Mapping Non-perennial Streams and Inland Wetlands: Status and Future Directions

Non-perennial headwater streams and inland wetlands are vulnerable waters that provide essential functions supporting healthy watersheds and downstream waters. The size, abundance, and hydrological variability of these systems make mapping their extent and characterizing their temporal dynamics challenging, yet such information is critical for understanding the ecosystem functions they provide. Water managers, planners, scientists, and the public-at-large therefore need reliable geospatial data on non-perennial streams and inland wetlands to inform water resource decisions across local-to-national scales. We address four questions in this presentation in order to synthesize the state-of-the-science and advance non-perennial stream and inland wetland mapping: 1) What is the current status of headwater stream and inland wetland mapping represented in geospatial datasets throughout the United States? 2) What emerging technologies can help fill data gaps we identify? 3) How can streams and wetlands be considered jointly as integrated surface water systems? and 4) What next steps are needed to further the understanding and management of these vulnerable systems? We review existing federal and state stream and wetland geospatial datasets, focusing on spatial extent, approaches for classifying temporal dynamics, and current limitations. We also review current and emerging methods - including remote sensing satellites, LiDAR-based technologies, and machine learning algorithms - for advancing the estimation, representation, and integration of stream and wetland datasets. We conclude by discussing the limited number of critically-needed models for understanding the roles and functions of non-perennial stream and inland wetland systems at watershed scales, and the role of field-based efforts, including citizen science, that must continue to support remote sensing and modeling efforts. Our synthesis reveals key next steps designed to enhance the mapping of non-perennial streams and inland wetland systems and inform water resources research and policy decisions.