Search results for "Ephemera"
showing 10 items of 68 documents
Rainfall-runoff modelling of ephemeral streams in the Valencia region (eastern Spain)
2002
This paper presents preliminary results from the application of a transfer-function rainfall–runoff model to ephemeral streams in Mediterranean Spain. Flow simulations have been conducted for two small catchments (Carraixet and Poyo basins), located in close proximity to one another yet with significantly different geological characteristics. Analysis of flow simulations for a number of high-flow events has revealed the dominant influence of the rainfall on the catchment response, particularly for high-rainfall events. Particular success has been attained modelling the highest magnitude events in both catchments and for all events in the faster responding (Poyo) catchment. In order to inves…
Assessment of channel changes in a Mediterranean ephemeral stream since the early twentieth century. The Rambla de Cervera, eastern Spain
2013
An analysis of morphological changes during the last six decades is presented for a 16.5-km reach of the Rambla de Cervera, a Mediterranean ephemeral stream located in eastern Spain. Channel changes were analysed through a range of techniques, specifically the analysis of aerial photographs with geographical information systems (GIS) and comparison of topographic surveys. The gravel channel underwent a general decline over the study period, losing width (68.5%) and surface area (45.7%). Incision ocurred along the entire study reach at an average depth of 3.5 m. Natural and human-induced factors producing contradictory effects are considered responsible for changes in the Rambla de Cervera
Evidence for an African-Iberian mammal dispersal during the pre-evaporitic Messinian
2013
The accurate timing of biogeographic dispersal can be determined by examining the age of fossiliferous strata on either side of a physical barrier. Here we show that African mammals migrated to Iberia and European mammals migrated to North Africa at the same time before isolation of the Mediterranean Sea during the Messinian. The fossil site of Venta del Moro (Spain) exhibits western Europe’s most complete vertebrate fauna for the latest Miocene. Its uniquely cosmopolitan assemblage is evidence of faunal dispersals from Africa and Asia to Europe during the latest Miocene glaciation. A preliminary paleomagnetic study suggested an age of 5.8 Ma for this site, but our expanded magnetostratigra…
Ecohydrological modelling of flow duration curve in Mediterranean river basins
2013
Abstract Flow duration curve provides an important synthesis of the relevant hydrological processes occurring at the basin scale, and, although it is typically obtained from field observations, different theoretical approaches finalized to its indirect reconstruction have been developed in recent years. In this study a recent ecohydrological model for the probabilistic characterization of base flows is tested through its application to a study catchment located in southern Italy, where long historical series of daily streamflow are available. The model, coupling soil moisture balance with a simplified scheme of the hydrological response of the basin, provides the daily flow duration curve. …
Las crecidas en ramblas valencianas mediterráneas
2001
This paper takes into account the characterisation of ephemeral stream hydrology from Mediterranean environments. The heavy floods that these countries suffer are due to firstly, the physical watershed features (steep slopes, scarced vegetation cover and thin soils) and, secondly, to the intense and variable rainfall. Large quantities of precipitation fall in a matter of hours, or even minutes, over very steep catchments, causing catastrophic flash-floods, with very pointed hydrographs and short time lags. Using hydrological daily data from the Rambla de la Viuda basin and five-minute data from both Barranc de Carraixet and Rambla de Poyo basins, we have analysed the rainfall- runoff proces…
Climate change effects on the hydrological regime of small non-perennial river basins.
2015
Recent years have been witnessing an increasing interest on global climate change and, although we are only at the first stage of the projected trends, some signals of climate alteration are already visible. Climate change encompasses modifications in the characteristics of several interrelated climate variables, and unavoidably produces relevant effects on almost all the natural processes related to the hydrological cycle. This study focuses on potential impacts of climate variations on the streamflow regime of small river basins in Mediterranean, seasonally dry, regions. The paper provides a quantitative evaluation of potential modifications in the flow duration curves (FDCs) and in the p…
Annual flow duration curves assessment in ephemeral small basins
2014
Flow duration curve (FDC) represents a comprehensive signature of temporal runoff variability often used to synthesize catchment rainfall-runoff responses. A new model, the ModABa (MODel for Annual flow duration curves assessment in ephemeral small BAsins), is here introduced. It can be thought as a wide mosaic whose tesserae are frameworks, models or conceptual schemes separately developed in different studies and harmoniously interconnected with the final aim of reproducing the annual FDC in intermittent small catchments. Two separated seasons within the hydrological year are distinguished: a dry season, characterized by absence of streamflow, and a non-zero season. Streamflow is disaggre…
Temporalization of the Body Within Phenomenology and the Metaphysics of Manifestation
2004
In this paper, I would like to discuss some problems concerning the question of manifestation of time, its Erscheinung, or its coming-to-be-experienced. Since Aristotle, philosophers have found themselves in paradoxical questioning about the nature of time. Indeed, a major obstacle found its clearest expression in Augustine’s famous dictum: “If you ask me what time is, then I do not know anything about it any more.” So, one would say with him that the whole task is to translate the experience of time into discourse, even if it has been set out as “simply” descriptive. Curiously enough, philosophers seem to have not been at ease with Aristotle’s rather straightforward decision to link time w…
Rainfall and water yield in Macizo del Caroig, Eastern Iberian Peninsula. Event runoff at plot scale during a rare flash flood at the Barranco de Ben…
2021
[EN] Floods are a consequence of extreme rainfall events. Although surface runoff generation is the origin of discharge, flood research usually focuses on lowlands where the impact is higher. Runoff and sediment delivery at slope and pedon scale receiving much less attention in the effort to understand flood behaviour in time and space. This is especially relevant in areas where, due to climatic and hydrogeological conditions, streams are ephemeral, so-called dry rivers (¿wadis¿, "ramblas" or ¿barrancos¿) that are widespread throughout the Mediterranean. This paper researches the relationship between water delivery at pedon and slope scale with dry river floods in Macizo del Caroig, Eastern…
Cyclicity of Triassic to Lower Jurassic continental red beds of the Argana Valley, Morocco: implications for palaeoclimate and basin evolution
2000
Abstract Cyclical playa deposits form a prominent part of the continental clastic succession of the Argana Valley, Western High Atlas of Morocco. The red beds formed in Triassic to Lower Jurassic times during rifting of the North American and African plates. Detailed stratigraphic work revealed asymmetrical, metre-scale cycles in mudstone-dominated successions that constitute the intermediate and upper portion of the basin fill. Sedimentary cycles commonly comprise ephemeral lake shales at the base, playa mudflat mudstones in the intermediate part, and both fluvial and aeolian sandstones at the top. Cycles of the Aglegal Member (T4) are mainly characterized by analcime-rich playa mudflat de…