Sampling the water in Halema'uma'u - Kīlauea Volcano Watch, as USGS-Hawaiian Volcano Observatory scientists Frank Younger and Patricia Nadeau describe how HVO sampled water in the pond at the bottom of Halemaʻumaʻu and what lab results tell us about its origin. On October 26, 2019, an unmanned aircraft systems (UAS) collected a water sample from the pond at Halemaʻumaʻu (Kīlauea's summit) to investigate its source and composition. The lab analyses of anions, cations and then, later, water isotopes indicate that the water originated as rainwater but didn’t fall directly into the lake – the rainwater made its way into the ground and then flowed as groundwater into the lake. The lake is dissolving sulfur gases that are being released from the magma below. HVO is working on a strategy to create a follow-up sample schedule and routine to track changes with time. Limited UAS flights into the are conducted with permission and coordination with Hawai‘i Volcanoes National Park. The information is used to assess hazards and is shared with the National Park Service and emergency managers. https://www.youtube.com/watch?v=pR5D6FZIaOI