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Linear spectral unmixing algorithm for modelling suspended sediment concentration of flash floods,upper Tekeze River,Ethiopia

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International Journal of Sediment Research 2020年第1期35卷 79-90页

作者： Hagos g.gebreslassie Assefa M.Melesse Kevin Bishop azage g.gebremariam Ethiopian Institute of Water Resources Addis Ababa University Department of NRM Adigrat University Department of Earth and Environment Florida International Universities Department of Aquatic Sciences and Assessment Swedish Universities of Agricultural Science

Flash floods are the highest sediment transporting agent,but are inaccessible for in-situ sampling and have rarely been analyzed by remote sensing *** and field experiments were done to develop linear spectral unmixing(LSU) remote sensing model and evaluate its performance in simulating the suspended sediment concentration(SSC) in flash *** models were developed from continuous monitoring in the laboratory and the onsite spectral signature of river bed sediment deposits and flash floods in the Tekeze River and in its tributary,the Tsirare *** Pearson correlation coefficient was used to determine the variability of correlations between reflectance and *** coefficient of determination(R2) and root mean square of error(RMSE) were used to evaluate the performance of the generated *** results found that the Pearson correlation coefficient between SSCs and reflectance varied based on the level of the SSCs,geological colors,and grain *** performance of the LSU model and empirical remote sensing approaches were computed to be R2=0.92,and RMSE=±0.76 g/1 in the Tsirare River and R2=0.91,and RMSE=±0.73 g/1 in the Tekeze River and R2=0.81,RMSE=±2.65 g/l in the Tsirare river and R2=0.76,RMSE=±10.87 g/l in the Tekeze River,***,the LSU approach of remote sensing was found to be relatively accurate in monitoring and modeling the variability of SSCs that could be applied to the upper Tekeze River basin.

关键词： Empirical remote sensing Flash floods Linear spectral unmixing Suspended sediment concentration Tekeze River

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Heavy Metals in Agricultural Soils of Central Ethiopia: The Contribution of Land Use Types and Organic Sources to Their Variability

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Open Journal of Soil Science 2016年第6期6卷 99-112页

作者： Nigatu Alemayehu Minase Mary M. Masafu Abule Ebro geda azage Tegegne Wolde International Livestock Research Institute Addis Ababa Ethiopia University of South Africa Pretoria South Africa

In the present study, about 94% of the arable land had a phosphorus deficiency (available P ·kgǃ). To compensate for this deficiency, high amounts of phosphorous fertilization were applied to soils to get better crop yield. In the past two decades, soil organic matter has sharply declined from 34.8 g/kg in late 1980s’ to 12.0 g/kg in 2010. The soil has moderate to high cation exchanging capacity (CEC) in the range of 45 - 58 Meq/100 gm. The low soil organic carbon, high CEC and high phosphorus fertilization could lead to poor heavy metal availability to plants. Nevertheless, DTPA extractable concentrations were 40.5 mg/kg for copper, 35.5 mg/kg for iron, 134 mg/kg for manganese, 2.1 mg/kg for nickel, 2.6 mg/kg for lead and 53.5 mg/kg for zinc. All the available micronutrients seem to be adequate for plant growth. In terms of toxicity, the values of Cu, Fe, Mn, Zn, Ni and Pb found in the present investigation were lower than those of above critical value set by the international guidelines and other researchers. Variations in heavy metal content in the soil were attributed due to differences in land use types and disparity in organic sources amongst the plant and animal composites. For better crop productivity, more organic matter should be added to the soils. The traditional nutrient cycling practices, such as manure application, allow crop residue to decay on fields, fallowing and rotational cropping has to be followed to rehabilitate the soil and buildup both macro-and micro-nutrients to their natural level.

关键词： Phosphorous Toxicity Micronutrients Organic Carbon Nutrient Cycle

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