Long-term experimental watershed studies have significantly influenced our global understanding of hydrological processes. The discovery and characterization of how stream water quantity and quality respond to a changing environment (e.g., land use change and acidic deposition) has only been possible due to the establishment of catchments devoted to long-term study. One such catchment is the Fernow Experimental Forest (FEF) located in the headwaters of the Appalachian Mountains in West Virginia, a region that provides essential freshwater ecosystem services to eastern and mid-western USA communities. Established in 1934, the FEF is among the earliest experimental watershed studies in the Eastern USA that continues to address emergent challenges to forest ecosystems, including climate change and other threats to forest health. This data note summarizes some of the seminal findings from more than 50 years of hydrologic research in the FEF. During the first few decades, research at the FEF focused on the relationship between forest management and hydrological processes – especially those related to the overall water balance. Later, research efforts included the examination of interactions between hydrology and soil erosion, biogeochemistry, N-saturation, and acid deposition. Hydro-climatologic and water quality datasets from long-term measurements and data from short-duration studies are publicly available to provide new insights and foster collaborations that will continue to advance our understanding of hydrology in forested headwater catchments. As a result of its rich history of research and abundance of long-term data, the FEF is uniquely positioned to continue to advance understanding of forest ecosystems in a time of unprecedented change.

Managers are often inadequately informed to make decisions for municipal watersheds, in which sources of impairment are shifting due to the combined influences of land use change, rapid ongoing human population growth, and changing environmental conditions. To progressively pursue best-managed, science-based futures, municipal watersheds can be studied using an experimental watershed approach. To demonstrate this approach in a contemporary watershed, a nested-scale experimental watershed study design was implemented in a representative, mixed-use watershed located in the Midwestern USA. Results to date show that urban/suburban development and agriculture are primary (often combined) drivers of alterations to watershed hydrology, streamflow regimes, transport of multiple water quality constituents, and stream physical habitat. However, several natural processes and watershed characteristics, such as surficial geology and stream system evolution, are likely compounding observed water quality impairment and aquatic habitat degradation. Given the varied and complicated set of factors contributing to issues in the study watershed, watershed restoration is likely subject to physical limitations and should be conceptualized in the context of achievable goals/objectives. Results demonstrate the capacity of the experimental watershed approach to objectively identify causal factors, target critical source areas, and provide the science-based information, and shared data, necessary to make effective, collaborative, and adaptive management decisions. Results further demonstrate the immense, globally transferable value of the experimental watershed approach to address municipal watershed management challenges.