Background: The use of existing land use/cover type exerts more pressure on the natural dynamism of the watersheds and hydrology due to continued cultivation and mismanagement of land resource. The objectives of this study was to assess the combined effects of land use/cover types and slope gradient on watershed hydrology in terms of sediment and nutrient losses/transport from HRU of each land use/cover types. Integrated soil and water assessment tools (SWAT) model with Arc-GIS was used for simulation of sediment and nutrient loss by using land use/cover, soil, slope and climatic data as input. Analysis of variance (ANOVA) for mean comparison and correlation was used for data analysis. Result: Combined effects of urban land and slope gradient produced more sediment than other land use/cover types followed by cultivated land. In cultivated land as slope gradient increased values of sediment and nutrient losses also increased until it reaches to 30% slope and then declined. In Forest and grassland sediment loss increased until 15% slope then after declined, but in urban land as slope gradient increases sediment and nutrient loss are also increased. Conclusion: Cultivated land and difference in its slope gradient had more significant effect on watershed dynamics and hydrology in terms of loss of fertile top soil from upland, downstream water quality reduction and sedimentation of water structures than others land use/cover types and need to avoid steep slope and continuous cultivation and implementing integrated watershed management strategies in order to keep the natural dynamism of the watersheds.
To minimize severe soil erosion ,Physical soil and water conservation practices are being implemented by community campaign, NGOs and individually by farmers in Ethiopia, because it was resulting in reduction of crop production. Hence, the objective of this study was to assess the role of physical SWC practices mainly soil bund in improving soil fertility. 18 Soil sample were taken from purposively selected four years, two years and non-conserved field. To analyze the collected data; SPSS V.21 and SAS (9.1 Version) were used both for descriptive and inferential data analysis. The study Results showed that significant relationship ( p < 0.05) was found between the plot relative to the soil bund and levels of pH, Available phosphorus,(P-av),Available Potassium(K av),Cation Exchange Capacity(CEC),Elictrical Conductivity(EC,Ntot) and SOC,SOM and Exchangeable bases(Mg,Na,Ca,) which are higher in conserved land which improve soil fertility status of the study area. From the study it was concluded that the conservation practices age have significant effects on selected soil fertilities. As the age of soil bund increase, fertility gain shown increment. The un-expected out come in this study is that available phosphorus showed no significant difference between two years and four years conserved farmland with soil bund. To realize sustainable development goals, it needs integrated planning, selecting the desired SWC structures, implementing and maintaining of soil conservation measures to save its consequence on the life of community .
The urbanization process has led to the steady growth of cityat the expense of peri-urban natural environment. This study was conducted in the Nekemte city, Oromia Region at Western part of Ethiopia. The research was aimed to assess the effects of urban land use/ cover dynamics on natural environment through the interpretation of three years' time series images and psycho-chemical analysis of surface water quality of the study site. Land use classification maps were developed by using geos patial methods, remote sensing and Geographic Information System (GIS). Study area land use/ cover mapping and change detection analysis was conducted by Arc-GIS software. Urban land use and cover dynamic analysis revealed that built-up areas have been increased during 1996 to 2016 resulting in substantial reduction of forest area, cultivated land, grazing land, wetland and riparian forest. Forest and wetland, which are the focuses of this research, have been continuously decreased from 17%, and 14% in 1996 to 5.1% and 2.7% in 2016, respectively, with an average annual urban growth rate of 3.65% within 20 years, resulted in an increased mean annual local temperature, variability of rainfall and relative humidity and surface water quality reduction. Projected values indicated that built up areas will be increased continuously for the coming 10 years. Continuous conversion of forest, wetl and land and other land cover type to urban land had resulted into varied and extensive natural ecosystem disturbances; local climate change biodiversity loss and surface water quality reduction. Population growth, migration and economic development are the main identified factors contributing for urban land expansion. Impacts of urban expansion on peri-urban environment can be reduced through controlling population growth and incorporating environmental issues in any urban and economic development program.
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