TITLE:
Influence of Land Cover and Watershed Scale on Climate-Streamflow Relationships in the Upper Midwest
AUTHORS:
Brooke Payne, Molly Wells, Katherine Clancy
KEYWORDS:
Streamflow, Land Cover Changes, SPEI
JOURNAL NAME:
Open Journal of Modern Hydrology,
Vol.16 No.4,
October
23,
2026
ABSTRACT: Understanding how land cover influences hydrologic response is critical for interpreting regional variability in streamflow. This study examines how climate-streamflow relationships vary across watersheds differing in land-cover composition, land-cover change, and watershed scale across 73 USGS-gauged watersheds in the Upper Midwestern United States. To reduce the confounding influence of climatic variability, climate conditions were characterized using the Standardized Precipitation-Evapotranspiration Index (SPEI). Hydrologic response was evaluated using baseflow and total streamflow derived from daily discharge records. Results reveal a pronounced north-to-south gradient in hydrologic behavior associated with land cover and long-term landscape change. Northern watersheds, dominated by forest cover and exhibiting minimal land cover change, show higher and more stable baseflow and relatively consistent, though dampened, relationships with SPEI. Central watersheds display intermediate conditions characterized by mixed land cover, moderate change, and localized areas of strong climate-baseflow coupling. Southern watersheds, characterized by extensive agriculture, increasing development, and greater land cover change, exhibit lower baseflow contributions, greater hydrologic variability, and more heterogeneous correlations with SPEI. Watershed scale also influences these relationships. Larger watersheds exhibit stronger and more stable correlations with climatic variability, whereas smaller watersheds show weaker and more variable responses, particularly in the southern region. Overall, hydrologic responses differ systematically with land cover and watershed size despite broadly similar climatic forcing. These findings demonstrate that climatic indices alone are insufficient to reliably predict hydrologic behavior in human-modified watersheds.