1,720,962 research outputs found
Curve Number Method Runoff Estimation in the Kardeh Watershed, Iran
Full text linkThe major problem in the assessment of the relationship between rainfall and runoff occurs when a study is carried out in ungauged watersheds, in particular, the absence of hydro-climatic data. This study aims to determine the runoff depth using NRCS-CN method with GIS and the effect of slope on runoff generation in the Kardeh watershed, located between 59º 26´ 3˝ to 59º 37´ 17˝ E longitude and 36º 37´ 17˝ to 36º 58´ 25˝ N latitude, about 42 km north of Mashhad, Khorasan Razavi province, Iran. The US Department of Agriculture, Natural Resources Conservation Service Curve Number (USDA-NRCS-CN) method was applied for estimating the runoff depth in the semi-arid Kardeh watershed. Hydrologic soil group, land use and slope maps were generated in GIS environment. The curve number values from NRCS standard tables were assigned to the intersected hydrologic soil groups and land use maps to generate CN values map. The curve number method was followed to estimate runoff depth for selected storm events in the watershed. Effect of slope on CN values and runoff depth was determined. Estimated runoff depth and slope-adjusted runoff depth were statistically compared with the corresponding observed runoff data. Pair wise comparisons by the t-test, Pearson correlation analysis and percent error were used to investigate the accuracy of estimated data and relationship between estimated and observed runoff depth. The results showed that there was no significant difference between the means of observed and estimated runoff depths (P > 0.05). Fairly positive correlations were detected between observed with estimated runoff and slope-adjusted runoff depth (r = 0.55; P < 0.01) and (r = 0.56; P < 0.01), respectively. About 9 % and 6 % of the estimated and slope-adjusted runoff values were within ±10% of the recorded values, respectively. In addition, about 43 and 37 percent of the estimated and slope-adjusted values were in error by more than ±50 %, respectively. Statistical analysis indicated that percent error of estimated slope-adjusted runoff depth was significantly (p < 0.01) lower than the percent error of estimated runoff depth. This decline in percent error can be explained by the role of slope in runoff generation in steep slope watershed. The results of study indicated that the CN is an effective method for homogenous watersheds in terms of land use, soil, and climate rather than heterogeneous ones like Kardeh watershed. In such watersheds it can be employed with about 60 percent accuracy only for management and conservation purposes however and probably not for computation of design floods.
Keywords: Curve Number, Geographic Information System, Kardeh watershed, Slope-adjusted runoff dept
Hydrological responses to climate and land use change in upper Langat Basin, Peninsular Malaysia
Full text linkIt is undeniable that climate and land use changes affect the major components of hydrological cycle such as streamflow and water availability in river basins.However, the magnitude and contributions of their effects are still uncertain. It is highly required to study the individual and combined impacts of changes in climate and land use on streamflow and consequently flood vulnerability in tropical river basins particularly those basins which experience rapid changes in land use. Langat River basin which experiences flooding as a response to both climate variability and rapid urbanization and industrialization was chosen to investigate the hydrological responses of the basin to both factors. This research aimed to evaluate past and probable future environmental changes and their effects on the hydrological response of the Hulu Langat river basin. More specifically the study provides a framework to analyze the historic trends of major hydro-climatic variables as secondary data including rainfall, temperature and streamflow (1984-2010) and land cover changes (land use maps of 1984-2006-2008) and also to quantify their individual and combined impacts on streamflow through designed scenarios of different combinations of land use and climate conditions. The trends of historical time series of temperature, rainfall and streamflow were determined with the Mann-Kendall method. The study applied the semi-distributed hydrological model, SWAT, and calibrated and validated
against observed streamflow using SWAT-CUP (SUFI-2). The land use/land cover changes were examined using LCM model and future land use change scenarios were developed using the combination of Markov chain and Multi-Layer Perceptron (MLP_Markov) model. The climate change scenarios were based on the combination of one RCM (PRECIS) and stochastic weather generator (LARS-WG). To this end, the daily temperature and precipitation projection of A1B emission scenario by the PRECIS model and A2, B1 emission scenarios by LARS-WG for 2020s, 2050s and 2080s were superimposed in the calibrated SWAT model. Annual streamflow in three stations (F1, F2, and F4) out of four exhibited significant increasing trend at α = 0.01 significance level.The annual streamflow had been significantly increasing at the rate of 0.036,ii 0.023 and 0.001 ×103 m3/year in those stations,respectively, from 1980 to 2010.Seasonal streamflow showed significant increasing trend in the upper part of basin in all seasons. Significant increasing trend for monthly streamflow was detected for January and August, but insignificant trends were found in May,September and November in all hydrological stations. Streamflow was primarily correlated to rainfall (P<0.05). Land use change analysis indicated that forest cover, short-term crops and permanent crops were notably decreased from 1984 to 2006. The area of permanent crop and forest area in 2006 was 48.5 % and 3.1% lower than that in 1984, respectively, but the built-up and residential areas were increased distinctly. The simulation results of the hydrological model under
land use change scenarios showed that the magnitude of streamflow was impacted by land use change in all scenarios. Streamflow was highest due to expansion of urban area and contraction of forest and croplands. Future land use change would account for increase in streamflow about 20%, 61% and 71% for the 2020s, 2050s and 2080s land use scenario maps, respectively. Under only climate change scenarios, streamflow was predicted to increase 8.7% in 2020s, 54.7 % in 2050s and 21% in 2080s under A2 scenario, 14.7%, 21.4% and 75.7% for the 2020s, 2050s and 2080s under B1 scenario, respectively. Streamflow was also projected to decrease about 3.1% and 10.4% under A1B scenario for the 2020s and 2050s, but it showed an increase of about 28% in the 2080s. The intensification of streamflow is in maximum percent (92%) in 2080s under B1 scenario. The combined scenarios of land use and climate indicated that climate variables change coupled with land use change have resulted significant increase in streamflow about 9%, 20.1%, 9% for the 2020s, 2050s and 2080s under A2 scenario, and 14.9%, 24.4% and 19.7% for the 2020s,2050s and 2080s under B1 scenario. Under A1B scenario, 19% decrease in streamflow in the 2020s was predicted, but the streamflow increases 25.6% and 65.4% for the 2050s and 2080s, respectively. This study concludes that under different designated scenarios, streamflow is expected to experience significant increase in the future decades as a consequence of land use and climate changes, but changes in land use have led to greater streamflow changes against climate change. Consequently, there is an urgent need to reverse land use change trends such as afforestation, conservation on natural habitat and control on urban expansion for future development programs and land use planning to mitigate probability of possible flooding which is a major problem in this region.
Keywords: climate change, hydrological processes, hydroclimatic variables,land use conversion, trend analysis, streamflo
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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