Abstract:
Hydrological modeling and forecasting are being
carried out all over the world to enable proper water resource
management. Relationship between spatial variability of
precipitation and runoff modeling remains an open scientific
topic, which arises frequently in hydrologic modeling. The
objective of this study is to find the effect of spatial variability of
precipitation on stream flow modeling of Maha Oya river basin.
A model was developed by using HEC-HMS 4.2.1 software and
automatic calibration using Nelder-Mead method with Nash-
Sutcliffe coefficient as objective function was applied. Pearson
Correlation (PC) coefficient and Mean Relative Error (MRE)
were also used to evaluate the model performance. Change in
accuracy in simulated stream flow with the increase in number
of rainfall stations used to produce input rainfall was compared.
Overall accuracy of the modeling increased with number of
rainfall stations. Minimum number of stations required to
satisfy the objective function was three which gave Nash-
Sutcliffe efficiency, Pearson correlation coefficient and mean
relative error as 0.61, 0.78 and 0.13, respectively. The change in
accuracy after three stations was not significant as it was before
three stations. Based on these results, it could be concluded that
there is a significant impact on stream flow modeling from
spatial variability of rainfall in Maha Oya basin and this
significance reduces after a certain limit of consideration given
to the spatial nature of rainfall.
