Browsing by Author "Tumbo, Siza D."

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Smallholder System Innovations in Integrated Watershed Management (SSI) Strategies of Water for Food and Environmental Security in Drought-Prone Tropical and Subtropical Agro-Ecosystems
(2006) Bhatt, Yogesh; Bossio, Deborah; Enfors, Elin; Gordon, Line; Kongo, Victor; Kosgei, Job Rotich; Makurira, Hodson; Masuki, Kenneth; Mul, Marloes; Tumbo, Siza D.
"Rapidly increasing population in the dynamic semi-arid agro-ecosystems in sub-Saharan Africa (SSA) highlights the necessity to increase food production, while at the same time safe-guarding other ecological systems that support human development and well-being. In the past, increases in crop production to keep pace with population growth in this region were largely achieved through the expansion of cultivated area. Today, we must also consider ways of improving the productivity of already existing cropping systems. This working paper frames the critical questions that must be addressed through development-oriented research and describes the integrated research approach of the SSI program, its interconnected research projects - their scope and methodologies."
Use of a Hydrological Model for Environmental Management of the Usangu Wetlands, Tanzania
(2006) Kashaigili, Japhet J.; McCartney, Matthew; Mahoo, Henry F.; Lankford, Bruce; Mbilinyi, Boniface P.; Yawson, Daniel K.; Tumbo, Siza D.
"This report presents the findings of a study to assess changes to flows into, and downstream of, the Usangu Wetlands, located in the headwaters of the Great Ruaha River, Tanzania. Hydrological data, in conjunction with remote sensing techniques, were used to provide insights into changes that have occurred to the Eastern Wetland. Results indicate that, between 1958 and 2004, inflows to the wetland declined by about 70 percent in the dry season months(July to November) as a consequence of increased human withdrawals, primarily for irrigation. This resulted in a decrease in the dry season area of the wetland of approximately 40 percent (i.e., from 160 km2 to 93 km2). In the last decade, outflows from the wetland have ceased for extended periods. An environmental flow model indicates that a minimum dry season outflow of approximately 0.6 m3 s-1 is essential to sustain the basic ecological condition of the river. To maintain this outflow from the wetland, a minimum average dry season inflow of approximately 7 m3 s-1 (i.e., approximately double current dry season flows) is required. To achieve this, dry season flows in the perennial rivers discharging into the wetland would have to be apportioned so that 20 percent is used for anthropogenic purposes and the remaining 80 percent discharges into the wetland. There is significant potential for improving water use efficiency. However, to ensure minimum downstream flow requirements, consideration should also be given to active water management within the wetland itself."