Eye in the Sky Focuses on Plant Health, Water Conservation

Markus Hogue using drone data

Markus Hogue, UT Austin Landscape Services’ irrigation and water conservation coordinator, studies a map of the LBJ Library lawn derived from photos taken by a drone-mounted NDVI camera. The map indicates the health status of trees and vegetation.

The University of Texas at Austin has reduced water usage for irrigation by 70% or 125 millions of gallons annually since 2009. Yet, the Landscape Services irrigation team led by Markus Hogue, irrigation and water conservation coordinator, wants to do even more to save valuable water resources. So, Landscape Services has turned to drone and camera technology.

For Hogue, the thought of having an “eye in the sky” was inspired by looking at Google Earth a few years ago, seeing how trees and landscapes changed over long periods of time. He says he began to think, “If I had something in the air, I could see the changes in the landscape over weeks or months,” which would be a powerful tool for irrigation management and other landscape applications.

Finding that right “something in the air” took time. First, he looked into remote controlled planes, but found they crashed too easily. Small gas-powered helicopters were too noisy. Finally, he began to hear about unmanned aerial vehicles, drones, which were becoming more affordable and were quiet and easy to fly.

Drones seemed promising, but Hogue had to research cameras as well. He found the right type of camera for looking at trees, plantings and turf over time: an NDVI, normalized difference vegetation index camera. An NDVI camera detects plant health based on how a plant reflects light at specific frequencies. Stressed or even dead vegetation looks distinctly different from healthy vegetation seen through NDVI photos. The combination of drone and NDVI seemed an efficient way to check vegetation health. It also had the benefit of allowing inspection of tree canopies for safety issues such as broken limbs not visible from the ground.

A partnership with UT Austin student Marwan Madi took the drone idea a step forward. Previously, Madi and fellow high school student Michael Liu won a national Innovation Award for the Real World Design Challenge in for their concept of using drone and NDVI technology to reduce water usage. When Madi and Hogue connected, they began building on that concept. The team applied for and was awarded a Green Fund grant to purchase equipment. Green Fund is a competitive grant program funded by UT Austin tuition fees to support sustainability-related projects and initiatives on campus.

In fall 2018, in a joint research project with Madi, Hogue will overlay an NDVI map of the LBJ lawn with a map of the irrigation zones in an area where moisture sensors are installed. This research project will collect base data for a year. Next year, using the data collected, the irrigation team will modify the irrigation in the target area and data gathering will continue. The following year, the pair will gather more data and publish results.

“Our research project is important for UT Austin, as it demonstrates how new drone and sensor technology can be used to help conserve water and save the environment in addition to its traditional usage of monitoring crop health,” says Madi. “We hope that these methods can help campuses and farmers save water, especially in drought-stricken areas where water is scarce.”

Hogue hopes the data will show that a relatively small reduction in irrigation has minimal impact on vegetation health. A small reduction applied campus-wide can mean big water savings. Hogue estimates that a 10 percent reduction in evapotranspiration due to reduced irrigation across the main campus could save 3.5 to 4.5 million gallons of water annually. (Evapotranspiration is the process by which water transfers from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants. Transpiration occurs when plants absorb water through their roots and then give off water vapor.)  Hogue hopes a positive conservation impact for UT Austin could inspire other campuses and communities to use drone and camera technology for their own strategies to reduce water use for irrigation.

Already, Landscape Services is not the only unit on campus interested in the landscape mapping made possible by the drone and NDVI. Professors in both the School of Architecture and the Jackson School of Geosciences are using maps Hogue has made available to them. The Wildflower Center is planning to use the drone and camera to look at the impact on trees of prescribed burns by gathering images before and during a burn.

Author Laurie Lentz is a communications manager in Financial and Administrative Services at UT Austin.