Watershed
162.035 km²
Five subbasins, S_1 to S_5, draining toward the Hare Weir.
HEC-HMS · Technical workspace
Simulation Runs
The Hare HEC-HMS model was prepared as an event-based design-flood model. Each simulation uses the same basin geometry, hydrologic parameters, routing configuration and computational time step. Only the adopted 24-hour design rainfall depth changes with return period.
Model consistency:
All design runs use the 162.035 km² Hare watershed, five subbasins,
SCS Curve Number losses, SCS Unit Hydrograph transformation,
Muskingum routing, no baseflow, a 15-minute computation interval
and a 72-hour simulation window.
1. Design Simulation Register
The table below provides the working register for the principal design-storm simulations. It distinguishes between completed runs and events that have been configured but still require final simulation and result extraction.
| Run ID | Return Period | 24-h Rainfall | Outlet | Status |
|---|---|---|---|---|
| RUN_HARE_10YR | 10 years | 49.61 mm | Sink-1 / Hare Weir | Configured / not yet finalised |
| RUN_HARE_25YR | 25 years | 54.99 mm | Sink-1 / Hare Weir | Configured / result to be confirmed |
| RUN_HARE_50YR | 50 years | 58.98 mm | Sink-1 / Hare Weir | Completed and accepted |
| RUN_HARE_100YR | 100 years | 62.95 mm | Sink-1 / Hare Weir | Configured / not yet finalised |
2. Adopted Design Rainfall
The final HEC-HMS event simulations use the adopted 24-hour design rainfall depths obtained from the frequency analysis prepared for the Hare watershed.
| Return Period | Adopted 24-h Rainfall | HEC-HMS Event |
|---|---|---|
| 10-year | 49.61 mm | P24,T=10 |
| 25-year | 54.99 mm | P24,T=25 |
| 50-year | 58.98 mm | P24,T=50 |
| 100-year | 62.95 mm | P24,T=100 |
Important:
These values supersede earlier preliminary rainfall depths tested during
model development. Only the final adopted design rainfall series should
be used for the website, book and final design comparisons.
3. Common Model Configuration
To permit direct comparison among return periods, the basin model and hydrologic parameters are kept unchanged between runs. The design rainfall depth is the principal input that varies.
Loss Method
SCS Curve Number
Weighted Curve Numbers assigned individually to each subbasin.
Transform
SCS Unit Hydrograph
Final adopted lags of 118, 76, 65, 52 and 62 minutes for S_1 to S_5.
Baseflow
None
Event simulations represent direct storm runoff.
Routing
Muskingum
R_1 and R_2 route the flood hydrograph toward the project outlet.
Computation Interval
15 minutes
The same time step is maintained for all design simulations.
Storm Duration
24 hours
Synthetic design rainfall is applied over one day.
Simulation Duration
72 hours
Allows the complete flood hydrograph and recession to pass through the watershed.
4. Accepted 50-Year Design Run
The 50-year event was used as the principal completed design simulation during the current stage of the Hare headworks reassessment.
Run Name
RUN_HARE_50YR
Design Rainfall
58.98 mm / 24 h
Outlet Peak Discharge
114.4 m³/s
Runoff Depth
16.84 mm
Approximate Runoff Volume
2.73 million m³
Peak Time
Simulation Day 1 · approximately 16:15
The peak discharge of 114.4 m³/s is reported at Sink-1, the HEC-HMS element representing the Hare Weir and irrigation headworks outlet.
At the time of peak discharge, the routed flow from reach R_2 contributes approximately 111.1 m³/s, while the local contribution from S_4 is approximately 3.2 m³/s. Their combination produces the reported outlet peak.
Interpretation:
The 50-year result is the accepted balanced design-event result currently
retained for the Hare headworks analysis.
5. 25-Year Design Run
The 25-year event is configured using the same basin model, loss method, transform parameters, routing parameters, computation interval and simulation duration as the accepted 50-year run.
Run Name
RUN_HARE_25YR
Design Rainfall
54.99 mm / 24 h
Outlet
Sink-1 / Hare Weir
Status
Configured — final outlet result to be confirmed
Once the final 25-year simulation output is confirmed, the outlet peak discharge, runoff depth, runoff volume and peak time should be inserted here so that the 25-year and 50-year hydrographs can be compared directly.
6. Reproducibility Checklist
Each simulation should be reproducible from the stored HEC-HMS project by maintaining the following settings.
| Item | Adopted Setting |
|---|---|
| Basin model | Final Hare basin model |
| Total area | 162.035 km² |
| Subbasins | S_1, S_2, S_3, S_4, S_5 |
| Loss method | SCS Curve Number |
| Transform method | SCS Unit Hydrograph |
| Baseflow | None |
| Routing method | Muskingum |
| Computation interval | 15 minutes |
| Storm duration | 24 hours |
| Simulation period | 72 hours |
| Design outlet | Sink-1 / Hare Weir |
7. Preliminary and Superseded Runs
A number of preliminary simulations were carried out while the basin lag times, design rainfall and routing representation were being reviewed. Those simulations were useful during model development but should not be treated as final design results.
Design record:
Earlier high-flow test results and simulations based on preliminary
rainfall depths have been superseded by the final adopted rainfall series
and balanced basin configuration documented on this website.
8. Design Run Comparison
| Return Period | P24 (mm) | Peak at Hare Weir | Runoff Depth | Status |
|---|---|---|---|---|
| 10 years | 49.61 | — | — | Not yet finalised |
| 25 years | 54.99 | — | — | Result to be confirmed |
| 50 years | 58.98 | 114.4 m³/s | 16.84 mm | Completed / accepted |
| 100 years | 62.95 | — | — | Not yet finalised |
9. Role of the Simulation Runs
The HEC-HMS design runs provide the flood hydrographs required for the hydraulic assessment of the Hare diversion structure. The outlet hydrograph provides more information than a single peak-flow value, because it also describes the timing, duration and total volume of the flood event.
The final HEC-HMS design results will subsequently be compared with independent SWAT watershed modelling. This provides an additional check on the hydrologic basis adopted for the reconstructed Hare Irrigation Project.