EGU General Assembly 2020
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Monitoring and Mapping of Soil and Snow Water Across Scales with Cosmic-Ray Neutron Sensor Networks and Mobile Platforms

Martin Schrön1, Sascha E Oswald2, Steffen Zacharias1, Peter Dietrich1, and Sabine Attinger1
Martin Schrön et al.
  • 1Helmholtz Centre for Environmental Research GmbH - UFZ
  • 2University of Potsdam

Cosmic-ray neutron albedo sensing (CRNS) is a modern technology that can be used to non-invasively measure the average water content in the environment (i.e., in soil, snow, or vegetation). The sensor footprint encompasses an area of 10-15 hectares and extends tens of decimeters deep into the soil. This method might have the potential to bridge the scale gap between conventional in-situ sensors and remote-sensing data in both, the horizontal and the vertical domain.

Currently, more than 200 sensors are operated in the growing networks of national and continental observatories. While single CRNS stations are continuously monitoring the local water dynamics at fixed field sites, mobile CRNS platforms are used for on-demand soil moisture mapping at the regional scale. The sensors are rapidly operational on any ground- or airborne vehicle. The data is particularly useful to study hydrological extreme events, heatwaves, and snow melt/accumulation, and it is being applied in hydrological models and agricultural irrigation management.

In the presentation we will explore the potential of the CRNS method to support and complement in-situ and remote-sensing data for hydrological event monitoring. We will discuss ongoing research activities that are aimed at improving the operationality, frequency, and spatial extend of CRNS measurements. New measurement strategies that are currently explored are, for example: dense clusters of 20 CRNS stations fully covering a 100 hectare catchment; heat wave monitoring with mobile car-based CRNS; regular soil/snow water mapping using mobile CRNS on cars and trains; and airborne surveys using CRNS on gyrocopters.

Future CRNS observations could provide a valuable contribution to the multi-sensor approach, e.g. to help tracking and characterizing surface water movement, to map regional-scale soil moisture patterns, or to calibrate and evaluate satellite data.

How to cite: Schrön, M., Oswald, S. E., Zacharias, S., Dietrich, P., and Attinger, S.: Monitoring and Mapping of Soil and Snow Water Across Scales with Cosmic-Ray Neutron Sensor Networks and Mobile Platforms, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22317,, 2020.


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displays version 1 – uploaded on 04 May 2020
  • CC1: Comment on EGU2020-22317, Katya Dimitrova Petrova, 04 May 2020

    Hi, thanks for sharing this research. I was especially mindblown by the airborne application (using the gyrocopter). I am curious, do you need to do any additional correction to account for the fact that you are using CRNS several meters aboveground?

    (If I remember correctly, a couple of years ago, there was an ongoing discussion on whether installing the static CRNS 1.5 or 2 m aboveground made a difference).

    • AC1: Reply to CC1, Martin Schrön, 04 May 2020

      Hi Katja, the intensity of relected neutrons decreases significantly with height in the first few hundred meters. This tightens the range between wet-soil-neutrons and dry-soil-neutrons and therefore increases uncertainty, the higher we go. Since we know the intensity-height relationship from simulations, it is however possible to correct for this effect. You can see chapter 10 in my dissertation to catch a glimpse on our first measurements and simulation results:

      Since you mentioned the discussion with stationary probes, to my experience the neutron intensity difference is visible in the first 1 m above the surface, but quickly becomes insignificant in the range of 1-5 meters. However, I think the height above ground does have a significant effect on the footprint, as low hanging sensors are more exposed to the near-field than higher hanging sensors. So, in very heterogeneous terrain you might be able to see differences related to vertical sensor position.


      • CC2: Reply to AC1, Katya Dimitrova Petrova, 04 May 2020

        Many thanks for your reply, Martin, it is very insightful.