Temporal Stability of Soil Moisture Spatial Pattern and Subsurface Preferential Flow Pathways in the Shale Hills Catchment

Abstract:

Hydropedologic approaches utilize a strategy of ‘‘map first, then
design’’ and ‘‘direction first, then velocity’’ in enhancing the understanding
of complex landscape processes. This is illustrated in this
study by examples dealing with (i) the mapping of soils and landforms
in monitoring and interpreting soil moisture dynamics and (ii) the
identification of flow pathways in determining landscape water fluxes.
Year-round monitoring at 77 sites in the Shale Hills Catchment in
central Pennsylvania revealed a temporal stability of soil moisture
spatial pattern as governed by soil types and landforms, and suggested
the significance of subsurface preferential flow in rapid channeling
of precipitation to stream discharge. The five soil series identified
in the catchment had the following decreasing trend of moisture
storage within the upper 1.1-m solum: Ernest . Blairton $ Rushtown
$ Berks . Weikert. The four landform units showed a decreasing
trend of soil moisture storage: Valley . Swale . Hillslope . Hilltop.
The 77 monitoring sites exhibited considerable ranking stability
throughout the monitoring year at multiple depths, with the subsurface’s
moisture ranking stability being slightly stronger than that at the
surface. A slope-intercept analysis of linear regression further described
the four conditions of temporal stability as related to soil moisture and
hydrologic dynamics. Because of more extensively distributed deeper
soils and hydrologically active swales, plus favorable subsurface lateral
flow pathways and slightly higher cumulative rainfall, the south-facing
slope in this V-shaped catchment was hydrologically more active than
the north-facing slope in terms of draining more water at a faster rate
to the stream. Approximately two-thirds of the soil horizons measured
in the catchment had lateral saturated hydraulic conductivity (Ksat)
values 1.5 to 142.5 higher than vertical values. Because of a moderate
slope (up to 25–48%), horizontally dipping shale bedrock (11.5–17.1
),
and shallow tree rooting systems (branching laterally), subsurface
lateral flow was prominent in this humid forested catchment.

Attach file: 

Lin_2006_VZJ.pdf