Channel water balance and exchange with subsurface flow along a mountain headwater stream in Montana, United States

Water Resources Research
By: , and 



Channel water balances of contiguous reaches along streams represent a poorly understood scale of stream-subsurface interaction. We measured reach water balances along a headwater stream in Montana, United States, during summer base flow recessions. Reach water balances were estimated from series of tracer tests in 13 consecutive reaches delineated evenly along a 2.6 km valley segment. For each reach, we estimated net change in discharge, gross hydrologic loss, and gross hydrologic gain from tracer dilution and mass recovery. Four series of tracer tests were performed during relatively high, intermediate, and low base flow conditions. The relative distribution of channel water along the stream was strongly related to a transition in valley structure, with a general increase in gross losses through the recession. During tracer tests at intermediate and low flows, there were frequent substantial losses of tracer mass (>10%) that could not be explained by net loss in flow over the reach, indicating that many of the study reaches were concurrently losing and gaining water. For example, one reach with little net change in discharge exchanged nearly 20% of upstream flow with gains and losses along the reach. These substantial bidirectional exchanges suggest that some channel interactions with subsurface flow paths were not measurable by net change in flow or transient storage of recovered tracer. Understanding bidirectional channel water balances in stream reaches along valleys is critical to an accurate assessment of stream solute fate and transport and to a full assessment of exchanges between the stream channel and surrounding subsurface.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Channel water balance and exchange with subsurface flow along a mountain headwater stream in Montana, United States
Series title Water Resources Research
DOI 10.1029/2008WR007644
Volume 45
Issue 11
Year Published 2009
Language English
Publisher AGU
Contributing office(s) Branch of Regional Research-Western Region, Toxic Substances Hydrology Program
Description W11427
Country United States
State Montana
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