Federal Satellites Gather Critical Data for Managing California’s Water

California relies on federal satellites to understand and manage its water resources every day. Data from these satellites are used to estimate irrigation use, manage groundwater, predict storms, assess flooding, and track water quality, among many other applications. And as the changing climate brings weather whiplash and warmer temperatures to California, these data are becoming increasingly key for adaptation efforts across the state.

One of the most important sources of images has been the federal Landsat program, which has sent a series of satellites into space to observe the Earth continuously for over 50 years through a partnership between the National Aeronautics and Space Administration (NASA) and the US Geological Survey (USGS). Some readers might know Landsat from the beautiful images it has captured of the Earth: there's even a delightful website that allows you to spell your name with them. What may not be as well known is that Landsat-along with other federal satellites-also plays a key role in California water management.

While it would take too much time to catalogue all the ways California uses federal satellite data to manage our water resources, a few examples illustrate the importance of these data.

Tracking agricultural water and groundwater use

California's growers rely on data from federal satellites to estimate water consumption, plan for irrigation, and track water quality. For example, OpenET provides farmers and water managers with estimates of water use based on data from federal satellites, particularly Landsat. Farmers in the Sacramento-San Joaquin Delta can use OpenET to measure and report their water use to comply with California State Water Resources Control Board requirements. Some of the state's groundwater sustainability agencies (GSAs), including the Mid-Kaweah GSA in the San Joaquin Valley, use other products derived from Landsat data, such as Land IQ, to track water budgets and fine-tune irrigation to optimize yields. The California Department of Water Resources uses data from the GRACE follow-on satellite mission (a partnership between NASA and a German center) for its semi-annual updates on groundwater conditions, as well as data from a European satellite to estimate changes in specific basins.

Increasing flexibility in reservoir management

Federal satellite data are used in forecast informed reservoir operations or FIRO, a tool that gives reservoir operators more flexibility. As weather and atmospheric river forecasting have improved in recent years, dam operators can use satellite-informed forecasts to decide whether to retain or release water before a big storm, thereby increasing flexibility to balance multiple objectives such as maximizing water storage while mitigating downstream flood risks. FIRO relies on weather predictions from satellites including the GOES-16 satellite, operated by the National Oceanic and Atmospheric Administration (NOAA). Current FIRO pilot projects are taking place across the state at Oroville Dam on the Feather River, at Lake Mendicino and Lake Sonoma on the Russian River, and at the Prado and Seven Oaks dams on the Santa Ana River.

Federal satellite data provide the state-and the world-with profound economic benefits. The economic value of the federal Landsat program alone was estimated to be over $25 billion during the year 2023. Yet federal funding, which supports the launch of new satellites as others reach the end of their lifespans, is currently in question.

Landsat 7, for instance, provided its last images of the earth a few months ago. NASA and USGS have been planning for the launch of a new Landsat satellite, Landsat Next, to replace the aging Landsat 8 and 9 and to better meet resource management needs with improved and more frequent observations. The plans are currently being reviewed to better meet the president's 2026 budget request, which proposed to cut the NASA earth science budget by about 50%. In contrast, the House bill proposes a cut of about 40%, while the Senate only proposes a 1.3% cut. Funding for ground-based observations, which are needed to calibrate and validate Landsat and other federal satellite data, is also at risk.

Freely provided federal earth science satellite data advance transparency and shared understanding of California's water, as well as the state's land, vegetation, and even dust. While new technologies like artificial intelligence and machine learning show promise for capturing current and emerging trends, these methods rely on robust amounts of high-quality data. Continuous federal satellite data documenting the Earth play a pivotal role in informing evidence-based water and natural resources policies and management.