Feasibility of irrigation monitoring with cosmic-ray neutron sensors
Accurate soil moisture (SM) monitoring is key in irrigation as it can greatly improve water use efficiency. Recently, cosmic-ray neutron sensors (CRNSs) have been recognized as a promising tool in SM monitoring due to their large footprint of several hectares. CRNSs also have great potential for irr...
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Published in | Geoscientific instrumentation, methods and data systems Vol. 11; no. 2; pp. 451 - 469 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Gottingen
Copernicus GmbH
14.12.2022
Copernicus Publications |
Subjects | |
Online Access | Get full text |
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Summary: | Accurate soil moisture (SM) monitoring is key in
irrigation as it can greatly improve water use efficiency. Recently,
cosmic-ray neutron sensors (CRNSs) have been recognized as a promising tool
in SM monitoring due to their large footprint of several hectares. CRNSs also
have great potential for irrigation applications, but few studies have
investigated whether irrigation monitoring with CRNSs is feasible, especially
for irrigated fields with a size smaller than the CRNS footprint. Therefore,
the aim of this study is to use Monte Carlo simulations to investigate the
feasibility of monitoring irrigation with CRNSs. This was achieved by
simulating irrigation scenarios with different field dimensions (from 0.5
to 8 ha) and SM variations between 0.05 and 0.50 cm3 cm−3.
Moreover, the energy-dependent response functions of eight moderators with
different high-density polyethylene (HDPE) thickness or additional
gadolinium thermal shielding were investigated. It was found that a
considerable part of the neutrons that contribute to the CRNS footprint can
originate outside an irrigated field, which is a challenge for irrigation
monitoring with CRNSs. The use of thin HDPE moderators (e.g. 5 mm) generally
resulted in a smaller footprint and thus stronger contributions from the
irrigated area. However, a thicker 25 mm HDPE moderator with gadolinium
shielding improved SM monitoring in irrigated fields due to a higher
sensitivity of neutron counts with changing SM. This moderator and shielding
set-up provided the highest chance of detecting irrigation events,
especially when the initial SM was relatively low. However, variations in SM
outside a 0.5 or 1 ha irrigated field (e.g. due to irrigation of
neighbouring fields) can affect the count rate more than SM variations due
to irrigation. This suggests the importance of retrieving SM data from the
surrounding of a target field to obtain more meaningful information for
supporting irrigation management, especially for small irrigated fields. |
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ISSN: | 2193-0864 2193-0856 2193-0864 |
DOI: | 10.5194/gi-11-451-2022 |