Ola i ka Wai, Freshwater Aquatic Life

Ola i ka wai a ka ‘ōpua, “There is life in the water from the clouds.” Fresh water originates from clouds formed over the ocean that bring rain to the mountain forests. Healthy forests channel water underground to fill aquifers. A raindrop can travel underground for 25 years or more before returning to the ocean. Water eventually returns to the ocean from springs, streams, and rivers full of dissolved minerals and organic nutrients.

Freshwater is the foundation of life on the land. Fresh water is also important to the health of the ocean. Fish and algae depend on brackish water habitats where nutrient rich fresh water mixes with salt water. We have a healthy ecosystem when we can see thriving freshwater habitats.

Fish like the ‘O‘opu Hi‘ukole (Lentipes concolor) thrive in clean flowing water. They travel upstream from the ocean to feed and lay eggs. Freshwater shrimp, ‘ōpae kala‘ole (Atyoida bisulcata), used to be abundant too. Their many legs allow them to climb waterfalls and reach the highest streams in the Hawaiian Islands. Freshwater snails like hīhīwai (Neritina granosa) also migrate upstream from the ocean. They can be found as high as 1200 feet (365 m).

Several species of endemic dragonflies and damselflies, called pinao in Hawaiian, can be seen flying near water. The Hawaiian giant dragonfly (Anax strenuus) is the largest dragonfly in the United States, with a wingspan of 6 inches (15 cm).

Healthy fresh water streams are endangered in the Islands. Much of the water that used flow continuously in streams has been diverted to irrigate plantation land. The tunnels dug to divert water also damage the underground hydrological structures. The underground dikes of impermeable rock that channel water down into the aquifer are penetrated by the diversion tunnels. The water that would normally be slowly released from the mountains to feed streams during the dry season is bled out of the mountains by the tunnels. Irrigation tunnel waters are sent to reservoirs on the dry leeward side of the islands, leaving natural windward streams dry.

Another threat to the health of streams is when they are confined to concrete channels, where they pass through developed urban areas. Natural stream vegetation like makaloa provides habitat for fresh water animals, and captures silt flowing downstream. Trees along the streams keep the water temperature cool for fish. The concrete channels do not allow vegetation to grow alongside the streams and the water becomes overheated. Concrete channels cut off the uplands from the ocean.