Water flowing from the mountainside is called a kahena wai or a kahawai, a watercourse or stream. The spot from which water begins to flow is the po‘owai, it is the source of the water. The bank on either side is called kapana wai or kaʻe no ka wai or ikana wai, and the water amid-stream is called the holomoku or ihiakala.
Where the water of a slow moving stream, a muliwai, meets the sea is called a nuku muliwai, and the mouth of a shallow rushing stream, a kahawai, is called a nuku kahawai.
Water flowing over a cliff is called a wailele, waterfall. If the water divides in falling (kahe makawalu), it is called a waihi, cascade; if the water sprays (kulu makaliʻi) in falling over a cliff it is called hunawailele or wai puhia or wai ehu. (Kamakau; Maly)
There are several types of muliwai (muli, the remains; and wai, water – estuarine systems) in Hawai‘i. The two most common are at stream mouths or where surface flow is absent but with significant groundwater discharge.
Whether they’re called a stream mouth, bay, harbor, inlet or lagoon, muliwai are the transition zones between and connecting two major land/sea habitats – the mauka forest and the ocean.
They are among the most productive ecosystems on Earth. The muliwai is an essential nursery habitat for certain fish species in their larval and juvenile growth stages.
The muliwai is the brackish area between the stream (land) and the sea and hosts many different species of fish, birds, plants and other biodiversity and helps to filter the stream before it empties into the ocean; and, is an important area for certain fish to gather and grow.
When the ocean was rough for the fishing canoes to go out, the families would catch fish like awa, ʻaua and ʻāholehole. (Maly) “The families fished for ʻoʻopu nākea and ʻakua and ʻōpae in the streams and muliwai; in the muliwai had plenty ʻoʻopu, the head big like this (the size of a fist.)” “Young awa, ʻamaʻama were abundant.” (Chun, Davis; Maly)
Some familiar examples of estuary ecosystems include Kāneʻohe Bay, Oʻahu; Keālia Ponds, Maui; Waipiʻo Bay, Hawaiʻi and Wainiha Bay, Kauai.
Threats to muliwai/estuaries are real and diverse, including development (draining, filling, damming and dredging,) fishing, recreational use, pollutants and excess nutrients, invasive species, etc.
While I was at DLNR, the issue of muliwai/estuary protection was a growing concern. As the Hawaiʻi representative to the Coastal States Organization, we had ongoing discussions with the NOAA and others on a national level.
Locally, through the inspiration and actions by Bob Nishimoto at DLNR’s Division of Aquatic Resources, there were discussions on establishing a Center for Stream and Estuarine Research, while a partner, the Hawaii Institute of Marine Biology, would focus on marine issues.
On a national level, NOAA established the National Estuarine Research Reserve System (NERR,) a network of 29 areas representing different biogeographic regions of the United States, to protect estuaries and provide long-term research, water-quality monitoring, education and coastal stewardship.
Each research reserve is made up of a core area and a buffer area. The core area around the estuary is managed for long-term research, water-quality monitoring, education and coastal stewardship.
The reserves are run cooperatively with governmental and local partners. The goal of the reserve system is to support local knowledge and management decisions pertaining to the coastal resources of the region.
Site Selection committee members picked Heʻeia Estuary in Kāneʻohe Bay to be Hawaiʻi’s first NERR site (Hilo Bay was also considered, but, apparently, the decision was to move forward with only one, at this time.)
Designated as the 29th site in the National Estuarine Research Reserve System in 2017, Heʻeia NERR represents a partnership among federal, state, and community-based entities, all committed to a vision of resilient estuaries and coastal watersheds where human and natural communities thrive.
He‘eia National Estuarine Research Reserve encompasses 1,385 acres of unique and diverse upland, wetland, stream, estuarine, coastal, and marine habitats within the He‘eia ahupua‘a.
It encompasses He‘eia State Park to the north, He‘eia Fishpond in the center, the wetlands of Hoi to the west and south, Moku o Lo‘e (Coconut Island) to the east, and a large expanse of marine waters with patch and fringing reefs.