Browsing by Author "Kivegalo, Clement Lenard"

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    Estimation of actual evaporation from Pangani River Basin
    (University of Dar es Salaam, 1999) Kivegalo, Clement Lenard
    Estimates of actual evaporation play a significant role in the regulation and control of water along any natural and man-made water body. They are also important for water balance computations and other obvious applications in any river basin. This study was aimed at quantifying the amount of actual evaporation and actual evapotranspiration from the Nyumba ya Mungu reservoir and some catchments respectively within the Pangani River Basin. It has been realised from the study that, about 1393 millimetres (depth of water) is actually lost annually from the Nyumba ya Mungu Reservoir. Also about 1551 mm, 1138mm, 1029 mm, and 1174mm of water are actually lost annually from the catchments 1DC2A, 1DA3A, 1DB17, and 1DD1 respectively. The majority of the stations used have coefficient of variation of annual estimates of actual evaporation and evapotranspiration, ranging between 3% and 9%. Eleven meteorological stations with available climatic data were used. The meteorological stations lie within and just outside four different sub-catchments, which are Kikuletwa catchment (1DD1), Mkomazi Gomba catchment (1DB17), Rau catchment (1DA3A), and Ruvu catchment (1DC2A). Langasani and Moshi Airport meteorological stations lie within the Kikuletwa catchment. The meteorological stations Buiko, Kalimawe, Mnazi, and Lushoto lie within the Mkomazi catchment. The meteorological stations Mazumbai and Magoma lie within the Rau catchment and the Ruvu catchment comprises of Nyumba ya Mungu and Moshi Airport meteorological stations. Two methods have been used for estimation of actual evaporation from Nyumba ya Mungu reservoir. The methods are, reservoir water balance, and Morton model. The estimation of actual evapotranspiration was done using the methods of simplified water balance, Bruitsaert-Stricker, Bouchet, Difference, Morton model, and soil moisture recharge method. The difference method is a new method first proposed in the study of `Estimation of actual evapotranspiration in Malawi', Mandeville A. N and Batchelor C. H (1990). In the case of actual evapotranspiration, the study has generally shown that most of the estimates computed by the methods of Brutsaert-Stricker, and Bouchet are questionable, since they have shown high overestimation of the estimates computed by the simplified water balance method. The Morton model and Difference method to some extent have shown reasonable level of justification. However, the Morton model overestimates the estimates of actual evaporation from Nyumba ya Mungu reservoir determined by the method of reservoir water balance.