Ricardo Hirata

Groundwater Quality Protection : A Guide for Water Utilities, Municipal Authorities, and Environment Agencies

This publication provides guidance to water-sector decision makers and planners on how to deal with the quality dimension of groundwater resources management in the World Banks client countries. There is growing evidence of increasing pollution threats to groundwater and some well-documented cases of irreversible damage to important aquifers. This guide has been produced in the belief that groundwater pollution hazard assessment must become an essential part of environmental best practice for water supply utilities. The guide is particularly relevant for the World Banks Latin American and Caribbean Region, where many countries have initiated major changes to modernize their institutional and legal framework for water resources management, but may not yet have considered groundwater at the same level as surface water, because of lack of awareness and knowledge of groundwater issues and policy options.

The aquifer pollution vulnerability concept: aid or impediment in promoting groundwater protection?

The term ‘aquifer pollution vulnerability’ was first coined by Margat (1968), and subsequently given a working definition plus a practical tool-box in the mid-1980s by the US Environmental Protection Agency (EPA) through DRASTIC (Aller et al. 1987) and by WHO and the Pan American Health Organization (PAHO) through GOD (Foster 1987; Foster and Hirata 1988). The concept attempted to represent the sensitivity of an aquifer to being adversely affected at any given point by an imposed contaminant pressure (or load) from the land surface. It being possible to:

Origins and processes of groundwater salinization in the urban coastal aquifers of Recife (Pernambuco, Brazil): A multi-isotope approach

In the coastal multilayer aquifer system of a highly urbanized southern city (Recife, Brazil), where groundwaters are affected by salinization, a multi-isotope approach (Sr, B, O, H) was used to investigate the sources and processes of salinization. The high diversity of the geological bodies, built since the Atlantic opening during the Cretaceous, highly constrains the heterogeneity of the groundwater chemistry, e.g. Sr isotope ratios, and needs to be integrated to explain the salinization processes and groundwater pathways. A paleoseawater intrusion, most probably the 120 kyB.P. Pleistocene marine transgression, and cationic exchange are clearly evidenced in the most salinized parts of the Cabo and Beberibe aquifers. All (87)Sr/(86)Sr values are above the past and present-day seawater signatures, meaning that the Sr isotopic signature is altered due to additional Sr inputs from dilution with different freshwaters, and water-rock interactions. Only the Cabo aquifer presents a well-delimitated area of Na-HCO3 water typical of a freshening process. The two deep aquifers also display a broad range of B concentrations and B isotope ratios with values among the highest known to date (63-68.5‰). This suggests multiple sources and processes affecting B behavior, among which mixing with saline water, B sorption on clays and mixing with wastewater. The highly fractionated B isotopic values were explained by infiltration of relatively salty water with B interacting with clays, pointing out the major role played by (palaeo)-channels for the deep Beberibe aquifer recharge. Based on an increase of salinity at the end of the dry season, a present-day seawater intrusion is identified in the surficial Boa Viagem aquifer. Our conceptual model presents a comprehensive understanding of the major groundwater salinization pathways and processes, and should be of benefit for other southern Atlantic coastal aquifers to better address groundwater management issues.

Natural occurrence of hexavalent chromium in a sedimentary aquifer in Urânia, State of São Paulo, Brazil

Anomalous concentrations of hexavalent chromium have been detected in ground-water of the Adamantina Aquifer inat least 54 municipalities located in the northwestern region of the State of Sao Paulo, southeast Brazil, occasionallyexceeding the permitted limit for human consumption (0.05 mg.L-1). An investigation was conducted in the municipality of Urânia, where the highest concentrations of chromium were detected regionally. It was defined that the originof this contamination is natural, since high concentrations of chromium were detected in aquifer sandstones (averageof 221 ppm) and also in pyroxenes (6000 ppm), one of the main heavy minerals found in the sediments. Besides, noother possible diffuse or point sources of contamination were observed in the study area. Stratification of ground-waterquality was observed and the highest concentrations of Cr6+ were detected at the base of the aquifer (0.12 mg.L-1),where ground-water shows elevated values for redox potential (472.5 mV) and pH (8.61). The origin of Cr6+ in water may be associated with the weathering of pyroxene (augite), followed by the oxidation of Cr3+ by manganese oxides. The highest concentrations of Cr6+ are probably related to desorption reactions, due to the anomalous alkaline pHfound in ground-water at the base of the aquifer.

Groundwater resources in the State of São Paulo (Brazil): the application of indicators

Indicators, for groundwater resources, have mostly been employed to define the present status and the degradation tendency, regarding both quantity (under- or overexploitation) and quality (natural and anthropic contamination). This work presents the application of indicators in order to draw a picture of the groundwater resources situation in the 22 Water Resource Management Units (WRMU) of the State of São Paulo. The seven Indicators (I1 to I7) applied provide a general overview of groundwater dependence (I1, I2), availability (I3, I4), and quality (I5, I6, I7). Considering public supply (Indicator 1), one observes that 9 WRMUs show high (>50% of the population supplied by groundwater), 6, intermediate (49-25%), and 7, low (<24%) dependence on groundwater. Indicators 3 and 4 show that the resource still presents a great potential for further abstractions in most of the WRMUs, although there is evidence of overexploitation in the Upper Tietê, Turvo/Grande, and Pardo basins, and low availability in the Upper Tietê, Piracicaba/Capivari/Jundiai, and Turvo/Grande. Indicator 5 (aquifer natural vulnerability) denotes that the WRMUs 2, 4, 8, 13, 14 and 18-22 (part of the recharge area of Guarani Aquifer System) need more attention mainly where large contaminant loads are present. Indicator 6 shows the general excellent natural quality of groundwater, although it also denotes that 3 WRMUs need special consideration due to chromium and fluoride contamination. Indicator 7 demonstrates a close relationship between groundwater contamination occurrence and density/type of land occupation.

Glacial recharge, salinisation and anthropogenic contamination in the coastal aquifers of Recife (Brazil)

Implying large residence times and complex water origins deep coastal aquifers are of particular interest as they are remarkable markers of climate, water use and land use changes. Over the last decades, the Metropolitan Region of Recife (Brazil) went through extensive environmental changes increasing the pressure on water resources and giving rise to numerous environmental consequences on the coastal groundwater systems. We analysed the groundwater of the deep aquifers Cabo and Beberibe that are increasingly exploited. The processes potentially affecting groundwater residence times and flow paths have been studied using a multi-tracer approach (CFCs, SF6, noble gases, 14C, 2H and 18O). The main findings of these investigations show that: (1) Groundwaters of the Cabo and Beberibe aquifers have long residence times and were recharged about 20,000years ago. (2) Within these old groundwaters we can find palaeo-climate evidences from the last glacial period at the tropics with lower temperatures and dryer conditions than the present climate. (3) Recently, the natural slow dynamic of these groundwater systems was significantly affected by mixing processes with contaminated modern groundwater coming from the shallow unconfined Boa Viagem aquifer. (4) The large exploitation of these aquifers leads to a modification of the flow directions and causes the intrusion through palaeo-channels of saline water probably coming from the Capibaribe River and from the last transgression episodes. These observations indicate that the current exploitation of the Cabo and Beberibe aquifers is unsustainable regarding the long renewal times of these groundwater systems as well as their ongoing contamination and salinisation. The groundwater cycle being much slower than the human development rhythm, it is essential to integrate the magnitude and rapidity of anthropogenic impacts on this extremely slow cycle to the water management concepts.

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.

Groundwater contamination in coastal urban areas: Anthropogenic pressure and natural attenuation processes. Example of Recife (PE State, NE Brazil)

In a context of increasing land use pressure (over-exploitation, surface-water contamination) and repeated droughts, identifying the processes affecting groundwater quality in coastal megacities of the tropical and arid countries will condition their long-term social and environmental sustainability. The present study focuses on the Brazilian Recife Metropolitan Region (RMR), which is a highly urbanized area (3,743,854 inhabitants in 2010) on the Atlantic coast located next to an estuarial zone and overlying a multi-layered sedimentary system featured by a variable sediment texture and organic content. It investigates the contamination and redox status patterns conditioning potential attenuation within the shallow aquifers that constitute the interface between the city and the strategic deeper semi-confined aquifers. These latter are increasingly exploited, leading to high drawdown in potenciometric levels of 20-30m and up to 70m in some high well density places, and potentially connected to the surface through leakage. From a multi-tracer approach (major ions, major gases, δ(11)B, δ(18)O-SO4, δ(34)S-SO4) carried out during two field campaigns in September 2012 and March 2013 (sampling of 19 wells and 3 surface waters), it has been possible to assess the contamination sources and the redox processes. The increasing trend for mineralization from inland to coastal and estuarial wells (from 119 to around 10,000μS/cm) is at first attributed to water-rock interactions combined with natural and human-induced potentiometric gradients. Secondly, along with this trend, one finds an environmental pressure gradient related to sewage and/or surface-channel network impacts (typically depleted δ(11)B within the range of 10-15‰) that are purveyors of chloride, nitrate, ammonium and sulfate. Nitrate, ammonium and sulfate (ranging from 0 to 1.70mmol/L, from 0 to 0,65mmol/L, from 0.03 to 3.91mmol/L respectively are also potentially produced or consumed through various redox processes (pyrite oxidation, denitrification, dissimilatory nitrate reduction to ammonium) within the system, as is apparent within a patchwork of biogeochemical reactors. Furthermore, intensive pumping in the coastal area with its high well density punctually leads to temporary well salinization ([Cl] reaching temporarily 79mmol/L). Our results, summarized as a conceptual scheme based on environmental conditions, is a suitable basis for implementing sustainable management in coastal sedimentary hydrosystems influenced by highly urbanized conditions.

Basic oxygen furnace slag as a treatment material for pathogens: contribution of inactivation and attachment in virus attenuation.

Basic oxygen furnace (BOF) slag media were studied as a potential treatment material in on-site sanitation systems. Batch and column studies were conducted to evaluate attenuation of the bacteriophage PR772 and 0.190 microm diameter microspheres by BOF media, and to delineate the relative contributions of two principle processes of virus attenuation: inactivation and attachment. In the batch studies, conducted at 4 degrees C, substantial inactivation of PR772 did not occur in the pH 7.6 and 9.5 suspensions. At pH 11.4, bimodal inactivation of PR772 was observed, at an initial rate of 2.1 log C/C(0) day(-1) for the first two days, followed by a much slower rate of 0.124 log C/C(0) day(-1) over the following 10 days. Two column studies were conducted at 4 degrees C at a flow rate of 1 pore volume day(-1) using two slag sources (Stelco, Ontario; Tubarão, Brazil) combined with sand and pea gravel. In both column experiments, the effluent microsphere concentration approached input concentrations over time (reductions of 0.1-0.2 log C/C(0)), suggesting attachment processes for microspheres were negligible. Removal of PR772 virus was more pronounced both during the early stages of the experiments, but also after longer transport times (0.5-1.0 log C/C(0)). PR772 reduction appeared to be primarily as a result of virus inactivation in response to the elevated pH conditions generated by the BOF mixture (10.6-11.4). On-site sanitation systems using BOF media should be designed to maintain sufficient contact time between the BOF media and the wastewater to allow sufficient residence time of pathogens at elevated pH conditions.

Evaluating karst geotechnical risk in the urbanized area of Sete Lagoas, Minas Gerais, Brazil

An increase in groundwater consumption in the municipality of Sete Lagoas (Minas Gerais, Brazil) has induced subsidence and collapse in the last three decades. The area is associated with natural karst conditions. The primary objective of this research was to evaluate and identify the potential subsidence or collapse risk zones. Aerial photographs, lithologic well profiles, optical well logs, and geologic mapping were utilized to categorize risk factors influencing karst subsidence and collapse, which were then applied to an index system. The study showed that the majority of the urbanized area overlies mantled limestone from the Sete Lagoas Formation covered with unconsolidated sediments, contained within a graben, resulting in barrier boundaries for groundwater flow. This structure, together with natural karst processes, explains the location of solutionally enlarged bedding-plane conduits and high hydraulic conductivity in the limestone. Five risks zones in the municipality were identified (negligible, low, moderate, considerable, and high risks) related to geologic and hydrologic risk factors. The urbanized area is located largely in the high risk zone where the majority of the collapse features are located. Additional intensive groundwater extraction in that area will likely generate additional events.RésuméLa consommation croissante d’eau souterraine de la ville de Sete Lagoas (Minas Gerais, Brésil) a provoqué une subsidence et un affaissement au cours des trois dernières décennies. La région présente des caractéristiques naturelles karstiques. Le premier objectif de cette recherche était d’évaluer et d’identifier les zones de subsidence potentielle ou d’affaissement. Des photographies aériennes, des profils lithologiques et des logs optiques en puits ainsi que la cartographie géologique ont été utilisés pour caractériser les facteurs de risque de subsidence karstique et d’affaissement, qui sont ensuite appliqués dans un système d’indices. L’étude a montré que la plus grande partie de la région urbanisée est située sur un niveau calcaire de la formation de Sete Lagoas recouvert de sédiments meubles, dans un graben faisant barrage à l’écoulement des eaux souterraines. Cette disposition, ainsi que les processus naturels de karstification, expliquent la localisation de conduits suivant les joints de stratification élargis par la dissolution et la grande conductivité hydraulique de ces calcaires. Cinq zones à risques ont été identifiées dans la ville (risque négligeable, faible, modéré, important et très important) en relation avec les facteurs de risques géologiques et hydrogéologiques. La région urbanisée est largement localisée dans la zone à risque très important où se trouve la majorité des structures d’affaissement. Des pompages additionnels intensifs des eaux souterraines dans cette région généreront vraisemblablement de nouveaux mouvements de sol.ResumenUn aumento en el consumo de agua subterránea en la municipalidad de Sete Lagoas (Minas Gerais, Brasil) ha inducido a la subsidencia y el colapso en las últimas tres décadas. El área está asociada con condiciones kársticas naturales. El objetivo principal de esta investigación fue evaluar e identificar las posibles zonas de riesgo de subsidencia ó de colapso. Se utilizaron fotografías aéreas, perfiles litológicos de pozos, perfilajes ópticos de pozos, y mapeos geológicos para categorizar los factores de riesgos influyentes en la subsidencia y colapso kárstico, los cuales fueron luego aplicados a un sistema de índices. El estudio mostró que la mayoría de las áreas urbanizadas recubren el manto de calizas de la Formación Sete Lagoas cubierto por sedimentos no consolidados, contenidos dentro de un graben, lo que resulta en límites de barreras para el flujo de agua subterránea. Esta estructura, junto con los procesos kársticos naturales, explican la ubicación de conductos de planos de estratificación agrandados por disolución y la alta conductividad hidráulica en la caliza. Se identificaron cinco zonas de riesgo en la municipalidad (riesgos insignificante, bajo, moderado, considerable y alto) relacionado a factores de riesgo geológico e hidrológico. El área urbanizada se ubica en gran parte en zonas de alto riesgo donde se localiza la mayoría de los rasgos de colapsos. La extracción de agua subterránea intensiva adicional en esa área probablemente generará eventos adicionales.摘要最近三十年(巴西米纳斯吉拉斯州)Sete Lagoas市地下水消耗量的增加引起了地面沉降和塌陷。这一地区具有天然岩溶条件。本研究的主要目标就是评价和确定潜在的沉降或塌陷风险带。利用航拍照片、岩井剖面、光学测井和地质填图对影响岩溶沉降和塌陷的风险因素进行了分类,然后把这些风险因素应用到一个指数系统中。研究结果显示,大部分城市化地区位于Sete Lagoas组石灰岩之上,上面覆盖着松散沉积物,处于一个地堑之内,构成了地下水流的屏障边界。这种构造,连同天然岩溶进程,产生了溶解作用扩大的层理面通道并使石灰岩中的水力导水率很高。确定了该市与地质和水力风险因素相关的五个风险带(可忽略的风险带、低风险带、中风险带、相当大风险带和高风险带)。城市化区主要位于高风险带,此高风险带也是多数塌陷出现的地带。这个地区额外的强烈抽取地下水还可能产生其他问题。ResumoO aumento no consumo de água subterrânea no município de Sete Lagoas (Minas Gerais, Brasil) tem induzido a subsidência e o colapso nas últimas três décadas. A área é associada a condições cársticas naturais. O objetivo principal deste trabalho foi avaliar e identificar zonas com potencial risco de subsidência e colapso. Fotografias aéreas, perfis litológicos, perfilagem ótica e mapeamento geológico foram utilizados para categorizar os fatores de risco que influenciam na subsidência e no colapso cárstico, e então foram aplicados a um sistema de indexação. O estudo mostrou que a maior parte da área urbanizada está sobre o manto calcário da Formação Sete Lagoas (coberta por sedimentos inconsolidados), contido em um graben, resultando em barreiras limítrofes para o fluxo de águas subterrâneas. Esta estrutura, juntamente com os processos naturais cársticos, explica a localização de condutos de dissolução alargados no plano de estratificação e a alta condutividade hidráulica no calcário. Foram identificadas cinco zonas de risco no município (insignificante, baixo, moderado, considerável e alto) relacionadas a fatores de riscos geológicos e hidrológicos. A área urbanizada está amplamente localizada em zona de alto risco, onde se encontra a maioria das feições de colapso. A extração intensiva da água subterrânea neste local provavelmente irá gerar eventos adicionais.