6.15. `jules_rivers.nml`¶

This file sets the river routing options. It contains two namelists called JULES_RIVERS and JULES_OVERBANK.

River routing introduces two more grids to a JULES run: the river routing input grid and the river routing model grid. The river routing input grid must always be specified as a 2D grid in JULES_RIVERS_PROPS. This is not required to be identical to the input or the model grid. Internally the model compresses this to the river routing model grid, which is a 1D grid with length np_rivers, which is the number of valid routing points in the river routing input grid. All river routing output will be on the river routing model grid, or will be regridded to the model grid.

Note

The river routing code in JULES is still in development. Users should ensure that results are as expected, and provide feedback where deficiencies are identified.

6.15.1. `JULES_RIVERS` namelist members¶

JULES_RIVERS::l_rivers¶

Type: logical
Default: F

Switch for enabling river routing.

TRUE: Use the river routing algorithm specified by i_river_vn to route runoff along river pathways.
FALSE: No river routing.

JULES_RIVERS::i_river_vn¶

Type: integer
Default: None

Switch to select the river routing algorithm to use for river routing.

1: Use a UM-coupled JULES implementation of the TRIP model (see Oki et al. 1999). This value is not allowed in standalone JULES
2: Use a standalone JULES implementation of the RFM kinematic wave model (see Dadson and Bell 2010, Bell et al. 2007).
3: Use a standalone JULES implementation of the TRIP model (see Oki et al. 1999).

JULES_RIVERS::l_riv_overbank¶

Type: logical
Default: F

Switch for enabling river overbank inundation. Only used if l_rivers is TRUE.

TRUE: Calculate frac_fplain_lp, i.e. overbank inundation area as a fraction of gridcell area.
FALSE: No overbank inundation calculations

Note

If l_riv_overbank = FALSE, then optional namelist JULES_OVERBANK is not required.

JULES_RIVERS::nstep_rivers¶

Type: integer
Permitted: > 0
Default: None

The number of model timesteps per routing timestep.

For example, nstep_rivers = 5 means that runoff will be accumulated for 5 model timesteps before being routed on the 5th timestep.

Warning

The river routing parameter values can be highly dependent on model resolution, so care is required by the user to ensure that appropriate values are selected, tested and adjusted as required.

Suggested values for global and high-resolution runs are listed below, however these should be treated as a starting point only.

RFM parameters - used if i_river_vn = 2

JULES_RIVERS::a_thresh¶

Type: integer
Default: None
Suggested: 1 (spatial resolution coarser than 20 km gridcells), ~10 (high-resolution)

The threshold drainage area (specified in number of cells) draining to a gridbox, above which the grid cell is considered to be a river point (see a_T in Bell et al. 2007:541).

Remaining points are treated as land (drainage area = 0) or sea (drainage area < 0). See Bell et al. (2007).

JULES_RIVERS::cland¶

Type: real
Permitted: > 0
Default: None
Suggested: 0.20 m/s (global), 0.40 m/s (1 km resolution, Bell et al. 2007)

The land wave speed (kinematic wave speed for surface flow in a land grid box on the river routing grid, m s^-1). This is the speed at which water moves through surface soil in a non-river grid cell (even without major rivers, there are always minor water courses so these cells do still contribute flow to neighbouring cells).

JULES_RIVERS::criver¶

Type: real
Permitted: > 0
Default: None
Suggested: 0.62 m/s (global), 0.50 m/s (1 km resolution, Bell et al. 2007)

The river wave speed (kinematic wave speed for surface flow in a river grid box on the river routing grid, m s^-1). This value should be close to the rivers_speed used by TRIP, but not identical because RFM makes different assumptions about e.g. meandering.

JULES_RIVERS::cbland¶

Type: real
Permitted: > 0
Default: None
Suggested: <= cland. 0.10 m/s (global), 0.05 m/s (1 km resolution, Bell et al. 2007)

The subsurface land wave speed (kinematic wave speed for subsurface flow in a land grid box on the river routing grid, m s^-1).

JULES_RIVERS::cbriver¶

Type: real
Permitted: > 0
Default: None
Suggested: <= criver. 0.15 m/s (global), 0.05 m/s (1 km resolution, Bell et al. 2007)

The subsurface river wave speed (kinematic wave speed for subsurface flow in a river grid box on the river routing grid, m s^-1).

JULES_RIVERS::retl¶

Type: real
Permitted: -1 to 1
Default: None
Suggested: 0.005 (1 km resolution, Bell et al. 2007)

The (resolution dependent) land return flow fraction. Bell et al. (2007:Table1) suggested value 0.005. On non-river grid cells in the land mask: if retl>0 then fraction retl of the subsurface flow moves to the surface per routing timestep; if retl<0 then fraction retl of the surface flow moves to the subsurface per routing timestep.

JULES_RIVERS::retr¶

Type: real
Permitted: -1 to 1
Default: None
Suggested: 0.005 (1 km resolution, Bell et al. 2007)

The (resolution dependent) river return flow fraction. On river grid cells in the land mask: if retr>0 then fraction retr of the subsurface flow moves to the surface per routing timestep; if retr<0 then fraction retr of the surface flow moves to the subsurface per routing timestep.

JULES_RIVERS::runoff_factor¶

Type: real
Permitted: > 0
Default: None

Values !=1.0 are generally used to correct biases in precipitation when the model is forced with observed data It is highly recommended that this is set to 1.0 (i.e. no runoff adjustment).

TRIP parameters - used if i_river_vn = 1,3

JULES_RIVERS::rivers_speed¶

Type: real
Permitted: > 0
Default: None

The effective river velocity (m s^-1). See Oki et al. (1999). rivers_speed should equal (river flow velocity / rivers_meander). A value of 0.4 can be used, while Oki et al. (1999) used a value of 0.5.

JULES_RIVERS::rivers_meander¶

Type: real
Permitted: > 0
Default: None

The ratio of the actual to calculated river lengths in a river routing gridbox. See Oki et al. (1999). Oki & Sud (1998) called this the Meandering Ratio r_M and suggested an average global value of 1.4.

TRIP parameters for UM-TRIP only - i.e. only used if i_river_vn = 1

JULES_RIVERS::lake_water_conserve_method¶

Type: integer
Default: 1

Selects different fields for use in water conservation of lake evaporation

1: fqw_surft: This is the moisture flux on each tile, in which case the inland water tile is used. Snow sublimation has already been removed from fqw_surft at the point in the code that this is used.
2: elake_surft: This is the lake evaporation component of fqw_surft. This avoids the impact that snow melt has on modifying fqw_surft.

JULES_RIVERS::trip_globe_shape¶

Type: integer
Default: 2

The shape of the Earth in the UM-TRIP river routing scheme.

1: Spherical: Consistent with other component models (e.g. UM and NEMO) and is better at conserving water when passing water between these other models.
2: Ellipsoidal: Closer to the actual shape of the Earth.

6.15.2. `JULES_OVERBANK` namelist members¶

Warning

The overbank inundation parameter values can be highly dependent on model resolution, so care is required by the user to ensure that appropriate values are selected, tested and adjusted as required.

Suggested values for global and high-resolution runs are listed below, however these should be treated as a starting point only.

JULES_OVERBANK::l_riv_overbank¶

Type: logical
Default: F

Switch for enabling river overbank inundation. Only used if l_rivers is TRUE.

TRUE: Calculate overbank inundation area as a fraction of gridcell area.
FALSE: No overbank inundation calculations

Note

If l_riv_overbank = FALSE, no further variables are needed from this namelist.

JULES_OVERBANK::overbank_model¶

Type: integer
Permitted: 1, 2, 3
Default: none

Choice of model of overbank inundation.

Simple model using an allometric (scaling) relationship to estimate river width, without use of topographic data.
Simple model using allometric relationships to estimate river width and depth, and the Rosgen (1994) entrenchment ratio, without use of topographic data. When river flow rates are higher than the estimated bankfull flow, river width is constrained so that when river depth = 2 x bankfull depth then width = ent_ratio * bankfull width.
The inundated area is calculated using a hypsometric integral based on a lognormal area-altitude distribution and an allometric relationship to estimate river depth. The parameters of the lognormal distribution are specified via JULES_OVERBANK_PROPS. (This is the recommended approach.)

River depth allometry (used if overbank_model = 2 or 3)

Allometry is: (DEPTH in m) = riv_c * ( (SURFACE RIVER INFLOW in m3 s^-1) ^ riv_f) (Leopold & Maddock 1953:eqn2)

JULES_OVERBANK::riv_c¶

Type: real
Default: none
Permitted: >=0 and <=(1/riv_a)
Suggested: 0.27 (global, from Andreadis et al. 2013)

Coefficient in the allometry for river depth (units are (m / ((m3/s)^riv_f)), i.e. dependent on the value of riv_f)

JULES_OVERBANK::riv_f¶

Type: real
Default: none
Permitted: >=0 and <=(1-riv_b)
Suggested: 0.30 (global, from Andreadis et al. 2013)

Exponent in the allometry for river depth (dimensionless)

River width scaling (used if overbank_model = 1 or 2)

River width allometry

Allometry is: (WIDTH in m) = riv_a * ( (SURFACE RIVER INFLOW in m3 s^-1) ^ riv_b) (Leopold & Maddock 1953:eqn1)

JULES_OVERBANK::riv_a¶

Type: real
Default: none
Permitted: >=0 and <=(1/riv_c)
Suggested: 7.20 (global, from Andreadis et al. 2013)

Coefficient in the allometry for river width (units are (m / ((m3/s)^riv_b)), i.e. dependent on the value of riv_b)

JULES_OVERBANK::riv_b¶

Type: real
Default: none
Permitted: >=0 and <=(1-riv_f)
Suggested: 0.50 (global, from Andreadis et al. 2013)

Exponent in the allometry for river width (dimensionless)

Bankfull flow allometry (used if overbank_model = 2)

Allometry is: (BANKFULL DISCHARGE RATE QBF in m3 s^-1) = coef_b * ( (CONTRIBUTING AREA in km2) ^ exp_c ) (see e.g. Andreadis et al. 2013)

JULES_OVERBANK::coef_b¶

Type: real
Default: none
Suggested: 0.08 (for “several drainages in western Washington State, USA”, Cragun 2005)

Coefficient in the allometry for bankfull flow (see Sen 2018:eqn3.33).

JULES_OVERBANK::exp_c¶

Type: real
Default: none
Suggested: 0.95 (for “several drainages in western Washington State, USA”, Cragun 2005)

Exponent in the allometry for bankfull flow (see Sen 2018:eqn3.33).

JULES_OVERBANK::ent_ratio¶

Type: real
Default: none

The Rosgen entrenchment ratio (single value for all water courses in the simulation): when river depth = 2 x bankfull depth then width = ent_ratio * bankfull width (i.e. ent_ratio can be used to specify how wide floodplains are allowed to be).

6.15. `jules_rivers.nml`¶

6.15.1. `JULES_RIVERS` namelist members¶

6.15.2. `JULES_OVERBANK` namelist members¶

Table Of Contents

Previous topic

Next topic

6.15. jules_rivers.nml¶

6.15.1. JULES_RIVERS namelist members¶

6.15.2. JULES_OVERBANK namelist members¶

6.15. `jules_rivers.nml`¶

6.15.1. `JULES_RIVERS` namelist members¶

6.15.2. `JULES_OVERBANK` namelist members¶