InfiltrationReading AH Sec 4.3 to 4.4
InfiltrationGeneralProcess of water penetrating from ground into soilFactors affectingCondition of soil surface, vegetative cover, soil properties, hydraulic conductivity, antecedent soil moistureFour zonesSaturated, transmission, wetting, and wetting front
InfiltrationInfiltration rateRate at which water enters the soil at the surface (in/hr or cm/hr)Cumulative infiltrationAccumulated depth of water infiltrating during given time period
InfiltrometersSingle RingDouble Ringhttp://en.wikipedia.org/wiki/Infiltrometer
Infiltration MethodsHorton and Phillips Infiltration models developed as approximate solutions of an exact theory (Richards Equation)Green AmptInfiltration model developed from an approximate theory to an exact solution
Hortonian InfiltrationRecall Richards EquationAssume K and D are constants, not a function of q or zSolve for moisture diffusion at surface
f0 initial infiltration rate, fc is constant rate and k is decay constant
Hortonian Infiltration
Chart1
333
2.15582950581.84905840252.5339458274
1.60017068091.23441905642.1558295058
1.23441905640.90618213571.8490584025
0.99367015640.73089320121.6001706809
0.83520187090.63728334621.398244563
0.73089320120.58729271221.2344190564
0.66223404620.56059612691.1015051129
0.61704049150.5463393030.9936701564
0.58729271220.53872570640.9061821357
0.56771181460.53465980420.8352018709
0.55482306920.53248848340.7776145813
0.5463393030.53132892910.7308932012
0.54075502870.53070969030.6929874868
0.53707928870.53037899720.6622340462
0.53465980420.53020239650.6372833462
0.53306722560.53010808620.6170404915
0.53201894160.53005772140.600617178
0.53132892910.53003082510.5872927122
0.53087474180.53001646160.5764823853
0.53057578180.5300087910.5677118146
k1
k3
k2
k1 < k2 < k3
fc
f0
f1
f2
f3
Time
Infiltration rate, f
Sheet1
4.1826.2732.091
tf1f2f3
0333
0.12.15582950581.84905840252.5339458274
0.21.60017068091.23441905642.1558295058
0.31.23441905640.90618213571.8490584025
0.40.99367015640.73089320121.6001706809
0.50.83520187090.63728334621.398244563
0.60.73089320120.58729271221.2344190564
0.70.66223404620.56059612691.1015051129
0.80.61704049150.5463393030.9936701564
0.90.58729271220.53872570640.9061821357
10.56771181460.53465980420.8352018709
1.10.55482306920.53248848340.7776145813
1.20.5463393030.53132892910.7308932012
1.30.54075502870.53070969030.6929874868
1.40.53707928870.53037899720.6622340462
1.50.53465980420.53020239650.6372833462
1.60.53306722560.53010808620.6170404915
1.70.53201894160.53005772140.600617178
1.80.53132892910.53003082510.5872927122
1.90.53087474180.53001646160.5764823853
20.53057578180.5300087910.5677118146
Sheet2
Sheet3
MBD000A3D93.unknown
Philips EquationRecall Richards EquationAssume K and D are functions of q, not zSolutionTwo terms represent effects of Suction headGravity headS SorptivityFunction of soil suction potentialFound from experiment
Green Ampt InfiltrationWetted ZoneWetting FrontPonded WaterGround SurfaceDry Soil
Green Ampt Infiltration (Cont.)Apply finite difference to the derivative, between Ground surfaceWetting frontWetted ZoneWetting FrontGround SurfaceDry Soil
Green Ampt Infiltration (Cont.)Wetted ZoneWetting FrontGround SurfaceDry SoilIntegrateEvaluate the constant of integration
Green Ampt Infiltration (Cont.)Wetted ZoneWetting FrontGround SurfaceDry SoilNonlinear equation, requiring iterative solution.
Soil ParametersGreen-Ampt model requires Hydraulic conductivity, Porosity, Wetting Front Suction HeadEffective saturationEffective porosity
Soil Class
Porosity
Effective Porosity
Wetting Front Suction Head
Hydraulic Conductivity
n
e
(
K
(cm)
(cm/h)
Sand
0.437
0.417
4.95
11.78
Loam
0.463
0.434
9.89
0.34
Clay
0.475
0.385
31.63
0.03
Ponding timeElapsed time between the time rainfall begins and the time water begins to pond on the soil surface (tp)
Ponding TimeUp to the time of ponding, all rainfall has infiltrated (i = rainfall rate)
ExampleSilty-Loam soil, 30% effective saturation, rainfall 5 cm/hr intensity
Top Related