Model data

River Flow & Discharge

River discharge is the link between watershed hydrology and irrigation design. The HARE reconstruction keeps event flood discharge, long-term watershed flow and irrigation diversion requirements separate so that each quantity is used for the correct engineering purpose.

Important distinction. Peak flood discharge is used mainly for the safety and hydraulic design of the diversion weir and associated river structures. Irrigation canal discharge is instead governed by crop-water demand, available river flow and the capacity of the conveyance system.

Hare catchment

≈163 km²

Modern catchment area used for HEC-HMS and SWAT hydrological analysis.

HEC-HMS 25-year

97 m³/s

Modelled peak discharge from the 25-year design-event simulation.

HEC-HMS 50-year

114 m³/s

Modelled peak discharge from the 50-year design-event simulation.

Irrigation system

1.55 m³/s

Historical full-supply discharge of the main irrigation canal in the original Hare design.

Discharge types

Different Flows for Different Design Questions

Flow quantity	Typical source	Main purpose	Do not confuse with
Peak flood discharge	HEC-HMS design storm simulation	Weir safety, river control structures, scour protection and flood passage.	Normal irrigation diversion flow.
Daily / seasonal river flow	Observation, reconstruction or continuous watershed model	Water availability and reliability assessment.	Design flood peak.
SWAT streamflow	Continuous watershed simulation	Long-term watershed response, seasonal flow pattern and hydrological consistency.	Event-specific HEC-HMS design flood.
Irrigation diversion discharge	Crop demand, command area and irrigation efficiency	Canal sizing, irrigation scheduling and water distribution.	River flood discharge.
Minimum available flow	Dry-season records, observations or modelled low-flow analysis	Determine whether the planned irrigation demand can actually be supplied during critical periods.	Full-supply canal capacity alone.

HEC-HMS

Design Flood Hydrographs

HEC-HMS is used as the principal event-based model for estimating design flood hydrographs at the Hare outlet. Frequency-based design rainfall is transformed through basin losses and runoff-routing methods to obtain both peak discharge and the complete discharge hydrograph.

Return period	HEC-HMS peak discharge	Current interpretation	Status
25 years	97 m³/s	Modern design-flood estimate available for comparison with the original headworks design.	Completed
50 years	114 m³/s	Higher design event used as an additional structural and flood-passage check.	Completed
100 years	—	Add after the corresponding HEC-HMS design-event run has been completed and checked.	Pending

SWAT

Long-Term Streamflow Context

SWAT complements the event-based HEC-HMS analysis by representing continuous watershed processes. It helps explain how precipitation is divided among evapotranspiration, surface runoff, lateral flow, groundwater return flow and stream discharge over longer periods.

Hydrological component	SWAT annual average	Relation to streamflow
Precipitation	1665.5 mm	Total climatic water input to the simulated watershed.
Surface runoff	267.63 mm	Rapid runoff contribution to the drainage network.
Lateral flow	250.62 mm	Subsurface lateral contribution to streamflow.
Groundwater return flow	182.06 mm	Groundwater contribution sustaining streamflow.
Actual evapotranspiration	928.9 mm	Water removed from the watershed before it can contribute to streamflow or storage.

Irrigation design

Available Flow vs Irrigation Demand

The canal cannot deliver water that is not available in the river. For that reason, canal capacity, CROPWAT irrigation demand and dry-season river availability must ultimately be checked together.

1. River availability Determine seasonal and critical low-flow availability at the diversion.

2. Crop demand Calculate monthly and peak irrigation requirement using CROPWAT.

3. Scheme demand Aggregate crop demand across the irrigable command area.

4. Canal capacity Compare required diversion discharge with the main canal capacity.

5. Scheduling If demand exceeds available supply or canal capacity, operate secondaries and tertiaries according to an irrigation schedule.

Current design issue. The reconstructed main-canal supply capacity is approximately 1.55 m³/s. Because this capacity cannot necessarily supply all secondary canals simultaneously, irrigation scheduling remains an important part of the final operational design.

Data quality

Discharge Data Status

Dataset / result	Use	Status
25-year HEC-HMS hydrograph	Weir and headworks flood-design check.	Available
50-year HEC-HMS hydrograph	Higher-return-period flood check.	Available
HEC-HMS outlet time series	Complete event hydrograph and peak-discharge archive.	Export / archive
SWAT continuous streamflow	Seasonal and long-term hydrological behaviour.	Review output
Dry-season / minimum river flow	Irrigation reliability and water-availability check.	To be finalized
CROPWAT scheme discharge	Compare irrigation requirement with available flow and canal capacity.	Next stage