There are few things on Hawaii that are more valuable than fresh water. This is not because the island is dry. It gets rained on a whole lot. The trouble is the nature of the volcanic rocks that it is made of. These rocks are exceptionally porous and allow water to run right through them. This makes water collection challenging and the price of water rather high. Now geologists are reporting the discovery of a huge fresh water river that is running through volcanic rocks beneath Hawaii's salt water lagoon.
Fresh water below
Hawaii is like an iceberg. Only a tiny fraction of it is sticking up out of the water. The rest of the island is submerged. This new work used marine electrical imaging to study the geology of these submerged sections of the island and this analysis revealed that, below the salty waves, fresh water is flowing through volcanic aquifers.
These aquifers have porous rocks filled with salt water above and below them but appear to be immediately surrounded by layers of volcanic rock that are less permeable. These less permeable layers run for miles inland and allow rain water that has soaked into the island to flow out to sea in underground rivers. Crucially, tapping into these rivers just before they mix with ocean water ought to have precious little ecological impact since the water is not being used by endangered island species by the time it gets that far below ground anyway.
This finding alone is important since it looks like there is a major source of drinking water that Hawaiians can now tap in to. However, what is truly important here is that this mechanism looks like it ought to be found on most islands that have a volcanic history. If this is ultimately proved to be true, then the water challenges faced by islanders all over the world might soon become a lot less challenging. You can read more in The New York Times article that I wrote on this here.