Water Science in Your Back Pocket


A new app turns your smartphone into a mobile sensing instrument.

Dr. Thomas Leeuw takes measurements with the Hydrocolor app in the equatorial Pacific. Image Credit: Thomas Leeuw

It’s been said that every idea has its time. With advances in smartphone technology and the growing acceptance of citizen science, the idea to blend the two has spread across the globe.

Technology to monitor the health of Earth’s water has advanced significantly in the last 50 years. With the information gathered from satellites and ground-based sensing instruments comes the ability to track changes in water quality and what causes them. These observations make it possible to find solutions to the complex problem of managing a compromised, critical resource under ever-increasing demand. Cost, lack of portability and the sometimes intensive, specialized training the instruments require limits the use of these technologies and the amount of information that can be gathered.

A recent technological innovation that many people carry around in their back pocket, however, has appeared at the convergence of the crisis and the possible solutions. This technology is a smart phone app, and it could exponentially multiply the amount of water quality data available to scientists.

An image of the Hydrocolor smartphone app screen. Image Credit: Thomas Leeuw

‰ÛÏSmartphones are so ubiquitous that they can be used for crowd sourcing,‰Û says Thomas Leeuw, developer of a water quality monitoring smartphone app called Hydrocolor.

Leeuw is a research associate with Sequoia Science Inc. He studied marine biology and oceanography at the University of Maine, where he became interested in marine optics and remote sensing. Recognizing the expense of traditional instruments as an impediment to data gathering led him to develop the app as part of his master’s thesis.

‰ÛÏThe cost is really prohibitive to a lot of people that want to make these type of measurements, especially in educational settings where teachers want to take students and collect them,‰Û he said. ‰ÛÏIt’s a cheaper method of doing basic water quality measurements that’s more available to people.‰Û

The app sells for $2.99, available for Apple and Android devices. Leeuw says it’s essentially a hack of the smartphone camera that takes what ocean scientists do with radiometers and satellites and applies it to a readily available tool.

‰ÛÏIn pretty much all digital cameras these days, there’s a special filter in there that filters the light that comes into the camera,‰Û he said. ‰ÛÏUsing the light in the red, green and blue portions known as RGB, the app essentially looks at the light that’s coming out of the water and it analyzes the color of that light. That color can tell us things like how much sediment is in the water or how much algae is in the water.‰Û

Both are important parameters in water quality monitoring that scientists watch for changes in over time.

The two most common methods of taking instrument-based water quality measurements are reflectance and fluorescence. Fluorescence is the absorption of a particular wavelength, or color, of light followed by the emission of another color. Reflectance is the proportion of light that bounces off of a surface, rather than being absorbed. The Hydrocolor app uses reflectance to measure turbidity, the amount of sediment suspended in the water.

‰ÛÏThese techniques, I think, are a long way from being a replacement for more accurate lab methods, but I think it’s an interesting extension of it that will potentially allow us to monitor a lot more areas and monitor them more frequently.‰Û – Dr. David Gillette

To take a measurement, the user takes three photographs. The first is of a photographer’s gray card, which has a known reflectance of 18 percent, to calibrate the app based on ambient light. That tells the app how much light is entering the water at that location. Next, pictures are taken of the sky and water. Based on the calculated reflectance, the app determines the quantity of particles in the water. The color of the light reflected can indicate whether the particles are organic or inorganic.

Hydrocolor calculates turbidity based on the reflectance of a photographer’s gray card and photographs of the sky and water. Image Credit: Thomas Leeuw

‰ÛÏThe hardware that are on board these smartphones are all very similar, so we can standardize how these measurements are made,‰Û Leeuw said. ‰ÛÏIt’s not subjective user observations anymore.‰Û

The data can then be uploaded to a database. Leeuw hopes there will be a central database in the future. ‰ÛÏWe are hoping to partner with other organizations to achieve this,‰Û Leeuw said. ‰ÛÏWe are currently working with the GLOBE Program (GLOBE.gov) to see if we can integrate our measurements with their database.”

Although Leeuw says the app is less accurate than more expensive instruments, he believes it will allow a greater amount of data to be gathered by many more people.

The accuracy of the technology raises questions for Dr. David Gillette, an associate professor of Environmental Studies at the University of North Carolina in Asheville who is active in water quality monitoring projects with the Environmental Quality Institute ((EQI)).

‰ÛÏHydrocolor, the things that it’s supposed to measure are things that we have equipment to measure as well,‰Û Gillette said. ‰ÛÏWhat I’m interested in doing is to actually measure the water turbidity using those instruments … and then use that to calibrate this app and see what the percentage error is.‰Û

That percentage will determine the scope of the app’s use, Gillette says.

Gillette questions the extent to which the technology will be defensible in court. Only data from U.S. Environmental Protection Agency-certified labs using methods that have been verified for accuracy can be used to bring court action against a Clean Water Act violator. Gillette said the role of the Hydrocolor app may be to alert scientists to an issue that can then be verified by more accurate instruments.

‰ÛÏThese techniques, I think, are a long way from being a replacement for more accurate lab methods, but I think it’s an interesting extension of it that will potentially allow us to monitor a lot more areas and monitor them more frequently,‰Û he said.

Gillette also believes smartphone apps like Hydrocolor could be valuable in remote areas where other instruments aren’t available or feasible.

Hydrocolor is one of many water monitoring apps in development across the globe. There are basic apps to create and submit water quality reports in remote locations after testing has been done with portable kits and to identify or to count organisms that are indicators of water quality to upload that information to a database. Others allow the user to upload photos. CitClops, an app that uses fluorescence rather than reflectance to take water quality measurements, is part of a European project called Citizens’ Observatory for Coast and Ocean Optical Monitoring. Mobosens was developed in the U.S. to measure nitrate concentration in water.

Each app is a variation on the theme of putting an inexpensive, user-friendly, standardized tool in the hands of as many people as possible to gather large amounts of data. It’s an idea whose time has come and with the potential to significantly impact research and education.

Lorelei GoffåÊwrites about science and the environment from Greeneville, Tennessee.