Research Counts

By Esther Oyedele

Groundwater in the Colorado River Basin is disappearing rapidly, unevenly, and unfairly. As climate extremes intensify and water supplies from rivers, reservoirs, and snowpack dwindle, communities across the American Southwest are relying on groundwater at unsustainable rates.

When these invisible reserves run dry, communities do not have equal capacity to respond. Smaller, rural, and economically and racially marginalized communities are often impacted most severely because they lack the money or political capital to drill deeper wells, import water, or influence regional water policy. These disparities are compounded by gaps in groundwater information, leaving many of the same communities underrepresented or undercounted in the data used to guide water management decisions.

Uncovering a Hidden Crisis

My research investigates the human-driven depletion of groundwater in the Colorado River Basin using satellite observations and high-resolution climate models. This 250,000 square-mile region supplies water to more than 40 million people across seven southwestern U.S. states and Mexico. It is also home to areas that are among the most water-stressed and agriculturally productive in North America—overlapping factors that intensify risk. By mapping where groundwater losses are occurring most rapidly, and identifying the climate and human drivers behind them, my work aims to support more equitable and inclusive responses. This can ultimately help mitigate a mostly hidden crisis that is unfolding and already affecting lives and economic systems.

Unlike more sudden-onset events like floods or wildfires, groundwater depletion is a slow-motion disaster that is hard to see, easy to ignore, and profoundly unjust in how it impacts communities. In Arizona’s Pinal County, for instance, small-scale farmers’ water wells have run dry while larger, well-capitalized agricultural producers drill deeper with expensive new infrastructure. On tribal lands, legal and infrastructure barriers prevent many Indigenous communities from accessing the groundwater beneath their sovereign territories. Migrant farmworkers face compounded risks—as laborers they depend on irrigation for their livelihoods, but they are also residents living in informal housing with limited infrastructure and other basic services. As such, their water supplies are among the most precarious in the region.

These are obviously not just environmental problems—they are systemic, social, and deeply tied to histories of exclusion. Many vulnerable communities lie in data blind spots that further inequity by erasing people and the specific problems they face. For example, because ground-based monitoring wells are generally clustered around urban centers and major agricultural districts, they leave water supplies in rural, tribal, and marginalized communities under-measured. In many parts of the Southwest, households depend on shallow domestic wells that are rarely monitored and can fail quickly as groundwater levels decline—a vulnerability that researchers have documented across thousands of wells in the United States. Without clear information about where and how groundwater is being lost in these unmonitored areas, those who live there are often left out of policy decisions that directly affect their survival. Improving visibility of groundwater conditions is therefore not only a scientific challenge but also a question of fairness in how water risks are recognized and addressed.

Addressing the Data Drought

That’s where satellites come in. In my work, I use data from the National Aeronautics and Space Administration's Gravity Recovery and Climate Experiment (GRACE) Follow-On satellites, which detect changes in Earth’s gravity field to track variations in total water storage above and below ground. I also use GPS data and radar images from satellites such as NASA’s newly launched NISAR and ESA’s Sentinel-1 to see how the land surface rises or sinks as groundwater is lost or refilled. Various satellite missions provide information on surface water, snowpack, and soil moisture, helping us see how these parts of the water cycle are connected to groundwater. By combining these observations, I can estimate the extent of groundwater loss across the Colorado River Basin. These tools help reveal changes that would otherwise remain hidden and show how groundwater decline is linked to both prolonged droughts and human influences, such as heavy pumping for irrigation.

More importantly, they can help bring overlooked communities into the conversation. Satellite observations have already helped researchers identify rapid groundwater depletion in agricultural regions of central Arizona, including Pinal County, where reductions in Colorado River allocations have pushed farmers to rely heavily on groundwater. By revealing these trends at the basin scale, satellite data can provide communities and local officials with evidence that the problem is not hypothetical but already unfolding. Similar approaches could help rural or tribal communities that lack dense monitoring networks by providing independent data on where groundwater losses occur and how quickly conditions are changing. In this way, satellite observations can strengthen the information communities bring to regional water negotiations and planning discussions.

In the face of a slow-moving groundwater crisis, we must consider not only how much water remains, but also who has more access when it declines, and whose voices are included in understanding the problem and shaping responses to it. Satellite data can make hidden groundwater changes more visible, but they are only one part of the picture. When combined with local knowledge and the perspectives of communities most affected, they can contribute to a more equitable understanding of water scarcity and to decisions that do not place the greatest burden on those with the fewest resources to adapt.