massbal.c File Reference

Runoff, routing, and pollutant continuity accounting. More...

#include <string.h>
#include <stdlib.h>
#include <math.h>
#include "headers.h"

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Macros
#define	_CRT_SECURE_NO_DEPRECATE

Functions
double	massbal_getBuildup (int p)
	Computes current total buildup of a pollutant over study area.
double	massbal_getStorage (char isFinalStorage)
	Computes total system storage (nodes + links) filled.
double	massbal_getStoredMass (int p)
	Computes mass of pollutant stored in conveyance network.
double	massbal_getLoadingError ()
	Finalize surface pollutant loading totals and their continuity errors.
double	massbal_getGwaterError ()
	Compute the signed groundwater continuity error from accumulated totals.
double	massbal_getQualError ()
	Finalize routed pollutant mass totals and select the largest absolute error.
int	massbal_open ()
	Opens and initializes mass balance continuity checking.
void	massbal_close ()
	Frees memory used by mass balance system.
void	massbal_report ()
	Reports mass balance results.
void	massbal_updateRunoffTotals (int flowType, double v)
	Updates runoff totals after current time step.
void	massbal_updateGwaterTotals (double vInfil, double vUpperEvap, double vLowerEvap, double vLowerPerc, double vGwater)
	Updates groundwater totals after current time step.
void	massbal_initTimeStepTotals ()
	Initializes routing totals for current time step.
void	massbal_addInflowFlow (int type, double q)
	Adds flow inflow to routing totals for current time step.
void	massbal_updateLoadingTotals (int type, int p, double w)
	Adds inflow mass loading to loading totals for current time step.
void	massbal_addInflowQual (int type, int pollutIndex, double w)
	Adds quality inflow to routing totals for current time step.
void	massbal_addOutflowFlow (double q, int isFlooded)
	Adds flow outflow over current time step to routing totals.
void	massbal_addOutflowQual (int p, double w, int isFlooded)
	Adds pollutant outflow over current time step to routing totals.
void	massbal_addReactedMass (int pollutIndex, double w)
	Adds mass reacted during current time step to routing totals.
void	massbal_addSeepageLoss (int pollutIndex, double w)
	Adds mass lost to seepage during current time step to routing totals.
void	massbal_addToFinalStorage (int pollutIndex, double w)
	Adds mass remaining on dry surface to routing totals.
void	massbal_addNodeLosses (double evapLoss, double seepLoss)
	Adds node losses over current time step to routing totals.
void	massbal_addLinkLosses (double evapLoss, double seepLoss)
	Adds link losses over current time step to routing totals.
void	massbal_updateRoutingTotals (double tStep)
	Updates overall routing totals with totals from current time step.
void	massbal_getSysFlows (double f, double sysFlows[])
	Retrieves time-weighted average of old and new system flows.
double	massbal_getRunoffError ()
	Compute the signed surface runoff continuity error from accumulated totals.
double	massbal_getFlowError ()
	Compute the signed flow routing continuity error from accumulated totals.
double	massbal_getStepFlowError ()
	Computes flow routing mass balance error at current time step.

Variables
TRunoffTotals	RunoffTotals
TLoadingTotals *	LoadingTotals
TGwaterTotals	GwaterTotals
TRoutingTotals	FlowTotals
TRoutingTotals *	QualTotals
TRoutingTotals	StepFlowTotals
TRoutingTotals	OldStepFlowTotals
TRoutingTotals *	StepQualTotals
double *	NodeInflow
double *	NodeOutflow
double	TotalArea

Detailed Description

Runoff, routing, and pollutant continuity accounting.

Author

Caleb Buahin caleb.nosp@m..bua.nosp@m.hin@g.nosp@m.mail.nosp@m..com (OpenSWMM maintenance and extensions)

Copyright

Copyright (c) 2026 Caleb Buahin. OpenSWMM contributions only; original EPA SWMM credits are retained.

License

Apache-2.0 for OpenSWMM contributions; original EPA SWMM provenance is retained.

Macro Definition Documentation

_CRT_SECURE_NO_DEPRECATE

#define _CRT_SECURE_NO_DEPRECATE

Function Documentation

massbal_getBuildup()

double massbal_getBuildup

(

int

p

)

Computes current total buildup of a pollutant over study area.

Parameters

[in]

p

Pollutant index.

Returns

Total pollutant buildup (lbs or kg).

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massbal_getGwaterError()

double massbal_getGwaterError

(

void

)

Compute the signed groundwater continuity error from accumulated totals.

Returns

Percent discrepancy, positive for excess inflow and negative for excess outflow; a difference below one cubic foot returns TINY.

Postcondition

Updates GwaterTotals.finalStorage and pctError and the corresponding global error value. Recomputes final groundwater volume over all subcatchments.

Precondition

The global model and mass-balance totals are initialized; values use internal cubic-foot volume accounting, not report-scaled totals.

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massbal_getLoadingError()

double massbal_getLoadingError

(

void

)

Finalize surface pollutant loading totals and their continuity errors.

Returns

Largest signed pctError starting from zero, so all-negative errors produce zero; zero also results when no pollutants exist. Differences below 0.001 mass units produce TINY.

Postcondition

Adds remaining buildup to each finalLoad, computes percent errors, and converts COUNT-pollutant totals in place to log10 reporting values.

Note

This is a finalization operation, not an idempotent query: repeated calls add final buildup again and may transform COUNT totals repeatedly.

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massbal_getQualError()

double massbal_getQualError

(

void

)

Finalize routed pollutant mass totals and select the largest absolute error.

Returns

Signed percent error with the greatest absolute magnitude among pollutants, or zero when there are none. Tiny absolute mass discrepancies below 0.001 produce TINY.

Postcondition

Adds current stored mass to QualTotals[].finalStorage, sets pctError and QualError, and converts totals in place to lb/kg or log10 count reporting units.

Note

Call once during finalization. Repeated calls add storage and apply reporting conversions again; this is not an idempotent accessor.

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massbal_getStorage()

double massbal_getStorage

(

char

isFinalStorage

)

Computes total system storage (nodes + links) filled.

Parameters

[in]

isFinalStorage

TRUE if at final time period.

Returns

Storage volume used (ft3).

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massbal_getStoredMass()

double massbal_getStoredMass

(

int

p

)

Computes mass of pollutant stored in conveyance network.

Parameters

[in]

p

Pollutant index.

Returns

Mass of pollutant.

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massbal_getSysFlows()

void massbal_getSysFlows	(	double	f,
		double	sysFlows[] )

Retrieves time-weighted average of old and new system flows.

Parameters

[in]	f	Time weighting factor.
[out]	sysFlows	Array of total system flows.

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Variable Documentation

FlowTotals

TRoutingTotals FlowTotals

GwaterTotals

TGwaterTotals GwaterTotals

LoadingTotals

TLoadingTotals* LoadingTotals

NodeInflow

double* NodeInflow

NodeOutflow

double* NodeOutflow

OldStepFlowTotals

TRoutingTotals OldStepFlowTotals

QualTotals

TRoutingTotals* QualTotals

RunoffTotals

TRunoffTotals RunoffTotals

StepFlowTotals

TRoutingTotals StepFlowTotals

StepQualTotals

TRoutingTotals* StepQualTotals

TotalArea

double TotalArea