////////////////////////////////////////////////////////////
// This function has been totally rewritten. (LR - 7/5/06 )
////////////////////////////////////////////////////////////
//float landuse_getWashoff(int i, float area, TLandFactor landFactor[],
// float fPpt, float runoff, float wUpstrm[],
// float wTotal[], float tStep)
void landuse_getWashoff(int i, float area, TLandFactor landFactor[],
float qRunoff, float tStep, float washoffLoad[])
//
// Input: i = land use index
// area = subcatchment area (ft2)
// landFactor[] = array of land use data for subcatchment
// runoff = runoff flow rate (ft/sec) over subcatchment
// tStep = time step (sec)
// Output: washoffLoad[] = pollutant load in surface washoff (mass/sec)
// Purpose: computes surface washoff load for all pollutants generated by a
// land use within a subcatchment.
//
{
int p; //pollutant index
float fArea; //area devoted to land use (ft2)
//added
float iArea; //impervious area (ft2)
// --- find area devoted to land use
fArea = landFactor[i].fraction * area;
// --- find impervious area devoted to land use
iArea = fArea * Landuse[i].pctimp;
// --- initialize washoff loads from land use
for (p = 0; p < Nobjects[POLLUT]; p++) washoffLoad[p] = 0.0;
// --- compute contribution from direct runoff load
for (p = 0; p < Nobjects[POLLUT]; p++)
{
if (Pollut[p].sedflag > 0) // the pollutant is sediment
// calculate sediment washoff on impervious area
washoffLoad[p] +=
landuse_getRunoffLoad(i, p, iArea, landFactor, qRunoff, tStep);
else
// calculate pollutant washoff on total landuse area
washoffLoad[p] +=
landuse_getRunoffLoad(i, p, fArea, landFactor, qRunoff, tStep);
}
// --- compute contribution from co-pollutant
for (p = 0; p < Nobjects[POLLUT]; p++)
{
washoffLoad[p] += landuse_getCoPollutLoad(p, washoffLoad, tStep);
}
}
void subcatch_getWashoff(int j, double runoff, double tStep)
//
// Input: j = subcatchment index
// runoff = total subcatchment runoff (ft/sec)
// tStep = time step (sec)
// Output: none
// Purpose: computes new runoff quality for subcatchment.
//
// Considers two separate pollutant generating streams that are combined
// together:
// 1. complete mix mass balance of pollutants in surface ponding due to
// runon, wet deposition, infil., & evap.
// 2. washoff of pollutant buildup as described by the project's land
// use washoff functions.
//
{
int i, p;
double massLoad;
// --- return if there is no area or no pollutants
if ( Nobjects[POLLUT] == 0 || Subcatch[j].area == 0.0 ) return;
// --- intialize outflow loads to zero
for (p = 0; p < Nobjects[POLLUT]; p++)
{
WashoffLoad[p] = 0.0; // load just from washoff function
OutflowLoad[p] = 0.0; // Washoff load + ponded water load
}
// --- add outflow of pollutants in ponded water to outflow loads
// (Note: at this point, Subcatch.newQual contains mass inflow
// from any upstream subcatchments draining to this one)
updatePondedQual(j, Subcatch[j].newQual, Subcatch[j].pondedQual, tStep);
// --- add washoff loads from landuses to outflow loads
if ( runoff >= MIN_RUNOFF )
{
for (i = 0; i < Nobjects[LANDUSE]; i++)
{
if ( Subcatch[j].landFactor[i].fraction > 0.0 )
{
landuse_getWashoff(i, Subcatch[j].area, Subcatch[j].landFactor,
runoff, tStep, WashoffLoad);
}
}
// --- compute contribution from any co-pollutant
for (p = 0; p < Nobjects[POLLUT]; p++)
{
WashoffLoad[p] += landuse_getCoPollutLoad(p, WashoffLoad);
OutflowLoad[p] += WashoffLoad[p];
}
}
// --- switch from internal runoff (used in washoff functions) to
// runoff that actually leaves the subcatchment
runoff = Subcatch[j].newRunoff;
// --- for each pollutant
for (p = 0; p < Nobjects[POLLUT]; p++)
{
// --- update subcatchment's total runoff load in lbs (or kg)
massLoad = OutflowLoad[p] * Pollut[p].mcf;
Subcatch[j].totalLoad[p] += massLoad;
// --- update overall runoff mass balance if runoff goes to
// conveyance system
if ( Subcatch[j].outNode >= 0 || Subcatch[j].outSubcatch == j )
massbal_updateLoadingTotals(RUNOFF_LOAD, p, massLoad);
// --- save new outflow runoff concentration (in mass/L)
if ( runoff > MIN_RUNOFF )
Subcatch[j].newQual[p] = OutflowLoad[p] / (runoff * tStep * LperFT3);
else Subcatch[j].newQual[p] = 0.0;
}
}
