Exploring the untapped potential of managed aquifer recharge

• As the world spotlights the importance of groundwater throughout 2022, a promising approach for ensuring sustainable use and management of this precious resource is gaining steam

By Karen G. Villholth and Russell Sticklor

It is underneath our feet and invisible, everywhere and nowhere at once. But groundwater — a crucial freshwater source for humanity since time immemorial — today remains little understood and under-valued.

Because there are inherent challenges in managing an unseen resource, groundwater generally remains poorly mapped and inadequately governed. Meanwhile, its extraction is often encouraged through subsidies, providing conditions for a perfect storm.

Across much of the world today, the resource is being pumped at an alarming and unsustainable pace — continuing a trend that has indeed been underway for decades — to facilitate food production for a growing population and cope with climate change-induced shifts in precipitation patterns and surface water availability.

At the same time, if managed intelligently and sustainably, groundwater has significant untapped potential to serve as a potent source of climate resilience in the uncertain years and decades that lay ahead. Indeed, as rising global temperatures reduce the effectiveness of water storage in surface reservoirs, managing water storage in aquifers is emerging as an appealing alternative, as groundwater is naturally insulated from surface evaporation and therefore protected — to some degree, at least — from climate change impacts.

Making the invisible visible

The concept of purposefully storing water underground, known as “managed aquifer recharge” (MAR), has been around for more than a century, but it has been gaining renewed attention and newfound prominence since the late 20th century as our climate crisis has intensified across the world. In a new book seeking to further elevate the visibility of groundwater as a vital piece for solving the 21st’s century’s increasingly complicated climate puzzle, “Managing aquifer recharge: A showcase for resilience and sustainability”, edited by IWMI’s Karen Villholth alongside Peter Dillon, Andrew Ross, and Yan Zheng, places groundwater front and centre.

Released just in time for the “Year of Groundwater,” which throughout 2022 is raising awareness about groundwater and the aquifers that house this vital resource, the book makes a compelling case that MAR technology is ripe for outscaling. A joint project of UNESCO’s Intergovernmental Hydrological Programme (UNESCO-IHP), the International Association of Hydrogeologists’ Commission on Managing Aquifer Recharge, and the IWMI-led Groundwater Solutions Initiative for Policy and Practice (GRIPP), the book features nearly 30 in-depth case studies from across the world.

“Thousands of examples of managing aquifer recharge can be found, but few are documented in a way to give a clear picture of the sustainability and economics of such supplies,” says Villholth. “This book, which illustrates that the benefit-cost ratio generally is more than two for these solutions compared to more traditional alternatives, was produced as a significant product of a chain of activities that goes back 20 years,” coinciding with the establishment of the International Association of Hydrogeologists’ Commission on Managing Aquifer Recharge.

The book’s wealth of case studies, as reported by local implementers and managers, spans the transboundary to local levels and provides important contexts related to the types of economic and environmental conditions and level of technical capacity needed to successfully and sustainably implement MAR. The book also details how communities utilising the technology fared in terms of their water security and resilience both before and after MAR, providing valuable before-and-after comparisons.

Such real-world examples should encourage greater uptake of MAR in the years ahead, as its current level of deployment only scratches the surface in terms of the urgent needs for better water storage management and taking advantage of the technology’s full potential. After all, MAR cannot only be utilised to strengthen water security in semi-arid and arid regions, it can also be implemented in cities, where healthier groundwater stocks could help reduce the prevalence of land subsidence, aquifer compaction, and saltwater intrusion — all frequent byproducts of growing water needs and groundwater overuse, especially in coastal areas.

The frontier for MAR today clearly lies in the safe reuse of reclaimed water through sub-surface solutions, which typically have much smaller land footprints than surface water storage and hence are well-suited for urban and peri-urban contexts, provided proper nature-based solutions are incorporated to protect groundwater from contamination. Israel, for example, has the world’s largest MAR scheme, which is dedicated to recycling more than 75% of its reclaimed water and satisfies about 50% of its total water supply for irrigated agriculture. This level of recycling is around four times higher than any other country in the world.

Despite the technology’s significant promise and potential to be applied at scale, it is important to note that MAR is not a unilateral solution. Indeed, there are local contexts in which environmental and geologic conditions make the technology less ideal from a water storage standpoint, and other instances in which successful MAR implementation has proven challenging from a technological and socioeconomic perspective. “MAR increasingly needs to be seen as an integrated solution, requiring conjunctive management of multiple water resources and storages, land use, and environmental and socioeconomic imperatives — and not just a simple groundwater storage solution,” notes Villholth.

Nevertheless, drawing upon a vast body of research and evidence, the book does illustrate in compelling fashion that, generally speaking, MAR technology is not only proven but also available to implement at scale. Applicable in a broad range of biophysical contexts, it can help provide water-stressed communities with a reliable freshwater resource available to be tapped throughout the seasons to ensure a steady water supply at the surface for crops, livestock, industry, drinking, and other household needs, or as a strategic water resource in times of emergency. To ensure the successful and sustainable application of MAR technology, the book emphasises that gaining public buy-in is essential, as are smart groundwater governance, cost recovery, and routine groundwater monitoring.

Heading underground to help ensure a climate-resilient future

While the renewed attention being afforded to MAR is long overdue, it is well-deserved because of the mostly underappreciated yet vitally important solutions the technology offers. This interest may, as a spillover effect, increase appreciation of (and investments in) groundwater solutions and management. Refinements in satellite mapping technology coupled with improved on-the-ground and in-the-ground monitoring capacity are shedding more light than ever before on our aquifers — and just in time too, as climate change tightens its grip on communities around the world.

Going forward, as we continue to deepen our understanding of the locations and capacity of the planet’s aquifers, groundwater-based water security solutions such as MAR indeed may be more attainable than ever.

This upcoming World Water Day and throughout the Year of Groundwater, IWMI and our partners look forward to advancing the regional and global conversations about MAR and the sustainable management of groundwater more broadly. We invite you to join us — virtually or otherwise — for a series of planned groundwater-related events and engagements in the months ahead, including sessions at next month’s 9th World Water Forum in Dakar, Senegal and the 11th International Symposium on Managed Aquifer Recharge (ISMAR11) in California in April.

Citation:

Zheng, Y.; Ross, A.; Villholth, K.G.; Dillon, P. (Eds.) 2021. Managing aquifer recharge: A showcase for resilience and sustainability. Paris, France: United Nations Educational, Scientific and Cultural Organization (UNESCO). 379p. ISBN: 978-92-3-100488-9

(Karen G. Villholth is Principal Researcher and Russell Sticklor is Senior Communications Coordinator at IWMI.)