Abstract:
The paper describes a case study of event based and continuous hydrologic
modeling of inflows to the Tittawella tank in Kurunegala using the
Hydrologic Engineering Center – Hydrologic Modeling System (HEC–
HMS). A high rainfall event in Oct-Nov 1995 was used for calibration of
model parameters and high rainfall events in Oct 1996 and May 1995 were
used for validation of the event based model. The calibrated model
parameters were used in the continuous hydrologic model. Time series data
of Sep-Nov 1995 were used for calibration of the continuous model, while
three months, one year and two year time series data were used for validation
of continuous simulations. The initial and constant infiltration loss method
was used to account infiltration loss in event based modeling and 5–layer soil
moisture accounting loss method was utilized in continuous modeling. Clark
unit hydrograph method and recession base flow method were used to
simulate direct runoff and base flow, respectively. The validation results
reveal the capability of HEC–HMS to reproduce stream flows in the
catchment to a high accuracy with averaged computed Nash Sutcliffe
efficiencies of 0.89 for event based simulations and 0.76 for continuous
simulations. The calibrated model can be used to water management studies
in Deduru Oya development project
