Karen Villholth

Water Cycle Innovation

Water is a critical resource, but ensuring its availability faces challenges from climate extremes and human intervention. In this Review, we evaluate the current and historical evolution of water resources, considering surface water and groundwater as a single, interconnected resource. Total water storage trends have varied across regions over the...

Water is a critical resource, but ensuring its availability faces challenges from climate extremes and human intervention. In this Review, we evaluate the current and historical evolution of water resources, considering surface water and groundwater as a single, interconnected resource. Total water storage trends have varied across regions over the...

Study region The study region is the Kamadhiya catchment (1150 km²), located in the Saurashtra region of the western state of Gujarat, India. The region has seen intensive development of check dams (CDs) for groundwater recharge with an estimated 27,000 CDs constructed up until 2018. Study focus The impact of CDs on groundwater storage, food produ...

While extreme rainfall events may provide rare opportunities for replenishment of surface water and groundwater resources in vulnerable (semi)arid areas, they are typically also associated with widespread flooding. The impacts on contaminant movement associated with spatio-temporally complex relationships between surface water and groundwater durin...

Climate change strongly influences freshwater supply and demand globally. Warming of ~1°C over the last half century globally has directly impacted the supply of freshwater through the amplification of precipitation extremes, more frequent and pronounced floods and droughts, increasing evapotranspiration rates, rising sea levels, and changing prec...

Groundwater offers smallholder farmers in the lowlands of Lao PDR opportunities to diversify cropping beyond wet season paddy and thus enhance their livelihoods while reducing climate risks. This chapter focuses on evaluating existing and specifically developed groundwater irrigation options on the Vientiane Plain, and framing the findings around t...

E-flows for the Limpopo River in southern Africa. This is the basin report that presents all of the water resources and ecosystem background to the study. Mostly gleaned from existing reports.

E-flows for the Limpopo River in southern Africa making use of the Probflo framework. This is the report that presents the actual e-flow results and data.

E-flows for the Limpopo river in southern Africa. This reports describes the risks of altered flows to the basin ecosystem and users.

While drinking water is known to create significant health risk in arsenic hazard areas, the role of exposure to arsenic through food intake is less well understood, including the impact of food trade. Using the best available datasets on crop production, irrigation, groundwater arsenic hazard, and international crop trade flows, we estimate that g...

There is a scarcity of long-term groundwater hydrographs from sub-Saharan Africa to investigate groundwater sustainability, processes and controls. This paper presents an analysis of 21 hydrographs from semi-arid South Africa. Hydrographs from 1980 to 2000 were converted to standardised groundwater level indices and rationalised into four types (C1...

Overview of how groundwater relates to water security.

Valuation of hydraulic infrastructure

In semi-arid India, managed aquifer recharge (MAR) is often used to enhance aquifer storage, and by implication, water security, and climate resilience, by capturing surface runoff, mainly through check dams implemented at the community level. Despite their extensive use, the design of these structures typically does not follow a systematic method...

We have one Earth and one water resource defining our living space. We are the key custodians for safeguarding these resources, which underpin the healthy and peaceful environment in which we all want to live. We cannot expand the physical boundaries, but we can stretch our perspectives to achieve water sustainability through global solidarity and...

With the impulse to control and order the disorderly, the threads or tributaries of affect and emotion, which mimic the meanderings of the aquifer itself, are often oversimplified or ignored. These are not anomalies of citizen science (CS) but ‘normal’ and expected ‘disconnects’ that surface when working within a multidisciplinary environment. The...

Pragmatic, cost-effective, socially inclusive and scalable solutions that reduce risks from recurrent cycles of floods and droughts would greatly benefit emerging economies. One promising approach known as Underground Transfer of Floods for Irrigation (UTFI) involves recharging depleted aquifers with seasonal high flows to provide additional ground...

Pragmatic, cost-effective, socially inclusive and scalable solutions that reduce risks from recurrent cycles of floods and droughts would greatly benefit emerging economies. One promising approach known as Underground Transfer of Floods for Irrigation (UTFI) involves recharging depleted aquifers with seasonal high flows to provide additional ground...

e-flows for the Limpopo River in southern Africa. This report contains the specialist literature review as well as detailed data on the drivers and response indicators for the river ecosystem

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Climatic variability and change result in unreliable and uncertain water availability and contribute to water insecurity in Africa, particularly in arid and semi-arid areas and where water storage infrastructure is limited. Managed aquifer recharge (MAR), which comprises purposeful recharge and storage of surface runoff and treated wastewater in aq...

This study attempted to conceptualize the hydrogeological setting of the Hout River Catchment, located in the Limpopo River Basin, using multiple methods that include groundwater flow patterns, structural analysis, stable (¹⁸O, ²H and ¹³C) and radiogenic (¹⁴C) isotopes of water and Water Table Fluctuation (WTF) methods. The hydrogeological system o...

This chapter establishes linkages between climate change and various aspects of water management. Adaptation and resilience-building options are presented with respect to water storage – including groundwater – and water supply and sanitation infrastructure, and unconventional water supply options are described. Mitigation options for water managem...

The cover image is based on the Overview Groundwater Governance: Addressing core concepts and challenges, by Alvar Closas and Karen Villholth. https://doi.org/10.1002/wat2.1392 Abstract The cover image is based on the Overview Groundwater Governance: Addressing core concepts and challenges, by Alvar Closas and Karen Villholth. https://doi.org/10.1...

With decreasing aquifer levels, increasing groundwater pollution, inequitable access, and generally poor management outcomes, better groundwater governance has been put forward as a recipe to address these challenges worldwide. Existing recommendations focus on improved legal frameworks, monitoring and control of access and abstraction through perm...

Groundwater in sub-Saharan Africa supports livelihoods and poverty alleviation1,2, maintains vital ecosystems, and strongly influences terrestrial water and energy budgets³. Yet the hydrological processes that govern groundwater recharge and sustainability—and their sensitivity to climatic variability—are poorly constrained4,5. Given the absence of...

An integrated hydrogeological modelling approach applicable to hard-rock aquifers in semi-arid data-scarce Africa was developed using remote sensing, rainfall-runoff modelling, and a three-dimensional (3D) dynamic model. The integrated modelling approach was applied to the Hout catchment, Limpopo Province, South Africa, an important agricultural re...

The impact of climate variability on groundwater storage has received limited attention despite widespread dependence on groundwater as a resource for drinking water, agriculture and industry. Here, we assess the climate anomalies that occurred over Southern Africa (SA) and East Africa, south of the Equator (EASE), during the major El Niño event of...

In Sub-Saharan Africa, groundwater use is a vital strategy to meet rapid increases in freshwater demand projected this century and to adapt to the region’s substantial variabilities in rainfall and surface water resources, amplified by climate change. Four studies are considered, which constitute a topical collection of articles that provide new in...

The FAO are custodians of the SDG 6.4.2 indicator on Water Stress. A new component of this indicator subsequent to the MDGs, is the inclusion of environmental flows. Because these need to be reported at a global level, this guideline document provides direction on using the IWMI GEFIS model to estimate e-flows per country, or per basin. The approac...

Groundwater quantity and quality may be affected by climate change through intricate direct and indirect mechanisms. At the same time, population growth and rapid urbanization have made groundwater an increasingly important source of water for multiple uses around the world, including southern Africa. The present study investigates the coupled huma...

Groundwater represents 97% of the world’s available freshwater resources and is extensively abstracted throughout the world. While abundant in a global context, it can only de developed to a certain extent without causing environmental impacts. Also, it is highly variable across the globe, and where it is heavily relied on, it is less renewable. He...

The impact of climate variability on groundwater storage has received limited attention despite widespread dependence on groundwater as a resource for drinking water, agriculture and industry. Here, we assess the climate anomalies that occurred over Southern Africa (SA) and East Africa, south of the equator (EASE), during the major El Niño event of...

Study region Transboundary aquifers (TBAs) of Africa. Study focus Review of work on TBAs in Africa, including an overview of assessments and management efforts that have taken place over the last half century. New hydrological insights Seventy-two TBAs have been mapped in Africa. They underlie 40% of the continent, where 33% of the population liv...

This paper explores the agricultural groundwater management system of Mogwadi (Dendron), Limpopo, South Africa – an area associated with intensive use of hard rock aquifers for irrigation – and the potential contribution of seasonal forecasts. These relatively shallow aquifers are often perceived as ‘self-regulating’, yet climate variability and in...

Cooperative management of transboundary river basins is widely recognized as important. Emphasis on joint management of shared aquifers has also grown in recent years. Perhaps surprisingly, despite abundant focus on transboundary surface water and growing focus on shared groundwater, there is scant focus on their intersection. To address this knowl...

Implementation of MAR can strengthen resilience in Africa, particularly in the semi-arid context in which Ramotswa is located. Climatic variability results in inadequate water supply and contributes to food insecurity in Africa particularly in rural dry land areas. Introducing surface runoff and wastewater into subsurface aquifers when it is availa...

El Niño events have major impacts on Africa. Little research on effects on groundwater resources.  Groundwater is an essential resource in Africa providing most of the drinking water and a vital resource for irrigation development.  Groundwater recharge may be very sensitive to climate extremes (e.g. Taylor et al., 2012).  This study aims to res...

Groundwater has become a central element of global water and food security, supplying around 40% of all irrigated areas globally. Groundwater extraction is greatest in the three largest staple-food producers, China, India and the US, but also rapidly increases in Sub-Saharan Africa. Agriculture groundwater use is particularly important in regions w...

Environmental flows (EF) are an important component of Goal 6 (the ‘water goal’) of the Sustainable Development Goals (SDGs). Yet, many countries still do not have well-defined criteria on how to define EF. In this study, we bring together the International Water Management Institute’s (IWMI’s) expertise and previous research in this area to develo...

Denmark is making continuous efforts to attain sustainable groundwater management. With groundwater constituting virtually the only resource for all water uses, groundwater management was addressed early on and has progressed over the last century. This article gives an overview of the advances, along with past and present challenges in securing su...

Groundwater is an important resource for multiple uses in South Africa. Hence, setting limits to its sustainable abstraction while assuring basic human needs is required. Due to prevalent data scarcity related to groundwater replenishment, which is the traditional basis for estimating groundwater availability, the present article presents a novel m...

Around 27% of aquifers in Tunisia are being overexploited. Groundwater extractions is mainly for the irrigation sector, where more than 40% of the water used for irrigation comes from GW sources. The objective of this study is to critically review and analyze GW management instruments adopted in Tunisia during the last four decades. Evaluation of c...

Groundwater provides an important buffer to climate variability in Africa. Yet, groundwater irrigation contributes only a relatively small share of cultivated land, approximately 1% (about 2 × 106 hectares) as compared to 14% in Asia. While groundwater is over-exploited for irrigation in many parts in Asia, previous assessments indicate an underuti...

Temperatures will likely increase by 1-2 degrees by the middle of the century and 3-4 degrees by the end of the century. A likely overall increase in precipitation and larger seasonal variation might lead to water related stress during a prolonged dry season and flood risks during the wet season. The overall climate related effect on water resource...

Groundwater provides an important buffer to climate variability in Africa. Yet groundwater irrigation contributes only a relatively little share of cultivated land, approximately 1% (about 2 million hectares) as compared to 14% in Asia. While groundwater is over-exploited for irrigation in many parts in Asia, previous assessments indicate an under-...

A simple but comprehensive framework for analysing the potential for and constraints to groundwater development for irrigated agriculture in sub-Saharan Africa is proposed. The framework, based on food value chain principles, is applied to the sub-Saharan context and a specific catchment in Tanzania, the Usangu plains, where groundwater has been pr...

Recent attention to transboundary aquifers (TBAs) in Africa reflects the growing importance of these resources for development in the continent. However, relatively little research on these aquifers and their best management strategies has been published. This report recapitulates progress on mapping and management frameworks for TBAs in Africa. Th...

The government of Ethiopia has invested in groundwater development for smallholder irrigation in the Raya Valley and Kobo Valley, north-eastern Ethiopia, where the hydrogeological potential is large but not fully developed. A cost-benefit analysis shows that investment in deep groundwater irrigation development is viable at a 9.5% discount rate in...

Groundwater irrigation for smallholder farmers in Sub-Saharan Africa is growing in extent and importance. This growth is primarily driven spontaneously by the farmers themselves, spurred by improved access to low-cost technologies for pumps and drilling services as well as market opportunities for produce. This paper presents a review of the curren...

The abundance of groundwater resources of Sub-Saharan Africa is generally well recognized, but quantitative estimates of their potential for irrigation development are lacking. This study derives estimates using a simple and generic water balance approach and data from secondary sources for 13 countries. Even with conservative assumptions and accou...

Groundwater drought denotes the condition and hazard during a prolonged meteorological drought when groundwater resources decline and become unavailable or inaccessible for human use. Groundwater drought risk refers to the combined physical risk and human vulnera-bility associated with diminished groundwater availability and access during drought....

The integrated hydrological model MIKE SHE was applied to a part of the North China Plain to examine the dynamics of the hydrological system and to assess water management options to restore depleted groundwater resources. The model simulates the spatio-temporal distribution of recharge to and the associated dynamics of the alluvial aquifers based...

On December 26, 2004, the earthquake off the southern coast of Sumatra in the Indian Ocean generated far-reaching tsunami waves, resulting in severe disruption of the coastal aquifers in many countries of the region. The objective of this study was to examine the impact of the tsunami on groundwater in coastal areas. Field investigations on the eas...

Rural coastal aquifers are undergoing rapid changes due to increasing population, high water demand with expanding agricultural and domestic uses, and seawater intrusion due to unmanaged water pumping. The combined impact of these activities is the deterioration of groundwater quality, public health concerns, and unsustainable water demands. The Ka...