Drought is a widespread concern within the Western U.S., and water managers across the region are developing groundwater management plans to conserve the essential resource. Groundwater is usually pumped to the surface to irrigate crops, and meters that measure the flow of pumped water have historically offered the very best information on groundwater use. These meters are rare, nonetheless, so DRI scientists set out to find out whether OpenET, a platform that measures evapotranspiration using satellite data, could help fill this information gap.
The brand new study, published August eighth in a special issue of Agricultural Water Management, compared groundwater meter data with OpenET estimates for agricultural fields in Nevada and Oregon. The outcomes show that OpenET could be used to accurately estimate the quantity of groundwater used for crop irrigation at the extent of individual fields. That is the primary research to follow water from a groundwater well to a single field of crops, assess how much of that water the crops consumed, and supply insights into irrigation efficiencies at the identical time. The tactic can inform water use for groundwater management planning across the country.
“We knew where the water was drawn from and where it was being applied, and we showed that the satellite data could tell us how much crop water use and pumping occurred for individual fields,” said Thomas Ott, assistant research scientist of hydrology at DRI and a lead writer of the study. Access to detailed meter data is rare, Ott adds, so past studies focused on broader regions and couldn’t assess water use at the extent of individual fields.
Evapotranspiration refers back to the combined processes of evaporation and transpiration, or the return of water to the atmosphere from Earth’s surface and thru plant photosynthesis. OpenET uses data from NASA and U.S. Geological Survey Landsat satellites combined with weather variables like humidity, air temperature, and solar radiation to estimate evapotranspiration for landscapes world wide.
The study centered on two agricultural regions with irrigation water flow meters that might be in comparison with the OpenET data: Diamond Valley, Nevada and Harney Basin, Oregon. Each regions have 1000’s of acres of irrigated alfalfa and hay and rely heavily on groundwater. In Diamond Valley, there was a 7% difference between the metered data and the OpenET estimates for water use, while Harney Basin showed a lower accuracy rate at a 17% difference. The researchers wanted to look at how the OpenET results would perform across different irrigation systems, with Diamond Valley counting on center-pivot sprinklers and Harney Basin utilizing a combination of flood irrigation and sprinklers.
“Our study shows that OpenET can really advance our understanding of agricultural water use, especially in basins without monitoring in place,” Ott says. “Traditional methods often use an estimate of the utmost water use for a typical healthy field in a typical yr, but plenty of aspects can bring that number down. Using satellite data gives a more realistic value.”
In truth, by comparing the metered data and OpenET estimates, the study found that assumed values for water use in Diamond Valley were far higher than the quantity of water actually used, says Sayantan “Monty” Majumdar, assistant research professor of hydrologic sciences and distant sensing at DRI and a lead writer on the study. With details about the whole amount of groundwater pumped to a field and the OpenET estimate of water utilized by the crop, the researchers also found that water use within the two study areas was highly efficient, with 90% of irrigation water utilized by the crop in Diamond Valley, in comparison with 83% in Harney Basin.
Ott, Majumdar, and the remaining of the DRI OpenET team plan to expand this research to quantify the quantity of water utilized in agriculture across Nevada as a part of the Nevada Water Initiative. Nevada is the driest state within the nation and currently relies on estimates of water availability and use which might be a long time old, and the initiative will utilize advances in research methods and technology to supply a more robust assessment for informing water management moving forward. The project is a collaboration between DRI, the Nevada Division of Water Resources, and the USGS Nevada Water Science Center, in addition to agricultural stakeholders across the state.
“The stakeholder engagement for this work is so necessary,” Ott says. “Having grown up on a dairy farm myself, it was amazing to enter different parts of Nevada and see how the farmers work. One farmer graciously hosted me for a month while I used to be doing field surveys of meters and irrigation systems, and constructing those relationships is admittedly necessary for our future work.”
