Remote Sensing Technologies Mitigate Drought Folsom Lake, located at the base of the Sierra foothills in California, provides hydroelectricity and drinking water for Folsom City as well as irrigation water for the Central Valley. The before-and-after image of the lake shows the severity of the state’s current drought. NASA Technology certain regions, this pumped groundwater contains higher square miles of white snowpack should have been, there concentrations of various minerals that can lead to salt was only bare dirt and rock. In other words, the snowpack California is an agricultural powerhouse. In 2012, buildup, damaging soils over the long term. The heavy in the Sierra Nevada was far below average. That matters its 81,500 farms and ranches produced $42.6 reliance on pumping water from wells has also led to because melting snow from the range provides a critical billion in cash receipts, the most by any state. rapid depletion of groundwater resources in numerous source of water for both agricultural and urban regions But that abundance is threatened by what’s been called regions around the state. of the state. one of the worst droughts in the state’s history. For the last few years, “The Golden State” has been wilting under NASA’s satellites have captured the despair from up But NASA is doing more than just taking pictures. By a dry spell that has left hundreds of thousands of acres high. On January 18, 2014—the day after California accessing high spatial-resolution satellite data, the agency idle and many contract farm workers jobless. governor Jerry Brown declared a state of emergency— has been working in collaboration with the California To save their most valuable crops, some growers have NASA’s Terra satellite snapped a striking image of the Department of Water Resources (CDWR) to provide had to rely on pumping irrigation water from wells. In Sierra Nevada mountain range. Where thousands of water managers with more tools to plan for, and mitigate, 108 Energy and Environment Spinoff 2015 the impacts of drought and also help the state better assist regions suffering from drought-related economic hardships. Ever since NASA launched the first Landsat satellite in 1972, the agency (in partnership with the US Geological Survey (USGS), which currently operates the current Landsat 8 spacecraft and collects incoming data) has provided a continuous global record of Earth’s surface. Gathered by sensors that can collect measurements in multiple spectral bands, data from the program has been used to analyze a wide range of environmental changes over time, from the recession of glaciers to coral reef health, to the impacts of natural disasters. To complement Landsat, by 2002 NASA had launched the Terra and Aqua satellites, each of which carries an instrument known as the Moderate Resolution Imaging Spectroradiometer (MODIS). MODIS provides daily global coverage and has been used to detect and monitor fires, study multiple aspects of the carbon cycle, track harmful algae blooms in the ocean, and collect aerosol measurements, among other environmental monitoring applications carried out on a global scale. Both of these Earth-observing satellites also figure prominently in vegetation research, as they are used to measure canopy density in rainforests and to track defor- estation. The wealth of plant-related data they offer, combined with NASA’s push to make both Landsat and MODIS data more utilized by the public, culminated in a partnership between the agency and the CDWR to develop new information products designed to assist farmers in calculating crop water requirements across mil- lions of acres of irrigated farmland in California. Technology Transfer Since the early 1980s, the CDWR, through its California Irrigation Management Information System NASA’s Moderate Resolution Imaging Spectrometer (MODIS) provided the data that (CIMIS), has utilized ground-based weather stations— was used to draw up this map, which uses and, more recently, satellite data—to estimate what’s what’s called a Normalized Difference Vegetation known as reference evapotranspiration (ETo): the total Index to assess California’s crop health. potential amount of water that can be transferred to the Acquired on February 1, 2014, the map shows the drought’s impact on California agriculture, as atmosphere in a given time through evaporation and the shades of brown represent areas where plant plant transpiration (a plant’s release of water vapor) for growth is drier than normal. a reference crop, typically a short, well-watered grass or Spinoff 2015 Energy and Environment 109 alfalfa crop. The CDWR distributes ETo information them. The power of the technology, Melton says, is its That information will be used by the state to help through CIMIS as a reference to help farmers and ability to quantify the estimated amount of water required allocate resources to nearby farmworker communities irrigation managers determine how much water their for specific crops at different phases of their growing that, because of the water shortages, are facing loss of crops need at any given period in the growing season. cycles, and it can do this plot by plot in agricultural income, resulting in economic hardship. “One potential As helpful as ETo data is, farmers and irrigators must regions throughout the state. application of this will be to support California agencies still perform additional calculations to convert the ETo “Ultimately, a grower will be able to specify a in identifying counties that are likely to need extra emer- information into a number specific to their fields and particular field or orchard, and the resulting information gency relief to support food banks for workers and their crops. For example, the utility of ETo information is might include the latest satellite observation and families,” Melton says. increased when paired with another piece of data called information on the crop canopy development, crop NASA’s commitment to helping the state manage its the crop coefficient. Specific to the crop type and its stage water resources flows in still other directions. Another condition, and its water requirements under well-watered of growth, the number, when multiplied by ETo, results ongoing project involves measuring rates of land subsid- conditions,” he explains. in a more refined measurement of evapotranspiration ence, or sinking, caused by depletion of groundwater, In conjunction with the particulars of the irrigation specific to a particular crop and field. As it turns out, in which can cause damage to water delivery infrastructure. system, soil type, and production goals, growers can then recent years NASA and the US Department of Agriculture And the Airborne Snow Observatory, headed by Tom use the information from SIMS to adjust for how much (USDA) together were discovering that Landsat and Painter at the Jet Propulsion Laboratory (JPL), uses an water is needed. “It allows growers to use water more MODIS data could be used to map vegetation conditions aircraft equipped with an imaging spectrometer and a efficiently if they choose to use irrigation-scheduling tech- and, from that, derive crop coefficients. scanning lidar system to collect snowpack depth and niques,” says Jeanine Jones, interstate resources manager What make that possible are the satellites’ complemen- water measurements in the Sierra Nevada mountain and deputy drought manager for CDWR. For example, tary strengths, explains Forrest Melton, who is a senior range. Snowmelt supplies water to more than 25 million irrigation trials conducted on lettuce and broccoli crops scientist both at Ames Research Center’s Cooperative people and sustains nearly a million acres of farmland, in Salinas that were watered according to SIMS showed for Research in Earth Science and Technology and at which means the more accurate its estimation, the better no reduction in yields while reducing the amount of water the Division of Science and Environmental Policy at the state’s predictive capability for both drought condi- California State University, Monterey Bay. MODIS is used by up to 33 percent relative to standard practice. tions and flood risk. able to provide daily observations at a resolution of about “It’s important for us to validate elements of the sat- “The idea is to expand the ability to monitor the 15 to 16 acres. Landsat, while only gathering data once ellite-based procedure in controlled commercial settings snowpack in otherwise difficult-to-get-to places and every eight days, is able to zoom in to a resolution as and understand any limitations of the approach,” says hopefully allow us to provide more accurate runoff sharp as a quarter of an acre. “We found that by using NASA Ames and California State University, Monterey forecasts,” Jones explains. them in tandem we could reliably map crop coefficients Bay senior research scientist Lee Johnson, who led the Another project she’s keen on is JPL’s research on the yield trials. Madden-Julian Oscillation, a recurring pattern of tropi- on a regular basis throughout the year,” he says. As a result of those findings, NASA and CDWR, with In addition to these water-saving technologies, the cal climate and weather that affects Earth’s mid-latitudes, funding from the American Recovery and Reinvestment agency, in partnership with the USGS and the USDA, including California. “We’re really interested in efforts to Act of 2009, initiated the Satellite Irrigation Management is also advancing tools to spot areas where water short- better understand it for improved climate forecasting.” Support (SIMS) project, whose goal, Melton says, is “to ages have led to reductions in farmed acreage. This is She adds, “We look forward to a long-term working deliver a consistent reference that can help growers adjust being accomplished by utilizing Landsat’s quarter-acre relationship with NASA on all of these projects. The their irrigation to match each crop’s biological demand resolution capability to track crop development and agency’s remote sensing-based data provides us with very useful information.” v for water.” uncultivated lands in “just about every field in the Central Valley,” Melton says. “We can map the canopy condi- Benefits tions every eight days throughout each growing season In the years since the collaboration was formed, web and identify fields with bare soil or low vegetation cover, and mobile prototypes of the technology have been which is a very strong and clear signal, and use that to developed, and growers across the state are now testing identify fields that are idle.” 110 Energy and Environment Spinoff 2015 NASA’s Airborne Observatory mission, flying over Mt. Dana and Dana Plateau in the Tuolumne River Basin within Yosemite National Park in California on April 3, 2013, utilizes a Twin Otter aircraft equipped with a scanning lidar system and an imaging spectrometer to measure snow depth and snowmelt speed, respectively. The resulting data will be used to estimate how much water will flow out of the basins when the mountain snow melts. A color-coded map (inset) visualizes the results of the flight. The top image displays the amounts of water contained in the snow in the millions of cubic meters, and the bottom image projects snowmelt speed, with the blue sections indicating a faster snowmelt rate and runoff. Spinoff 2015 Energy and Environment 111