Browsing by Author "Massawe, Grace"

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    Rainfall-run off modelling in Pangani river basin sub-catchments: a case study of Nkomazi and luengera catchments
    (University of Dar es Salaam, 2007) Massawe, Grace
    Different rainfall-runoff models ranging from the system, namely Simple Linear Model (SLM) and Linear Perturbation Model (LPM), the conceptual model called SMAR and the Semi-distributed model such as HEC-HMS were applied to Mkomazi and Luengera sub-catchments. Luengera and Mkomazi sub-catchments cover an area of 1230km2 and 3600km2 respectively. Data used for modeling ranges from 1977-1985 and from 1 976-1988 for Luengera and Mkomazi sub-catchments respectively. Two third of the time series data records were used for calibration and one third for verification. The time series data were analyzed by the rainfall, flow and evaporation seasonality. A seasonal pattern of rainfall indicates the binomial rainfall regimes with two rainy seasons, the short rains in October-December (OND) and the long rains in March-May (MAM). The peak vary in magnitude and occur in November and March/April. Comparisons of the models were made by using the efficiency criteria R2 (Nash and Sutcliffe) and the index of volumetric fit (IVF). Each model performs differently in Mkomazi and Luengera sub-catchments. All models except HEC-HMS performs better in 1 DA 1 A with R2 value of more than 70% other sub-catchments results are not much good for 1DA3A R2 value of 44.98% using LPM, 1DB17 R2 value of 25.23% using LPM and 1DB19 R2 value of 33.38% using SMAR. From the application of four models, it was found that the LPM and SMAR models are suitable for the rainfall-runoff transformation in Luengera and Mkomazi sub-catchments. Finally the autoregressive component was used in the three models i.e. SLM, LPM and SMAR in which the results are much improved.