Observed controls on resilience of groundwater to climate variability in sub-Saharan Africa

Groundwater in sub-Saharan Africa supports livelihoods and poverty alleviation, maintains vital ecosystems, and strongly influences terrestrial water and energy budgets. Yet the hydrological processes that govern groundwater recharge and sustainability—and their sensitivity to climatic variability—are poorly constrained. Given the absence of firm observational constraints, it remains to be seen whether model-based projections of decreased water resources in dry parts of the region are justified. Here we show, through analysis of multidecadal groundwater hydrographs across sub-Saharan Africa, that levels of aridity dictate the predominant recharge processes, whereas local hydrogeology influences the type and sensitivity of precipitation–recharge relationships. Recharge in some humid locations varies by as little as five per cent (by coefficient of variation) across a wide range of annual precipitation values. Other regions, by contrast, show roughly linear precipitation–recharge relationships, with precipitation thresholds (of roughly ten millimetres or less per day) governing the initiation of recharge. These thresholds tend to rise as aridity increases, and recharge in drylands is more episodic and increasingly dominated by focused recharge through losses from ephemeral overland flows. Extreme annual recharge is commonly associated with intense rainfall and flooding events, themselves often driven by large-scale climate controls. Intense precipitation, even during years of lower overall precipitation, produces some of the largest years of recharge in some dry subtropical locations. Our results therefore challenge the ‘high certainty’ consensus regarding decreasing water resources in such regions of sub-Saharan Africa. The potential resilience of groundwater to climate variability in many areas that is revealed by these precipitation–recharge relationships is essential for informing reliable predictions of climate-change impacts and adaptation strategies

Observed controls on resilience of groundwater to climate variability in sub-Saharan Africa

Groundwater in sub-Saharan Africa supports livelihoods and poverty alleviation1,2, maintains vital ecosystems, and strongly influences terrestrial water and energy budgets. Yet the hydrological processes that govern groundwater recharge and sustainability—and their sensitivity to climatic variability—are poorly constrained4. Given the absence of firm observational constraints, it remains to be seen whether model-based projections of decreased water resources in dry parts of the region4 are justified. Here we show, through analysis of multidecadal groundwater hydrographs across sub-Saharan Africa, that levels of aridity dictate the predominant recharge processes, whereas local hydrogeology influences the type and sensitivity of precipitation–recharge relationships. Recharge in some humid locations varies by as little as five per cent (by coefficient of variation) across a wide range of annual precipitation values. Other regions, by contrast, show roughly linear precipitation–recharge relationships, with precipitation thresholds (of roughly ten millimetres or less per day) governing the initiation of recharge. These thresholds tend to rise as aridity increases, and recharge in drylands is more episodic and increasingly dominated by focused recharge through losses from ephemeral overland flows. Extreme annual recharge is commonly associated with intense rainfall and flooding events, themselves often driven by large-scale climate controls. Intense precipitation, even during years of lower overall precipitation, produces some of the largest years of recharge in some dry subtropical locations. Our results therefore challenge the ‘high certainty’ consensus regarding decreasing water resources in such regions of sub-Saharan Africa. The potential resilience of groundwater to climate variability in many areas that is revealed by these precipitation–recharge relationships is essential for informing reliable predictions of climate-change impacts and adaptation strategies

Development of a decision support system for groundwater pollution assessment.

Computers have become the main tooi used in groundwater management. Computer software has been developed for storage, processing and presentation of information on groundwater pollution problems. Continuing demands for more efficie͏̈nt handling of information have resulted in increasing integration of the software into Decision Support Systems (DSSs). Both quantitative (numerical) and qualitative (knowledge) information are required to support decision-making processes. To date, software development and integration were dedicated much more to numerical information than to knowledge. However, without knowledge components DSSs remain integrated software systems, whereas they should be primarily regarded as integrated information systems. The DSS for Groundwater Pollution Assessment was conceptualised as an integrated information system. It consists, basically, of a DSS kemel, an application environment and a knowledge component. Design and development (and integration) of the knowledge component are the steps of the knowledge encapsulation process that is much more than transformation of knowledge in electronic form and its storage in the computer. The process begins with the definition of the problem and also includes (equally important) acquisition, systematisation and formalisation of knowledge. The case-specific nature and interdisciplinary character of groundwater problems are recognised as the main obstacles to effective encapsulation of knowledge in the field of groundwater management. The knowledge component of the DSS for Groundwater Pollution Assessment is composed of task-oriented Knowledge-Based Modules (KBMs). Content and design of KBMs are strongly dependent on the tasks that they support, but in principle, they provide information on operations required for task accomplishment: which operations are required or recommended (e.g. acquisition, processing, presentation, etc), why, how to perform them and when. So far, three KBMs have been designed and developed, namely: the Site Characterisation Module, the Vulnerability Assessment Module and the Groundwater Modelling Module. Various forms of knowledge representation, as offered by Artificial Intelligence, have been used in KBMs development. In addition, Case-Based Reasoning is anticipated as a promising approach to electronic encapsulation and processing of knowledge

Can water stressed regions be characterised when there is sparse data?

In the identification of effective mitigation strategies to combat water stress, indicators for natural hydrological potential, water stress and mitigation measures are important. Ideally, such indicators should meet two conditions: (1) public availability (preferably in digital format), and (2) distinguishing capacity at the required scale of drainage sub-basins. However, water stress indicators tend to be available, if at all, only for large-scale administrative units (country or province), and there is a clear need to consider how water stress can be assessed in unmonitored regions. In this paper, an attempt has been made to define a simple approach for indicator mapping, using a few key indicators based on information from water management practices in eight selected test sites of the EU funded Aquastress project. Within this project, the approach outlined here will be tested and validated

Hazards in Karst and Managing Water Resources Quality

The peculiarities of karst environment make it highly vulnerable to a number of geohazards: As concerns the natural hazards, the main categories are sinkholes, slope movements, and floods. To these, anthropogenic hazards have to be added, as pollution events, land use changes resulting in loss of karst landscape, destruction of karst landforms, etc. Even carrying out engineering works without taking into the due consideration, the peculiar aspects of karst can be extremely dangerous and cause risk to the natural environment, as well as to the man-made infrastructures and buildings. In the second half of last century, man has definitely become one of the most powerful factors that can cause changes in the karst environment, produce direct damage, predispose the territory to threatening events, and increase with mismanagement actions the negative effects deriving from natural hazards. In this chapter, the main hazards in karst are briefly described with particular focus on the natural hazards and with the help of some case studies

Water management capacity building through the FREEWAT platform

Groundwater governance comprises the promotion of responsible collective action to ensure socially sustainable utilisation, control and protection of groundwater resources (Foster van der Gun, 2016). To this purpose, sharing the same collective knowledge is essential (Brugnach Ingram, 2012). To achieve this task, Information and Communication Technology (ICT) can provide relevant tools. An innovative ICT tool is the result of the H2020 FREEWAT project (www.freewat.eu), aimed at developing a free and open source software tools for water resources management (WRM) and to perform extensive capacity building activities. The capacity building activities performed during the project aimed at: (i) building knowledge capacity on using innovative scientific software for WRM; (ii) improving the professional level of technical staff in water authorities, water utilities, private companies, and any other organization involved in WRM; and (iii) disseminating the use of the FREEWAT platform as a standard software for modelling surface-/sub-surface water quantity and quality. To guide and to demonstrate the FREEWAT platform capabilities, several training courses where held worldwide. A compilation of manuals, lectures, tutorials and exercises were prepared and improved with the feedbacks collected during these courses. More than 1000 persons were trained in the use of FREEWAT during these activities, coming from more than 400 institutions worldwide. About 40% of the downloads of the software and the training material are for training purposes, and this clearly shows that ICT tools are not still widespread instruments used in WRM and that these kind of training is needed