![]() ![]() Irrigation accounts for 80 percent of fresh water use across the United States. (These satellites are built by NASA and operated by the National Oceanic and Atmospheric Administration.)īecause geostationary orbit keeps a satellite over the same geographical region, Tule is able to get short-wave radiation measurements up to every five minutes. The first is the “downward component,” he explains, “the sunshine you feel.” Tule measures it using infrared imagery from the GOES system. “We use NASA technology for the energy-in part of the equation,” Shapland explains, to accurately measure how much heat is going into the field from the sun. However, even though Tule doesn’t rely exclusively on satellite imagery, it does rely heavily on it. That gives them an input to the energy balance equation, resulting in a more accurate number for heat going to water vaporization. “We’re measuring the turbulence within the field and measuring the rate at which the wind is taking water vapor away from the field,” he explains, using very sensitive temperature sensors. The difference between Tule’s model and the ones based entirely on satellite imagery is this measurement. That new eddy is then poised to absorb a new round of moisture and heat before being pushed off by a fresh one yet again. These eddies, or packets, come in contact with the surface, heat and water vapor transfers into them, and then a new eddy comes from above and pushes the old one away,” he explains. “Turbulence is individual eddies of wind carried in the mean flow. But it doesn’t capture the turbulent transfer in the field, Shapland says. Wind speed, the basic measurement that might show up in a weather report, reflects the “mean flow” of wind, or about how fast the air is moving on average across a wide area. “The reason there’s so much error,” he explained, is because “wind is a significant driver of the evapotranspiration rate.” Specifically the turbulent motion of wind plays an important role in how quickly water vapor transfers away from the plant. But he says the key difference is in how his company measures the second energy sink, the heat warming the air. So far, this method is not hugely different from the error-prone models he wanted to replace. The outgoing energy goes into the ground, warms the air, and vaporizes water, and a negligible amount goes to other miscellaneous but important processes including photosynthesis.īy measuring the first two of these heat sinks, Shapland explains, they are able to calculate the third-the amount of energy that goes into vaporizing water, through which they can then extrapolate just how much water has been vaporized. This measures the energy coming into the field, that is, the energy coming in from the Sun, and the energy going out. In short, Tule uses a surface energy balance approach. Other methods, like using a lysimeter to measure water loss from plants by weight, were more accurate but prohibitively expensive and impossible to do on a large scale.īut Shapland had an idea to adapt the evapotranspiration method in a way that would reduce the error rates significantly. ![]() One method to estimate evapotranspiration, or the total amount of water evaporating from the ground and transpiring from plants, relied on satellite imagery, but it had large error margins. “That context just astounded me, that farmers didn’t know how much water their plants were using.”īut he quickly realized it wasn’t so simple to find out. “Water use is so critical to how plants grow and how much money a farmer can make,” Shapland emphasizes. Tom Shapland, who founded Tule Technologies Inc., studied agriculture as a college student at the University of California-Davis, where he was surprised to learn that most farmers didn’t know how much water their plants actually needed. Improving irrigation efficiency, to ensure only enough water is being used when and where it is needed, can increase profitability for farms while also conserving water for other uses.Īn Oakland, California start-up is helping farmers do just that-and the company says it couldn’t do it without data provided by NASA imagery from the Geostationary Operational Environmental Satellites (GOES) and Landsat satellites. Across the United States, for example, a full 80 percent of fresh water gets used for irrigation, and in western states, that figure can rise as high as 90 percent. * Irrigation-supplying water to growing crops-is one of the most important ways humans use water. ![]() Source: NASA Spinoff Tule says it is able to calculate evapotranspiration more accurately than its competitors because of the sensors it places in the field to measure turbulent airflow, which plays an important role in how quickly water vapor moves away from the plant. ![]()
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