Three applications of cosmic-ray probe in hydrology
Marek Zreda
University of Arizona
Examples:
1. Soil moisture 2. Rainfall rate
3. Hydraulic conductivity Problem:
Usually done at points
Single point measurements not representative Solutions:
Measurements at many points, followed by aggregating and, if necessary, upscaling
or
Measurements that use scale-integrating methods
Measurements of states, fluxes and properties at field scale
Focus of this talk
Example 1: Variations in soil moisture, circle, 400 m diameter
Soil moisture, m
3m
-30.1 0.2 0.3
Depth, cm
0
5
10
15
20
25
30
San Pedro, Arizona, USA
Coring and oven drying
Jul/11 Nov/11 Mar/12 Jul/12 Nov/12
Rainfall (mm)
0 5 10 15 20
25 Santa Rita, Arizona, USA
Example 2: Variations in rainfall rate, circle, 400 m diameter
Tipping bucket rain gauge, Santa Rita, Arizona, USA.
Example 3: Variations in soil hydraulic conductivity, circle, 400 m diameter
Soil moisture (m3 m-3)
0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
log[Hydraulic conductivity (cm/d)]
-4 -3 -2 -1 0 1
-4 -3 -2 -1 0 1 Manitou, Colorado, USA
HYPROP device
Scale-integrating measurements using cosmic rays
Neutrons are measured at the the horizontal scale of a few hectometers and vertical scale of a few decimeters with the use of cosmic-ray probes (stationary or mobile).
Production and removal of fast neutrons
Space:
incoming high-energy cosmic-ray protons
Atmosphere:
generation of
secondary cosmic rays
Ground:
scattering thermalization absorption
• Primary - mostly protons and alphas
• Interact with magnetic field
- intensity depends on solar activity and geomagnetic latitude
• Interact with atmospheric nuclei
• Produce secondary particles - cascade - intensity depends on barometric pressure
• Produce fast neutrons
• Remove fast neutrons
- slowing down by elastic collisions - leads to thermalization
- and then absorption
The last three processes depend on the chemical composition of the medium, in particular on its hydrogen content.
Zreda et al., 2012.
Moderating power and neutron intensity
φ(E) - flux of neutrons of energy E Q - strength of source function N - number of atoms of an element
σsc- scattering cross section for an element ξ- log decrement of energy per collision σ ⋅ ξ- moderating power
)]
( [
E ) Q E
( σ ξ σ ξ
φ = ⋅ ⋅ + Σ ⋅ ⋅
N
N
H H HSoil moisture at the horizontal scale of hectometers
San Pedro, Arizona, USA, 2007 - 2012
2008 2009 2010 2011 2012
Soil moisture, m3 m-3
0.0 0.1 0.2 0.3
0.4 Soil samples
COSMOS probe
200 m Soils
COSMOS
Example 1: Soil moisture: cosmic-ray soil moisture probe
Example 2: Rainfall: cosmic-ray rain gauge
Santa Rita COSMOS probe, Arizona, USA.
Santa Rita, AZ
07/11 08/11 09/11 10/11 11/11 12/11 01/12 02/12 03/12
SM, v. % P, mm/h
0 3 6 9 12 15 18 21
Neutron-derived soil moisture vs. rainfall
Manitou, CO
06/10 07/10 08/10 09/10 10/10 11/10 12/10 01/11
SM, v. % P, mm/h
0 10 20 30 40 50
7Jul11 8Jul11 9Jul11
SM, v. % P, mm/h
0 3 6 9 12
23Jul11 24Jul11 25Jul11 0
3 6 9 12
13Dec11 14Dec11 15Dec11 0
3 6 9 12 15 18 21
13 mm
19 mm
22 mm 18 mm
18 mm
24 mm
13Nov11 14Nov11
SM, v. % P, mm/h
0 2 4 6 8 10
7 mm 14 mm
9Sep11 10Sep11 11Sep11 0
3 6 9 12 15
45 mm 33 mm
10Aug11 11Aug11 0
3 6 9 12
11 mm
12 mm
4Nov11 5Nov11 6Nov11
SM, v. % P, mm/h
0 1 2 3 4 5 6
7 mm 10 mm
13Sep11 14Sep11 15Sep11 0
3 6 9 12 15 18
14 mm
14 mm
14Feb12 15Feb12 0
2 4 6 8 10
4 mm
10 mm
Neutron-derived rainfall amounts, Santa Rita
8Jul10 9Jul10 10Jul10
SM, v. % P, mm/h
0 3 6 9 12 15 18
20Jul10 0 21Jul10 22Jul10 5
10 15 20 25 30 35 40
29Jul10 30Jul10 31Jul10 03
69 1215 1821 2427 3033
8 mm 58 mm 17 mm
10 mm
50 mm
20 mm
5Aug10 6Aug10 7Aug10
SM, v. % P, mm/h
0 10 20 30 40 50
17 mm 20 mm
9Aug10 10Aug10 11Aug10 0
5 10 15 20 25 30 35 40
19 mm 24 mm
Neutron-derived rainfall amounts, Manitou
Rainfall: cosmic-ray vs. rain gauge
Manitou, CO
Rainfall from rain gauge, mm
0 10 20 30 40 50 60
Rainfall from neutrons, mm
0 10 20 30 40 50 60
Santa Rita, AZ
P, rain gauge, mm
0 10 20 30 40 50
Rainfall from neutrons, mm
0 10 20 30 40 50
Example 3: Unsaturated hydraulic conductivity: cosmic- ray hydraulic conductivity meter
Manitou COSMOS probe, Colorado, USA.
Measuring soil hydraulic conductivity
2010
Jun Jul Aug Sep Oct
Soil moisture (m3 m-3 ) 0.0 0.1 0.2 0.3 0.4 0.5
Rainfall (cm hr-1 ) 0 1 2 3 4 5
Drying time, t (h)
0 100 200 300 400 500 600
Soil moisture, SM (m3 m-3 )
0.0 0.1 0.2 0.3 0.4 0.5 0.6
SM = a0exp(-a1 t) + a2
Soil moisture (m3 m-3)
0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
log[Hydraulic conductivity (cm/d)]
-4 -3 -2 -1 0 1
-4 -3 -2 -1 0 1
Keff
Soil moisture (m3 m-3)
0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
log[Hydraulic conductivity (cm/d)]
-4 -3 -2 -1 0 1
-4 -3 -2 -1 0 1 Kmeas
Kagg
Hydraulic conductivity: cosmic-ray vs. HYPROP
Soil moisture (m
3m
-3)
0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
lo g[ Hydrauli c conduct ivi ty (cm/ d)]
-4 -3 -2 -1 0 1
-4 -3 -2 -1 0 1
K
aggK
effscale
scale
