Explore Maui's Water Quality

​Download our Coastal Water Quality Report 2016 | 2023

DOWNLOAD REPORT

This report summarizes coastal water quality findings at sites from Honolua Bay to Pāpalaua and from Mā'alaea to 'Āhihi-Kīna'u Natural Area Reserve, revealing high levels of turbidity and nitrates in many areas along the coast and includes recommendations for reducing these pollutant levels to help communities focus their efforts in areas that need it most.

​Since 2016, Hui O Ka Wai Ola has collected and analyzed over 4,300 water quality samples from 52 sites and has found that these coastal waters are often degraded by land-based pollutants, including sediments, fertilizers, and wastewater. The report also highlights findings at new sites added in West Maui following the Lāhainā fire, and also on Lāna'i. Keālia Pond continues to be an area where pollutant levels are low, likely due to the wetlands’ ability to filter and absorb pollutants before they reach the ocean.

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Key Findings | Turbidity

​Turbidity levels always exceed DOH standards. Turbidity is a measure of water clarity. High turbidity levels in leeward Maui are associated with coastal erosion and rains that carry sediments from streams and gulches to coastal waters. Turbidity levels can also be elevated when previously deposited sediments are disturbed and recirculate (aka resuspension). Elevated turbidity associated with rainfall often prompts brown water advisories, and consistently high turbidity is damaging to corals.

The DOH standard for turbidity is 0.2 NTU. Our data show levels of 6.0 NTU or higher at five West Maui sites.

Turbidity in West Maui

• Far exceeds DOH standards from Honolua to Pāpalaua.
• Increasing over time in northern West Maui, as coastal erosion worsens with sea level rise.
• Pōhaku has highest level of turbidity driven solely by coastal erosion in West Maui.
• Declined at Camp Olowalu.
• Increased at Ukumehame.

Turbidity in South Maui

• Moderately high from Mā'alaea Harbor to South Kīhei.
• Much lower from Wailea to Mākena, yet still exceed DOH standards.
• Highest at Waipu'ilani Park, where levels are 2x higher than other South Maui sites.
• Brown water caused by coastal erosion and storms is a concern from Mā'alaea to North Kīhei.

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Key Findings | Nitrates

​Nitrate levels often exceed DOH standards. Elevated nitrate levels at leeward Maui sites are associated with fertilizers and wastewater that seep into
groundwater systems and emerge through springs on the ocean floor. Elevated nitrate levels can cause algae
blooms and smother, weaken, and kill coral reefs.

Nitrates in West Maui

• Far exceed DOH standards at Kapalua, Ka'ōpala, Nāpili, Pōhaku, and Hanaka'ō'ō (Canoe Beach), though levels at Kapalua have dropped significantly in the last two years.

Nitrates in South Maui

• High from Mā'alaea Harbor to South Kīhei.
• Highest at Cove Park, where levels are more than 2x higher than any other leeward Maui site.
• Levels from Mā'alaea to North Kīhei are second only to Cove Park.
• Consistently low at Keālia Pond.

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Great advice from the Hawai'i Department of Health (DOH)
IF THE WATER IS BROWN STAY OUT! Storm water runoff starts far up in the watershed. This water can pick up all kinds of contaminants as it travels towards the ocean. Please heed the advice from the DOH and don't head to the beach to swim, snorkel, or surf when storm water has been running into the ocean. Even if the DOH hasn't issued a brown water advisory, IF THE WATER IS BROWN STAY OUT!
​​Visit the Department of Health's Clean Water Branch site for DOH Water Quality Advisories and  DOH Water Quality Data.

Photos: Header, Why we care - The Nature Conservancy (Alana Yurkanin)