In this exercise, we will create a continuous VO model using a single-event model and then run the simulation with 10 years of climate data from Toronto Pearson Airport.
This exercise covers the basic work flow in a continuous simulation. You will find that the interface and work flow is similar compared to the single-event simulation.
Please download the attachment to practice and view results.
tutorial – continuous model
!The VO model uses the unit hydrograph method to generate hydrographs, representing storm flow caused by excess rainfall under extreme conditions. This approach is suitable for modelling peak flows during design storms and extreme rainfall events. However, it is essential to understand the implications of this method when applying it to continuous modelling.
In continuous modelling, rainfall and runoff are simulated over an extended period, accounting for daily variations, seasonal changes, and long-term patterns. Since the unit hydrograph is inherently designed to represent storm flow, the resulting hydrographs in continuous modelling may overestimate flow compared to real-world observed values, especially for non-extreme rainfall events. This discrepancy arises because the unit hydrograph assumes idealized conditions that emphasize runoff generation from excess rainfall, often overlooking subtleties like baseflow contributions, antecedent moisture conditions, infiltration variability, and subsurface flow processes.
!Implications for Users
When using VO for continuous modelling:
Hydrograph Magnitude: The hydrograph generated may be larger than observed flow values, particularly for small to moderate rainfall events.
Calibration Requirement: To achieve results that closely match observed flow values, users must calibrate the model against measured flow data.
Extreme Events: For extreme rainfall conditions, the default behavior of the unit hydrograph is more representative, as these scenarios align better with its assumptions.
!Recommendations for Users
For applications requiring realistic simulation of long-term hydrologic behavior, calibration is essential. This ensures the model reflects the actual hydrologic response of the watershed.
Users should validate the model against multiple observed events.
