Climate Period
2020–2025
Six complete years of daily climate forcing.
SWAT • Technical workspace
Calibration & Verification
Calibration and verification are treated separately from model setup and final result interpretation. The present Hare River SWAT model has completed two successful continuous simulations, but formal hydrological calibration has not yet been performed because an observed streamflow record overlapping the current 2020–2025 climate-forcing period is not presently available.
The current simulations are therefore interpreted as baseline and sensitivity / stability runs. They demonstrate that the model is functioning correctly and provide preliminary information on watershed water balance, daily streamflow, erosion and sediment deposition.
Important distinction:
a successful SWAT run is not the same as a calibrated model.
Calibration requires comparison between simulated and observed values
for the same period.
Current status
Calibration and Verification Status
| Component | Current HARE SWAT Status | Status |
|---|---|---|
| Watershed delineation | 161.95 km², 17 subbasins | Completed |
| HRU development | Land use, soil and slope overlay completed | Completed |
| Climate forcing | NASA POWER daily data, 2020–2025 | Completed |
| Warm-up period | 2020 | Applied |
| Analysis period | 2021–2025 | Active |
| Simulation 1 | Baseline continuous daily simulation | Completed |
| Simulation 2 | Hare-specific weather-generator assignment | Completed |
| Observed concurrent flow record | No confirmed observed daily discharge record presently available for 2020–2025 | Unavailable |
| Formal streamflow calibration | Requires observed and simulated flows for matching dates | Not yet performed |
| Historical comparison | 1980–1990 Hare River flows from the original 1995 study available as an independent benchmark | Available |
| Sediment field verification | Present-day photographs and video document substantial sediment accumulation at the Hare diversion structure | Qualitative check available |
Simulation basis
Current Continuous Simulation
The present SWAT configuration uses six years of daily meteorological forcing covering 1 January 2020 through 31 December 2025.
Warm-up
1 Year
The 2020 simulation year is excluded from primary interpretation.
Evaluation Period
2021–2025
Daily hydrological and sediment outputs are interpreted for these five years.
The warm-up period allows soil-water, groundwater and other internal model stores to develop before the principal analysis period begins.
Model stability
Simulation 1 and Simulation 2
Two successful continuous runs have now been completed. Their overall water-balance and sediment behaviour is similar, providing an important preliminary check on model stability.
| Water-Balance Component | Simulation 1 | Simulation 2 | Interpretation |
|---|---|---|---|
| Precipitation | 1665.5 mm | 1665.5 mm | Essentially unchanged |
| Potential ET | 1570.7 mm | 1570.7 mm | Unchanged |
| Actual ET | 955.5 mm | 928.9 mm | Modest reduction |
| Surface runoff | 262.27 mm | 267.63 mm | Small increase |
| Lateral flow | 247.2 mm | 250.62 mm | Small increase |
| Percolation | 209.48 mm | 224.09 mm | Moderate increase |
| Groundwater return flow | 168.6 mm | 182.06 mm | Increased groundwater contribution |
| Deep recharge | 10.47 mm | 11.2 mm | Very small change |
| Average upland sediment yield | 59.15 Mg/ha | 58.4 Mg/ha | Essentially unchanged |
Preliminary stability result:
Simulation 2 did not produce a major change in the overall watershed
response. This suggests that the baseline model behaviour is relatively
stable with respect to the tested weather-generator assignment.
Outlet response
Preliminary Hare Weir Streamflow Results
Reach 17 represents the downstream Hare River outlet in the present SWAT configuration and has a contributing drainage area of approximately 161.9 km².
The first continuous simulation produced the following annual maximum daily flows during the principal analysis period:
| Year | Maximum Daily Flow | Date | Comment |
|---|---|---|---|
| 2021 | 113.2 m³/s | 1 January 2021 | Influenced by rainfall immediately preceding the analysis period |
| 2022 | 78.75 m³/s | 16 April 2022 | Annual maximum daily flow |
| 2023 | 64.18 m³/s | 17 November 2023 | Annual maximum daily flow |
| 2024 | 211.6 m³/s | 15 April 2024 | Largest simulated daily flow |
| 2025 | 70.28 m³/s | 10 March 2025 | Annual maximum daily flow |
Important:
these are SWAT daily flow values. They should not be interpreted as
equivalent to instantaneous event peaks produced by HEC-HMS.
Historical benchmark
Observed Hare River Peak Flows from the 1995 Study
The original Hare Irrigation Project report contains eleven annual momentary peak-flow observations covering 1980–1990.
| Year | Observed Momentary Peak Flow |
|---|---|
| 1980 | 19.14 m³/s |
| 1981 | 11.70 m³/s |
| 1982 | 10.10 m³/s |
| 1983 | 14.01 m³/s |
| 1984 | 10.95 m³/s |
| 1985 | 41.11 m³/s |
| 1986 | 18.00 m³/s |
| 1987 | 14.45 m³/s |
| 1988 | 19.60 m³/s |
| 1989 | 41.45 m³/s |
| 1990 | 16.83 m³/s |
The largest observed annual momentary peak in this historical record was approximately:
41.45 m³/s in 1989
These observations cannot yet be used for direct numerical
calibration of the 2020–2025 model.
The historical observations and the current NASA-driven simulation
represent different time periods.
Additional historical evidence
Historical Monthly Flow Record
The 1995 report also provides monthly Hare River discharge records for 1980–1990, together with monthly flows representing the 1-in-5-year dry-period condition.
| Month | Historical 1-in-5-Year Dry Flow |
|---|---|
| January | 0.285 m³/s |
| February | 0.429 m³/s |
| March | 0.502 m³/s |
| April | 2.308 m³/s |
| May | 4.179 m³/s |
| June | 2.110 m³/s |
| July | 2.015 m³/s |
| August | 2.170 m³/s |
| September | 2.740 m³/s |
| October | 2.275 m³/s |
| November | 1.500 m³/s |
| December | 0.649 m³/s |
These historical monthly flows are particularly valuable because SWAT is a continuous model. If daily historical meteorological forcing can be reconstructed for the same period, monthly simulated discharge can be compared directly with the original observed record.
Data limitation
Why the Model Has Not Yet Been Formally Calibrated
Calibration requires the simulated and observed series to represent the same hydrological period.
Current SWAT climate:
2020–2025
Historical observed Hare flow:
1980–1990
Directly adjusting model parameters until the 2020–2025 SWAT flows resemble the 1980–1990 observations would therefore not constitute valid calibration.
Differences could reflect genuine changes in rainfall, land cover, watershed condition, channel geometry or climate rather than errors in SWAT parameters.
Current approach:
retain the successful baseline model, document its behaviour and obtain
or reconstruct historical climate forcing before undertaking formal
streamflow calibration.
Proposed validation strategy
Historical SWAT Validation Run
The strongest future calibration strategy is to reproduce the historical 1980–1990 flow-record period using corresponding daily climate forcing.
Historical Climate → SWAT 1980–1990 → Simulated Hare Flow → Compare with 1995 Observations
The historical run could then be evaluated against:
- monthly observed Hare River flow;
- annual momentary peak-flow information;
- seasonal high-flow timing;
- dry-period discharge;
- overall water-balance behaviour; and
- available historical project observations.
Potential calibration controls
Parameters to Review During Formal Calibration
No systematic parameter calibration has yet been applied. When an overlapping observed-flow period becomes available, physically relevant SWAT parameters can be assessed through controlled sensitivity analysis.
| Parameter Group | Typical SWAT Parameters | Primary Influence |
|---|---|---|
| Surface runoff | CN2 | Rainfall partitioning and surface-runoff generation |
| Soil water | SOL_AWC, SOL_K | Soil-water storage, infiltration and percolation |
| Evapotranspiration | ESCO | Soil evaporation and water-balance response |
| Groundwater | ALPHA_BF, GW_DELAY, GWQMN, RCHRG_DP | Baseflow timing, groundwater contribution and recharge |
| Channel routing | CH_N2, CH_K2 | Channel flow timing and transmission losses |
| Erosion | USLE-related HRU and management parameters | Upland sediment production |
No parameter should be changed solely to make SWAT reproduce
the HEC-HMS 50-year peak.
SWAT and HEC-HMS represent different modelling approaches and different
hydrological quantities.
Future performance assessment
Calibration Statistics
Formal performance statistics will only be calculated when observed and simulated discharge are available for matching dates.
NSE
Nash-Sutcliffe Efficiency can be used to evaluate how well the simulated hydrograph reproduces observed temporal variability.
PBIAS
Percent Bias can identify systematic overprediction or underprediction of total streamflow volume.
R² / KGE
Correlation and Kling-Gupta-type measures can provide additional information on timing, variability and bias.
No NSE, PBIAS, R² or KGE value is presently reported because a concurrent observed discharge series has not yet been established.
Sediment verification
Modelled Sediment and Field Evidence
Although measured sediment-discharge data are not presently available, the current field condition of the Hare diversion structure provides an important qualitative check on the SWAT sediment results.
Simulation 2 produced:
Average Upland Yield
58.4 Mg/ha
Basin-average simulated upland sediment yield.
Channel Deposition
96.23%
Strong simulated depositional behaviour within the channel system.
Bare-Ground Hotspot
1,549.33 Mg/ha
Localized simulated sediment yield associated with the BARR land-use class.
Field photographs and video show substantial gravel, sand and finer sediment accumulation both upstream and downstream of the existing Hare diversion weir.
This does not constitute quantitative sediment calibration. However, the agreement between the modelled depositional tendency and the observed physical condition provides a useful qualitative verification of the importance of sediment processes in the Hare River.
Current interpretation
What Can Be Concluded at This Stage?
The present model is a successfully functioning continuous watershed model with encouraging internal consistency, but it should still be described as uncalibrated.
- Two simulations have completed successfully.
- Their water-balance results are very similar.
- Daily streamflow behaviour is physically responsive to major rainfall events.
- Surface runoff, groundwater return flow and evapotranspiration show coherent seasonal behaviour.
- SWAT identifies localized erosion hotspots.
- The model predicts strong channel sediment deposition.
- Present-day field observations independently confirm substantial sediment accumulation around the Hare diversion structure.
Present model classification:
successful baseline continuous simulation with preliminary stability
testing and qualitative field verification. Formal streamflow and
sediment calibration remain future stages.
Next calibration stage
Recommended Next Steps
- Preserve the current successful Simulation 2 configuration as the present reference run.
- Complete analysis of Reach 17 daily discharge, monthly flow and sediment transport.
- Obtain or reconstruct daily historical climate data covering as much of the 1980–1990 observed-flow period as possible.
- Run a historical SWAT simulation using the same watershed and HRU framework.
- Compare simulated monthly flows with the historical Hare River observations.
- Conduct parameter sensitivity analysis only after a valid same-period comparison dataset has been established.
- Calculate formal calibration statistics such as NSE, PBIAS, R² and KGE where the data permit.
- Retain present-day sediment photographs and video as field evidence supporting the sediment-deposition assessment.
View SWAT watershed delineation | View SWAT HRU analysis | View SWAT climate inputs