|Title (Primary)||Water storage change estimation from in situ shrinkage measurements of clay soils|
|Author||te Brake, B.; van der Ploeg, M.J.; de Rooij, G.H.|
|Journal||Hydrology and Earth System Sciences|
|UFZ wide themes||RU1|
|Abstract||The objective of this study is to assess the applicability
of clay soil elevation change measurements to
estimate soil water storage changes, using
a simplified approach. We measured moisture contents in
aggregates by EC-5 sensors, and in multiple
aggregate and inter-aggregate spaces (bulk soil) by CS616 sensors. In
a long dry period, the assumption of constant isotropic shrinkage proved
invalid and a soil moisture dependant geometry factor was applied.
The relative overestimation made by assuming constant isotropic shrinkage in
the linear (basic) shrinkage phase was 26.4% (17.5 mm) for
the actively shrinking layer between 0 and 60 cm.
Aggregate-scale water storage and volume change revealed
a linear relation for layers ≥ 30 cm depth.
The range of basic shrinkage in the bulk soil was limited by
delayed drying of deep soil layers, and maximum water loss
in the structural shrinkage phase was 40% of
total water loss in the 0–60 cm layer, and over
60% in deeper layers.
In the dry period, fitted slopes of the ΔV–ΔW relationship
ranged from 0.41 to 0.56 (EC-5) and 0.42 to 0.55 (CS616). Under a
dynamic drying and wetting regime, slopes ranged
from 0.21 to 0.38 (EC-5) and 0.22 to 0.36 (CS616). Alternating
shrinkage and incomplete swelling resulted in limited volume change
relative to water storage change.
The slope of the ΔV–ΔW relationship depended on the
drying regime, measurement scale and combined effect of different
soil layers. Therefore, solely relying on surface level
elevation changes to infer soil water storage changes will
lead to large underestimations. Recent and future developments might provide
a basis for application of shrinkage relations to field situations, but
in situ observations will be required to do so.
|Persistent UFZ Identifier||https://www.ufz.de/index.php?en=20939&ufzPublicationIdentifier=13706|
|te Brake, B., van der Ploeg, M.J., de Rooij, G.H. (2013):
Water storage change estimation from in situ shrinkage measurements of clay soils
Hydrol. Earth Syst. Sci. 17 (5), 1933 - 1949