A Rationale for Old Water Discharge Through Macropores in a Steep, Humid Catchment

A Rationale for Old Water Discharge Through Macropores in a Steep, Humid Catchment Simultaneous observations of rapid preferential flow through macropores and isotopically “Old” water displacement remain unresolved in the Maimai (M8) catchment. Continuous, three‐dimensional soil moisture energy conditions were monitored in two discrete catchment positions for a series of storm events in 1987. Tensiometric response was related to the soil water characteristic curve, hillslope throughflow, and total catchment runoff. For events yielding ≪2 mm hr−1 peak runoff, near‐stream valley bottom groundwater systems discharged water volumes sufficient to account for storm period streamflow. This process was assisted by regular low (<−40 cm H2O) matric potential conditions and rapid filling of available soil water storage. For events yielding >2 mm hr−1 peak storm flow, hillslope hollow drainage into steeply sloping first‐order channels dominated old water production and most of the catchment storm flow. Highly transient macropore‐driven processes of crack infiltration (bypass flow), slope water table development, and lateral pipe flow enabled large volumes of stored water to be delivered to the first‐order channel bank at the appropriate time to satisfy catchment storm flow volumes and water isotopic and chemical composition. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Water Resources Research Wiley

A Rationale for Old Water Discharge Through Macropores in a Steep, Humid Catchment

Water Resources Research, Volume 26 (11) – Nov 1, 1990

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Publisher
Wiley
Copyright
Copyright © 1990 by the American Geophysical Union.
ISSN
0043-1397
eISSN
1944-7973
D.O.I.
10.1029/WR026i011p02821
Publisher site
See Article on Publisher Site

Abstract

Simultaneous observations of rapid preferential flow through macropores and isotopically “Old” water displacement remain unresolved in the Maimai (M8) catchment. Continuous, three‐dimensional soil moisture energy conditions were monitored in two discrete catchment positions for a series of storm events in 1987. Tensiometric response was related to the soil water characteristic curve, hillslope throughflow, and total catchment runoff. For events yielding ≪2 mm hr−1 peak runoff, near‐stream valley bottom groundwater systems discharged water volumes sufficient to account for storm period streamflow. This process was assisted by regular low (<−40 cm H2O) matric potential conditions and rapid filling of available soil water storage. For events yielding >2 mm hr−1 peak storm flow, hillslope hollow drainage into steeply sloping first‐order channels dominated old water production and most of the catchment storm flow. Highly transient macropore‐driven processes of crack infiltration (bypass flow), slope water table development, and lateral pipe flow enabled large volumes of stored water to be delivered to the first‐order channel bank at the appropriate time to satisfy catchment storm flow volumes and water isotopic and chemical composition.

Journal

Water Resources ResearchWiley

Published: Nov 1, 1990

References

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