Impact of Pastoral land use change on Surface Water Quality in Kagera Sub-Basin

Abstract

Land use change is one of the key factors which strongly influence the process of pastoral development in the Kagera basin within which River Kagera, a principal river that drains into Lake Victoria flows through. The main objective of this study was to ascertain the impact of pastoral land use change on the Kagera sub-basin surface water quality. Satellite imagery from the periods of 1983, 1991, 2001 and 2011 where analyzed using Remote Sensing and Geographic Information System (GIS) techniques to monitor pastoral land use changes amongst other land uses to generate maps of the study area in these periods. More information was attained through 12 focus group discussions and questionnaire interviews of 120 randomly selected pastoral households to identify and explain the driving forces of pastoral land use change. The effect of pastoral land use change on Kagera sub-basin surface water quality with regards to critical nutrients which was determined in accordance to the Standard Methods for the Examination of Water and Wastewater, APHA (2005). Physical-chemical parameters were determined using GmbH CTD profile multi-parameter probe. This study revealed that pastoral land use shrunk from 43.8% total area coverage in 1983 to 32.3% in 2011, the Land Use Change dynamics degree (K1) indicated that pastoral land use lost 0.94% hectares to other land uses within the period (1983-2011) most notably to farmland, the key predictors of pastoral land use change were; expansion of farmland for subsistence agriculture (p=0.007), enactment of land use policies in Tanzania that curtailed the amount of land available within the sub-basin for pastoralism (p=0.003) and drought (p=0.021). All in all despite a large number of pastoralists spending more time than before grazing along River Kagera as an adoptive measure to the key predictors stated above among others, this new phenomenon has generally not had any significant impact (p=0.005) with exception of Nitrate-Nitrogen and Soluble Reactive Phosphorus on the river’s surface water quality. Keywords: Kagera, Pastoralism, GIS, Remote Sensing, Land use, Water quality