void gwater_getGroundwater(int j, double evap, double infil, double tStep)
//
// Purpose: computes groundwater flow from subcatchment during current time step.
// Input: j = subcatchment index
// evap = surface evaporation volume consumed (ft3)
// infil = surface infiltration volume (ft3)
// tStep = time step (sec)
// Output: none
//
{
int n; // node exchanging groundwater
double x[2]; // upper moisture content & lower depth
double vUpper; // upper vol. available for percolation
double nodeFlow; // max. possible GW flow from node
double area; // total subcatchment area
// --- save subcatchment's groundwater and aquifer objects to
// shared variables
GW = Subcatch[j].groundwater;
if ( GW == NULL ) return;
A = Aquifer[GW->aquifer];
// --- get fraction of total area that is pervious
FracPerv = subcatch_getFracPerv(j);
if ( FracPerv <= 0.0 ) return;
area = Subcatch[j].area;
// --- convert evap & infil volumes to rates
evap = evap / (FracPerv*area) / tStep; //(5.0.021 - LR)
infil = infil / (FracPerv*area) / tStep; //(5.0.021 - LR)
Infil = infil;
Tstep = tStep;
// --- save max. and available evap rates to shared variables
MaxEvap = Evap.rate;
AvailEvap = MAX((MaxEvap - evap), 0.0);
// --- save total depth & outlet node properties to shared variables
TotalDepth = GW->surfElev - A.bottomElev;
if ( TotalDepth <= 0.0 ) return;
n = GW->node;
// --- override node's invert if value was provided in the GW object
if ( GW->nodeElev != MISSING )
Hstar = GW->nodeElev - A.bottomElev;
else Hstar = Node[n].invertElev - A.bottomElev;
if ( GW->fixedDepth > 0.0 )
Hsw = GW->fixedDepth + Node[n].invertElev - A.bottomElev;
else Hsw = Node[n].newDepth + Node[n].invertElev - A.bottomElev;
// --- store state variables in work vector x
x[THETA] = GW->theta;
x[LOWERDEPTH] = GW->lowerDepth;
// --- set limits on upper perc
vUpper = (TotalDepth - x[LOWERDEPTH]) * (x[THETA] - A.fieldCapacity);
vUpper = MAX(0.0, vUpper);
MaxUpperPerc = vUpper / tStep;
// --- set limit on GW flow out of aquifer based on volume of lower zone
MaxGWFlowPos = x[LOWERDEPTH]*A.porosity / tStep;
// --- set limit on GW flow into aquifer from drainage system node
// based on min. of capacity of upper zone and drainage system
// inflow to the node
MaxGWFlowNeg = (TotalDepth - x[LOWERDEPTH]) * (A.porosity - x[THETA])
/ tStep;
nodeFlow = (Node[n].inflow + Node[n].newVolume/tStep) / area;
MaxGWFlowNeg = -MIN(MaxGWFlowNeg, nodeFlow);
// --- integrate eqns. for d(Theta)/dt and d(LowerDepth)/dt
// NOTE: ODE solver must have been initialized previously
odesolve_integrate(x, 2, 0, tStep, GWTOL, tStep, getDxDt);
// --- keep state variables within allowable bounds
x[THETA] = MAX(x[THETA], A.wiltingPoint);
if ( x[THETA] >= A.porosity )
{
x[THETA] = A.porosity - XTOL;
}
x[LOWERDEPTH] = MAX(x[LOWERDEPTH], 0.0);
if ( x[LOWERDEPTH] >= TotalDepth )
{
x[LOWERDEPTH] = TotalDepth - XTOL;
}
// --- save new state values
GW->theta = x[THETA];
GW->lowerDepth = x[LOWERDEPTH];
getFluxes(GW->theta, GW->lowerDepth);
GW->oldFlow = GW->newFlow;
GW->newFlow = GWFlow;
//--- get limit on infiltration into upper zone
GW->maxInfilVol = (TotalDepth - x[LOWERDEPTH])*
(A.porosity - x[THETA])/ FracPerv;
// --- update mass balance
updateMassBal(area, tStep);
}
void gwater_getGroundwater(Project* project, int j, double evap, double infil, double tStep)
//
// Purpose: computes groundwater flow from subcatchment during current time step.
// Input: j = subcatchment index
// evap = pervious surface evaporation volume consumed (ft3)
// infil = surface infiltration volume (ft3)
// tStep = time step (sec)
// Output: none
//
// Note: local "area" variable was replaced with shared variable "project->Area". // //(5.1.008)
{
int n; // node exchanging groundwater
double x[2]; // upper moisture content & lower depth
double vUpper; // upper vol. available for percolation
double nodeFlow; // max. possible project->GW flow from node
// --- save subcatchment's groundwater and aquifer objects to
// shared variables
project->GW = project->Subcatch[j].groundwater;
if ( project->GW == NULL ) return;
project->LatFlowExpr = project->Subcatch[j].gwLatFlowExpr; //(5.1.007)
project->DeepFlowExpr = project->Subcatch[j].gwDeepFlowExpr; //(5.1.007)
project->A = project->Aquifer[project->GW->aquifer];
// --- get fraction of total area that is pervious
project->FracPerv = subcatch_getFracPerv(project,j);
if ( project->FracPerv <= 0.0 ) return;
project->Area = project->Subcatch[j].area;
// --- convert infiltration volume (ft3) to equivalent rate
// over entire project->GW (subcatchment) area
infil = infil / project->Area / tStep;
project->Infil = infil;
project->Tstep = tStep;
// --- convert pervious surface evaporation already exerted (ft3)
// to equivalent rate over entire project->GW (subcatchment) area
evap = evap / project->Area / tStep;
// --- convert max. surface evap rate (ft/sec) to a rate
// that applies to project->GW evap (project->GW evap can only occur
// through the pervious land surface area)
project->MaxEvap = project->Evap.rate * project->FracPerv;
// --- available subsurface evaporation is difference between max.
// rate and pervious surface evap already exerted
project->AvailEvap = MAX((project->MaxEvap - evap), 0.0);
// --- save total depth & outlet node properties to shared variables
project->TotalDepth = project->GW->surfElev - project->GW->bottomElev;
if ( project->TotalDepth <= 0.0 ) return;
n = project->GW->node;
// --- establish min. water table height above aquifer bottom at which
// project->GW flow can occur (override node's invert if a value was provided
// in the project->GW object)
if ( project->GW->nodeElev != MISSING ) project->Hstar = project->GW->nodeElev - project->GW->bottomElev;
else project->Hstar = project->Node[n].invertElev - project->GW->bottomElev;
// --- establish surface water height (relative to aquifer bottom)
// for drainage system node connected to the project->GW aquifer
if ( project->GW->fixedDepth > 0.0 )
{
project->Hsw = project->GW->fixedDepth + project->Node[n].invertElev - project->GW->bottomElev;
}
else project->Hsw = project->Node[n].newDepth + project->Node[n].invertElev - project->GW->bottomElev;
// --- store state variables (upper zone moisture content, lower zone
// depth) in work vector x
x[THETA] = project->GW->theta;
x[LOWERDEPTH] = project->GW->lowerDepth;
// --- set limit on percolation rate from upper to lower project->GW zone
vUpper = (project->TotalDepth - x[LOWERDEPTH]) * (x[THETA] - project->A.fieldCapacity);
vUpper = MAX(0.0, vUpper);
project->MaxUpperPerc = vUpper / tStep;
// --- set limit on project->GW flow out of aquifer based on volume of lower zone
project->MaxGWFlowPos = x[LOWERDEPTH]*project->A.porosity / tStep;
// --- set limit on project->GW flow into aquifer from drainage system node
// based on min. of capacity of upper zone and drainage system
// inflow to the node
project->MaxGWFlowNeg = (project->TotalDepth - x[LOWERDEPTH]) * (project->A.porosity - x[THETA])
/ tStep;
nodeFlow = (project->Node[n].inflow + project->Node[n].newVolume/tStep) / project->Area;
project->MaxGWFlowNeg = -MIN(project->MaxGWFlowNeg, nodeFlow);
// --- integrate eqns. for d(project->Theta)/dt and d(LowerDepth)/dt
// NOTE: ODE solver must have been initialized previously
odesolve_integrate(project,x, 2, 0, tStep, GWTOL, tStep, getDxDt);
// --- keep state variables within allowable bounds
x[THETA] = MAX(x[THETA], project->A.wiltingPoint);
if ( x[THETA] >= project->A.porosity )
{
x[THETA] = project->A.porosity - XTOL;
x[LOWERDEPTH] = project->TotalDepth - XTOL;
}
x[LOWERDEPTH] = MAX(x[LOWERDEPTH], 0.0);
if ( x[LOWERDEPTH] >= project->TotalDepth )
{
x[LOWERDEPTH] = project->TotalDepth - XTOL;
}
// --- save new values of state values
project->GW->theta = x[THETA];
project->GW->lowerDepth = x[LOWERDEPTH];
getFluxes(project, project->GW->theta, project->GW->lowerDepth);
project->GW->oldFlow = project->GW->newFlow;
project->GW->newFlow = project->GWFlow;
project->GW->evapLoss = project->UpperEvap + project->LowerEvap;
//--- find max. infiltration volume (as depth over
// the pervious portion of the subcatchment)
// that upper zone can support in next time step
project->GW->maxInfilVol = (project->TotalDepth - x[LOWERDEPTH]) *
(project->A.porosity - x[THETA]) / project->FracPerv;
// --- update project->GW mass balance
updateMassBal(project,project->Area, tStep);
// --- update project->GW statistics //(5.1.008)
stats_updateGwaterStats(project, j, infil, project->GW->evapLoss, project->GWFlow, project->LowerLoss, //(5.1.008)
project->GW->theta, project->GW->lowerDepth + project->GW->bottomElev, tStep); //(5.1.008)
}