 Scientists in Central America are using nuclear techniques to monitor hidden groundwater supplies to try to minimize the impacts of catastrophic droughts. Climate change is threatening water resources around the world. For example, water across Latin America and the Caribbean is declining in quantity and quality because of extreme weather and abrupt changes in the way land is being used. With water demand increasing, countries are often relying on their limited supplies of groundwater instead. But we don't know enough about these groundwater stocks. How often they are naturally replenished and how quickly they can be exhausted. This concern of water consumption associated with the occurrence of more prolonged and frequent droughts has arisen in a deepening of underground water levels, difficulting its access to different users. The region that stretches down the Pacific Coast from Mexico to Panama is known as the Central American Dry Corridor. As it has been struggling with droughts caused by climate change for at least 20 years, this has led to significant food insecurity in the region. Scientists there are using nuclear techniques to understand the water scarcity with support from the International Atomic Energy Agency. Each water sample contains slightly different isotopes of oxygen and hydrogen. Depending upon the route it's taken through the water cycle, these isotopes can be measured using laser instruments to provide a fingerprint of that sample and learn how old it is, where it came from, and where it's been. Scientists can use this sample to measure the amount of oxygen and where it's been. Scientists can use this information to map groundwater reserves and see whether fresh water has been entering the system or whether we are draining ancient reservoirs that might not refill quickly enough. This information allows local authorities to better protect groundwater and the ecosystems they support.