SWMM 5.2.2 Code for LID Function getSoilPercRate

 This code defines a function called "getSoilPercRate" that takes in a single input, "theta", which represents the moisture content (fraction). The function then calculates the percolation rate of water through a LID's soil layer and returns this value as output (in units of ft/s). The function first checks if the soil moisture is less than or equal to the field capacity, and if so, the function returns 0.0 (no percolation). If the soil moisture exceeds the field capacity, the function calculates the percolation rate as the unsaturated hydraulic conductivity and returns this value.

double getSoilPercRate(double theta) // // Purpose: computes percolation rate of water through a LID's soil layer. // Input: theta = moisture content (fraction) // Output: returns percolation rate within soil layer (ft/s) // { double delta; // moisture deficit // ... no percolation if soil moisture <= field capacity if ( theta <= theLidProc->soil.fieldCap ) return 0.0; // ... perc rate = unsaturated hydraulic conductivity delta = theLidProc->soil.porosity - theta; return theLidProc->soil.kSat * exp(-delta * theLidProc->soil.kSlope);