The effect of land use change on water quantity in the Igombe river catchment in Tabora municipality, Tanzania

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University of Dar es Salaam
Land use change is an important driver in the runoff process that affects infiltration, interception, erosion, and evapotranspiration. These changes have caused severe stress on forest and water resources in the Igombe River catchment. The quantity of water available in the Igombe river catchment is changing overtime. There are rapid developments in the catchment because of increasing demand for land resources subjects land use to changes causing formation of impervious surfaces. There several factors that have significantly altered the maximum and minimum flows of Igombe River and its dam. These include deforestation, intensification of agricultural land; urbanization in the form of expansion of residential area land use. This study assesses the implications of increased land use change on water quantity of the Igombe River catchment in Tabora Municipality, Tanzania. Specifically, this study dwells on the changes of land uses or cover and trend of water quantity from the year 1986 to 2011 so as to establish the land use change implications on water quantity in the Igombe river catchment. The study used both primary and secondary data. Secondary data gathered from literatures, document and records. Primary data collected by means of field observations and by interviewing key informants. Interactions of land and water resource were from experienced key informants by interview. Data sorted and labelled to make judgement. The findings of this study indicate that there is a significant evidence of land use change resulting from human settlement development (36%), farm land expansion to meet household food supply (19%), overgrazing (15%), and clearing trees for charcoal for domestic consumption and for sale (10%) as well as legal and illegal harvesting of forests for timber production (8%). Three land use or cover types seem to have increased in the study period. These include; agriculture with scattered settlements by 244 hectares, bare soil by 8 hectares and bush land by 197 hectares. A simple linear regression analysis indicated presence of strong negative relationship between agriculture and scattered settlement and water levels in the Igombe river catchment. A trend line represented by coefficient of determination R2= -0.329 and the regression equation y= -0.38x+4.36 indicates a continuous decreasing trend of water levels in the Igombe dam in the period (1986-2011). The regression result shows that as area under agriculture and scattered settlements increased the water level in the Igombe dam decreased. Plots of the values for water levels and volumes in the Igombe dam showed to have decreased from 5m to 2.3m in the study years 1986 and 1999 respectively. This give a conclusion that, decrease of water quantity in the Igombe River catchment is not influenced by variation in temperature and rainfall inputs, instead, deterioration of natural environment in the catchment due to competing land uses and are fundamental on reduction of water level and overall water quantity in the Igombe river catchment. Since the current land use practices are not desirable as they accelerate land cover shrinkage, there is a need to deal with all the driving factors behind these changes to reverse the situation and restore the status of this catchment. For water resources to be managed from regular changes, the study recommended land use planning and management on catchment from upper, middle to lower segment of the catchment to enhance livelihood and ecological sustainability of the catchment.
Available in print form, East Africana Collection, Dr. Wilbert Chagula Library, Class mark (THS EAF HD 987.I48)
Land use, water quantity, Igombe river catchment, Tabora municipality, Tanzania
Ijukaine, S.B. (2015) The effect of land use change on water quantity in the Igombe river catchment in Tabora municipality, Tanzania, Master dissertation, University of Dar es Salaam, Dar es Salaam