Dynamic water source contributions to streamflow in a northern forested peatland watershed

Abstract

Boreal peatlands in northern Minnesota influence catchment hydrology by regulating streamflow generation under varying wetness conditions. A drier condition can reduce spring precipitation and snowpack accumulation, potentially lowering water tables and altering streamflow sources. This study investigates how source water contributions to streamflow vary during the melt season across two hydrologically contrasting years (2010 and 2011) in a forested upland–peatland catchment at the Marcell Experimental Forest (MEF), located 40 km north of Grand Rapids, MN. Using multiple-solute end-member mixing analysis (EMMA) and extensive hydrological and water chemistry data collected by the USDA Forest Service, this study explores dynamic hydrologic connectivity by analyzing delayed contributions and integral delay times from peatland and upland water sources. Results show that in 2011, greater snow accumulation and more frequent precipitation events led to less delayed and higher proportional contributions of bog porewater to streamflow. Temporal variability in both the chemical composition and timing of dominant source water contributions was captured through a newly developed dynamic EMMA approach. These findings highlight the importance of accounting for temporal variability in source waters when assessing catchment hydrology and flow pathways, as such variability affects both hydrological and biogeochemical processes. The results offer insights that can support more informed water resource management in northern landscapes.