Tracking the pulse of the Earth's fresh waters

Reliable accounting of freshwater resources is key to managing hydrologic risk and balancing freshwater allocations for ecosystems and society. However, recent claims have argued that the global hydrometric network is not keeping pace with monitoring needs. Here we examine this question globally and reveal that over the past four decades the number of streamgaging stations reporting to global, open datasets has been declining. In the United States, a declining trend was reversed by the turn of the century, but high volatility at the river basin scale threatens continued monitoring in over a quarter of the river basins of the conterminous United States. We propose to prioritize streamgaging rescue by identifying watersheds that heavily rely on hydrologic data to support freshwater biodiversity conservation, and to manage flood or water scarcity risk to human populations. We argue that actions at different institutional levels are needed to secure the accumulation of long-term data needed for sustainable water management.