Potential Impacts of Land Use Change on Sustainable Management of Water Bodies: the Case of Masinga Dam

Abstract

Land degradation poses a real threat to agricultural production and water availability in Sub-Saharan Africa. Land use and land cover change have critical environmental consequences at local, regional, and global levels. These changes have led to loss of biodiversity, disruption of hydrological ecosystems, soil degradation, and sedimentation. All these factors greatly affect communities. The existence of irregular and inconsistent geospatial distribution of global freshwater resources, human beings have been compelled to harness surface waters by constructing dams to retain water, especially during periods of scarcity. However, the efficiency of dams worldwide is undermined by the gradual loss of storage capacity due to sedimentation. Dams have traditionally played a pivotal role in providing water for domestic and commercial use, flood control, hydropower generation, irrigation, and fisheries. This study focused on land use changes within Mbiri Ward, situated in Murang'a County, within the upper Tana River Catchment. It examined the impacts of upstream land use changes on the sustainable management of downstream water bodies, specifically focusing on the Masinga Dam, which lies downstream in the lower Tana River catchment. The study's objectives were to assess the changes of land cover in Mbiri Ward over the past forty years, identify drivers of land use changes in the area, evaluate the implications of land use alterations on Masinga Dam, and recommend land use planning and management interventions to minimize sedimentation impacts on Masinga Dam. To achieve these objectives, a cross- sectional research design was used to collect data from various stakeholders in Mbiri Ward. The target population was stratified and included local farmers, businesspersons, and residents, officials from the Kenya Forest Service, Kenya Electricity Generating Company, the National Environment Management Authority, agricultural officers, catchment management officers, physical planners, and conservation officers. Stratified random sampling was used, with each stratum receiving an equal number of questionnaires through random selection. A total of 96 participants were interviewed. The data collection methods employed included questionnaire administration, interviews, observation, photography, mapping, and a comprehensive literature review. The study found that significant land use change had occurred within Mbiri Ward over the past forty years; water land use increased from 107.54 hectares in 1980 to 117.53 hectares in 2021, urban land use expanded from 2.031 hectares in 1980 to 542.17 hectares in 2021, while ploughed land increased from 3.04 hectares in 2000 to 184.37 hectares in 2021. Forest land use decreased notably from 2732.11 hectares in 1980 to 972.56 hectares in 2021, while cultivated land, increased from 214.20 hectares in 2000 to 4106.58 hectares in 2021. 86% of respondents reported a consistent decline in forest cover within the ward over the past four decades. Furthermore, 66% of respondents identified forests as the predominant land use cover in Mbiri Ward in the past. The major drivers for reduction of forest cover being population pressure and conversion of forest land to residential use being key drivers of land use changes, accounting for 41% of changes. Given the area's agricultural nature, forest land use is being converted to accommodate agricultural needs, with crop farming practices contributing to soil erosion and the introduction of loose soil into rivers. The study also found that 39% of migrants in Mbiri Ward relocated to engage in farming activities, and 48% of the population relied on firewood as their primary energy source, while 43% used charcoal, indicating a heavy dependence on trees to meet energy demands. Land use changes in Mbiri Ward have led to various adverse consequences, including environmental degradation, land and soil deterioration, and pollution, primarily due to inadequate agricultural and conservation practices. Agricultural activities result in a significant sediment load that is subsequently transported from the catchment area into the rivers. The study recommends a series of management practices and policy interventions to address these challenges including forest and agricultural management initiatives, riparian land management, and policy enforcement measures such as afforestation, natural regeneration, protection, regulated agriculture, prohibition of slope cultivation, adoption of food forest designs, comprehensive land management policies, monitoring and evaluation of catchment areas, enforcement of environmental laws, zoning for production and protected areas, village forest management, and multi-stakeholder engagement.