Findings

Download our Coastal Water Quality Report 2016 | 2025

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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 5,500 water quality samples and has found that these coastal waters are often degraded by land-based pollutants, including sediments, fertilizers, and wastewater. The report also highlights a new finding—salinity is increasing along leeward Maui. 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.

Summary of 2016-2025 Findings

Turbidity levels always 
exceed DOH standards.

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Turbidity in West Maui

• Far exceeds DOH standards from Honolua to Pāpalaua.
• Pōhaku has highest level of turbidity driven solely by coastal erosion in West Maui, and it’s still increasing.
• Increased at Camp Olowalu and Ukumehame.
• Decreased at Kahana Village and Kā`anapali Shores (Kahana & Honokōwai stream mouths).

Turbidity in South Maui

• Far exceeds DOH standards from Mā`alaea Harbor to South Kīhei.
• The most dramatic and persistent turbidity increases are in North Kīhei.
• Much lower from Wailea to Mākena, yet still exceed DOH standards.
• Highest turbidity at Waipu`ilani Park, where levels are 2x higher than most other South Maui sites.
• Brown water caused by coastal erosion and storms is a rising concern from Mā`alaea to North Kīhei. 

General

• ​​Turbidity is a measure of water murkiness. High turbidity in leeward Maui is associated with coastal erosion and rains that carry sediments from streams and gulches to coastal waters, often prompting brown water advisories. Turbidity levels also elevate when previously deposited sediments are disturbed and recirculated. Consistently high turbidity is damaging to coral health.

Nitrate levels often
​exceed DOH standards.

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Nitrates in West Maui

• Far exceed DOH standards at Kapalua, Kaʻōpala, Pōhaku, and Hanakaʻōʻō (Canoe Beach), though levels at Kapalua have dropped significantly in 2020 and remain lower than prior due to sewer repairs.
• Lowest coastal stretch from Olowalu to the Pali.

Nitrates in South Maui

• Far exceeds DOH standards from Māʻalaea Harbor to South Kīhei.
• Highest at Cove Park, where levels are more than 2x higher than any other leeward Maui site.
• Levels from Māʻalaea to North Kīhei are second only to Cove Park.
• Generally low at Keālia Pond and south of Wailea. 

General

• ​Elevated nitrate levels in leeward Maui 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 corals. 

Salinity is increasing along
​leeward Maui due to extreme drought.

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Salinity in leeward Maui

• ​Salinity shows a clear gradient towards saltier water over the years, particularly from 2022 to 2025, while no evident gradient appears for temperature over time. This suggests warming seas are not evident, so are not the driver for increased coastal salinity.
• According to the Hawaiʻi Annual Climate Report, 2025 was the driest year on record for Maui since tracking began in 1920 and was the third warmest year since 1990. 
  

Photos: Header - Kelly James, Turbidity - Kelly James, Nitrates - Sarah Sugidono, Salinity - Kelly James

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.