1,720,956 research outputs found
Field-based estimation and modelling of distributed groundwater recharge in a Mediterranean karst catchment, Wadi Natuf, West Bank
No full textWhile groundwater recharge is one of the most prominently covered subjects in hydrogeology, the spatial distribution of recharge has been given relatively little attention, especially in semi-arid, karstic aquifers. Under conditions of highly diverse geology, relief, vegetation and land use, the complexity and variability of spatially distributed hydrological processes remains a challenge in many regions around the world. This is particularly true for hitherto ungauged basins, such as Wadi Natuf, a 103 km2 large karstic Eastern Mediterranean watershed in the Palestinian upstream mountain and recharge area of the Western Aquifer Basin (WAB), which is shared with Israel in the coastal plain. In this first in a series of two papers, distributed recharge is estimated and represented, based on 7 years of extensive field observations and measurements and based conceptually on observable physical landscape features such as geology, land use and land cover (LU/LC) and especially soil conditions. For the first time in the WAB, a forward calculated soil moisture and percolation model (SMSP) was set up with parameters directly gained from field observations. The model was parameterised in a strictly parsimonious manner, as a one-dimensional model (a.k.a. “tank”, bucket or box model). This is based on dominant hydrological processes, in particular saturation excess in the soil column, and identifying patterns of linkage between different landscape features. Average soil thickness was encountered at the range of decimetres, rarely above one metre. Both soil thickness and LU/LC features, such as terraced olive groves or forests as well as grassland or barren rock outcrops, were found to be highly formation specific. This linkage allowed us to further simplify the model and its requirements in a realistic manner for eight soil moisture stations, chosen at six different geological formations with typical soil and LU/LC representations. The main result of the model was the determination of formation-specific recharge coefficients, spatially ranging between 0 % and almost 60 % of annual rainfall or up to 300 mm a−1 in Wadi Natuf's climate. The karstified main aquifers showed recharge coefficients (RC) above 40 % and even the less prominent slightly aquitardal local aquifers reached RC values above 30 %. The model was separately tested on two conceptual levels: on the level of basin form (soil moisture) and basin response (signatures of peak recharge and local spring discharge events) under well-controlled conditions in isolated sub-catchments. In principle, our approach is applicable in many of the scarcely gauged karstic groundwater basins around the world with a highly diverse landscape and geology
Assessment of transmission loss in a Mediterranean karstic watershed (Wadi Natuf, West Bank)
No full textAbstract Run‐off transmission loss into karstified consolidated aquifer bedrock below ephemeral streams (wadis) has rarely been described nor quantified. This study presents unique data of long‐term high‐resolution field measurements and field observations in a semiarid to subhumid Mediterranean carbonatic mountainshed. The catchment with a 103 km 2 surface area is subdivided into 5 subcatchments. Coupled run‐off measurements were made in the different stream sections (reaches), and transmission loss calculated from differences in discharge. Rainfall and run‐off observations from 9 automated precipitation gauging stations and 5 pressure transducers for automatic water level recording are complemented by manual measurements during 34 run‐off events covering a total measurement period of 8 consecutive years. Run‐off generation is strongly event based depending on rainfall intensities and depths. Both, run‐off generation and transmission losses are related to spatial patterns of bedrock lithologies (and hydrostratigraphy). Transmission losses range between 62% and 80% of generated run‐off, with most of the smaller events showing 100% transmission loss. Therefore, although event run‐off coefficients in the mountains can reach up to 22%, only 0.11% of total annual precipitation leaves the catchment as run‐off. Most run‐off infiltrates directly into the regional karst aquifers (Upper Cretaceous carbonate series), with transmission loss intensities of up to 40 mm/h below the stream channels. The factors determining run‐off—such as geology, pedology, vegetation cover and land use, relief and morphology, the semiarid to subhumid Mediterranean climate with a strong elevation gradient, and the patchiness of individual storm events distributed over the winter seasons—as well as the lithology and epikarst features of the bedrock are all characteristic for larger areas in the Mediterranean region. Therefore, we expect that our findings can be generalized to a large extent
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
Field-measurement based recharge assessment in Wadi Natuf, shared Palestinian-Israeli Western Aquifer Basin
No full textSummary The main objective of this doctoral research is the determination of groundwater recharge and its spatial distribution in a mountainous karst catchment area of the eastern Mediterranean. The basin was previously almost ungauged and it is characterised by very limited data availability and strong obstacles to any observation of the underground processes (except spring discharge). Therefore the study used the more readily accessible surface features, such as geology in the outcrop, soils and land use and land cover observations. The study area, Wadi Natuf, shows a high spatial variability of these land forms. All lithostratigraphic formations of the regional Western Aquifer Basin (WAB) crop out and most of the land use and land cover (LU/LC) types of the WAB can be found here (with the exception of the arid zone types of the Negev). A dense measurement network for precipitation and other meteorological drivers and for hydrological processes such as surface runoff, spring discharge and soil moisture was established and operated for almost a decade, in order to obtain a data set of empirical field measurements that is unique in this region. The physical characteristics and their classification were comprehensively and intensively recorded and related to each other.The starting point was a detailed description of the WAB’s litho-facies and its spatial distribution. Special attention was paid to the refinement of the conventional regional litho-stratigraphy and especially the hydro-stratigraphy of the catchment area and overall aquifer basin. Previously unknown aquifer properties of the so-called "aquicludes" were detected, measured and described. The location and separation of the different catchment areas within the WAB was studied; this was a fundamental prerequisite for the spatial differentiation of groundwater recharge.In the Wadi Natuf catchment area, a close correlation between geology and soil thickness, as well as land cover and land use was observed. These patterns were spatially recorded (mapped) and categorized as classes of different recharge potential, they were integrated into a specific basin classification framework of Wadi Natuf. In addition and for the first time in the West Bank, the occurrence of shallow, perched aquifers was recognized and documented. These perched groundwater reservoirs are bound to certain surface landforms in central Wadi Natuf, erosionally isolated hilltop aquifers. Hereby it was noted that these isolated perched aquifers lack any lateral subsurface flow connections. Instead, all recharging groundwater either emerges in the respective measurable spring groups of the hilltops or seeps further downward into the underlying regional aquifers as downward leakage.For study of indirect groundwater recharge, the surface runoff behaviour was examined in more detail and five stations were equipped with pressure transducers for runoff measurements in high temporal resolution. The five stations form three so-called “reaches”, two of them midstream and one downstream. One of the studies then examined changes over time in total annual and main event runoff. These changes were found to be the result of rapid land use changes in Wadi Natuf, which were documented and analysed in high spatial resolution under additional consideration of changes in the other two landform groups – soil and geology. Most wadis showed increases in runoff and decreases in transmission losses as a consequence of land use changes upstream and inside the wadis, but to very different degrees. Some Wadis remained almost stable (Shibteen-North and Wadi Zarqa), while others showed strong and very strong increases in event and annual runoff (Ne’alin and Shibteen-South).For the first time, transmission losses through the wadi gravels into underlying aquifer bedrock could be measured in the field and quantified in high temporal resolution and, above all, in their spatial distribution. Hereby, a clear dependence on the respective rock facies and water absorption capacity of the respective formations could not only be postulated, but spatially determined and quantified. The runoff generation in Wadi Natuf was found to be exceptionally low, not only as a result of the transmission losses, but also due to the pronounced development of epikarst. Annual runoff leaving the catchment area amounts to merely 0.11 % of annual area, much less than hitherto assumed and reported.Therefore, the focus in the determination of groundwater recharge was laid on the determination and description of direct recharge processes, and the modelling and calculation of deep percolation from the soil cover into the aquifer bedrock. Attention was paid to the use of quantitative process descriptions and models, which are as simple as possible and easy to use and which are considered particularly suitable for unmeasured basins; these parsimonious but empirically based methods mark a departure from the current trend towards increasingly refined calculation models with increasingly sophisticated mathematical codes and model parameter diversifications, which however rely less and less on robust, observable and empirically verifiable field data as input. In this dissertation, all model parameters are based on real-time measurements in the field. The parsimonious model used only one parameter, soil water absorption capacity, which was found spatially variable at the eight soil moisture measuring stations in the work. The only drivers were precipitation and real evapotranspiration in daily time steps. The model then considered and calculated percolation as a function of soil moisture saturation excess.As already described in neighbouring semi-arid areas of the West Bank, recharge was determined to be primarily a process of brief, separated pulses of intensive precipitation events during the winter months. In the rest of the year, no recharge occurred – in spring and autumn because the soils were insufficiently saturated and in summer because there was no precipitation and the soils dried up completely. This semi-arid, typically Mediterranean seasonality facilitates the model description, as well as the verification of model results, e.g. by comparing modelled and observed soil moisture, which oscillates between minimum values at the end of summer and maximum at the height of the rainy season. The eight individual models at the respective soil moisture measurement stations resulted, for the first time in the region if not far beyond, in spatially distributed annual recharge coefficients, which can be considered as representative for respective formations on the catchment area scale: These formation-specific recharge coefficients were based on empirically observed and measured processes and derived by simple, globally applicable methods. The research approach was based on the novel combination of parsimonious modelling with a description and classification of the three groups of physical basin characteristics (basin form) under high spatial resolution that can be observed on the surface and used as a proxy for the hydrogeological processes (basin impact) above and below surface.Based on these model results and with the help of a basin classification framework, which was empirically recorded on site, the specific recharge coefficients could be applied to the non-modelled formations and thus extrapolated to the scale of the entire catchment area (103 km2). This categorization and extrapolation was carried out separately for each of the groups of physical features. The three independent calculations resulted in similar sums of annual groundwater recharge in Wadi Natuf in a range between 24 and 28 million cubic meters per year as multi-annual averages; on the catchment scale, this rate is equivalent to values between 235 and 274 mm/year or a portion of 39.4–46.1% of the annual area precipitation. It should be noted that these values match well with the conventional recharge estimates by other studies, which however were performed on the overall basin scale of the WAB.Finally, the formation-specific recharge coefficients were applied to the local, perched groundwater deposits on isolated hilltops in the central study area; local water balances for each of these perched aquifer formations then compared this recharge with the formation-specific outflows of the respective catchment areas, which in total issued discharges in over one hundred small and very small field-recorded springs. This simple water budget calculation resulted in average annual rates of downward leakage from the floating groundwater deposits into the regionally widespread aquifers below; it should be noted here that from the point of view of the receiving regional aquifers underneath, such leakage can also be considered as recharge. The annual leakage rates thus obtained ranged between 64 and 89% of the annual groundwater recharge of the respective perched aquifers (or 169 to 287 mm/year). These simple methods of leakage determination by empirically recorded groundwater flow budgets can only be used in areas where any other – lateral – groundwater losses can be excluded, i.e. in areas with controlled boundary conditions and a well-defined groundwater catchment area. This requirement somewhat limits the applicability of the method used. Nevertheless, such quantifications of downward leakage, based on empirical observations and measurements, are globally so rare that the a.m. results deserve special attention and reporting
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
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