Integral quantification of seasonal soil moisture changes in farmland by cosmic-ray neutrons

Abstract

The 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 a few methods are on the way to close this gap between point measurements and remote sensing. One method that could determine an integral soil moisture at this scale is the so called cosmic ray sensing that was introduced to soil hydrology very recently the first time. The present study performed cosmic ray sensing at an agricultural field in a Central European lowland. To test the method it was accompanied by other soil moisture measurements for a summer period with corn crops growing on the field and a later autumn-winter period without crops and a longer period of snow cover. Additionally, meteorological data and above-ground crop biomass was included into the evaluation. Hourly values of cosmic ray sensing showed a high statistical variability. Six-hourly values corresponded well with classical soil moisture measurements, after calibration based on one dry and three wet periods of a few days each. Crop biomass seemed to influence the measurements only to minor degree, opposed to snow cover which has a more substantial impact on the measurements. The latter could be quantitatively related to count rates in two different variants of cosmic ray counters. Overall, our study outlines a procedure to apply the cosmic ray sensing method based on devices now commercially available, without the need for accompanying numerical simulations and suited for longer monitoring periods after initial calibration

Accuracy of the cosmic-ray soil water content probe in humid forest ecosystems: The worst case scenario

“…[7] Studies evaluating the use of CRP measurements for soil water content sensing have been restricted to high altitudes (Mt. Lemmon Cosmic Ray Laboratory, Arizona, at 2745 m above sea level (asl), and Lewis Springs, Arizona, at 1233 m asl), coastal sites on Hawaii [Desilets et al, 2010], a site within a desert area in Arizona, USA [Franz et al, 2012b], and a site within an agricultural field with sandy soils and relatively low soil water content in Germany [Rivera Villarreyes et al, 2011]. Because of the high altitude and/or low soil water content, these three test sites had rather favorable conditions for soil water content sensing with the CRP.…”

Storage-discharge relationships at different catchment scales based on local high-precision gravimetry

“…New methods such as cosmic-ray soil moisture probes (e.g. Zreda et al, 2008;Rivera Villarreyes et al, 2011), electromagnetic methods (electrical resistivity (e.g. Samouelian et al, 2005), ground penetrating radar (e.g.…”

Inverse modelling of cosmic‐ray soil moisture for field‐scale soil hydraulic parameters

“…In our study we investigate the feasibility of soil moisture data that have become available recently at the intermediate scale and use inverse modelling to overcome previous limitations. Cosmic-ray neutron sensing (CRS) Rivera Villarreyes et al, 2013), also known as ground albedo neutron sensing (GANS) (Rivera Villarreyes et al, 2011), provides continuous measurements of field soil moisture with greater penetration depth than remote sensing methods. Therefore, the CRS approach is an ideal way to investigate effective soil hydraulic properties of the root zone with inverse modelling at a small-catchment or agricultural-field scale.…”