Measurement of Hydrogen Pools at Intermediate Spatial Scales Using Cosmic-Ray Neutron Probes
Location
ECC 216
Event Website
http://water.usu.edu/
Start Date
4-3-2012 4:15 PM
End Date
4-3-2012 4:20 PM
Description
The recently developed cosmic-ray method for measuring soil moisture over a horizontal footprint of hectometers and the depth of decimeters is currently being implemented in the COsmic-ray Soil Moisture Observing System (COSMOS) (data available at http://cosmos.hwr.arizona.edu/Probes/probemap.php). Currently 50 probes are operational around the continental US and Hawaii, with future expansion consisting of a network with 500 probes. The probe measures cosmic-ray fast neutrons that are generated within air and soil and are moderated mainly by hydrogen atoms in soil water, and emitted to the atmosphere where they form a well-mixed reservoir of neutrons whose density is inversely correlated with soil moisture. In addition, each probe measures thermal neutrons, which are thought to be more sensitive to changes in hydrogen from other sources including: vegetation, intercepted water, and snow. Here we compare thermal and fast neutron measurements from the TW Daniel Experimental Forest, which began in August 2011, with in-situ measurements of soil moisture and snow water equivalent (SWE) surveys. In addition to the observations, we present some numerical modeling results from the neutron transport code MCNPx with the goal of finding relationships to decouple the two pools of hydrogen with fast and thermal neutron measurements. Given the relative ease of the continuous measurements, sensor robustness, cost ($15 to 20k per sensor), and spatial scale of measurements, the sensor provides a unique dataset to assist in hydrologic models. The novel soil moisture and SWE datasets at this intermediate scale are useful for calibrating and validating existing hydrological models as well as soil moisture and snow depth data retrieved from satellite and airborne remote sensing.
Measurement of Hydrogen Pools at Intermediate Spatial Scales Using Cosmic-Ray Neutron Probes
ECC 216
The recently developed cosmic-ray method for measuring soil moisture over a horizontal footprint of hectometers and the depth of decimeters is currently being implemented in the COsmic-ray Soil Moisture Observing System (COSMOS) (data available at http://cosmos.hwr.arizona.edu/Probes/probemap.php). Currently 50 probes are operational around the continental US and Hawaii, with future expansion consisting of a network with 500 probes. The probe measures cosmic-ray fast neutrons that are generated within air and soil and are moderated mainly by hydrogen atoms in soil water, and emitted to the atmosphere where they form a well-mixed reservoir of neutrons whose density is inversely correlated with soil moisture. In addition, each probe measures thermal neutrons, which are thought to be more sensitive to changes in hydrogen from other sources including: vegetation, intercepted water, and snow. Here we compare thermal and fast neutron measurements from the TW Daniel Experimental Forest, which began in August 2011, with in-situ measurements of soil moisture and snow water equivalent (SWE) surveys. In addition to the observations, we present some numerical modeling results from the neutron transport code MCNPx with the goal of finding relationships to decouple the two pools of hydrogen with fast and thermal neutron measurements. Given the relative ease of the continuous measurements, sensor robustness, cost ($15 to 20k per sensor), and spatial scale of measurements, the sensor provides a unique dataset to assist in hydrologic models. The novel soil moisture and SWE datasets at this intermediate scale are useful for calibrating and validating existing hydrological models as well as soil moisture and snow depth data retrieved from satellite and airborne remote sensing.
https://digitalcommons.usu.edu/runoff/2012/Posters/21