Groundwater

"The dynamic thread that ties the environment together is water. Water rises from the sea, travels across the sky, falls on the mountains and rushes through the land back to the sea. The land, sea, and sky act as carriers for this valuable resource and make possible the settlement of man."

—The Spirit of Kaloko-Honokōhau

 

Rain clouds gather at the top of Hualālai volcano.

NPS Photo

At Kaloko-Honokōhau National Historical Park, life is shaped by water both above and below the surface. While the dry Kona coast may seem an unlikely place for wetlands and fishponds, these thriving natural habitats originate beneath the ground from the islandʻs complex groundwater ecosystem.

 

Schematic cross sections showing possible groundwater structures.

Scientific measurement and monitoring of groundwater resources is a key focus of Kaloko-Honokōhau National Historical Park.

USGS (2021)

The Unique Groundwater Ecosystem of Kona

Kona's groundwater system is uniquely shaped by its volcanic geology.

The rain falling on the slopes of Hualālai doesn’t just nourish the uplands of Kona. It also travels through the porous lava rock, flowing underground on a journey all the way to the coast.

Beneath the park, this freshwater floats on top of denser saltwater, creating a “lens” of brackish water. This mixing zone creates brackish ecosystems like ʻAimakapā and Kaloko fishponds, as well as over 180 smaller anchialine pools within the park. These rare brackish-water ponds exist only in volcanic island settings like Hawaiʻi.

 

Ecosystem Balance

Kaloko-Honokōhau’s ecosystems depend on this constant flow of groundwater. Anchialine pools host native and endangered species like the orangeblack Hawaiian damselfly (Megalagrion xanthomelas) and the tiny red shrimp known as ʻōpaeʻula (Halocaridina rubra). These species rely on stable salinity and temperature conditions, which are sensitive to changes in freshwater flow.

Similarly, the park’s fishponds depend on cool, clean groundwater to maintain water quality and support native mullet and other aquatic life. Wetlands provide nesting and feeding habitat for native Hawaiian waterbirds, such as the endangered Hawaiian coot (ʻAlae keʻokeʻo).

When groundwater levels drop or become more saline, these habitats suffer. Rising sea levels, declining rainfall, and increased demand for water from development in the surrounding area all threaten to disrupt delicate balance of this system

 

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  Anchialine Pools

  Learn more about these unique aquatic ecosystems.

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  Invertebrates

  Many of our parkʻs invertebrate species depend on a balanced and healthy groundwater system.

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  Fishponds at Kaloko-Honokōhau

  Fishponds have played a major role in Kaloko-Honokōhauʻs history for centuries.

 

Science & Measurement

To understand and protect this vital resource, the U.S. Geological Survey and National Park Service monitor water levels, salinity, and temperature at several wells and sites throughout the park.

This data helps scientists track seasonal patterns, long-term changes, and how the system responds to pressures like pumping or climate shifts. These monitoring efforts are key to ensuring that future decisions are guided by science and stewardship.

 

Groundwater & Conservation

Groundwater is out of sight, but it is vitally important. Its health affects everything from native species and traditional Hawaiian fishponds to coral reefs offshore. By understanding how groundwater flows, and how it connects ecosystems across the park, we can better protect this hidden source of life.

Kaloko-Honokōhau is more than a historic site. It is a living landscape, shaped by water moving through volcanic rock. Preserving this flow ensures that the spirit of Kaloko-Honokōhau continues for generations to come.

 

Ola I Ka Wai

Ola I Ka Wai — translated to English as "life is in the water," or "water is life."