Background: This study was aimed at examining land use/cover changes over 48 years and its causative factors in the Gumara watershed of Lake Tana basin, Northwestern Ethiopia. Two sets of aerial photograph (1957 and 1985) and a multispectral Spot5 image (2005) were used as inputs to produce three GIS-based land cover maps of the study area. Socio-economic surveys, focus group discussion and field observation were also used to determine the cause and effects of these land use/cover dynamics. Results:The results showed that cultivated and settlement land expanded by 21.99 %, whereas forest land, shrub land, grass land and wetland declined by 85.30, 91.39, 76.15 and 72.54 % over the analysis period respectively. Population pressure, demand for fuel wood and construction material, agricultural expansion and policy and tenure insecurity were the major driving forces behind the land use/cover change. Environmental and local livelihoods implications such as lake water and its aquatic resources and soil degradation, biodiversity loss and forest cover decline are resulted from the changes. Conclusion:The cumulative effect of these implications caused poverty and environmental degradation. Hence, there should be strategies of managing open access resources through participation of local people in the management. There should also be appropriate land use planning by identifying the proper land for specific purpose so that the marginal lands will not be put into agricultural use.

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The generation of scientific information for improved understating of the physical dynamics of a lake is fundamental for guiding lake stakeholders and managers at the local level to implement best management practices and help design effective management strategies and policies at higher levels. Multitemporal bathymetric information on lakes is very important in hydrology and sediment studies to more clearly indicate environmental changes and to understand the effects of land processes on the hydrology of lakes. Accordingly, the purpose of this study was to map bathymetric charts of Lake Hayq † in Ethiopia and to derive morphometric parameters, including depth, volume, area, width and length, and to plot curves illustrating the relationships between these parameters. The bathymetric survey was carried out using a combination of a SonarLite Portable Echo Sounder and Global Positioning System (GPS) to generate three-dimensional (XYZ) hydrographic data. Surfer 8.01 and ArcGIS 9.3 software program were used for surface, gridding and morphometric analyses. Comparison of the results of this study with a previous study conducted in 1941 indicated the lake has experienced changes in depth and surface area. To reduce the negative impacts of human-induced activities on the ecohydrology of the lake, and to maintain its ecological integrity, appropriate and integrated lake management practices must be adopted. This will necessitate policy formulation, active lake basin stakeholder involvement and implementation of basin-wide lake management to ensure sustainable use of the lake and its basin resources.

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Background: Assessment of soil loss rates is crucial to sustainably enhance the benefits of land resources and diminish the adverse impacts of land degradation thereby areas requiring immediate soil erosion management practices can be identified. The study aimed to examine the impacts of land cover dynamics on the spatiotemporal patterns of erosion hotspots. RUSLE factors were produced using GIS and remote sensing techniques. Results: The RUSLE model adapted to Ethiopian conditions was run for 2004 and 2014 where input data layers were overlaid. The results of the model showed clear patterns of changes characterized by gradual shifting of one erosion soil loss severity class into next higher class. There was a net increase in the total soil loss largely under the very high, low and very low soil loss severity classes by 8%, 21% and 9% despite a decline in other severity classes, respectively. It also revealed that more than two-third of the catchment has experienced soil losses rates higher than the tolerable value reported for Ethiopia over which agriculturists should be concerned. Conclusions: Therefore, the observed soil loss rate and sediment yield in the study catchment would lead to further ecological deterioration unless site-specific participatory watershed management practices are employed.

Climate analysis at relevant time scales is important for water resources management, agricultural planning, flood risk assessment, ecological modeling and climate change adaptation. This study analyses spatiotemporal variability and trends in rainfall and temperature in Alwero watershed, western Ethiopia. Our analysis is focused on describing spatial and temporal variability of rainfall in the study area including detection of trends, with no attempt at providing meteorological explanations to any of the patterns or trends. The study is based on gridded monthly rainfall and maximum and minimum temperature data series at a resolution of 4 × 4 km which were obtained from the National Meteorological Agency of Ethiopia for the period 1983–2016. The study area is represented by 558 points (each point representing 4 × 4 km area). Mean annual rainfall of the watershed is > 1600 mm. Annual, June–September (Kiremt), March–May (Belg) rainfall totals exhibit low inter-annual variability. Annual and October-February (Bega) rainfalls show statistically significant increasing trends at p = 0.01 level. May and November rainfall show statistically significant increasing trends at p = 0.01 level. March shows statistically significant decreasing trend at p = 0.1 level. The mean annual temperature of the watershed is 25 °C with standard deviation of 0.31 °C and coefficient of variation of 0.01 °C. Mean annual minimum and maximum temperatures show statistically non-significant decreasing trends. Bega season experienced statistically significant deceasing trend in the maximum temperature at p = 0.01 level. The year-to-year variability in the mean annual minimum and maximum temperatures showed that the 2000s is cooler than the preceding decades. Unlike our expectations, annual and seasonal rainfall totals showed increasing trends while maximum and minimum temperatures showed decreasing trends. Our results suggest that local level investigations such as this one are important in developing context-specific climate change adaptation and agricultural planning, instead of coarse-scale national level analysis guiding local level decisions.

This study aimed to determine the spatial variation of topsoil properties as influenced by slope aspects and vegetation types. Three vegetation types and two slope aspects were considered. Disturbed and undisturbed samples were taken from the top soils. A two-way analysis of variance was used to test significant mean differences (a = 0.05). Results showed that contents of bulk density, total porosity, organic matter and exchangeable magnesium were significantly different with changes in slope aspect (P < 0.05). Textural classes, organic matter, available phosphorus, carbon-to-nitrogen ratio, cationexchange capacity, per cent base saturation and exchangeable bases demonstrated significant variation among vegetation types (P < 0.05). The south-facing aspect and the grass vegetation showed higher bulk density but lower organic matter and total porosity. As a remedy for the identified problems, there is a need to undertake plantation of indigenous trees. R esum eCette etude visait a d eterminer les variations spatiales des propri et es de la couche sup erieure du sol en fonction de l'orientation de la pente et des types de v eg etation. Nous avons pris en compte trois types de v eg etation et deux orientations de la pente. Nous avons pr elev e des echantillons perturb es et non perturb es de la couche sup erieure des sols. Une analyse de variance a deux voies fut utilis ee pour tester les diff erences de moyennes significatives (a = 0.05). Les r esultats montrent que la densit e apparente, la porosit e totale, le contenu en mati ere organique et en magn esium echangeable etaient significativement diff erents selon les orientations de la pente (P < 0.05). Les classes texturales, la mati ere organique, le phosphore disponible, le rapport entre le carbone et l'azote, la capacit e d' echanges cationiques, le taux de saturation en bases et les bases echangeables montraient des variations significatives selon le type de v eg etation (P < 0.05). Une orientation au sud et une v eg etation herbac ee montraient une plus grande densit e apparente mais de plus faibles taux de mati ere organique et de porosit e totale. Pour rem edier au probl eme identifi e, il convient d'entreprendre la plantation d'arbres indig enes.