Watershed Area
161.95 km²
Final ArcSWAT watershed corresponding closely to the Hare Weir catchment.
HARE Revisited · Continuous watershed modelling
SWAT
The SWAT model provides the continuous-watershed component of the HARE Irrigation Project hydrological reassessment. Watershed delineation, HRU development, climate preparation and two continuous simulations have now been completed for the approximately 161.95 km² Hare River catchment.
The current analysis examines daily and seasonal streamflow, watershed water balance, evapotranspiration, surface runoff, lateral flow, groundwater contribution, upland erosion and sediment transport and deposition.
Current model status
Hare River SWAT Model
Subbasins
17
Hydrologically connected subbasins generated from the DEM-derived drainage network.
Climate Period
2020–2025
Daily NASA POWER climate forcing represented by 16 spatial weather points.
Warm-up
2020
The first simulation year is used for model initialization.
Interpretation Period
2021–2025
Principal period used for hydrological and sediment assessment.
Continuous Runs
2
Two successful daily SWAT simulations with similar overall watershed response.
Current results
Key Findings from the First SWAT Simulations
Mean Annual Precipitation
1665.5 mm
Mean annual precipitation reported by the Simulation 2 SWAT Error Checker.
Surface Runoff
267.63 mm
Basin-average annual surface runoff from Simulation 2.
Groundwater Return Flow
182.06 mm
Simulated groundwater contribution to the stream system.
Largest Daily Outlet Flow
211.6 m³/s
Largest current SWAT daily outlet flow, simulated on 15 April 2024.
Average Upland Sediment Yield
58.4 Mg/ha
Basin-average upland sediment yield in Simulation 2.
Channel Deposition
96.23%
SWAT diagnostic indicating very strong simulated in-stream sediment deposition.
Calibration status:
the present SWAT model is functioning successfully and provides useful
preliminary hydrological and sediment information, but it is
not yet formally calibrated against an observed
same-period discharge record.
SWAT technical record
Completed Model Components
Climate
Daily NASA POWER precipitation, temperature, solar radiation, relative humidity and wind-speed forcing for 2020–2025, represented by a 16-point spatial weather grid.
Status: Completed
Climate →Watershed
DEM processing, flow direction, flow accumulation, stream definition, outlets and the final 17-subbasin watershed.
Status: Completed
Watershed →HRUs
Full land-use, soil and five-class slope overlay with zero-percent elimination thresholds and HRU-scale runoff and erosion assessment.
Status: Completed
HRUs →Results
Water balance, seasonal response, daily outlet flow, groundwater contribution, erosion hotspots, sediment yield and channel deposition.
Status: Active interpretation
Results →Calibration & Verification
Historical 1980–1990 Hare River observations are available, but matching historical climate forcing is still required before formal same-period calibration.
Status: Framework prepared
Calibration →
Complementary hydrological models
HEC-HMS and SWAT
The HARE reassessment uses HEC-HMS and SWAT for different but complementary purposes.
| Model | Primary Role | Current Status |
|---|---|---|
| HEC-HMS | Event-based rainfall-runoff modelling and design-flood hydrograph estimation at the Hare diversion weir. | Completed |
| SWAT | Continuous watershed water balance, streamflow, groundwater, erosion and sediment-routing assessment. | Simulation completed; results under interpretation |
The models should not be expected to return identical discharge values. HEC-HMS resolves individual design-flood events, while the present SWAT analysis represents continuous daily watershed behaviour.
Engineering interpretation
Emerging Importance of Sediment Management
One of the strongest findings from the SWAT assessment is the importance of sediment production and deposition within the Hare River system.
Simulation 2 indicates an average upland sediment yield of approximately 58.4 Mg/ha, identifies localized high-erosion HRUs and indicates strong net deposition within the stream network.
Current field photographs and video of the Hare diversion structure independently show substantial gravel, sand and finer sediment accumulation both upstream and downstream of the weir.
Current engineering implication:
sediment exclusion, flushing, scour facilities and desilting should be
considered important elements in the reassessment of the Hare diversion
headworks.
Current SWAT workflow
Model Development Sequence
DEM + Drainage Network
↓
17 Subbasins
↓
Land Use + Soil + Slope
↓
HRUs
↓
NASA POWER Climate 2020–2025
↓
Continuous SWAT Simulation
↓
Hydrology + Streamflow + Sediment
↓
Field Evidence + Historical Comparison
↓
Calibration and Engineering Interpretation