Supporting environmental justice and equity - Water can act as a driver, symptom, or solution to issues of environmental justice. We encourage sessions that focus on unequal exposure to hazards and risk, unequal access to water of sufficient quality and quantity for local needs, water in built systems (e.g., drinking water infrastructure), native population and water, water and health, and the role of water in creating and resolving conflict.

Developing the next generation – Training and career development in water-related disciplines must prepare students and early career professionals for a wide range of careers in academia, governmental, nonprofit and for-profit sectors. With the rapid evolution of technology, we must find new ways to support mid-career re-training. We encourage sessions that focus on all aspects of hydrologic training, education, and career advancement.

Managing scarce resources - Clean and abundant water is an increasingly scarce resource subject to many competing demands. We encourage sessions that focus on water resources management and environmental resource policy, governance, and planning. Sessions that include speakers from different disciplinary backgrounds and foster a dialog between scientists, policymakers, and resource managers are of particular interest.

Designing for change - Too much, too little, too dirty. The impacts of climate change are generating never-before seen combinations of conditions, more frequent extremes compared to past distributions, and challenging social and ecological availability of water resources. The timing, amounts, and quality of water resources -- either alone or in combination -- are increasingly challenging sustainable use of and access to water resources for human and ecological needs. Sessions in this theme should relate water resource quality and quantity outcomes to climate extremes and adaptation or discuss novel approaches to develop resilient infrastructure for a changing climate.

Projecting the future - Hydrologic and water resources forecasts and projections play an important role in water resources and emergency management. We encourage sessions that focus on hydrologic predictions across all time scales, from monitoring of drought conditions and nowcasting of flash floods, to subseasonal and seasonal forecasts and long-term climate projections of water conditions. Sessions that discuss how these forecasts and projections inform decision-making are of particular interest. 

Learning from observations - Novel and innovative measurement techniques continue to expand our understanding of all elements of the hydrologic cycle. New real-time data streams and retrospective data sets, combined with new analytical techniques provide new opportunities for extracting information from measurements, such as machine learning and deep learning applications. We encourage sessions that focus on environmental measurements, dataset development and distribution, big data applications, machine learning and deep learning approaches, and the software systems that support them.

Simulating complex systems - Hydrology is an inherently interdisciplinary field and hydrologic simulating approaches invariantly must include processes that act over a wide range of temporal and spatial scales. Under this theme, we encourage sessions that discuss all aspects of hydrologic simulation, including model development, parameter estimation, data assimilation, and model application. Of particular interest are sessions that discuss simulation approaches that account explicitly for humans as active agents in the hydrologic cycle.