1 MOTIVATION

Increasing population and resource‐intensive lifestyles are driving enhanced demands for clean water, food, and energy. In parallel, land‐use change, climate change, and perturbations—including drought, floods, fires, and early snowmelt—are significantly reshaping interactions within watersheds throughout the world. While watersheds are the Earth's key functional unit for assessing and managing water resources, hydrological processes in watersheds also mediate biogeochemical interactions that support terrestrial life on Earth (Kaushal, Gold, Bernal, & Tank, 2018; National Research Council, 2012). Although society is dependent upon clean water availability, tractable prediction of watershed hydrobiogeochemical behavior, including watershed response to perturbations, remains a challenge. Central to the challenge are complex, multiscale interactions between plants, microorganisms, organic matter, minerals, dissolved constituents, and migrating fluids, which occur within and across bedrock‐to‐canopy compartments and along extensive lateral gradients of a watershed. Several recent community reports have synthesized formidable challenges associated with watershed science and technology (AGU, 2018; Blöschl et al., 2019). Here, we discuss emerging technologies and collaboration modes that are critical for developing generalizable insights about and predictive understanding of complex watershed hydrobiogeochemical behavior, which are important for underpinning optimized natural resource management.

Recent developments in field observatories and open‐science principles provide foundational pillars for advancing predictive understanding of watershed hydrobiogeochemistry using emerging technologies. Field observatories have fostered crossdisciplinary collaboration and provided platforms for quantifying hydrological, biological, geological, geochemical, and atmospheric processes and their couplings (Bogena, White, Bour, Li, & Jensen, 2018). Observatory networks in the United States include the Critical Zone Observatories (Brantley et al., 2017), National Ecological Observatory Network (Loescher, Kelly, & Lea, 2017), the Long‐Term Ecological Research Network (Hobbie, Carpenter, Grimm, Gosz, & Seastedt, 2003), and the Department of Energy (DOE) Watershed Network (U.S. DOE, 2019). Select international observatory networks include the German Terrestrial Environmental Observatories (Zacharias et al., 2011), the French OZCAR network (Gaillardet et al., 2018), and the Chinese observatories (Li et al., 2013). The observatories are complemented by long‐term distributed measurement suites, such as the US Geological Survey stream discharge and concentration measurements (NASEM, 2018a) and the DOE AmeriFlux network carbon, water, and energy flux measurements (Novick et al., 2018). Open‐science concepts (NASEM, 2018a), which have recently started to permeate watershed science, provide another foundational pillar. While the open‐data FAIR (findable, accessible, interoperable, and reusable) principles (Wilkinson et al., 2016) are perhaps the most recognized aspect of open‐science, open‐science concepts are also critical for generating and sharing data, knowledge, and models in a manner that promotes transferability and generalizability across watershed networks (U.S. DOE, 2019).