The fundamental human right to water and sustainable supplies of water, particularly groundwater, are inextricably linked. To effectively exercise that right, one must understand the sustainability of water supplies and how to enhance that sustainability.

The focus on accessing groundwater is critical because, as reported by UN Water in its 2022 report, “Groundwater, Making the Invisible Visible,” groundwater accounts for 99 percent of all liquid fresh water on Earth. Importantly, the report notes groundwater dependence is expected to rise as surface water availability becomes increasingly limited due to climate change.

The World Bank’s study “The Hidden Wealth of Nations: The Economics of Groundwater in Times of Climate Change” conveys that in the Middle East and South Asia, where irrigation has been a cornerstone of agriculture, up to 55 percent of irrigated lands use groundwater. In Sub-Saharan Africa, around 44 percent of the population relies on groundwater for drinking water.

In the United States, according to the U.S. Geologic Survey’s National Water-Quality Assessment Project, more than 155 million people rely on groundwater for drinking water. Groundwater provides about 40 percent of California’s total annual water supply and serves as a critical buffer against drought and climate change.

Globally, groundwater supplies are diminishing. NASA’s Gravity Recovery and Climate Experiment has reported that 21 of the world’s 37 major aquifers exceeded sustainability tipping points. California’s Central Valley is one of the most over stressed, along with such aquifers as the Arabian aquifer system and the Indus basin in Northwest India and Pakistan.

While supplies dwindle, demand for water is and will be at critical levels. UNESCO reports that the global urban population facing water scarcity is projected to double from 930 million in 2016 to 1.7–2.4 billion people in 2050. UNICEF reports that as of 2022 almost 1 billion children are exposed to high or extremely high water stress. The Food and Agriculture Organization estimates agriculture will need to produce almost 50 percent more food, and this will require more water.

Replenishing groundwater requires a systems approach, including nature-based solutions; storage; non-conventional water uses; and governance.

Nature-based solutions to groundwater replenishment encompass conserving and restoring natural and working lands, rotating non-marketable crops in the fallow season between main crops, protecting watersheds, restoring wetlands, and creating natural replenishment sinks.

Increasing both the built surface storage of water and natural storage of groundwater takes some of the pressure off depleted aquifers. The World Bank in its report “What the Future Has in Store: A New Paradigm for Water Storage” explains how the city of Windhoek improved its water security by raising new built storage infrastructure, investing in direct potable reuse, implementing water demand management and conservation measures, and exploiting the strategic potential of the Windhoek Aquifer as a “water bank.”

Utilizing advances in wastewater treatment, California‘s Orange County Groundwater Replenishment System pumps purified wastewater to recharge basins where it naturally percolates into the Orange County Groundwater Basin and becomes part of the drinking water supply for 2.5 million people.

The California Sustainable Groundwater Management Act empowers local water districts to develop and implement plans to come into water balance. Other regions in the United States and developing countries might also take a hard look at SGMA for its replicability.

We need to move quickly to set in place the leadership, institutions, programs, funding, and skilled workforce needed to sustainably manage groundwater and enable people to fully realize their right to water. While we understand a good deal about groundwater use and the very broad parameters of groundwater supply, we do not know with precision how much water remains in the aquifers. That is a very risky position to be in.