Canadian scientists have mapped vast reserves of water stored within the earth’s crust. New calculations estimate that the crust harbors about 43.9 million cubic kilometers of water, a volume that surpasses every glacier on the planet combined. The researchers published their findings in the journal Geophysical Research Letters, offering a revised view of where Earth keeps its liquid treasure and how much might be accessible under various conditions.
To put those numbers in perspective, Antarctica contains roughly 27 million cubic kilometers of water in its ice sheets, while Greenland holds about 3 million cubic kilometers of frozen water. The remaining glaciers around the world contribute another 158 thousand cubic kilometers, a fraction of the total global ice. The study emphasizes that the majority of this water is trapped in solid form as ice, but it also highlights substantial stores that reside as groundwater within rock layers beneath the surface. A long-standing estimate placed groundwater resources in the upper crust at about 22.6 million cubic kilometers. The new analysis doubles that prior figure by examining a broader range of rock types and their porosity, from low-porosity crystalline rocks such as granite to more porous sedimentary rocks that can hold larger volumes of water over time, thereby expanding the potential size of accessible groundwater resources.
Shallow groundwater aquifers, which are typically fresh, support drinking water supplies and agricultural irrigation in many regions. In contrast, deep groundwater tends to be saline and moves slowly, if at all, toward the surface. This makes deep aquifers less readily replenished and more challenging to utilize for everyday needs, a nuance the researchers note as they map the larger water picture beneath the continents and oceans. The ongoing global hydrological cycle constantly shifts water between surface, soil, and subsurface reservoirs, but substantial questions remain about how groundwater systems respond to climate change, geological activity, and human extraction.
The world’s oceans continue to represent the single largest reservoir of liquid water, containing roughly 1.3 billion cubic kilometers. They dominate the planetary balance, driving climate, weather patterns, and life-support systems across every ecosystem. The study draws attention to the interplay between surface water and subterranean stores, urging a more integrated understanding of water security that includes deep groundwater alongside surface lakes, rivers, and ice masses.
Researchers also address the broader implications for resource management and environmental stewardship. Groundwater depletion has been a growing concern in many regions, with impacts on agriculture, freshwater availability, and ecosystem health. While the deep crustal stores are immense, their accessibility depends on rock porosity, permeability, and the energy required to extract water from deep formations. The new findings encourage policymakers, engineers, and scientists to re-evaluate groundwater monitoring programs, recharge strategies, and sustainable extraction practices to ensure a resilient water future for both Canada and the United States.
Cited data and models from this line of research contribute to a clearer picture of how the planet holds its water between the surface and the solid Earth. By expanding the known range of groundwater reserves and clarifying where they exist, the study helps stakeholders assess potential risks and opportunities for water supply, climate adaptation, and long-term resource planning across North America. The revised estimates invite further study and cross-disciplinary collaboration to translate deep geologic insights into practical, responsible water management strategies for communities, industries, and natural systems alike. Attribution: Geophysical Research Letters, with ongoing research informing dialogue on groundwater availability and planetary water balance.