SGD Thermal Imaging Drone Project

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Kākou defines the Hawaiian value of inclusiveness. It means “all of us” and “we are in this together.” No one understands the power of kākou more than Cindi Punihaole of the Kahalu'u Bay Education Center (KBEC). In order to begin studying the effects of Submarine Groundwater Discharge (SGD) on Kahalu'u Bay, Cindi brought folks together from many walks of life who were willing to donate their time and resources to this important cause. The Submarine Groundwater Discharge project embodies this beautiful and unifying "language of we.”

What is SGD? Are there submarines in the bay emptying their holding tanks? No worries! SGD is a hydrological process involving the inflow of fresh (or brackish) groundwater from the land into the ocean. SGD is important because it relates to pollution, the release of nutrients, plankton blooms, and other factors that influence coral health.

Recognizing the extreme and immediate dangers from multiple sources faced by our sweet little Kahalu'u Bay, citizens, scientists, and organizations from a variety of disciplines have banded together under the kākou spirit of Cindi Punihaole in an attempt to diagnose and mitigate the most immediate stressors.


Many of the corals in Kahalu'u Bay are declining. That means they’re dying. Or dead. Numerous coral heads that have lived in the bay for hundreds of years, sheltering fish and providing habitat, have recently deteriorated or died.

Image from Silver Spiral Seas video survey of Kahalu'u Bay, November, 2018

Image from Silver Spiral Seas video survey of Kahalu'u Bay, November, 2018

But why? Is it climate change? Oxybenzone contamination? Overuse? Pollution? Trampling by visitors? Ocean acidification? Sewage runoff?

The bay is facing many threats simultaneously which may very well be subject to interaction effects— that means that some combinations of stressors may be more detrimental to the coral than the sum of their parts.


The first step in mitigating the damage being done to the bay involves gaining a greater understanding of the magnitude and nature of the threats it’s facing. It’s also important to comprehend the ways in which the stressors behave once they’re introduced in the water. Once we have a clear and integrated picture of the ecosystem and how it interacts with the harmful influences, we can begin to implement comprehensive management programs.


First, Dr. Steven Colbert and his team from the Marine Science department at UH Hilo, in conjunction with KBEC, deployed temperature loggers at strategic points throughout the bay to calibrate the IR data that would eventually be collected by the drone. Preliminary temperatures were recorded between 26°C and 29°C depending upon their location in the bay. It was likely that daytime warming in shallow water led to the higher temperatures recorded, so it was important to plan the drone flyover during the early hours of the morning to avoid this confounding factor.

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Once the loggers were in place, the nighttime flyover with the drone was possible. Everyone arrived for setup around 3:00 am, and it was cold. Ok… perhaps folks in Chicago wouldn’t think it was cold, but we did! Ideally, the temperatures in the ocean should be as warm as possible so the SGD plumes will be more visible because SGD water is typically colder than the surrounding ocean water. Similarly, ideal conditions would include flat surf and super low tide, which are also harder to come by in January than they are during the summer. But, because this was a pilot run, it wasn’t as much of a concern. Rather, this preliminary examination was designed to provide guidance for future investigations because data now will exist for winter weather and they can be compared to summertime findings. And, issues such as communications interference from the heavy rebar in the concrete by the beach were identified and solved.

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And this is where the fun began! The totally cool scientists from the Spatial Data Analysis & Visualization Lab, Timo Sullivan and Dr. Ryan Perroy, deployed their drone equipped with a thermal imaging camera in hope of capturing images of discrete SGD plumes in both the north and south bay.

Once the flyover was complete, folks from KBEC and Silver Spiral Seas went out to retrieve the temperature loggers so they could be used on other projects. Fortunately, Kathleen Clark from KBEC was able to find them like a homing pigeon!

The data collected will begin to guide our efforts in decoding the complex, interactive, and likely synergistic effects of the environmental threats to the bay as information is compiled and correlated across measures of coral health, water quality analysis, levels of contaminants, SGD, run-off, and changes in temperature.

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The team learned a great deal during this exercise that will facilitate the next flyover. For instance, we’ll plan many months ahead to converge on the best set of environmental conditions: specifically, the dates with the lowest tide, lowest predicted surf, and warmest ocean water available at 3:00 a.m.

Image courtesy of your friendly neighborhood drone

Image courtesy of your friendly neighborhood drone


All of us are committed to preventing the horrific consequences from sewage that many other countries are experiencing, including St. Maarten. A 2019 article on St. Maarten coral reefs dying due to disease and sewage reports that 90 percent of coral in many locations is either infected or dead from “Tissue Loss Disease” which is able to kill corals within weeks or months and affects 20 different species. Prevention is key to protecting Kahalu'u Bay, and understanding the nature of the threats is a critically important step in this process.

It’s exciting that research is being done on the character of submarine groundwater discharges. I believe this is key to education relating to wastewater pollution and it is important to make the connection scientifically that not only do the SGDs deliver nutrients to the ocean, but that the source of the nutrients is very likely cesspits.
— Dr. Dee Fulton

Silver Spiral Seas has been thrilled to play a small part in this multidisciplinary project studying submarine groundwater discharge at Kahalu'u Bay.

In collaboration with:

Timo Sullivan and Dr. Ryan Perroy
Spatial Data Analysis & Visualization Lab
University of Hawaii at Hilo

Cindi Punihaole Kennedy
Director, Kahalu'u Bay Education Center
Program of The Kohala Center

Kathleen Clark
Operation and Education Specialist
Kahalu'u Bay Education Center

Dr. Steven Colbert
Associate Professor
Marine Science Department

Guidance and support was also kindly provided by Craig Downs, Ph.D. of Haereticus Environmental Laboratory, a non-profit scientific organization dedicated to understanding and protecting our natural resources.

Title banner image courtesy of Timo Sullivan and Dr. Ryan Perroy

NOTE: sUAS night flight operations were conducted in full compliance with FAA requirements and waivers.

Further Readings: