RDII objects

The RDII API exposes both EPA SWMM RTK unit hydrographs and the swmmrs Antecedent Moisture Model (AMM) extension. RTK uses Simulation.unit_hydrographs and Simulation.rdii_assignments; AMM uses Simulation.amm_models and Simulation.amm_assignments. Python can edit existing models and replace assignment lists, but it cannot create or delete top-level RTK or AMM models.

Model views stay connected to one project generation. Their parameter and assignment objects are detached, so editing one is only the first half of the job. Assign the complete parameter or assignment sequence back to apply it. Edits are allowed while a simulation is Open or Ended, not while it is Running. The next Simulation.start() validates and prepares the changed configuration.

RTK unit hydrographs

RTK models come from [HYDROGRAPHS]. UnitHydrograph.rain_gage and monthly_responses are writable individually or together through update(). The returned tuple contains January through December. Each UnitHydrographMonth exposes named short, medium, and long responses.

from swmmrs import Simulation

with Simulation("model.inp", "model.rpt") as simulation:
    unit_hydrograph = simulation.unit_hydrographs["UH1"]
    responses = unit_hydrograph.monthly_responses

    january_short = responses[0].short
    january_short.rainfall_fraction = 0.15
    january_short.time_to_peak_hours = 0.75
    january_short.recession_ratio = 2.0

    unit_hydrograph.update(
        rain_gage=simulation.rain_gages["GAGE"],
        monthly_responses=responses,
    )

Every month must provide short, medium, and long responses. Monthly rainfall must be nonnegative and sum to no more than 1.01.

Replace RTK node assignments

Simulation.rdii_assignments represents [RDII] rows and returns detached RdiiAssignment values in node order. Each node can have at most one RTK assignment.

from swmmrs import Simulation
from swmmrs.objects import RdiiAssignment

with Simulation("model.inp", "model.rpt") as simulation:
    simulation.rdii_assignments = [
        RdiiAssignment(
            node=simulation.nodes["J1"],
            unit_hydrograph=simulation.unit_hydrographs["UH1"],
            area=3.5,
        )
    ]

Antecedent Moisture Model

AMM models come from [AMM_MODELS] and [AMM_COMPONENTS]. AmmModel.update() changes the rain gage, temperature bounds, and complete component list atomically.

from swmmrs import Simulation
from swmmrs.objects import AmmStandardComponent

with Simulation("model.inp", "model.rpt") as simulation:
    model = simulation.amm_models["SAN1"]
    print(model.rain_gage.id, model.cold_temperature, model.hot_temperature)

    components = list(model.components)
    standard = next(
        component
        for component in components
        if isinstance(component, AmmStandardComponent)
    )
    standard.hot_shcf = 0.06

    model.update(
        cold_temperature=25.0,
        hot_temperature=75.0,
        components=components,
    )

Temperatures use the project's temperature units. Component averaging windows and half-lives use hours. See the AMM input reference for every AMM parameter's meaning and units.

Replace AMM node assignments

Simulation.amm_assignments represents [AMM_RDII] rows. Unlike RTK, multiple AMM assignments may target one node.

from swmmrs import Simulation
from swmmrs.objects import AmmAssignment

with Simulation("model.inp", "model.rpt") as simulation:
    assignments = list(simulation.amm_assignments)
    assignments.append(
        AmmAssignment(
            node=simulation.nodes["J2"],
            model=simulation.amm_models["SAN1"],
            area=3.5,
        )
    )
    simulation.amm_assignments = assignments

RTK and AMM assignment areas use acres in US projects and hectares in SI projects.

              flowchart TD
              swmmrs.objects.UnitHydrograph[UnitHydrograph]
              swmmrs.objects._base._LiveView[_LiveView]

                              swmmrs.objects._base._LiveView --> swmmrs.objects.UnitHydrograph
                


              click swmmrs.objects.UnitHydrograph href "" "swmmrs.objects.UnitHydrograph"
              click swmmrs.objects._base._LiveView href "" "swmmrs.objects._base._LiveView"
            

monthly_responses: tuple[UnitHydrographMonth, ...]

rain_gage: RainGage

update(**changes: object) -> None

              flowchart TD
              swmmrs.objects.UnitHydrographMonth[UnitHydrographMonth]

              

              click swmmrs.objects.UnitHydrographMonth href "" "swmmrs.objects.UnitHydrographMonth"
            

              flowchart TD
              swmmrs.objects.AmmModel[AmmModel]
              swmmrs.objects._base._LiveView[_LiveView]

                              swmmrs.objects._base._LiveView --> swmmrs.objects.AmmModel
                


              click swmmrs.objects.AmmModel href "" "swmmrs.objects.AmmModel"
              click swmmrs.objects._base._LiveView href "" "swmmrs.objects._base._LiveView"
            

cold_temperature: float

components: tuple[AmmComponent, ...]

hot_temperature: float

rain_gage: RainGage

update(**changes: object) -> None