Subsurface Water
Infiltration
Surface Water Hydrology
Infiltration
• Readings:
– Applied Hydrology Sections 4.3 and 4.4;
– Handbook of Hydrology Sections 5.1 and 5.2
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Soil texture and classification
Soil water properties, K(q), Y(q)
Infiltration
Green-Ampt method
Particle size measurement
Seives of progressively smaller size to get size
Distribution of soil
http://www.soils.agri.umn.edu/academics/classes/soil2125/doc/s2chp1.htm
Soil
Classification
USDA particle size classification
< 0.002mm is clay
0.002 – 0.5mm is silt
0.5mm – 10mm is sand
> 10mm is gravel
USDA Soil Texture Triangle
A soil with 30% sand,
40% clay and 30% silt
is a Clay Loam
% Silt = 100 - %Sand - %Clay
Variation of Saturated Hydraulic
Conductivity with Soil Texture
K
Se
Y
K
q
q
K
Interconnection of
Soil water properties
Y
Double Ring Infiltrometer
Measure rate of fall in inner ring
Infilration
http://www.alwi.com/wastewater.php
Infiltration by Horton’s method
f  f c   f 0  f c e
 kt
Infiltration into a soil water column
1
2
 h1  h2 
f  K

 z1  z2 
F  Lq
Green-Ampt method
q qr
Se 
qi  q r
q    q i
Relative saturation
Incremental change
in soil water content
as wetting front passes
Green-Ampt Parameter Definitions
q qr
Se 
qi  q r
q    q i
Relative saturation
Incremental change
in soil water content
as wetting front passes
Math for Green Ampt
GreenAmpt
Parameters