Integrating natural and built water storage infrastructure so communities are provided with a reliable service is the best way to boost resilience in the face of increasing demand and climate change.
With much of the world’s surface water overexploited, attention is turning to the groundwater that makes up 99% of liquid freshwater stock. Though we all benefit from groundwater directly or indirectly, it remains largely untapped in sub-Saharan Africa and other regions of the Global South where there is a serious and deepening ‘water storage gap’ between supply and demand. This is especially worrying amid a climate crisis when an even larger water storage capacity is needed to manage the increase in hydrological variability (floods and droughts). Built storage such as dams and water tanks complement natural storage in aquifers and water bodies such as lakes or wetlands, but a practical agenda for integrating and managing water storage sustainably for the future is absent.
A joint paper from the International Water Management Institute (IWMI) and the Global Water Partnership (GWP), supported by WLE, advocates a new agenda on water storage. Rather than simply thinking in terms of how much water can be stored behind dams, for example, integrated storage seeks to harness the potential of both built and natural storage infrastructure, as units of a co-dependent system. This shift in focus aims to provide a reliable and high-quality service where it is needed by communities and the environment and considers how best to achieve this through a mix of centralized and distributed water storage solutions.
A key innovation is the concept of Underground Transfer of Floods for Irrigation (UTFI) promoted by the Groundwater Solutions Initiative for Policy and Practice (GRIPP), led by IWMI. The UTFI approach involves recharging depleted aquifers with seasonal high flows to provide additional groundwater for irrigated agriculture during dry periods, while also mitigating floods. A global spatial analysis has identified areas of high suitability for implementation, and a three-year pilot study on the Ramganga river in India found that UTFI has the potential to significantly enhance groundwater storage and control flooding if replicated over larger scales.
For such innovations to be implemented, assessments of groundwater resources have to be followed by capacity building and training, as well as policy development. This was the approach taken by IWMI in Laos, where a first national hydrogeological map was prepared and the local team provided input to a National Groundwater Action Plan, since devolved into plans for subnational regions.
On an even larger scale, IWMI created a 3D conceptual model of the transboundary Ramotswa Aquifer in the Limpopo Basin in southern Africa, the data collection for which uncovered crucial information about the structure of the aquifer and potential drilling locations, and enabled assessment of management scenarios, for instance through UTFI. This led to the setting up of the Ramotswa Information Management System, a joint strategic action plan between the countries that share the groundwater resource – Botswana, Mozambique, South Africa and Zimbabwe – and the formation of the LIMCOM Groundwater Committee. The project reached out to farmers on agricultural water management, adapting tools such as moisture probes and nutrient measurements to improve yields while reducing inputs. In 2020, IWMI piloted a transboundary groundwater monitoring system in the Tuli Karoo Aquifer area (a sub-basin) to gauge groundwater levels, with plans to expand to 58 more locations.
The primary challenge may lie in rethinking water storage as an integrated service for water users. To guide future investment, policy makers, financiers and planners require a framework to pragmatically develop and manage different, and often co-dependent, storage components. This requires a good understanding of the current water storage capabilities (green and grey infrastructure) and future needs in the light of climate change and other changes that might reduce water storage (e.g., reservoir sedimentation). Ensuring that the individual parts of natural and built water storage infrastructure work – and work together – demands engagement with upstream and downstream priorities as well as business stakeholders, and a robust system of governance.
A number of high-profile partnerships aim to improve groundwater management. GWP and IWMI have both launched calls to action on adaptation to climate change. The GRIPP partnership will strengthen, expand and connect current initiatives on groundwater, supporting the Groundwater Governance project funded by the Global Environment Facility. The success of these initiatives depends strongly on filling data and knowledge gaps on groundwater resources and piloting innovations to see what combinations of natural and built infrastructure can best deliver reliable water supplies to communities now and under future conditions.