#include <Reach.h>

Classes
struct	RoutingState

Public Types
enum class	Scheme { None , Lag , Muskingum , MuskingumCunge }

Public Member Functions
	Reach (Subbasin *subbasin)

void	Initialize ()

void	SetChannelRouting (const ChannelRoutingSettings &settings)

double	RouteUpstream (double inflowVolume, double timeStepInDays)

double	RouteLocal (double localVolume, double timeStepInDays)

bool	RoutesLocalRunoff () const

void	Reset ()

void	SaveAsInitialState ()

Subbasin *	GetSubbasin () const

Scheme	GetScheme () const

double	GetLength () const

double	GetSlope () const

double	GetWidth () const

double	GetManning () const

double	GetCelerity () const

double	GetCelerityForDischarge (double dischargeM3s) const

double	GetMuskingumX () const

double	GetTravelTimeInDays () const

int	GetSubreachCount () const

double	GetInflow () const

double	GetOutflow () const

double	GetStorage () const

Static Public Member Functions
static Scheme	SchemeFromString (const string &name)

static string	SchemeToString (Scheme scheme)

Protected Attributes
Subbasin *	_subbasin

Scheme	_scheme = Scheme::None

bool	_routeLocal = false

double	_length = 0

double	_slope = 0

const float *	_celerity = nullptr

const float *	_celerityExponent = nullptr

const float *	_referenceDischarge = nullptr

const float *	_x = nullptr

const float *	_width = nullptr

const float *	_manning = nullptr

double	_celerityOverride = NAN_D

double	_xOverride = NAN_D

double	_widthOverride = NAN_D

double	_manningOverride = NAN_D

double	_inflow = 0

double	_outflow = 0

RoutingState	_main

RoutingState	_local

Detailed Description

The channel reach of a subbasin: the main channel from the point where the upstream subbasins enter to the subbasin outlet. It routes the volume arriving from upstream (m3 per time step) to the outlet, where the subbasin's own runoff joins it.

Four routing schemes exist: instantaneous (the inflow leaves the reach in the same step), a pure translation (lag), the Muskingum method and Muskingum-Cunge. The first three use a celerity: the model-wide parameter (which a subbasin property may override reach by reach), optionally varying with the discharge through a power law. Muskingum-Cunge instead derives the celerity and the weighting factor from the channel geometry (length, slope, width and Manning roughness) and the discharge of the step, so its parameters are measured rather than calibrated. A Muskingum-Cunge reach is also divided into sub reaches short enough for the wave to be resolved (the Ponce and Theurer criterion), the sub reaches being routed in series.

The subbasin's own runoff joins at the outlet by default. With 'route_local_runoff' it is routed too, through half the reach: generated uniformly along the reach, it travels half of it on average.

Member Enumeration Documentation

◆ Scheme

enum class Reach::Scheme

strong

The routing schemes: how the inflow of a time step is spread over the following ones.

Constructor & Destructor Documentation

◆ Reach()

Reach::Reach ( Subbasin * subbasin )

explicit

Create the reach of a subbasin.

Parameters

subbasin The subbasin the reach belongs to (its outlet is the reach outlet).

Member Function Documentation

◆ GetCelerity()

double Reach::GetCelerity ( ) const

nodiscard

Get the celerity of this reach at the reference discharge [m/s]: the subbasin property when present, else the model-wide parameter, else 1.

Returns: the reference celerity.

◆ GetCelerityForDischarge()

double Reach::GetCelerityForDischarge ( double dischargeM3s ) const

nodiscard

Get the celerity of this reach at a given discharge [m/s].

With the Muskingum-Cunge scheme it comes from the Manning relation for a wide channel: the kinematic celerity is 5/3 of the flow velocity. With the other schemes it is the reference celerity scaled by the discharge ratio raised to 'celerity_exponent' (0, the default, keeps it constant). The result is clamped to a plausible range for a river so that a vanishing discharge cannot give an unbounded travel time.

Parameters

dischargeM3s The discharge [m3/s]; a non-positive value returns the reference celerity.

Returns: the celerity.

◆ GetInflow()

double Reach::GetInflow ( ) const

inlinenodiscard

Get the volume that entered the reach in the current time step [m3]: the upstream inflow, plus the sub basin's own runoff when it is routed.

Returns: the inflow volume.

◆ GetLength()

double Reach::GetLength ( ) const

inlinenodiscard

Get the reach length [m] (0 when the subbasin has no 'length' property).

Returns: the reach length.

◆ GetManning()

double Reach::GetManning ( ) const

nodiscard

Get the Manning roughness in use for this reach [s/m^(1/3)]: the subbasin property when present, else the model-wide parameter. Used by the Muskingum-Cunge scheme only.

Returns: the Manning roughness.

◆ GetMuskingumX()

double Reach::GetMuskingumX ( ) const

nodiscard

Get the Muskingum weighting factor in use for this reach [-]: the subbasin property when present, else the model-wide parameter, else 0.2. The Muskingum-Cunge scheme computes its own instead.

Returns: the weighting factor.

◆ GetOutflow()

double Reach::GetOutflow ( ) const

inlinenodiscard

Get the volume that left the reach in the current time step [m3].

Returns: the outflow volume.

◆ GetScheme()

Scheme Reach::GetScheme ( ) const

inlinenodiscard

Get the routing scheme.

Returns: the routing scheme.

◆ GetSlope()

double Reach::GetSlope ( ) const

inlinenodiscard

Get the reach slope [m/m] (0 when the subbasin has no 'slope' property).

Returns: the reach slope.

◆ GetStorage()

double Reach::GetStorage ( ) const

inlinenodiscard

Get the volume in transit in the reach [m3], in both the main channel and the local-runoff branch.

Returns: the storage.

◆ GetSubbasin()

Subbasin * Reach::GetSubbasin ( ) const

inlinenodiscard

Get the subbasin the reach belongs to.

Returns: the subbasin.

◆ GetSubreachCount()

int Reach::GetSubreachCount ( ) const

inlinenodiscard

Get the number of sub reaches the main channel is divided into for the routing. Always 1 except with the Muskingum-Cunge scheme, and only once the first time step has fixed it.

Returns: the number of sub reaches.

◆ GetTravelTimeInDays()

double Reach::GetTravelTimeInDays ( ) const

nodiscard

Get the travel time of the reach at the reference discharge [days]: length / celerity (0 without a length). With Muskingum-Cunge the celerity is the one the geometry gives at that discharge; with the other schemes it is the celerity parameter, which is defined at that same discharge.

Returns: the travel time.

◆ GetWidth()

double Reach::GetWidth ( ) const

nodiscard

Get the channel width in use for this reach [m]: the subbasin property when present, else the model-wide parameter. Used by the Muskingum-Cunge scheme only.

Returns: the channel width.

◆ Initialize()

void Reach::Initialize ( )

Read the reach geometry from the subbasin properties ('length' [m], 'slope' [-], 'width' [m] and 'manning' [s/m^(1/3)]) when present, as well as the reach-specific routing parameters ('celerity' [m/s] and 'muskingum_x' [-]) overriding the model-wide ones.

◆ Reset()

void Reach::Reset ( )

Reset the reach to its initial state (nothing in transit, or the saved initial state).

◆ RouteLocal()

double Reach::RouteLocal	(	double	localVolume,
		double	timeStepInDays )

Route the subbasin's own runoff, for the current time step. Called once per step, after the subbasin is processed. Without 'route_local_runoff' the runoff is returned unchanged (it joins at the outlet); with it, the runoff travels half the reach.

Parameters

localVolume	The subbasin's own runoff [m3 per time step].
timeStepInDays	The time step [days].

Returns: the volume of that runoff reaching the outlet [m3 per time step].

◆ RoutesLocalRunoff()

bool Reach::RoutesLocalRunoff ( ) const

inlinenodiscard

Check whether the subbasin's own runoff is routed through (half) the reach.

Returns: true when the local runoff is routed.

◆ RouteUpstream()

double Reach::RouteUpstream	(	double	inflowVolume,
		double	timeStepInDays )

Route the volume arriving from the upstream subbasins through the reach, for the current time step. Called once per step, before the subbasin is processed.

Parameters

inflowVolume	The volume entering the reach from upstream [m3 per time step].
timeStepInDays	The time step [days].

Returns: the volume leaving the reach at the subbasin outlet [m3 per time step].

◆ SaveAsInitialState()

void Reach::SaveAsInitialState ( )

Save the current state as the initial state restored by Reset().

◆ SchemeFromString()

Reach::Scheme Reach::SchemeFromString ( const string & name )

static

Parse a routing scheme name.

Parameters

name	The name of the scheme ('none', 'lag', 'muskingum' or 'muskingum_cunge').

Returns: the scheme.

◆ SchemeToString()

string Reach::SchemeToString ( Scheme scheme )

static

Get the canonical name of a routing scheme.

Parameters

scheme The scheme.

Returns: its name ('none', 'lag', 'muskingum' or 'muskingum_cunge').

◆ SetChannelRouting()

void Reach::SetChannelRouting ( const ChannelRoutingSettings & settings )

Set the channel routing scheme and bind the model-wide routing parameters.

Parameters

settings The channel routing settings of the model.

The documentation for this class was generated from the following files:

/github/workspace/core/src/spatial/Reach.h
/github/workspace/core/src/spatial/Reach.cpp

Classes

Public Types

Public Member Functions

Static Public Member Functions

Protected Attributes

Detailed Description

Member Enumeration Documentation

◆ Scheme

Constructor & Destructor Documentation

◆ Reach()

Member Function Documentation

◆ GetCelerity()

◆ GetCelerityForDischarge()

◆ GetInflow()

◆ GetLength()

◆ GetManning()

◆ GetMuskingumX()

◆ GetOutflow()

◆ GetScheme()

◆ GetSlope()

◆ GetStorage()

◆ GetSubbasin()

◆ GetSubreachCount()

◆ GetTravelTimeInDays()

◆ GetWidth()

◆ Initialize()

◆ Reset()

◆ RouteLocal()

◆ RoutesLocalRunoff()

◆ RouteUpstream()

◆ SaveAsInitialState()

◆ SchemeFromString()

◆ SchemeToString()

◆ SetChannelRouting()