Stream monitoring capabilities are falling globally and fluctuating in the United States, reports a paper published online this week in Nature Sustainability. As both warming climates and overuse endanger freshwater resources, the loss of monitoring endangers our ability to sustain water supplies and the ecosystems on which healthy streams depend.

Tracking freshwater resources reliably is vital to managing flood and drought risk and balancing water needs. These efforts depend on having functioning stream gauges and consistent monitoring and publicly accessible reporting, but experts have warned for years that data availability may be dwindling.

Albert Ruhi and colleagues examined the archives of both the Global Runoff Data Centre, which curates the largest international repository of stream runoff records, and the US Geological Survey’s National Water Information System, a US-focused data source.

The authors find that global monitoring efforts - as measured by the number of active stream gauges reporting to these sites - have decreased by over 50% since 1979. In the US, an upswing in the number of active reporting stations since the 1990s followed decades of decline, probably due to changes in the US Geological Survey’s funding. Of the US river basins at risk of losing their data-reporting capability, almost half experience water scarcity, about a third are at a high flood risk and around a third have high fish biodiversity. These findings suggest that, as governments and citizens debate infrastructure priorities, open-access freshwater data collection should also be considered as well as roads and bridges.