Abstract:
Prediction of stream flow of ungauged catchment is important for water resources design,
planning and management system. Runoff estimation in interest catchment is probably one of the
most basic and oldest tasks of hydrologists. This long-standing issue has received increased
attention recently due to the prediction in ungauged basin initiative by the International
Association Hydrological Science. In developing countries like Ethiopia most of the rivers are
ungauged. Therefore, applying regionalization techniques on an ungauged or poorly gauged river
basin is crucial. This thesis deals with stream flow prediction in an ungauged catchments using
hydrological model in Geba Sub-Basin. The HBV-96 model is selected to simulate discharge for
four gauged catchments on a daily basis in the period of 1998-2008 and with data input such as
precipitation, air temperature, potential evapotranspiration, and Geographical zones.
Four regionalization methods were applied to transfer model parameter values from the gauged
to the interest catchments. Those methods are regional model, sub basin mean, area ratio and
proximity methods. In regional model, gauged catchments model parameters and physical
catchment characteristics of ungauged catchments were used to develop the equations in order to
estimate stream flow from ungauged catchments. To have better understanding of model
parameter performance, the sensitivity analysis of eight model parameters were performed
manually by trial and error. The evaluation shows that the model parameters, runoff coefficient
(Beta), recession coefficient of upper reservoir zone (Khq), limit for evapotranspiration (LP), and
Field capacity (FC) are more sensitive than the others. The model performance was evaluated
using Nash Sutcliff efficiency and Relative volume error. The result shows that the four gauging
river have good agreement and distribution since Nash Sutcliff efficiency greater than 0.67 and
relative volume error lies between +10% and -10%. In predicting model parameters from
ungauged catchments in regional model method p-value ≤ 0.05 for 95% confidence interval and
determination coefficient (R2) ≥0.98 were obtained. Stream flow from ungauged catchments
simulated by regional model, spatial proximity, area ratio and sub-basin mean contribute high
and less runoff volume respectively.
