SWMM5 Delphi GUI Dunithyd.pas Summary

 Below is an overview of Dunithyd.pas, a Delphi unit from SWMM 5.2 that implements a dialog form (TUnitHydForm) for editing the properties of an RDII Unit Hydrograph (UH) group. In SWMM, RDII (Rainfall-Dependent Infiltration/Inflow) can be modeled by defining up to three “short-term,” “medium-term,” and “long-term” unit hydrographs, along with initial abstraction parameters, for each month of the year (plus an “All Months” option). This form lets the user specify all those parameters in a systematic way.

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1. Purpose and Context

RDII in SWMM is captured using Unit Hydrographs that describe how rainfall infiltrates and enters the sewer system as infiltration/inflow. Each set of unit hydrographs (short-, medium-, long-term) can vary by month. Additional parameters control initial abstraction—how much rainfall is withheld before generating RDII.

The TUnitHydForm helps the user:

1. Assign a unique name to the unit hydrograph group,
2. Specify which rain gage the RDII is associated with,
3. Provide UH parameters $(R, T, K)$ for each of the three unit hydrographs, for each month (January, February, etc.), or for “All Months,”
4. Provide initial abstraction parameters $(D_{max}, D_{rec}, D_0)$ similarly for each month and each of the three UHs.

Then these RDII definitions can be referenced by nodes that experience infiltration/inflow from that hydrograph group.

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2. Main Form: TUnitHydForm

2.1 Key Controls

1. UHName (TEdit):
   • The user-specified name of the unit hydrograph group.
2. RGname (TComboBox):
   • The name of the rain gage that drives this RDII. The user picks from among the project’s list of raingages.
3. PageControl1 with two tabs:
   • TabSheet1: A grid (UHGridEdit) for editing the $(R, T, K)$ parameters (fraction of rainfall, time to peak, and recession constant) for each of three unit hydrographs (“short-term,” “medium-term,” “long-term”).
   • TabSheet2: A grid (IAGridEdit) for editing the initial abstraction parameters ($D_{max}, D_{rec}, D_0$) for each of the three UHs.
4. MonthsCombo: A drop-down listing “All Months” plus each month (January ... December). The user can choose which set of monthly parameters to view/edit. Each month has its own set of $(R, T, K)$ or $(D_{max}, D_{rec}, D_0$).
5. OK, Cancel, Help buttons:
   • Finalize changes, discard, or open help topic about RDII hydrographs.

2.2 Internal Data Structures

The form uses:

• UHParams[0..12, 1..3, 1..3] to store $(R, T, K)$ for each month (0=All Months, 1=January, ..., 12=December) and each of the three UHs (1=short term, 2=medium term, 3=long term).
• IAParams[0..12, 1..3, 1..3] to store $(D_{max}, D_{rec}, D_0$` similarly.

The user sees these in the UHGridEdit.Grid or IAGridEdit.Grid depending on the tab. They pick which month to display from MonthsCombo, and the code copies the arrays to/from the grid for that month.

2.3 Key Methods

1. FormCreate:

   • Sets up the grids, ensuring 4 rows (one for “Response” label, plus short/medium/long) and 3 columns ($R, T, K$ or $(D_{max}, D_{rec}, D_0)$).
   • Fills MonthsCombo with “All Months,” “January,” “February,” etc.

2. SetData(Index, aUnitHyd):

   • Called to load the existing data for a unit hydrograph group:
     1. UHIndex := Index.
     2. UHName.Text with the name from Project.Lists[HYDROGRAPH].Strings[Index].
     3. RGname.Text with the stored raingage name.
     4. Copies each month’s $(R, T, K)$ and $(D_{max}, D_{rec}, D_0)$ from aUnitHyd.Params[] / aUnitHyd.InitAbs[] into UHParams[] / IAParams[].
     5. Finds the first month that has any data, sets MonthsCombo.ItemIndex to that month, and displays those data in the two grids.

3. GetData(S, aUnitHyd):

   • After user presses OK, retrieves the final name UHName.Text into S.
   • Copies the currently displayed month’s data from the grids to UHParams[] and IAParams[].
   • Then writes all months’ data back into aUnitHyd.Params[] and aUnitHyd.InitAbs[].
   • Also sets aUnitHyd.Raingage to RGname.Text.

4. MonthsComboClick:

   • Saves the currently displayed grid values to UHParams / IAParams for the old month.
   • Switches the displayed month to the newly selected month.
   • Loads that month’s stored values into the grids.

5. OKBtnClick:

   • If the data passes ValidateData (e.g., no empty name, no duplicate name, a valid raingage name), then ModalResult := mrOK, otherwise an error message appears.

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3. Validation Checks

• UHName must be non-empty, unique among Project.Lists[HYDROGRAPH].
• Raingage must be non-empty.
• The numeric fields can be left empty if the user is not using them for that month. Typically, $(R, T, K)$ or $(D_{max}, D_{rec}, D_0$) can be 0.0 if not used.

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4. Additional UI Behavior

• The user can define partial data for some months while leaving “All Months” or other months blank. If a month is set to “All Months,” the grids define the baseline parameters used if no monthly override is provided.
• The grids are small (4 rows, 4 columns). The row 0 is a heading, row 1..3 correspond to the short/medium/long UHs or infiltration sets. The code in SetData / MonthsComboClick copies data to/from arrays, thus letting each month have a separate set of UH/IA parameters.

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5. Summary

Dunithyd.pas provides TUnitHydForm, a specialized form in SWMM for editing an RDII unit hydrograph group. It organizes:

• Name of the hydrograph group,
• Associated rain gage,
• (R, T, K) triple for short/medium/long unit hydrographs,
• Initial abstraction data ($D_{max}, D_{rec}, D_0$),
• Month-by-month overrides (or “All Months” default).

Once the user finalizes, SWMM stores these parameters in a THydrograph object, enabling infiltration/inflow modeling in the sewer system.