Source
NASA POWER
Daily gridded meteorological data covering the Hare watershed and surrounding terrain.
SWAT • Technical workspace
Climate Inputs
Daily meteorological inputs for the Hare River SWAT model were prepared from NASA POWER gridded climate data for the period 2020–2025. A spatially distributed 16-point weather grid was used to represent climatic variation across and around the approximately 161.95 km² Hare Weir catchment.
The climate package includes daily precipitation, maximum and minimum temperature, solar radiation, relative humidity and wind speed. These datasets were checked for completeness before conversion to SWAT-compatible input files.
Current SWAT climate period:
1 January 2020 to 31 December 2025.
The year 2020 is used as model warm-up, while
2021–2025 forms the principal interpretation period.
Climate source
1. NASA POWER Climate Dataset
Climate Period
2020–2025
Six complete calendar years used for the present continuous SWAT simulations.
Weather Points
16
A 4 × 4 spatial grid was used instead of a single weather point.
Terminology:
NASA POWER provides gridded meteorological data. The present website
therefore refers to these records as climate forcing or gridded climate
data rather than describing them as local gauge measurements.
Spatial representation
2. NASA POWER Weather Grid
The weather grid extends beyond the delineated watershed so that SWAT can assign spatially representative meteorological conditions to the individual subbasins.
The wider climate grid does not change the watershed boundary or the 161.95 km² drainage area used by SWAT.
Grid Latitudes
5.80°
6.05°
6.30°
6.55°
Grid Longitudes
37.09°
37.34°
37.59°
37.84°
Grid spacing:
approximately 0.25° in latitude and longitude, equivalent to roughly
25–30 km depending on direction and location.
Meteorological variables
3. Climate Variables Supplied to SWAT
Precipitation
Daily NASA POWER rainfall forcing.
SWAT files: pcp.txt and pcp1–pcp16.
Temperature
Daily maximum and minimum air temperature.
SWAT files: temp.txt and temp1–temp16.
Solar Radiation
Daily solar-radiation input for evapotranspiration and vegetation-growth calculations.
SWAT files: solar.txt and solar1–solar16.
Relative Humidity
NASA POWER source data are expressed as percentages. SWAT-ready files were converted to fractions between 0 and 1.
SWAT files: rh.txt and rh1–rh16.
Wind Speed
Daily wind-speed forcing for all 16 grid points.
SWAT files: wind.txt and wind1–wind16.
Weather Generator
Monthly SWAT weather-generator statistics were developed specifically for the Hare model.
Stations: HARE01–HARE16.
Quality control
4. Data Completeness and Verification
The clean NASA POWER climate archive was checked before preparation of the SWAT input files.
Each of the 16 weather-grid files contains a continuous daily sequence from 1 January 2020 through 31 December 2025.
Records per Point
2,192
Daily observations contained in each weather-grid file.
Missing Dates
0
No missing calendar dates were identified.
Duplicate Dates
0
No duplicate daily records were retained.
Quality-control result:
the final precipitation, temperature, solar-radiation, humidity and
wind datasets form a continuous climate series suitable for the
present SWAT simulation.
SWAT formatting
5. Relative Humidity Conversion
Relative humidity required a specific conversion before the final SWAT files were prepared.
NASA POWER Source File
Relative humidity is stored as a percentage.
65.28%
SWAT Input File
The value is converted to a decimal fraction.
0.6528
65.28% → 0.6528
Archive distinction:
the clean NASA POWER source files should retain relative humidity in
percentage form. Only the SWAT-ready humidity input files use the
converted 0–1 fraction.
Rainfall record
6. Annual Rainfall from the 16-Point Climate Grid
Spatial averaging of the 16 NASA POWER grid points provides a useful summary of annual rainfall forcing used in the current SWAT analysis.
| Year | Annual Spatial-Average Rainfall | Maximum Daily Rainfall | Date of Maximum | Model Role |
|---|---|---|---|---|
| 2020 | 2,231.98 mm | 192.18 mm/day | 31 December 2020 | Warm-up year |
| 2021 | 1,552.83 mm | 120.02 mm/day | 27 November 2021 | Analysis |
| 2022 | 1,215.38 mm | 98.33 mm/day | 16 April 2022 | Analysis |
| 2023 | 1,952.07 mm | 42.66 mm/day | 17 November 2023 | Analysis |
| 2024 | 1,886.44 mm | 118.99 mm/day | 15 April 2024 | Analysis |
| 2025 | 1,723.98 mm | 52.70 mm/day | 10 March 2025 | Analysis |
2021–2025 mean annual rainfall:
approximately 1,666.14 mm/year from the 16-point
spatial-average climate record.
Independent input check
7. Agreement with the SWAT Water Balance
The rainfall calculated independently from the clean NASA POWER archive agrees very closely with the precipitation reported by the SWAT Error Checker.
Climate Files
1666.14 mm
Mean annual spatial-average rainfall for 2021–2025.
SWAT Error Checker
1665.50 mm
Mean annual precipitation reported by the current SWAT run.
Difference
0.64 mm
Approximately 0.04% difference between the two summaries.
Consistency check:
the exceptionally small difference confirms that the precipitation
forcing represented in the SWAT water balance is consistent with the
clean climate archive.
Rainfall-runoff response
8. Major Rainfall Events and SWAT Outlet Flow
The principal simulated Hare River flow peaks correspond closely with major rainfall events in the NASA POWER climate record.
| Year | Major Rainfall Date | Spatial-Average Rainfall | SWAT Outlet Flow | Response |
|---|---|---|---|---|
| 2021 | 27 November 2021 | 120.02 mm/day | Major 2021 event response | Strong rainfall-runoff event |
| 2022 | 16 April 2022 | 98.33 mm/day | 78.75 m³/s | Annual maximum daily flow |
| 2023 | 17 November 2023 | 42.66 mm/day | 64.18 m³/s | Annual maximum daily flow |
| 2024 | 15 April 2024 | 118.99 mm/day | 211.6 m³/s | Largest current SWAT daily flow |
| 2025 | 10 March 2025 | 52.70 mm/day | 70.28 m³/s | Annual maximum daily flow |
The correspondence between rainfall-event dates and simulated flow peaks provides an important internal check on the responsiveness of the current SWAT model.
Important:
SWAT outlet values shown here are daily simulated flows. They should not
be interpreted as instantaneous flood peaks.
Largest simulated flow event
9. April 2024 Rainfall Sequence
The largest current SWAT daily outlet flow occurred on 15 April 2024. The climate record shows that this event followed substantial antecedent rainfall.
| Date | Spatial-Average Rainfall | Hydrological Significance |
|---|---|---|
| 13 April 2024 | 9.11 mm | Initial wetting |
| 14 April 2024 | 55.04 mm | Strong antecedent rainfall |
| 15 April 2024 | 118.99 mm | Major rainfall event |
| 16 April 2024 | 19.16 mm | Continued rainfall following peak event |
The resulting SWAT outlet discharge on 15 April 2024 reached:
211.6 m³/s
This sequence indicates that the largest simulated daily flow was associated not only with a very large daily rainfall total but also with substantial rainfall on the preceding day.
Warm-up interpretation
10. December 2020 Carry-Over into January 2021
The initial 2021 SWAT outlet flow requires special interpretation because it immediately follows an exceptionally large rainfall event during the final day of the 2020 warm-up period.
31 December 2020
192.18 mm
Largest spatial-average daily rainfall in the six-year climate archive.
1 January 2021
113.2 m³/s
High SWAT outlet discharge affected by rainfall immediately preceding the analysis period.
This explains why the 1 January 2021 discharge should not be treated as an independent rainfall event arising entirely within the 2021 analysis period.
Interpretation:
the 1 January 2021 value reflects hydrological carry-over from the
extreme 31 December 2020 rainfall event during the warm-up year.
SWAT weather generator
11. Hare-Specific Weather Generator
A Hare-specific SWAT weather-generator dataset was prepared from the same 2020–2025 NASA POWER climate archive.
Sixteen weather-generator stations were prepared: HARE01 through HARE16.
Temperature
Monthly mean maximum and minimum temperature and corresponding variability statistics.
Rainfall
Monthly rainfall, daily variability, skewness, wet-day probabilities and wet-day frequency.
Atmospheric Variables
Solar radiation, dew-point information and wind-speed statistics.
The weather-generator record length was entered as:
RAIN_YRS = 6
RAINHHMX:
no measured sub-daily or 30-minute rainfall record was available.
Therefore an artificial short-duration rainfall maximum was not inserted
into the Hare WGEN dataset.
Simulation stability
12. Role of the Weather Generator
The present SWAT simulations use daily NASA POWER precipitation, temperature, solar radiation, relative humidity and wind-speed forcing.
The weather generator therefore supplies supporting monthly statistics required internally by SWAT rather than replacing the daily climate series used in the simulation.
A second simulation using the Hare-specific weather-generator assignment produced results very similar to the initial run.
| Component | Simulation 1 | Simulation 2 |
|---|---|---|
| Precipitation | 1665.50 mm | 1665.50 mm |
| Surface runoff | 262.27 mm | 267.63 mm |
| Actual ET | 955.50 mm | 928.90 mm |
| Groundwater return flow | 168.60 mm | 182.06 mm |
| Average upland sediment yield | 59.15 Mg/ha | 58.40 Mg/ha |
Simulation check:
the similarity between the two runs indicates that the principal
watershed response was not strongly altered by the weather-generator
reassignment.
Seasonal climate response
13. Rainfall and Seasonal SWAT Behaviour
The SWAT basin summary shows that the seasonal hydrological response follows the main rainfall periods in the climate record.
April Rainfall
332.13 mm
Highest monthly basin rainfall in the current Simulation 2 summary.
April Surface Runoff
76.62 mm
Highest monthly surface-runoff response.
April Water Yield
131.68 mm
Strongest monthly water-yield response.
A second period of strong rainfall-runoff response occurs during October and November, consistent with the seasonal climate pattern represented by the NASA POWER forcing.
Modelling limitation
14. Historical Calibration Limitation
The current climate dataset covers 2020–2025, whereas the original Hare River flow observations recovered from the 1995 project report cover 1980–1990.
The present NASA POWER dataset therefore cannot be used directly for a same-period calibration against those historical streamflow observations.
Formal historical SWAT calibration will require daily meteorological forcing corresponding to the period of the historical flow record.
Current interpretation:
the 2020–2025 run represents a modern continuous watershed
assessment. The 1980–1990 river-flow record remains an independent
historical benchmark until matching historical climate forcing is
prepared.
Climate-input status
Climate Input Status
NASA POWER Archive
Complete
Six years of daily meteorological data for 16 spatial grid points.
SWAT Formatting
Complete
Precipitation, temperature, solar radiation, relative humidity and wind converted to SWAT-ready files.
Model Simulation
Successful
Climate forcing successfully used in two continuous Hare River SWAT simulations.
Current status:
climate-data preparation is complete. The climate archive has been
independently checked against the SWAT precipitation summary and is now
supporting hydrological and sediment-result interpretation.
SWAT technical record
Related SWAT Documentation
Watershed
DEM processing, stream definition and the 17-subbasin watershed.
HRUs
Land use, soil, slope and Hydrologic Response Unit development.
Results
Water balance, daily flow, seasonal response and sediment results.
Calibration
Historical-flow benchmark and future validation strategy.