1,721,284 research outputs found
Controls on runoff generation along a steep climatic gradient in the Eastern Mediterranean
No full textAbstractStudy regionLower Jordan River.Study focusThe main aim of this study was to identify differences in catchment runoff reactions across a variety of scales and a strong climatic gradient and to correlate them to physical catchment properties. For this purpose we observed rainfall and runoff responses on a hillslope (1000m2) and in several nested catchments (3.2–129km2) over a period of five years. Catchment characteristics and surface cover types were derived from high-resolution aerial images. To gain process understanding a single high magnitude event was analysed in detail using information from soil moisture plots.New hydrological insights for the regionOur results show that runoff in the semi-arid headwater area is strongly related to long lasting rainfall events of high amounts and is predominantly generated by saturation excess overland flow (SOF). Observations from the arid runoff plot indicated a strongly contrasting behaviour with dominating Hortonian overland flow (HOF). At catchment scale we found an accentuated runoff response when we compared arid with semi-arid conditions, which can be attributed to different geological substrate, more abundant rock surfaces, shallower soil and sparser vegetation cover. Identified strong correlations between event rainfall and runoff volumes may provide promising options for the assessment and management of surface runoff as a water resource
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
Significance of preferential flow at the rock soil interface in a semi-arid karst environment
No full textIn many semi-arid environments, the surface materials are frequently characterized by thin soils and large proportions of bare rock, both of which are expected to considerably influence infiltration and groundwater recharge processes. In this study, small plot scale irrigation experiments in combination with dye tracer application, as well as real-time and subsequent soil moisture measurements and soil particle size analysis, were conducted to investigate the significance of preferential flow at the rock soil interface. Large scale assessments of soil depth and surface type distribution were used to upscale the findings of the irrigation experiments to the scale of a complete hillslope and, further, to estimate percolation properties of a hypothetical rainfall event. The two experimental plots were each located in the West Bank Mountains close to Ramallah. Each irrigation experiment was designed with 50 mm of precipitation, applied on an area of 1 m(2) during the course of ca. 2.5 h. Each irrigation plot had a surface share of approximately 50% rock outcrop and 50% soil surface. Percolation properties were investigated by subsequent soil moisture measurements at high spatial resolution on vertical soil profiles on the irrigated plot. Dye tracer application on the rock outcrop during the sprinkling allowed for tracking of resulting outcrop runoff in the subsurface. The soil depth survey included 2100 measurement points on 7 transects, which allowed the estimation of local soil depth distribution. Results of the irrigation experiments showed that precipitation-induced runoff from rock outcrops continued below ground as preferential flow along the rock-soil interface, while water from the soil surface percolated mainly vertically and much more homogeneously. This was evident from the high density soil moisture measurements, as well as from the dye tracer patterns. Outcrop runoff percolated faster and to greater depths than water infiltrating directly from the soil surface, thus possessing a greater potential for groundwater recharge. (C) 2014 Elsevier B.V. All rights reserved.BMBF [02WM0802, 02WM1081
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
Surprise me! On the impact of unexpected benefits on other-praising gratitude expressions
No full textGratitude reinforces social bonds. This relationship-regulating function depends on whether and how it is expressed. People can express gratitude in different ways: Beneficiaries may emphasize how they profited from a benefit (self-benefiting) or focus on the benefactor’s actions and characteristics related to it (other-praising). What underlies these expressive styles remains unclear. Based on findings that other-praising gratitude expressions have unique positive effects on interpersonal relationships, four studies (N = 1,188) investigated a novel antecedent of these expressions: unexpectedness of the benefit. In Study 1, we content-coded participants’ thank-you notes for an actual Christmas present. Path modeling revealed that unexpectedness of the benefit predicted other-praising, whereas happiness with the present predicted self-benefiting. These results were robust to relevant covariates and mirrored by participants’ self-reported self- benefiting and other-praising intentions. Studies 2-4 (preregistered) investigated samples from two different populations and experimentally manipulated (un)expectedness of recalled or imagined benefits. Given mixed experimental results, we conducted an internal meta-analysis. Across experimental studies, unexpected benefits increased other-praising, albeit weakly so, but not self-benefiting. In addition, the effect of unexpectedness on other-praising was significantly different from that on self-benefiting. We discuss potential processes and moderators of the effect of unexpected benefits on gratitude expressions
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
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