1,720,991 research outputs found
Drainage Morphometric Characterization of Megech River Watershed, North Western Ethiopia, Using Geospatial Tools
Get PDFDrainage morphometric characterization of a river catchment is important for appropriate preparation and administration of natural resources in sustainable growth. The main objective of this study was to extract and characterize the morphometric drainage parameters of the Megech River catchment, Northwestern Ethiopia. For this the Ethiopian mapping agency's 1:50,000 scale toposheets, STER (Advanced Spaceborne Thermal Emission and Reflection), and Landsat-8 Operational Land Imager (OLI) satellite data were used. Drainage morphometric parameters of the watershed were assessed by computations of linear, areal, and relief aspects using the standard formula in the Geographic Information System (GIS) environment. The Megech River catchment is spreading over an area of 560 km2. The watershed is drained by a fifth-order river and shown a dendritic stream pattern, which is an indication of the homogeneousness in rock texture. The watershed's mean bifurcation ratio is 1.84, representing that the drainage pattern is not much affected by tectonic and structural disturbances. Lower and middle-order drainages typically control the basin with the drainage density value of 5.5 km/km2, which displays mild to sharp slope topography. The mean bifurcation value of the basin is 1.84, revealing drainage networks formed on regular bedrocks when the influences of geologic structures on the drainage network are insignificant. The drainage texture of the watershed is 7.4, and it falls under the category of very fine drainage texture (>8). Elongation and circularity ratios for the basin are 0.61 and 0.3, which shows that Megech watershed is elongated, having a steep to moderate slope
Assessing Groundwater Recharge in the Wabe River Catchment, Central Ethiopia, through a GIS-Based Distributed Water Balance Model
No full textThe utilization of groundwater has emerged as an indispensable asset in facilitating economic advancement, preserving ecological integrity, and responding to the challenges posed by climate change, especially in regions characterized by aridity and semi-aridity. The sustainable management of water resources requires an assessment of the geographical and temporal patterns of groundwater recharge. The present study employed the GIS-based WetSpass-M model to model the water balance components by utilizing hydro-meteorological and biophysical data from the Wabe catchment, which spans an area of 1840 km2 in central Ethiopia, for a long time. The objective of this study was to assess the long-term average annual and seasonal groundwater recharge for the catchment area utilizing the WetSpass-M model. The input data were collected through remote sensing data and surveys in the field. The model was employed to gain insights into the process of groundwater recharge in a particular region and to facilitate effective management, prudent utilization, and sustainable planning of water resources in the long run. Water balance components were estimated using seasonal fluctuations in evapotranspiration, surface runoff, and groundwater recharge. The Wabe catchment’s summer, winter, and mean long-term yearly groundwater recharge were determined to be 125.5 mm, 78.98 mm, and 204.51 mm, respectively. The model indicates that summer seasons account for 86.5% of the mean annual precipitation, while winter seasons account for 13.5%. On the other hand, the groundwater system percolates 14.8% of the total annual rainfall (1374.26 mm). While evapotranspiration accounts for 51% of total precipitation and surface runoff accounts for 34.1%, the Wabe catchment’s mean annual evapotranspiration and surface runoff values are simulated at 701.11 mm and 485.58 mm, respectively. The findings suggest the use of the WetSpass-M model to precisely calculate the water balance components within the Wabe catchment
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Assessing landslide susceptibility in Lake Abya catchment, Rift Valley, Ethiopia: A GIS-based frequency ratio analysis
Get PDFEthiopia's varied landscape, significant rainfall, and diverse geological characteristics pose risks of landslides. The specific research area spans 40 km2 within the Lake Abaya catchment area in the Rift Valley of Ethiopia. This investigation aimed to map landslide susceptibility using remote sensing information, GIS technology, and frequency ratio analysis. It evaluated multiple factors influencing landslide susceptibility. The process involved meticulous mapping of thematic layers, utilizing GIS techniques and diverse data sources, including primary data, satellite imagery, and secondary sources. A combination of Google Earth image analysis and field surveys was used to map landslide susceptibility in inaccessible areas. It was determined that 138 landslide sites existed. Of these, 30% (41 points) were assigned to the test of the model and another 30% to the training of the model, for a total of 97 points. The landslide susceptibility was classified into five categories based on frequency ratio analysis of the landslide susceptibility index (LSI): very low, low, moderate, high, and very high. The northeastern sector of the study area demonstrated a comparatively diminished susceptibility to landslides, ranging from low to moderate, whereas the central and southern regions showcased markedly elevated vulnerability. An evaluation of the model's accuracy using the area under the curve (AUC) method based on test inventory landslide data produced encouraging results: 84.8% accuracy on the success rate curve and 78.8% accuracy on the prediction rate curve. Based on the frequency ratio model, a susceptibility map is derived to represent susceptibility levels accurately
Digital elevation model and satellite gravity anomalies and its correlation with geologic structures at Borena basin, in the Southern Main Ethiopian Rift
No full textThis study integrates remote sensing data via Digital Elevation Model (DEM) and satellite gravity data to detect geologic structurs at Borena and the surrounding regions in the Southern Main Ethiopia Rift (SMER). Shading from different sun azimuths with 45-degree intervals and the tilt angle method was used to map lineaments and detect edges of anomalies from the DEM and gravity data, respectively. The area’s geology comprises quaternary alluvial and eluvial sediments , pre-rift and rift volcanic rock , and Precambrian banded gneiss. The Ririba, Mega and Chew Bahir rift systems make the main structural fabric of the area. About 793 lineaments from DEM data and 441 from gravity data were outlined, and their orientations were analyzed using rose diagrams. These are trending dominantly in NW to SE and N to S directions. From the gravity data analysis, the depth of anomalies ranges from 300 m to more than 7 km below the ground, with most of the lineaments being at shallow depth. The results obtained agree with the main tectonic features found in the study area. The integration of remote sensing data has facilitated delineating structural features in studying the regional geology of the large area
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