Theses and Dissertations Collection

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Browsing Theses and Dissertations Collection by Author "Munishi, Pantalco K. T."

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    Two-decade variations in hydrology of two river basins in the Usambaras of north-eastern Tanzania
    (Duke University, 1994) Munishi, Pantalco K. T.
    Quantifying local, regional, and global climatic and hydrologic changes is relatively difficult due to high temporal and spatial variability, and to the length of time it takes for these changes to be monitored and detected. The study of precipitation and river flow patterns of two watersheds, Sigi and Soni Rivers, that drain the east and west Usambaras in northeastern Tanzania over a two decades period 1965 to 1989, show that there were varying patterns of precipitation and river flow on the Usambaras over the period. Though a non-significant trend, precipitation increased by 2.7% in the east Usambaras while it decreased by 7.7% in the west Usambaras during the period 1965-1990. The mean annual discharge increased by 2.6% in the east and 44% in the west Usambaras. During approximately two decades, discharge per unit of precipitation did not change significantly in the east Usambaras whereas it appeared to increase at a rate of 0.02 m3 s“lyr"l in the west Usambaras (P = 0.06). This is about 0.4 m3 s-1 yr-1 (1.2 cm ha-1 yr-1) more water flowing into the river today compared to 1965. There has been an increase in the proportion of precipitation reaching the rivers especially in the west Usambaras, which seems to have started about in the mid-1960’s. Such watershed response to rainfall may be attributed to climatic and land use factors. In the Usambaras, changes in hydrologic response coincide with high rates of deforestation and changes in land use patterns. It is recommended that the remaining catchment areas on the Usambaras, and vegetation filter strips along river/stream banks should be protected. Appropriate reforestation work in degraded lands including agroforestry in farmlands should form the framework of conservation measures.