groundwater flow and transport processes

This work presents a comprehensive methodology for the reduction of analytical or numerical stochastic models characterized by uncertain input parameters or boundary conditions. The technique, based on the Polynomial Chaos Expansion (PCE) theory, represents a versatile solution to solve direct or inverse problems related to propagation of uncertainty. The potentiality of the methodology is assessed investigating different applicative contexts related to groundwater flow and transport scenarios, such as global sensitivity analysis, risk analysis and model calibration. This is achieved by implementing a numerical code, developed in the MATLAB environment, presented here in its main features and tested with literature examples. The procedure has been conceived under flexibility and efficiency criteria in order to ensure its adaptability to different fields of engineering; it has been applied to different case studies related to flow and transport in porous media. Each application is associated with innovative elements such as (i) new analytical formulations describing motion and displacement of non-Newtonian fluids in porous media, (ii) application of global sensitivity analysis to a high-complexity numerical model inspired by a real case of risk of radionuclide migration in the subsurface environment, and (iii) development of a novel sensitivity-based strategy for parameter calibration and experiment design in laboratory scale tracer transport.

Tracing the source of groundwater for three different coastal peatlands along Lake Superior

The goal of this project was to investigate the influence of a large inland lake on adjacent coastal freshwater peatlands. The specific aim was to determine the source of groundwater for three differently formed peatlands located on the southern shore of Lake Superior. The groundwater study was conducted at Bete Grise, a peatland complex in a dune-swale system; Pequaming, a peatland developed in the swale of a tombolo; and Lightfoot Bay, a peatland developed in a barrier beach wetland complex. To determine the source of groundwater in the peatlands, transects of six groundwater monitoring wells were established at each study site, covering distinctly different vegetation zones. At Pequaming and Lightfoot Bay the transects monitored two vegetation zones: transition zone from upland and open fen. At Bete Grise, the transects monitored dunes and swales. Additionally, at all three sites, upland groundwater was monitored using three wells that were installed into the adjacent upland forest. Biweekly measurements of well water pH and specific conductance were carried out from May to October of 2010. At each site, vegetation cover, peat depths and surface elevations were determined and compared to Lake Superior water levels. From June 14 – 17, July 20 – 21 and September 10 – 12, stable isotopes of oxygen (18O/16O) ratios were measured in all the wells and for Lake Superior water. A mixing model was used to estimate the percentage of lake water influencing each site based on the oxygen isotope ratios. During the sampling period, groundwater at all three sites was supported primarily by upland groundwater. Pequaming was approximately 80 % upland groundwater supported and up to 20 % Lake water supported in the uppermost 1 m layer of peat column of the transition zone and open fen. Bete Grise and Lightfoot Bay were 100 % upland groundwater supported throughout the season. The height of Lake Superior was near typical levels in 2010. In years when the lake level is higher, Lake water could intrude into the adjacent peatlands. However, under typical hydrologic conditions, these coastal peatlands are primarily supported by upland groundwater.

Digital processing and data compilation approach for using remotely sensed imagery to identify geological lineaments in hard-rock terrains : an application for groundwater explorations in Nicaragua

Sustainable yields from water wells in hard-rock aquifers are achieved when the well bore intersects fracture networks. Fracture networks are often not readily discernable at the surface. Lineament analysis using remotely sensed satellite imagery has been employed to identify surface expressions of fracturing, and a variety of image-analysis techniques have been successfully applied in “ideal” settings. An ideal setting for lineament detection is where the influences of human development, vegetation, and climatic situations are minimal and hydrogeological conditions and geologic structure are known. There is not yet a well-accepted protocol for mapping lineaments nor have different approaches been compared in non-ideal settings. A new approach for image-processing/synthesis was developed to identify successful satellite imagery types for lineament analysis in non-ideal terrain. Four satellite sensors (ASTER, Landsat7 ETM+, QuickBird, RADARSAT-1) and a digital elevation model were evaluated for lineament analysis in Boaco, Nicaragua, where the landscape is subject to varied vegetative cover, a plethora of anthropogenic features, and frequent cloud cover that limit the availability of optical satellite data. A variety of digital image processing techniques were employed and lineament interpretations were performed to obtain 12 complementary image products that were evaluated subjectively to identify lineaments. The 12 lineament interpretations were synthesized to create a raster image of lineament zone coincidence that shows the level of agreement among the 12 interpretations. A composite lineament interpretation was made using the coincidence raster to restrict lineament observations to areas where multiple interpretations (at least 4) agree. Nine of the 11 previously mapped faults were identified from the coincidence raster. An additional 26 lineaments were identified from the coincidence raster, and the locations of 10 were confirmed by field observation. Four manual pumping tests suggest that well productivity is higher for wells proximal to lineament features. Interpretations from RADARSAT-1 products were superior to interpretations from other sensor products, suggesting that quality lineament interpretation in this region requires anthropogenic features to be minimized and topographic expressions to be maximized. The approach developed in this study has the potential to improve siting wells in non-ideal regions.