Abstract:
Streamflow modelling plays a vital role in
hydraulic design activities. As rainfall is the major input for the
modelling process, the accuracy of the output after modelling
directly depends on the accuracy of used rainfall data values.
Obtaining spatially distributed rainfall data to incorporate the
spatial variation of rainfall is achieved by using different
interpolation techniques. Depending on the interpolation
method used, accuracy varies and it is necessary to identify the
most suitable interpolation method for a specific basin. This
study is focused on the Ellagawa sub basin in Kalu Ganga basin,
Sri Lanka and it compares four Deterministic Spatial
Interpolation Methods (DSIMs); Simple Average Method (SA),
Thiessen Polygon Method (TP), Inverse Distance Weighting
Method (IDW) and Inverse Distance & Elevation Weighting
Method (IDEW) in both daily and monthly basis using Twoparameter
water balance model and Four-parameter (ABCD)
water balance model. After comparing Pearson Coefficient
(PC), Mean Relative Error (MRE) and Nash-Sutcliffe Efficiency
(NSE), TP Method was identified as the most suitable method
for both daily and monthly data for Kalu Ganga basin and
basins with similar characteristics.
