Hydrological Dynamics and Human Impact on Ecosystems of Lake Tana, Northwestern Ethiopia

Lake Tana, biggest lake in Ethiopia, is very important water resource for community living and depending on the lake’s resources. However, the recent development activities at the catchment areas have negatively affected the water of the lake, and the climate of the region. This study delineated how land cover modification, climate change, population increase and development activities within the catchment have influenced the hydrological dynamics of Lake Tana. The land cover modification of southern part of catchment of Lake Tana in the years 1973, 1986, 1995 and 2008 were examined using land sat images. For the last 30 years, temperature, rainfall and lake level data were evaluated to identify change in climate and lake level. The annual means of temperature, rainfall, and lake level with their decadal variation and trends were analyzed with the support of linear regression model to assess trend change. Population change for the last 25 years and development activities were also assessed. The results have revealed that within the last 35 years more than 6.2% of lake’s area was converted to other land covers. Parallel to this period within the catchment there was declining of rainfall and lake level and rise in temperature. There was also increase of population and intensification of use of lake’s water in recent times. Thus, it is implied that change in Lake Tana water was caused by human factors and climate changes.Key Words: Lake Tana; Hydrological Dynamics; Climate Change; Population Increase; Land Modification; Development Activitie

Solid waste dumping site suitability analysis using geographic information system (GIS) and remote sensing for Bahir Dar Town, North Western Ethiopia

Solid waste dumping is a serious problem in the urban areas because most solid wastes are not dumped in the suitable areas. Bahir Dar Town has the problem of solid waste dumping site identification. The main  objective of this study was to select potential areas for suitable solid wastedumping sites for Bahir Dar Town, which are environmentally suitable. The main data used for this study were spot image with a spatial resolution of 5 m; digital elevation model (DEM) with 30 m spatial resolution, and ground control point (GCP) collected by ground point survey (GPS) and topographical map of the study area. The maps were prepared by overlay and suitability analysis of geographic information system (GIS), remote sensing techniques and multi criteria analysis methods. The final suitability map was prepared by overlay analyses on Arc map and leveled as high, moderate, less suitable, and unsuitable regions of the study area were determined. The results indicate that 65% of the study area is unsuitable for solid waste dumping; 1.3% less suitable; 21.8% moderately suitable; and 11.9% most suitable. The potential most suitable areas for solid waste dumping sites fall on southern and south eastern part of the town where there are least environmental and health risks. The GIS andremote sensing techniques are important tools for solid waste site selection. Hence, the capacity to use GIS and remote sensing technology for the effective identification of suitable solid waste dumping site will minimize the environmental risk and human health problems.Key words: Dumping site, geographic information system (GIS), remote sensing, multi criteria analysis, solid waste, weight overlay