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| Titel |
Ground Albedo Neutron Sensing (GANS) method for measurements of soil moisture in cropped fields |
| VerfasserIn |
Carlos Andres Rivera Villarreyes, Gabriele Baroni, Sascha E. Oswald |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250072153
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| Zusammenfassung |
| Measurement of soil moisture at the plot or hill-slope scale is an important link between local
vadose zone hydrology and catchment hydrology. However, so far only few methods are on
the way to close this gap between point measurements and remote sensing. This study
evaluates the applicability of the Ground Albedo Neutron Sensing (GANS) for integral
quantification of seasonal soil moisture in the root zone at the scale of a field or small
watershed, making use of the crucial role of hydrogen as neutron moderator relative to other
landscape materials.
GANS measurements were performed at two locations in Germany under different
vegetative situations and seasonal conditions. Ground albedo neutrons were measured at (i) a
lowland Bornim farmland (Brandenburg) cropped with sunflower in 2011 and winter rye in
2012, and (ii) a mountainous farmland catchment (Schaefertal, Harz Mountains) since
middle 2011. At both sites depth profiles of soil moisture were measured at several
locations in parallel by frequency domain reflectometry (FDR) for comparison and
calibration.
Initially, calibration parameters derived from a previous study with corn cover were tested
under sunflower and winter rye periods at the same farmland. GANS soil moisture based on
these parameters showed a large discrepancy compared to classical soil moisture
measurements. Therefore, two new calibration approaches and four different ways of
integration the soil moisture profile to an integral value for GANS were evaluated in this
study. This included different sets of calibration parameters based on different growing
periods of sunflower. New calibration parameters showed a good agreement with FDR
network during sunflower period (RMSE = 0.023 m3 m-3), but they underestimated soil
moisture in the winter rye period. The GANS approach resulted to be highly affected by
temporal changes of biomass and crop types which suggest the need of neutron corrections
for long-term observations with crop rotation. Finally, Bornim sunflower parameters were
transferred to Schaefertal catchment for further evaluation. This study proves GANS
potential to close the measurement gap between point scale and remote sensing
scale; however, its calibration needs to be adapted for vegetation in cropped fields. |
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