Spatiotemporal processes that contribute to hydrologic exchange between hillslopes, valley bottoms, and streams

Abstract

Quantifying how watershed structure influences the exchanges of water among component parts of a watershed, particularly the connection between uplands, valley bottoms, and in‐stream hydrologic exchange, remains a challenge. However, this understanding is critical for ascertaining the source areas and temporal contributions of water and associated biogeochemical constituents in streams. We used dilution gauging, mass recovery, and recording discharge stations to characterize streamflow dynamics across 52 reaches, from peak snowmelt to base flow, in the Tenderfoot Creek Experimental forest, Montana, USA. We found that watershed‐contributing area was only a significant predictor of net changes in streamflow at high moisture states and larger spatial scales. However, at the scale of individual stream reaches, the lateral contributing area in conjunction with underlying lithology and vegetation densities were significant predictors of gross hydrologic gains to the stream. Reach lateral contributing areas underlain by more permeable sandstone yielded less water across flow states relative to those with granite gneiss. Additionally, increases in the frequency of steps across each stream reach contributed to greater hydrologic gross losses. Together, gross gains and losses of water along individual reaches resulted in net changes of discharge that cumulatively scale to the observed outlet discharge dynamics. Our results provide a framework for understanding how hillslope topography, geology, vegetation, and valley bottom structure contribute to the exchange of water and cumulative increases of stream flow across watersheds of increasing size.

Soil CO2 and O2 Concentrations Illuminate the Relative Importance of Weathering and Respiration to Seasonal Soil Gas Fluctuations

“…3 and 4). This signature at the valley floor positions is likely driven by the wetter soil throughout the growing season, as expected based on the greater accumulating area above the sites (Bergstrom et al, 2016; Jencso et al, 2010;). Li et al (2018) report that soil moisture is generally greater at the valley floor position of Shale Hills and Garner Run.…”

Temporal dynamics in dominant runoff sources and flow paths in the Andean Páramo

“…The water from Andosols underlined the importance of hillslopes in runoff generation, which should not be underestimated in catchment studies [ Iwasaki et al ., ] because of its important interaction with riparian zones [ Ali et al ., ] and relationship with the hydrological connectivity between uplands and streams [ Bergstrom et al ., ]. Based on our analysis, water from Andosols contributed to runoff primarily via the deeper soil horizons (AN1.3).…”

Forensic hydrology: what function tells about structure in complex settings

“…In addition, tracer tests can be used to assess gross inflow (Bencala et al 2011;Bergstrom et al 2016). It is recommended to perform these measurements during baseflow (Cey et al 1998;Ruehl et al 2006;Kalbus et al 2006;Kikuchi et al 2012) to minimize the effect of surface runoff or interflow feeding the stream.…”