Inland basin flow coupling and use land fractions on rivers grid

CONTRIBUTORS.md

@@ -13,3 +13,4 @@
 | eleanorgb       | Eleanor Burke    | Met Office  | 2026-03-06 |
 | Pierre-siddall  | Pierre Siddall| Met Office | 2026-02-06 |
 | tinyendian | Wolfgang Hayek | Earth Sciences New Zealand | 2026-04-24 |
+| DanCopsey       | Dan Copsey       | Met Office  | 2026-03-27 |

doc/source/namelists/initial_conditions.nml.rst

@@ -425,6 +425,11 @@ The required variables for a particular configuration, along with their 'type' a
 +----------------------------------+-----------------------------------------------------------------------------------------+---------+
 | ``rivers_outflow_rp``            | River outflow on river routing points (kg s\ :sup:`-1`)                                 | none    |
 +----------------------------------+-----------------------------------------------------------------------------------------+---------+
+| Required if :nml:mem:`JULES_RIVERS::l_rivers` = TRUE, :nml:mem:`JULES_RIVERS::i_river_vn` = '3',                                     |
+| :nml:mem:`JULES_INITIAL::dump_file` = TRUE and :nml:mem:`OASIS_RIVERS::send_fields` contains ``inland_outflow``.                     |
++----------------------------------+-----------------------------------------------------------------------------------------+---------+
+| ``inland_outflow_rp``            | Inland basin flow on river routing points (kg m\ :sup:`-2` s\ :sup:`-1`).               | none    |
++----------------------------------+-----------------------------------------------------------------------------------------+---------+
 | Required if :nml:mem:`JULES_VEGETATION::photo_acclim_model` = 2 or 3                                                                 |
 +----------------------------------+-----------------------------------------------------------------------------------------+---------+
 | ``t_growth_gb``                  | Running mean air temperature (K)                                                        | none    |

doc/source/namelists/jules_hydrology.nml.rst

@@ -97,6 +97,18 @@ This file sets the hydrology options. It contains one namelist called :nml:lst:`
        Allow the soil conductance to increase as the top layer soil moisture goes above the critical soil moisture, as in Best et al. (2011) equation 7.
 
 
+.. nml:member:: l_inland
+
+   :type: logical
+   :default: F
+
+   TRUE
+       Some rivers end at inland basin flow points. This inland basin flow is used to increase soil moisture at these locations for water conservation purposes. This is only available for coupled models i.e. UM or LFRic. When coupled to LFRic, the soil moisture flux correction applied by this switch must be calculated by the Rivers-standalone component (:nml:mem:`JULES_MODEL_ENVIRONMENT::lsm_id` = 3) and passed to LFRic via OASIS using :nml:mem:`OASIS_RIVERS::send_fields` = inland_outflow.
+
+   FALSE
+       No inland basin flow.
+
+
 .. nml:group:: Only used if :nml:mem:`JULES_HYDROLOGY::l_top` = TRUE
 
    .. nml:member:: zw_max

doc/source/namelists/model_grid.nml.rst

@@ -382,7 +382,7 @@ Examples of how to specify the model domain using through this namelist are prov
 
 .. nml:namelist:: JULES_LAND_FRAC
 
-Land fraction is the fraction of each gridbox that is land. Currently, JULES considers any gridbox with land fraction > 0 to be 100% land, and all others to be 100% sea (or sea-ice). Land fraction data can be used to select only land points from the full input grid (see below).
+Land fraction is the fraction of each gridbox that is land. By default, JULES considers any gridbox with land fraction > 0 to be 100% land, and all others to be 100% sea (or sea-ice). Rivers-standalone (TRIP) when coupled to LFRic needs to be able to determine coastal endorheic basins. In this case, :nml:mem:`l_use_land_fraction`, allows the land fractions to be kept. Land fraction data can be used to select only land points from the full input grid (see below).
 
 .. warning::
    When the input grid consists of a single location (1D and :nml:mem:`JULES_INPUT_GRID::npoints` = 1 or 2D and :nml:mem:`JULES_INPUT_GRID::nx` = :nml:mem:`JULES_INPUT_GRID::ny` = 1), that single location is assumed to be 100% land.
@@ -411,6 +411,21 @@ For any input grid with more than a single location, the following are used:
    In the file, the variable must have no levels dimensions and no time dimension.
 
 
+.. nml:member:: l_use_land_fraction
+
+   :type: logical
+   :default: F
+
+   Land fractions are used to determine coastal endorheic basins to calculate the inland basin flow diagnostic inland_outflow_rp or :nml:mem:`OASIS_RIVERS::send_fields` = inland_outflow.
+
+   TRUE
+       Supply land fractions (as fractions) to both the main grid and the rivers grid. This requires both grids and land-sea mask to be the same.
+
+   FALSE
+       Land fractions are not used and the land fraction field is set to either 1.0 (any land) or 0.0.
+
+   .. note:: This is only available in Rivers-standalone (TRIP) to calculate inland outflow fields.
+
 
 ``JULES_MODEL_GRID`` namelist members
 -------------------------------------

doc/source/namelists/oasis_rivers.nml.rst

@@ -40,12 +40,16 @@ This file contains a single namelists called :nml:lst:`OASIS_RIVERS`, which indi
 .. nml:member:: send_fields
 
    :type: character(:)
-   :permitted: 'outflow_per_river'
+   :permitted: 'outflow_per_river','inland_outflow'
    :default: ''
 
    List of fields to be sent via coupling from the river executable to other models. Names are case sensitive.
 
-.. note::  The only field that can be sent via coupling is the total river runoff (`outflow_per_river`).
+.. note::  The fields that can be sent via coupling are:
+
+           1. The total river runoff (`outflow_per_river`) which is sent to the ocean.
+
+           2. The inland basin flow (`inland_outflow`) which is sent to the land surface hydrology scheme. Turn on :nml:mem:`JULES_HYDROLOGY::l_inland` (in the land surface side of the coupler) to pass this inland basin flow into soil moisture.
 
 .. nml:member:: receive_fields
 

doc/source/output-variables.rst

@@ -434,6 +434,15 @@ Rivers
 |                               | This technically has dimensions of "np_rivers", although only ``[1:n_rivers]``, defined by    |            |
 |                               | the rivers_outflow_number (see :ref:`list-of-rivers-params`), is populated.                   |            |
 +-------------------------------+-----------------------------------------------------------------------------------------------+------------+
+| ``inland_outflow_rp``         | Inland basin flow on river routing points (kg m\ :sup:`-2` s\ :sup:`-1`).                     | np_rivers  |
+|                               | Only available if :nml:mem:`JULES_RIVERS::l_rivers` = TRUE.                                   |            |
+|                               |                                                                                               |            |
+|                               | Adding this diagnostic will turn on inland basin flow which diverts river water flowing       |            |
+|                               | into an inland basin flow point to this diagnostic. At the same time runoff feeding           |            |
+|                               | into an inland basin flow point will go to the oceans (via ``rivers_outflow_rp``). This is    |            |
+|                               | to stop water being caught in an infinite loop between soils and rivers. Therefore by         |            |
+|                               | adding this diagnostic the ``rflow`` and ``rivers_sto_rp`` diagnostics will also change.      |            |
++-------------------------------+-----------------------------------------------------------------------------------------------+------------+
 | ``rrun_rp``                   | River routing gridbox runoff rate received by river routing routine                           | np_rivers  |
 |                               | (kg m\ :sup:`-2` s\ :sup:`-1`).                                                               |            |
 |                               | Only available if :nml:mem:`JULES_RIVERS::l_rivers` = TRUE.                                   |            |

etc/fcm-make/make-river.cfg

@@ -69,6 +69,7 @@ extract.path-incl[river] = $extract_path_incl \
 			   src/control/standalone/var/model_grid_mod.F90 \
 			   src/control/standalone/var/model_time_mod.F90 \
 			   src/control/standalone/var/timestep_mod.F90 \
+			   src/initialisation/shared/check_compatible_options_rivers_mod.F90 \
 			   src/initialisation/standalone/ancillaries/ancil_namelist_mod.F90 \
 			   src/initialisation/standalone/ancillaries/init_ancillaries_coupling_mod.F90 \
 			   src/initialisation/standalone/ancillaries/init_rivers_process_data_mod.F90 \

rose-meta/jules-shared/jules-hydrology/HEAD/rose-meta.conf

@@ -17,6 +17,14 @@ trigger=namelist:jules_hydrology=l_var_rainfrac: .true.;
 type=logical
 url=https://metoffice.github.io/jules/latest/namelists/jules_hydrology.nml.html#JULES_HYDROLOGY::l_hydrology
 
+[namelist:jules_hydrology=l_inland]
+compulsory=true
+description=Apply inland basin water correction to soil moisture
+           =NOT AVAILABLE TO STANDALONE
+sort-key=Panel-G06
+type=logical
+url=https://metoffice.github.io/jules/latest/namelists/jules_hydrology.nml.html#JULES_HYDROLOGY::l_inland
+
 [namelist:jules_hydrology=l_var_rainfrac]
 compulsory=true
 description=Enable variable large scale and convective rain fractions

rose-meta/jules-shared/jules-model-environment/HEAD/rose-meta.conf

@@ -19,14 +19,14 @@ fail-if=this != 0 and this != 2; # This should only indicate that standalone (0)
 trigger=namelist:jules_deposition=l_deposition_from_ukca: 1;
        =namelist:jules_deposition=l_ukca_ddepo3_ocean: 1;
        =namelist:jules_deposition=l_ukca_dry_dep_so2wet: 1;
+       =namelist:jules_hydrology=l_inland: 1;
        =namelist:jules_irrig=l_irrig_limit: 0;
        =namelist:jules_pftparm=dust_veg_scj_io: 1;
        =namelist:jules_pftparm=fsmc_mod_io: 0;
        =namelist:jules_pftparm=pft_name_io: 3;
        =namelist:jules_radiation=l_cosz: 0;
        =namelist:jules_radiation=l_dolr_land_black: 1;
        =namelist:jules_radiation=l_sea_alb_var_chl: 1;
-       =namelist:jules_rivers=l_inland: 1;
        =namelist:jules_rivers=l_riv_overbank: 0;
        =namelist:jules_rivers=trip_globe_shape: 1;
        =namelist:jules_soil=l_bedrock: 0;
@@ -283,6 +283,7 @@ trigger=namelist:jules_pftparm: 1;
        =namelist:cable_soilparm=css_io: 2;
        =namelist:jules_spinup: 1,2;
        =namelist:jules_nlsizes: 1,2;
+       =namelist:jules_land_frac=l_use_land_fraction: 3;
 url=https://metoffice.github.io/jules/latest/namelists/model_environment.nml.html#JULES_MODEL_ENVIRONMENT::lsm_id
 value-titles='jules','cable','rivers-only'
 values=1,2,3

rose-meta/jules-standalone/HEAD/rose-meta.conf

@@ -2414,11 +2414,12 @@ fail-if=len(this) != namelist:jules_initial=nvars;
        = namelist:jules_initial=total_snow == '.false.' and namelist:jules_snow=nsmax > 0 and not any(this == "'tsnow'"); # tsnow must be given if total_snow = FALSE and nsmax > 0
        = namelist:jules_initial=total_snow == '.false.' and namelist:jules_snow=nsmax > 0 and namelist:jules_radiation=l_snow_albedo == '.true.' and not any(this == "'rgrainl'"); # rgrainl must be given if total_snow = FALSE, nsmax > 0 and l_snow_albedo = TRUE
        = namelist:jules_soil=l_bedrock == '.true.' and not any(this == "'tsoil_deep'"); # tsoil_deep must be initialised if bedrock is switched on
-       = namelist:jules_rivers=l_rivers == '.true.' and namelist:jules_rivers=i_river_vn == "3" and not any(this == "'rivers_sto_rp'"); # rivers_sto_rp must be initialised if rivers is switched on and i_river_vn='3' : trip
-       = namelist:jules_rivers=l_rivers == '.true.' and namelist:jules_rivers=i_river_vn == "2" and not any(this == "'rfm_surfstore_rp'"); # rfm_surfstore_rp must be initialised if rivers is switched on and i_river_vn='2' : rfm
-       = namelist:jules_rivers=l_rivers == '.true.' and namelist:jules_rivers=i_river_vn == "2" and not any(this == "'rfm_substore_rp'"); # rfm_substore_rp must be initialised if rivers is switched on and i_river_vn='2' : rfm
-       = namelist:jules_rivers=l_rivers == '.true.' and namelist:jules_rivers=i_river_vn == "2" and not any(this == "'rfm_flowin_rp'"); # rfm_flowin_rp must be initialised if rivers is switched on and i_river_vn='2' : rfm
-       = namelist:jules_rivers=l_rivers == '.true.' and namelist:jules_rivers=i_river_vn == "2" and not any(this == "'rfm_bflowin_rp'"); # rfm_bflowin_rp must be initialised if rivers is switched on and i_river_vn='2' : rfm
+       = namelist:jules_rivers=i_river_vn == 3 and not ( any(this == "'rivers_sto_rp'") or any(namelist:jules_rivers_props=var == "'rivers_storage'") ); # rivers_sto_rp or rivers_storage must be initialised if rivers is switched on and i_river_vn='3' : trip
+       = ( namelist:jules_rivers=i_river_vn == 3 and not any(this == "'inland_outflow_rp'") ) and any(namelist:oasis_rivers=send_fields == "'inland_outflow'"); # inland_outflow_rp must be initialised when i_river_vn='3' (TRIP) and inland_outflow is requested
+       = namelist:jules_rivers=i_river_vn == "2" and not any(this == "'rfm_surfstore_rp'"); # rfm_surfstore_rp must be initialised if rivers is switched on and i_river_vn='2' : rfm
+       = namelist:jules_rivers=i_river_vn == "2" and not any(this == "'rfm_substore_rp'"); # rfm_substore_rp must be initialised if rivers is switched on and i_river_vn='2' : rfm
+       = namelist:jules_rivers=i_river_vn == "2" and not any(this == "'rfm_flowin_rp'"); # rfm_flowin_rp must be initialised if rivers is switched on and i_river_vn='2' : rfm
+       = namelist:jules_rivers=i_river_vn == "2" and not any(this == "'rfm_bflowin_rp'"); # rfm_bflowin_rp must be initialised if rivers is switched on and i_river_vn='2' : rfm
 length=:
 sort-key=06
 url=https://metoffice.github.io/jules/latest/namelists/initial_conditions.nml.html#JULES_INITIAL::var
@@ -2430,7 +2431,7 @@ values='canht','canopy','cropcanht','cropdvi','cropharvc','croplai',
       ='snow_grnd','snow_ice','snow_liq','snow_tile','sthu_irr','sthuf',
       ='sthzw','t_growth_gb','t_soil','tsnow','tstar_tile','tsoil_deep',
       ='wood_prod_fast','wood_prod_med','wood_prod_slow','years_since_harvest',
-      ='zw'
+      ='zw','inland_outflow_rp'
 
 [namelist:jules_initial=var_name]
 compulsory=true
@@ -2500,6 +2501,7 @@ url=https://metoffice.github.io/jules/latest/namelists/model_grid.nml.html#JULES
 [namelist:jules_input_grid=nx]
 compulsory=true
 description=Size of the x dimension
+fail-if=this != namelist:jules_rivers_props=nx_rivers and namelist:jules_land_frac=l_use_land_fraction == '.true.'; # If using land fractions for rivers then the input grid needs to be the same as the rivers grid so that the land fractions are copied across to the rivers grid correctly
 range=1:
 sort-key=06
 type=integer
@@ -2508,6 +2510,7 @@ url=https://metoffice.github.io/jules/latest/namelists/model_grid.nml.html#JULES
 [namelist:jules_input_grid=ny]
 compulsory=true
 description=Size of the y dimension
+fail-if=this != namelist:jules_rivers_props=ny_rivers and namelist:jules_land_frac=l_use_land_fraction == '.true.'; # If using land fractions for rivers then the input grid needs to be the same as the rivers grid so that the land fractions are copied across to the rivers grid correctly
 range=1:
 sort-key=07
 type=integer
@@ -2749,6 +2752,14 @@ sort-key=1
 type=character
 url=https://metoffice.github.io/jules/latest/namelists/model_grid.nml.html#JULES_LAND_FRAC::file
 
+[namelist:jules_land_frac=l_use_land_fraction]
+compulsory=true
+description=Use land fractions and pass these to river routing
+fail-if=this == '.true.' and ( namelist:jules_rivers=i_river_vn != 3 or namelist:jules_model_environment=lsm_id != 3 ); # Land fractions are only used by TRIP in Rivers-standalone to determine coastal endorheic basins.
+sort-key=3
+type=logical
+url=https://metoffice.github.io/jules/latest/namelists/model_grid.nml.html#JULES_LAND_FRAC::l_use_land_fraction
+
 [namelist:jules_land_frac=land_frac_name]
 description=Name of the variable containing the land fraction data
 sort-key=2
@@ -3083,6 +3094,7 @@ description=Names of variables to output, as recognised by JULES
 # See:  https://github.com/metomi/rose/issues/2731
 fail-if=len(this) != namelist:jules_output_profile=nvars;
        =any(namelist:jules_output_profile=var == "'outflow_per_river'") and not any(namelist:jules_rivers_props=var == "'rivers_outflow_number'"); # outflow_per_river requires the rivers outflow numbers ancillary data
+       =any(namelist:jules_output_profile=var == "'inland_outflow_rp'") and ( namelist:jules_rivers=i_river_vn != 3 or namelist:jules_model_environment=lsm_id != 3 ); # Inland outflow calculation can only be used with TRIP Rivers-standalone
 length=:
 sort-key=11
 type=character
@@ -4064,17 +4076,6 @@ value-titles=RFM,TRIP
 values=2,3
 widget[rose-config-edit]=cylc8_compat.ComboBoxValueWidget
 
-[namelist:jules_rivers=l_inland]
-compulsory=true
-description=Re-routing inland basin water back to soil moisture
-help=Selecting 'Re-routing inland basin water back to soil moisture' is only
-    =applicable to the global river routing scheme 1A and fixes a bug where
-    =water from inland outflow points was previously 'lost' to the system on
-    =regridding. The re-routed water is held over until the next timestep
-    =and added to the change in top-level soil moisture.
-sort-key=aa2
-type=logical
-
 [namelist:jules_rivers=l_riv_overbank]
 compulsory=true
 description=Enable overbank inundation
@@ -4090,7 +4091,6 @@ description=Enable river routing
 sort-key=a
 trigger=namelist:jules_rivers=i_river_vn: .true.;
        = namelist:jules_rivers=nstep_rivers: .true.;
-       = namelist:jules_rivers=l_inland: .true.;
        = namelist:jules_rivers=l_riv_overbank: .true.;
        = namelist:jules_overbank: .true.;
        = namelist:jules_rivers_props: .true.;
@@ -4260,6 +4260,7 @@ url=https://metoffice.github.io/jules/latest/namelists/ancillaries.nml.html#JULE
 [namelist:jules_rivers_props=nx_rivers]
 compulsory=true
 description=Size of the x dimension of the river routing grid
+fail-if=this != namelist:jules_input_grid=nx and namelist:jules_land_frac=l_use_land_fraction == '.true.'; # If using land fractions for rivers then the input grid needs to be the same as the rivers grid so that the land fractions are copied across to the rivers grid correctly
 range=2:
 sort-key=07
 type=integer
@@ -4276,6 +4277,7 @@ url=https://metoffice.github.io/jules/latest/namelists/ancillaries.nml.html#JULE
 [namelist:jules_rivers_props=ny_rivers]
 compulsory=true
 description=Size of the y dimension of the river routing grid
+fail-if=this != namelist:jules_input_grid=ny and namelist:jules_land_frac=l_use_land_fraction == '.true.'; # If using land fractions for rivers then the input grid needs to be the same as the rivers grid so that the land fractions are copied across to the rivers grid correctly
 range=2:
 sort-key=08
 type=integer
@@ -7244,7 +7246,7 @@ compulsory=true
 description=Number of sent fields via OASIS
 fail-if=this < 0;
        =this == 0 and namelist:oasis_rivers=np_receive == 0; # Oasis coupling requested but no fields coupled
-range=0:1
+range=0:2
 sort-key=1
 trigger=namelist:oasis_rivers=send_fields: this > 0;
        =namelist:oasis_rivers=cpl_freq: this >= 0;
@@ -7264,13 +7266,13 @@ values='sub_surf_roff_rp','surf_roff_rp','sub_surf_roff','surf_roff'
 [namelist:oasis_rivers=send_fields]
 compulsory=true
 description=List of fields sent via OASIS coupling
-fail-if=len(this)>1;
+fail-if=len(this)>2;
        =len(this) != namelist:oasis_rivers=np_send;
        =any(this == "'outflow_per_river'") and not any(namelist:jules_rivers_props=var == "'rivers_outflow_number'"); # outflow_per_river requires the rivers outflow numbers ancillary data
 length=:
 sort-key=2
 url=https://metoffice.github.io/jules/latest/namelists/oasis_rivers.nml.html#OASIS_RIVERS::send_fields
-values='outflow_per_river'
+values='outflow_per_river','inland_outflow'
 
 [namelist:run_convection]
 compulsory=false