The lower Tordera River is a representative case of water and sediment dynamics and uses in a large river in the Western Mediterranean region. Along the study reach, the fluvial regime of the river ...changes, shifting from a perennial water and sediment circulation in the upper parts to an ephemeral flow pattern in the lower sections. The fluvial sediment budget of the lower Tordera was estimated based on field measurements of suspended and bedload and a survey of cross-sections. Field data were obtained between January 1997 and June 1999, a period that was dryer than the average. Most sediment is transported as bedload (more than 3/4 of the total load), both at the entrance section of the river reach and at the outlet section, close to the Mediterranean Sea. A total of 156,700 tonnes of sediment (62,680 tonnes/year) entered the system, mostly during discharges below bankfull, while 107,000 tonnes (42,800 tonnes/year) were exported to the sea, almost exclusively during floods. The net accumulation of sediment was 14,600 tonnes per year (as bedload), especially during the dry years of 1998 and 1999, when small floods circulated through the upper sections but did not reach the lowermost part of the river. As a consequence, a mean aggradation of the riverbed of around 6.8 mm/year has occurred, a figure that has been corroborated after the analysis of a series of cross-sections. Residence time of sediment in the perennial reach, calculated at a long-term, ranges from 6 years for sediments in the active base flow channel to 164 years for sediment placed above bankfull level, which is only entrained during high flows. Residence time of sediment in the ephemeral reach, calculated for the period 1997–1999, is only slightly higher than that of the perennial part of the river. This fact can be related to the current adjustment of the river system to historical mining. The riverbed is slowly adjusting to the new conditions, and important sedimentation is taking place in many upstream sections, while erosion still occurs in the lowermost reaches, thus causing the relatively low residence time of sediment.
The scarcity of grain-size data from gravel-bed rivers has traditionally hindered hydraulic, sediment transport and river habitat studies. A new remote sensing methodology to estimate grain-size ...distribution is presented. It combines textural digital images of the riverbed at 1
:
1000 and 1
:
40 scales with grain-size sampling. It was applied to a 12-km reach of the Isábena River (Central Pyrenees NE Spain). First, textural patterns for each grain-size range were obtained, selecting the most closely related texture variables, including the use of semivariograms. Second, multiple linear regression equations were derived from the textural variables to estimate each value of the grain-size distribution. The highest correlation values (
r
2) were obtained from the central part of the distribution (
D
50 with a RMS error of 12.7%). Finally, new multiple linear regression equations to estimate the
D
50 and
D
84 were obtained from 1
:
1000 images and four textural variables. These were used to derive
D
50 and
D
84 maps of the riverbed, re-sampled at a resolution of 1.5 m pixels, with RMS estimation errors of 26% and 32%, respectively. Downstream change in grain-size is also well reproduced by the method. The mean
D
50 of 72 and 32 mm were estimated in the upper and the lower reaches of the river, respectively. The methodology shows great potential for application, the relation between the spatial resolution of the images and the mean grain-size of the riverbed sediment being the main issue for future development.
As the share of renewable energy grows worldwide, flexible energy production from peak-operating hydropower and the phenomenon of hydropeaking have received increasing attention. In this study, we ...collected open research questions from 220 experts in river science, practice, and policy across the globe using an online survey available in six languages related to hydropeaking. We used a systematic method of determining expert consensus (Delphi method) to identify 100 high-priority questions related to the following thematic fields: (a) hydrology, (b) physico-chemical properties of water, (c) river morphology and sediment dynamics, (d) ecology and biology, (e) socio-economic topics, (f) energy markets, (g) policy and regulation, and (h) management and mitigation measures. The consensus list of high-priority questions shall inform and guide researchers in focusing their efforts to foster a better science-policy interface, thereby improving the sustainability of peak-operating hydropower in a variety of settings. We find that there is already a strong understanding of the ecological impact of hydropeaking and efficient mitigation techniques to support sustainable hydropower. Yet, a disconnect remains in its policy and management implementation.
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•We identify research gaps to support sustainable hydropeaking policy and management•We collect questions from 220 stakeholders and use a method for expert consensus•Many questions can be answered with long-term monitoring and digital twin approaches•Key gaps relate to implementation of mitigation in policy and markets•Open questions are no excuse for the lack of sustainable hydropeaking
Field studies have recently shown that quickflow may be produced in Mediterranean environments as the result of saturation mechanisms, considering that the dominant runoff processes may change ...throughout the year due to the significant seasonality. One of the most representative agriculture elements of Mediterranean-climate regions is rainfed herbaceous crops. The aim of this study is to achieve a better understanding of hydrological responses and the role played by under-drained systems in runoff variations under such climatic and land use conditions. Field measurements were conducted in Can Revull, a small catchment (1.03
km
2) in the island of Mallorca. The mean annual precipitation and potential evapotranspiration are 517
mm and 1010
mm, respectively. The hydrological regime is intermittent with a mean annual discharge of 4
l
s
−1. Based on 3
years of field data (July 2004–June 2007), this study presents a soil water balance of the catchment and an evaluation of the variability of runoff and its components on an annual and seasonal time scale. In addition, the response of runoff components at event-scale was analysed. At the annual and seasonal time scales, it was only possible to observe a succession of three different hydrological periods throughout the year conditioned by the evapotranspiration which also plays an important role in the baseflow response. Precisely, baseflow was predominant, presumably enhanced by the under-drained system. Furthermore, quickflow response was dominated by saturation mechanisms, whereas rainfall excess mechanisms were limited during study period to dry seasons when baseflow was not present and discharge values therefore were lower.
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•Badlands do not always control the export of sediments in intermittent streams.•At the annual scale, badlands supply less than half of the total sediment yield.•At season scale, ...sediment produced in badlands can be higher than the sediment yield.•Drainage network controls sediment export directly related with the flashiness.•Pulses will determine the role of the drainage network (i.e. source or sink)
The objective of this paper is to analyse the production and the yield of fine sediment in a small mountain catchment (10 km2), characterised by patches of badlands (25% of the catchment area) and drained by intermittent streams. The study area is located in the Southern Central Pyrenees. The study is performed at multiple temporal scales to further highlight: (i) the effect of pulses in the transfer of water and fine sediment; (ii) the contribution of the sediment production from badlands to the sediment yield of the catchment; and (iii) the role of the drainage network as fine sediment source and sink. Significant correlations between meteorological and flow variables were found; specifically, the strongest positive relations were observed between stream flashiness, the duration of the period in which the stream is dry and the suspended sediment concentration. Results indicated that badlands do not always control the export of sediments. At the annual scale badlands supply around 40% of the total catchment sediment yield. Seasonally sediment produced in badlands can be higher than the amount exported at the catchment outlet, suggesting the channel network acts as a sink. In terms of sediment production, badlands represent around of 53% of the total production taking also into account agricultural fields and forest areas. Results emphasise the key role of the channel network on controlling pulses of sediment transfer, in direct relation to the intermittent character of the streams. The frequency and magnitude of such pulses determines the catchment Sediment Delivery Ratio (SDR), depending on whether the drainage network acts as a sediment sink or source.
Our objective was to examine the association between myocardial infarction (MI) and two DNA-polymorphisms at the proinflammatory chemokine receptors CCR2 (I64V) and CCR5 (32 bp deletion, ...(Delta)ccr5), defining if these polymorphisms influence the age for the onset of MI. A total of 214 patients with an age at the first MI episode <55 years, 96 patients that suffered the first MI episode when older than 60 years, and 360 population controls were polymerase chain reaction genotyped for the CCR2-V64I and CCR5-Delta32/wt polymorphisms. Patients and controls were male from the same Caucasian population (Asturias, northern Spain). The frequency of the Deltaccr5 allele was significantly higher in controls compared to patients <55 years (P = 0.004), or in patients >60 years compared to patients <55 years (P = 0.002). Taking the patients >60 years as the reference group, non-carriers of the (Delta)ccr5-allele would have a three-fold higher risk of suffering an episode of MI at <55 years of age (OR = 3.06; 95% CI = 1.46-6.42). Gene and genotype frequencies for the CCR2 polymorphism did not differ between patients <55 years and controls or patients >60 years. Our data suggest that the variation at the CCR5 gene could modulate the age at the onset of MI. Patients carrying the (Delta)ccr5-allele would be protected against an early episode of MI. CCR5 and the CCR5-ligands are expressed by cells in the arteriosclerotic plaque. Thus, the protective role of (Delta)ccr5 could be a consequence of an attenuated inflammatory response, that would determine a slower progression of the arteriosclerotic lesion among (Delta)ccr5-carriers. Our work suggests that the pharmacological blockade of CCR5 could be a valuable therapy in the treatment of MI.
Water resources are directly and indirectly affected by anthropogenic activities (e.g., changes in land use) and natural factors (e.g., climate change), that is, global change. The Mediterranean ...basin is one of the most vulnerable regions of the world to global change, and one of the “hot spots” for forthcoming problems of water availability. The present review provides an overview about the relationship between chemical quality (especially concerning organic microcontaminants) and water scarcity, particularly in the Mediterranean area. We include an overview of environmental contaminants and analytical methodologies and consider the fate and the behavior of organic contaminants, and the effects of pollutants on ecosystems.
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