H.C. Bonsor

Quantitative maps of groundwater resources in Africa

In Africa, groundwater is the major source of drinking water and its use for irrigation is forecast to increase substantially to combat growing food insecurity. Despite this, there is little quantitative information on groundwater resources in Africa, and groundwater storage is consequently omitted from assessments of freshwater availability. Here we present the first quantitative continent-wide maps of aquifer storage and potential borehole yields in Africa based on an extensive review of available maps, publications and data. We estimate total groundwater storage in Africa to be 0.66 million km 3 (0.36‐1.75 million km 3 ). Not all of this groundwater storage is available for abstraction, but the estimated volume is more than 100 times estimates of annual renewable freshwater resources on Africa. Groundwater resources are unevenly distributed: the largest groundwater volumes are found in the large sedimentary aquifers in the North African countries Libya, Algeria, Egypt and Sudan. Nevertheless, for many African countries appropriately sited and constructed boreholes can support handpump

The internal structure of the Moine Nappe Complex and the stratigraphy of the Morar Group in the Fannichs – Beinn Dearg area, NW Highlands

Synopsis The Morar Group, the lowest group of the early Neoproterozoic Moine Supergroup in the Scottish Highlands, forms a >5 km thick metamorphosed siliclastic sequence, recently interpreted to form part of a Grenvillian (c. 1000 Ma) foreland basin. New mapping has elucidated the structure and stratigraphy of the Morar Group in the Fannich–Beinn Dearg area, where the Morar Group occurs in a single coherent thrust sheet (Achness Thrust Sheet), over 70 km long, 20 km wide, and up to 10 km thick. Within this thrust sheet, the strata are folded by two very large, west-vergent and west-facing cylindroidal anticline-syncline pairs that deform the overlying Sgurr Beag Thrust. The lowest long limb is parallel with and grades into the ductile Moine Thrust and Achness Thrust at its base. Low strain zones in steep limbs contain well preserved sedimentary structures. Reconstruction of the stratigraphical architecture shows five formations of metasandstone (psammite), alternating with meta-siltstone (semipelite). Large-scale lateral variations in the lowest metasandstone package are capped by a possible flooding surface of semipelite, followed by more metasandstone. The deformation history shows foreland-propagation of both deformation and metamorphism, from NNW-directed transport on the Sgurr Beag Thrust to WNW-directed transport on the Achness Thrust and Moine Thrust.

Sedimentology of the early Neoproterozoic Morar Group in northern Scotland: implications for basin models and tectonic setting

The metasedimentary rocks of the Morar Group in northern Scotland form part of the early Neoproterozoic Moine Supergroup. The upper part of the group is c. 2–3 km thick and contains two large kilometre-scale facies successions: a coarsening-upwards marine-to-fluvial regression overlain by a fining-upwards fluvial-to-marine transgression. Fluvial facies make up less than a third of the total thickness; shallow-marine lithofacies make up the remainder. Combining these new findings with previously published data indicates that the Morar Group represents, overall, a transgressive stratigraphic succession c. 6–9 km thick, in which there is both an upward and eastward predominance of shallow-marine deposits, and a concomitant loss of fluvial facies. Smaller-scale (hundreds of metres thick) transgressive–regressive cycles are superimposed on this transgressive trend. Collectively, the characteristics of the succession are consistent with deposition in a foreland basin located adjacent to the Grenville orogen, and possibly linked to the peri-Rodinian ocean. Subsidence and progressive deepening of the Morar basin may have, at least in part, been driven by loading of thrust sheets emplaced during the Grenville orogeny, and aided by sediment loading. However, the relative contributions of thrust loading versus plate boundary effects and/or eustatic sea-level rise on basin evolution remain speculative.

Potential Impact of Climate Change on Improved and Unimproved Water Supplies in Africa

With significant climate change predicted in Africa over the next century, this chapter explores a key question: how will rural water supplies in Africa be affected ? Approximately 550 million people in Africa live in rural communities and are reliant on water resources within walking distance of their community for drinking water. Less than half have access to improved sources (generally large diameter wells, springs or boreholes equipped with hand pumps); the majority rely on unimproved sources, such as open water and shallow wells. Major climate modelling uncertainties, combined with rapid socio-economic change, make predicting the future state of African water resources difficult; an appropriate response to climate change is to assume much greater uncertainty in climate and intensification of past climate variability. Based on this assumption the following should be considered:Those relying on unimproved water sources (300 million in rural Africa) are likely to be most affected by climate change because unimproved sources often use highly vulnerable water resources.Improved rural water supplies in Africa are overwhelmingly dependent on groundwater, due to the unreliability of other sources.Climate change is unlikely to lead to a continent-wide failure of improved rural water sources that access deeper groundwater (generally over 20 metres below ground surface) through boreholes or deep wells. This is because groundwater-based domestic supply requires little recharge, and the groundwater resources at depth will generally be of sufficient storage capacity to remain a secure water resource. However, a significant minority of people could be affected if the frequency and length of drought increases – particularly those in areas with limited groundwater storage.In most areas, the key determinants of water security will continue to be driven by access to water rather than absolute water availability. Extending access, and ensuring that targeting and technology decisions are informed by an understanding of groundwater conditions, will become increasingly important.Accelerating groundwater development for irrigation could increase food production, raise farm incomes and reduce overall vulnerability. However, ad hoc development could threaten domestic supplies and, in some areas, lead to groundwater depletion.Although climate change will undoubtedly be important in determining future water security, other drivers (such as population growth and rising food demands) are likely to provide greater pressure on rural water supplies.

Hydrogeological typologies of the Indo-Gangetic basin alluvial aquifer, South Asia

The Indo-Gangetic aquifer is one of the world’s most important transboundary water resources, and the most heavily exploited aquifer in the world. To better understand the aquifer system, typologies have been characterized for the aquifer, which integrate existing datasets across the Indo-Gangetic catchment basin at a transboundary scale for the first time, and provide an alternative conceptualization of this aquifer system. Traditionally considered and mapped as a single homogenous aquifer of comparable aquifer properties and groundwater resource at a transboundary scale, the typologies illuminate significant spatial differences in recharge, permeability, storage, and groundwater chemistry across the aquifer system at this transboundary scale. These changes are shown to be systematic, concurrent with large-scale changes in sedimentology of the Pleistocene and Holocene alluvial aquifer, climate, and recent irrigation practices. Seven typologies of the aquifer are presented, each having a distinct set of challenges and opportunities for groundwater development and a different resilience to abstraction and climate change. The seven typologies are: (1) the piedmont margin, (2) the Upper Indus and Upper-Mid Ganges, (3) the Lower Ganges and Mid Brahmaputra, (4) the fluvially influenced deltaic area of the Bengal Basin, (5) the Middle Indus and Upper Ganges, (6) the Lower Indus, and (7) the marine-influenced deltaic areas.RésuméL’aquifère de l’Indus et du Gange est une des ressources en eau transfrontalière la plus importante au monde et un des aquifères le plus exploité au monde. Pour mieux comprendre le système aquifère, des typologies ont été caractérisées pour cet aquifère ; elles intègrent pour la première fois un jeu de données disponibles sur l’ensemble du bassin de l’Indus et du Gange à une échelle transfrontalière, et apportent une conceptualisation alternative de ce système aquifère. Traditionnellement considéré et cartographié comme un simple aquifère homogène aux propriétés aquifères similaires et comme une ressource d’eau souterraine à l’échelle transfrontalière, les typologies mettent en évidence des différences significatives spatiales de la recharge, de la perméabilité, de la capacité de stockage et de la chimie des eaux souterraines sur l’ensemble du système aquifère à une échelle transfrontalière. Ces changements sont systématiques coïncidant aux changements à large échelle de la sédimentologie de l’aquifère alluvial du Pléistocène et de l’Holocène, du climat et des pratiques récentes d’irrigation. Sept typologies de l’aquifère sont présentées, chacune ayant un ensemble distinct de défis et d’opportunités pour le développement des eaux souterraines et une résilience différente à l’exploitation et au changement climatique. Les sept typologies sont: (1) la marge de piedmont, (2) Le haut Indus et le Ganges moyen supérieur, (3) le Ganges inférieur et le Brahmapoutre moyen, (4) la zone deltaïque du bassin du Bengale sous influence fluviale, (5) l’Indus moyen et le Ganges supérieur, (6) l’Indus inférieur, et (7) la zone deltaïque sous influence marine.ResumenEl acuífero Indo-Gangético es uno de los recursos hídricos transfronterizos más importantes y el acuífero más explotado del mundo. Para comprender mejor el sistema acuífero, por primera vez se han caracterizado tipologías para el acuífero, integrando los conjuntos de datos existentes a través de la cuenca hidrográfica Indo-Ganges a una escala transfronteriza, y proporcionando una conceptualización alternativa de este sistema acuífero. Tradicionalmente consideradas y cartografiadas como un solo acuífero homogéneo de propiedades acuíferas y recursos de agua subterránea comparables a escala transfronteriza, las tipologías iluminan diferencias espaciales significativas en la recarga, permeabilidad, almacenamiento y química del agua subterránea a través del sistema acuífero a esta escala transfronteriza. Estos cambios son mostrados por ser sistemáticos, coincidentes con cambios en gran escala en la sedimentología del acuífero aluvial del Pleistoceno y del Holoceno, en el clima y en las prácticas recientes de riego. Se presentan siete tipologías del acuífero, cada una con un conjunto distinto de desafíos y oportunidades para el desarrollo del agua subterránea y una diferente resiliencia a la extracción y al cambio climático. Las siete tipologías son: (1) el margen del piedemonte, (2) el Indus superior y el Ganges superior-medio, (3) el Ganges inferior y el Brahmaputra medio, (4) el área deltaica fluvialmente influenciada de la cuenca de Bengala, (5) el Ganges superior, (6) el Indo Inferior, y (7) las áreas deltaicas con influencia marina.摘要印度-恒河含水层是世界上最重要的跨界水资源之一,也是世界上开采量最大的含水层。为了更好地了解含水层系统,结合现有的印度-恒河流域盆地数据,第一次在跨界尺度上对含水层的类型进行了特征描述,提供了这个含水层系统供选择的概念模型。传统上,被认为并被绘制为可比较含水层特性的单一均质含水层及跨界尺度上地下水资源,类型学阐明了这个跨界尺度上含水层系统补给、透水率、储存量和地下水化学上的重要空间差别。这些变化显示与更新世和全新世冲积含水层、气候和最近灌溉实践沉积学上的大尺度变化是系统性的、也是一致的。展示了含水层的七个类型,每个类型都具有一套独特的地下水开发的挑战和机会以及针对抽水和气候变化的不同恢复力。七个类型为:(1)山前边缘;(2)印度河上游及恒河中上游;(3)恒河下游及雅鲁藏布江中游;(4)孟加拉流域洪积影响的三角洲地区;(5)印度河中游及恒河上游;(6)印度河下游;(7)海相影响的三角洲地区。ResumoO aquífero do Indo-Gangético é um dos recursos hídricos transfronteiriços mais importantes do mundo, e o mais explorado. Para melhor entender o sistema aquífero, tipologias foram caracterizadas para o aquífero, que integram pela primeira vez bancos de dados existentes sobre a bacia de abastecimento Indo-Gangética em uma escala transfornteiriça, e fornecem uma conceptualização alternativa desse sistema aquífero. Tradicionalmente considerado e mapeado como um aquífero homogêneo de propriedades aquíferas comparáveis e recursos subterrâneos em escala transfronteiriça, as tipologias elucidam diferenças espaciais significantes na recarga, permeabilidade, armazenamento, e química das águas subterrâneas pelo aquífero nessa escala transfronteiriça. Essas mudanças aparentam ser sistemáticas, concorrentes com mudanças em larga escala na sedimentologia do aquífero aluvial do Pleistoceno e Holoceno, clima e práticas recentes de irrigação. Sete tipologias do aquífero são apresentadas, cada uma tendo conjuntos de desafios e oportunidades distintos para o desenvolvimento das águas subterrâneas e uma resiliência diferente nas mudanças de extração e clima. As sete tipologias são: (1) a margem piemonte, (2) O Alto Indo e o Alto-médio Ganges, (3) O Baixo Ganges e o Médio Brahmaputra, (4) a área deltaica influenciada fluvialmente da Bacia de Bengala, (5) o Médio Indo e o Alto Ganges, (6) o Baixo Indo, e (7) as áreas deltaicas com influencia marinha.

The need for a standard approach to assessing the functionality of rural community water supplies

The Sustainable Development Goals have set an agenda for transformational change in water access, aiming for secure household connections globally. Despite this goal, communal groundwater supplies are likely to remain the main source of improved water supplies for many rural areas in Africa and South Asia for decades to come. Understanding the poor functionality of existing communal supplies remains, therefore, a priority. A critical first step is to establish a sector-wide definition of borehole supply functionality and a standard method of its assessment.RésuméLes objectifs du développement durable ont mis en place un programme de changement transformationnel de l’accès à l’eau, visant à assurer des connexions sûres des ménages à l’échelle mondiale. Malgré cet objectif, les approvisionnements en eaux souterraines à l’échelle communale sont susceptibles de demeurer le sujet principal à améliorer pour de nombreuses régions rurales d’Afrique et d’Asie du Sud pour les décennies à venir. La compréhension de la piètre fonctionnalité des approvisionnements existants à l’échelle communale reste donc une priorité. Une première étape cruciale consiste à établir une définition sectorielle de la fonctionnalité de l’approvisionnement par forage et une méthode normalisée de son évaluation.ResumenLos objetivos de desarrollo sostenible han establecido una agenda para un cambio transformacional en el acceso al agua, con la finalidad de establecer conexiones domiciliarias seguras a nivel mundial. A pesar de este objetivo, es probable que los suministros comunales de agua subterránea sigan siendo la principal fuente de mejoras en el abastecimiento de agua para muchas áreas rurales en África y el sur de Asia en las próximas décadas. Entender la funcionalidad deficiente de los suministros comunales existentes sigue siendo, por lo tanto, una prioridad. Un primer paso crítico es establecer una definición sectorial de la funcionalidad del suministro de los pozos y un método estándar para su evaluación.摘要可持续发展目标为供水转换变化确定了日程,目标就是为全球每家提供安全的供水连接管道。尽管确定了这一目标,但公共供水可能仍然是非洲和南亚许多农村地区未来几十年改善供水的主要水源。因此,了解现有公共供水功能性差的状况依旧是需要优先考虑的问题。关键的第一步是建立部门范围的钻孔供水功能性的定义及其评价的标准方法。ResumoOs Objetivos de Desenvolvimento Sustentável estabeleceram uma agenda para mudanças de paradigmas no acesso à água, visando abastecimento doméstico em escala global. Apesar desse objetivo, os suprimentos comunitários de águas subterrâneas provavelmente continuarão a ser a principal fonte de abastecimento de água potável para muitas áreas rurais da África e do sul da Ásia por décadas. Compreender a baixa funcionalidade desses atuais suprimentos comunitários torna-se, portanto, prioritária. Um primeiro passo crítico é estabelecer uma definição setorial de funcionalidade de fornecimento de poços e um método padrão de avaliação.