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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/2479

Advisors: Dr. SEMU AYALEW
Keywords: Ungauged Catchment
Rainfall-Runoff modeling
ILWIS (Integrated Land and Water Information System)
Nash IUH Model
Geomorphologic Instantaneous Unit Hydrograph (GIUH)
Copyright: Jun-2011
Date Added: 4-May-2012
Publisher: AAU
Abstract: Geomorphologic instantaneous unit hydrograph (GIUH) can be used as a transfer function for modeling the transformation of excess rainfall into surface runoff, in which excess rainfall is a production function to the hydrologic system. These models can be used to predict the temporal variation of the surface runoff at the outlet of ungauged catchment, which is useful in the hydrologic engineering applications. In this study the two types of geomorphologic approaches were studied, GIUH and GIUH based Nash IUH models, for unit hydrograph derivation from the observed data. The geomorphological characteristics of a catchment were related with the shape and scale parameters of the Nash IUH to derive the complete shape of the GIUH based Nash IUH model; and GIUH was developed from geomorphological characteristics of the catchments and probability density function of travel time of rainfall excess to the catchment outlet. These two models were developed in seven catchments in Abay basin (Fettam, Hoha, Neshi, Uke, Andassa, Azuari and Jedebe) with range of areas 161 to 573km2. In this study, velocity was set as a calibration parameter to calibrate the simulated unit hydrograph with the observed unit hydrograph in both models. A regionalized streamflow velocity equation was developed from the simulated data with R2 equal to 0.89 and 0.96 for GIUH and GIUH based Nash IUH model respectively. Then, these equations were applied on chemoga catchment, which was considered as ungauged catchment, to observe the reliability of the models. The performances of the calibrated models were evaluated using Nash-Sutcliffe efficiency (NSE), Error (ERR), percentage error in peak discharge (PEP) and percentage error in time to peak (PETP). From model evaluation results, GIUH model efficiency (EFF) varies from 81.95 to 97.9 percent while GIUH based Nash IUH model efficiency varies from 75.68 to 97.51 percent. GIUH model is efficient in peak discharge estimation (R2=0.988) than GIUH based Nash IUH model (R2=0.884). In general, the result of both GIUH and GIUH based Nash IUH models are almost comparable and their results are acceptable but the GIUH model is superior. i Moreover, a simple GIUH based regional triangular unit hydrograph equations were developed and compared with the SCS triangular unit hydrograph. The R2 value in peak discharge estimation using SCS method is 0.48 while using GIUH method is 0.95. This implies that the derived GIUH based regional triangular unit hydrograph equation is quite different from SCS triangular unit hydrograph and GIUH has better efficiency. Finally, this paper concludes that, the regionalized GIUH based equation for peak discharge, time to peak and base time of the triangular unit hydrograph can be used, within the errors specified in this research paper, for any ungauged catchment found in neighbor of the study area having similar character and varying in areas from 161 to 573km2. Further work may in the future be required to explain any non linear relationship of rainfall runoff and homogeneity of
URI: http://hdl.handle.net/123456789/2479
Appears in:Thesis - Civil Engineering

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