Abstract:
This paper deals with simulation of stream flow at ungauged catchments, the case of upper
Tekeze basin, using HBV-96 rainfall-runoff model. Parameters calibrated with the model are
extrapolated from gauged catchments to ungauged catchments of similar physical characteristics
with regionalization technique. In the upper Tekeze basin, most of the catchments are ungauged.
The basin has 9199km2
and 36381km2
gauged and ungauged catchments respectively. For this
study hydro-meteorological stations of the basins were used to calibrate and validate the model
parameters for gauged catchments from 1992-2006 years data by using HBV-96 rainfall-runoff
model. Key model parameters considered consist of runoff coefficient (Beta), recession
coefficient of upper reservoir zone (Khq), limit for evapotranspiration (Lp), field capacity (Fc),
percolation (Perc) and general correction factor for evapotranspiration (ecorr). To have a better
understanding of model parameter performance, sensitivity analysis of nine model parameters
were performed. The result shows that runoff coefficient (Beta), recession coefficient of upper
reservoir zone(Khq), limit for evapotranspiration(Lp), field capacity(Fc), percolation (Perc) and
general correction factor for evapotranspiration(ecorr) are more sensitive than others model
parameters. The gauged catchments satisfies objective function in the calibration and validation
period, for Gheba sub catchments NSE, RVE and R2
,0.81,-4.25,0.77 and 0.71,5.5,0.74
respectively. Four regionalization methods, multiple linear regression, spatial proximity, sub-
basin mean and area ratio were applied to transfer model parameters values from gauged to
ungauged catchments. Based on availability of required data, six physical catchment
characteristics (PCCs) are selected among those commonly used in many regionalization studies.
These are catchment area, mean annual precipitation, mean annual evapotranspiration, average
catchment slope, longest flow path and mean catchment elevation. Stream flow simulation at
ungauged catchments by using spatial proximity and sub basin mean method were
contributing high runoff volume compare to other methods Thus Current and future water
resources development endeavors may use apply such discharge data for planning and design
purposes
