Building new hydrography and virtual watersheds to conserve freshwater fisheries.

The increasing availability of high-resolution digital elevation data is enhancing the mapping of hydrography across Earth’s surface. As pressures on fluvial ecosystems grow, digital maps of river networks should include a data structure necessary to assess aquatic habitats and the environmental threats to them from resource development and climate change. Using examples from across Alaska, USA, we demonstrate how newly available radar and laser digital elevation products are being used to discover thousands of kilometers of previously unmapped channels, ranging from headwater to valley bottom streams. This comprehensive and attributed high-resolution hydrography that connects lentic, lotic, and terrestrial systems—a virtual watershed—has resulted in tens to hundreds of percent increases in potential salmonid habitats across landscapes ranging from the Arctic tundra to southeast rainforests. Our findings show how virtual watersheds enhance understanding of freshwater and diadromous fish habitats and serve as a model for supporting conservation efforts and environmental problem-solving in other regions globally.