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9.4.4 Groundwater Infiltration

The percolation equation used in SWMM (Rossman & Huber, 2016) is used to calculate the groundwater infiltration.

where:
K = the saturated hydraulic conductivity,
∅ = the soil total porosity,
θ = the soil moisture
HCO = the percolation coefficient depending on the soil texture.

The soil parameters are given in Table 11.

Table 11 Soil Parameter for Different Soil Types

Soil Type Porosity
(vol/vol) 		Field Capacity
(vol/vol) 		Wilting Point
(vol/vol) 		Saturated Hydraulic Conductivity
(mm/day)
Sand 0.437 0.062 0.024 2890
Loamy Sand 0.437 0.105 0.047 719
Sandy Loam 0.453 0.19 0.085 262
Loam 0.463 0.232 0.116 79
Silt Loam 0.501 0.284 0.135 158
Sandy Clay Loam 0.398 0.244 0.136 37
Clay Loam 0.464 0.31 0.187 24
Silty Clay Loam 0.471 0.342 0.21 24
Sandy Clay 0.43 0.321 0.221 12
Silty Clay 0.479 0.371 0.251 12
Clay 0.475 0.378 0.265 6