To better understand how tide change influences water quality, a group of Hui O Ka Wai Ola Team Leaders spent a full day in December 2019 (approximately 12 hours) measuring water quality parameters hourly at Cove Park in South Maui and Hanaka‘ō‘ō Park (Canoe Beach) in West Maui – a deviation from the Hui’s usual practice of monitoring 41 sites once every three weeks only in the morning.
 
During this one day study, as well as with our regular ocean water quality monitoring year-round, we measure nutrient levels. Nutrients, including nitrogen and phosphorus, can indicate pollution from wastewater, run-off from agriculture, landscaping and/or golf courses. Once in the ocean, these nutrients can lead to an overgrowth of algae. Algae, particularly invasive species, quickly out-compete corals for sunlight and overrun large tracts of living reef.
 
Nutrient values can vary a lot over the course of a tide cycle -- low nutrient levels at high tide and higher nutrient levels at low tide. Sites with higher nutrient levels acquire these nutrients via ground water that comes into the ocean as underground "springs.”
 
The fact that there is fresh water coming in from underground springs over the course of a day is shown by the change in salinity readings. This explains the ever-shifting levels that we see from the data we collect once every three weeks at each site.
 
During our one day experiment we took 4 nutrient samples, with the first sample at high tide and the last sample near low tide.  The accompanying chart (Figure 1) shows how salinity decreases as the tide goes out and the fresh water from underground springs comes in, while the nitrate levels increase as the amount of fresh water increases. 
 
Our ongoing Hui O Ka Wai Ola water quality sampling program was designed to catch a variety of tide states so that we can understand not only the average level of nutrients but also the range of nutrient levels each site exhibits. 
 
Another interesting observation is that other parameters vary during the day as well -- temperature rises as the sun comes up and heats the top layer of water and then starts to decrease as the sun goes down or if clouds come over (Figure 2). During our one-day experiment, temperatures varied over 2 degrees centigrade during the course of the day.

As of Monday, May 4, a small group of Hui O Ka Wai Ola staff members are monitoring coastal water quality at all 41 of our leeward Maui sample sites every three weeks. Sampling has been on hold since March 16 due to safety concerns during the COVID-19 pandemic. However, permission was recently granted from Maui County officials for our group to continue this essential work.
 
Working in teams of two, the Hui’s Project Manager and Team Leaders are following strict guidelines to maintain a six-foot distance from each other, wearing face masks and sanitizing while collecting and processing samples.
 
We are grateful to be monitoring at this unprecedented time when island activity is at an all-time low. We hope to learn if the decrease in visitors and changes in behavior may impact coastal water quality.
 
We plan to maintain this monitoring protocol for the next two months and hope to get our amazing volunteers back in the field as soon as it is safe to do so.

Our ocean water quality testing program, Hui O Ka Wai Ola, is made possible through the dedication of more than 35 adult volunteers who monitor water quality at 41 local beaches every three weeks.

And now, we're excited to report a new water quality monitoring partnership with students from Maui Preparatory Academy, reports James Strickland, Project Manager for Hui O Ka Wai Ola. 

Eight middle school students are conducting turbidity sampling in Napili Bay as part of their Project Based Learning program.  Based on student input, they have sectioned off the bay into four 250 foot increments and are sampling each of the four sites at two depths (2 feet and 6 feet).

We're grateful for these students and their dedication to monitoring ocean water quality, as a step toward achieving cleaner ocean water for Maui's coastlines. ​

Members of Hui O Ka Wai Ola took a deep dive into West Maui's water quality data during a free public presentation at Lahainaluna High School on July 30, 2019. You can watch the Akakū recording here!
Photo credit: Dakota Grossman

Click on the Report Photo to access Hui O Ka Wai Ola's Coastal Water Quality Report (2016 to 2018)! This report shares our mission, methods, findings, next steps, and most importantly, our thanks for all the ways the Maui community, donors, and funders have helped bring our partnership this far. We are seeing some compelling findings that will help address sources of pollution and poor water quality along Maui's coastline so the quality of life for people and nature may improve and persist. Want to learn more? Check out our report!

Michelle Griffoul, a volunteer with the Hui O Ka Wai Ola water quality testing program and board member of Maui Nui Marine Resource Council, beams after learning that the water quality testing program would receive the donations collected at the September meeting of  100+ Women Who Care - Maui. ​