Hydropeaked rivers need attention Batalla, R J; Gibbins, C N; Alcázar, J ...
Environmental research letters,
02/2021, Volume:
16, Issue:
2
Journal Article
Peer reviewed
Open access
Hydropower is considered a renewable form of energy production, but generating electricity from rivers is not always environmentally benign. The global demand for renewables is increasing rapidly as ...fossil fuels are gradually phased out, so rivers will continue to be subjected to the pressures imposed by hydropower for decades to come. Finding ways of operating hydropower plants that limit impacts on downstream river ecosystems is therefore a pressing global concern. Usually, these plants cause marked and rapid fluctuations in flow in downstream river reaches, termed 'hydropeaking'. Hydropeaks result in a variety of ecological changes in the dynamic mountain rivers they typically affect; declines in fish and insect populations are evident, especially in reaches immediately downstream from the plant. While these changes are often acute and readily apparent, the underlying causal mechanisms remain unclear. We argue here that riverbed sediments are a critical but neglected causal link between hydropeaking flow regimes and ecological changes. We outline how a variety of tools from different branches of river science can now be brought together to understand precisely why hydropeaking alters sediment dynamics; these tools provide a mechanistic explanation for changes in bed sedimentary conditions and channel form across multiple scales and, consequently, a better understanding of ecological changes. By allowing us to simulate the effects of flow fluctuations on sediment dynamics and channel form, these tools also allow us to develop ways of releasing water from hydropeaking dams that limit impacts on aquatic habitat and species.
It has been 100 years since Erwin Payr first developed an operation to improve the effects of a paralysed vocal fold, and operations based on this technique are still in use today. This technique, ...medialisation thyroplasty, aims to improve the symptoms caused by vocal fold palsy by realigning the lateralised vocal fold into the midline. Whilst the effects of vocal fold palsy were recognised in antiquity, it was only with the development of indirect laryngoscopy in the late nineteenth century that the vocal fold paralysis could be identified as an aetiology for poor phonation and dysphagia. Payr, in 1915, was the first to perform a recognisable form of medialisation thyroplasty, which was further developed in the early twentieth century, but medialisation thyroplasty did not begin to be widely used until the development of the modern technique by Isshiki et al., in 1974. Since then, medialisation thyroplasty has continued to be developed and is currently the most widely used technique for correcting the effects of vocal fold palsy. However, a wide array of therapeutic options is now available for vocal fold palsy and it is impossible to say whether or not medialisation thyroplasty will still be used in another 100 years.
OBJECTIVES Lymphoma often presents with a neck mass and while fine-needle aspiration cytology may be suggestive, tissue biopsy is required for reliable diagnosis and classification of a lymphoma that ...is sufficient to deliver the correct treatment for the patient. Traditionally, excisional biopsy of a lymph node has been the standard method of tissue sampling, providing ample tissue for assessment. However, this requires theatre time, and preceding fine-needle aspiration cytology, which may incur a delay. With careful use of tissue, coupled with advances in immunohistochemical and molecular investigative techniques, core biopsy provides a possible alternative to traditional fine-needle aspiration and excisional biopsy. In this study, we aimed to determine the efficacy of diagnosing neck masses. METHOD A retrospective analysis was performed of patients being investigated for a neck mass who were undergoing ultrasound-guided core biopsies of cervical lymph nodes over a 17-month period. The final histology report was scrutinised to assess whether adequate tissue was obtained to allow for full tissue diagnosis. RESULTS Over the 17-month period analysed, 70 patients with cervical lymphadenopathy underwent core biopsy. Of these, 63 (90%) were diagnostic for either lymphoma or other pathology and did not require further tissue sampling. Overall, 19 patients were diagnosed with lymphoma, of which only 1 required further biopsy due to inconclusive initial core biopsy. CONCLUSIONS Current guidelines for investigating lymphomas require that excisional biopsy be performed to obtain ample tissue to allow full nodal architecture assessment and ancillary investigation to reach an accurate histological classification. Within our head and neck multidisciplinary team, however, it is considered that results from core biopsies can be obtained in a more timely fashion and with histological accuracy equal to those of open biopsy. The results obtained demonstrate that core biopsy is an effective tool for investigation. We believe this should be the first-line investigation of choice, as it reduces the need for patients to undergo surgery, is more cost effective and offers a faster diagnosis.
Background
Fragmentation and habitat loss can restrict species movement and reduce connectivity, negatively impacting biodiversity. Characterising the overall connectivity of an area can inform ...better management of human modified landscapes. Contemporary connectivity modelling methods seldom incorporate fine-scale movement patterns associated with movement between fine-scaled structural connectivity elements such as scattered trees, roadside corridors and small patches of habitat. This study aims to characterise connectivity within the Karuah-Myall catchments, a typical woodland ecosystem that is fragmented by agriculture, using least-cost path analysis and a graph-theoretic approach; it focuses on how fine-scaled vegetation such as scattered trees support connectivity. We mapped scattered (and paddock) trees within this agricultural landscape where the main human modified land use was pasture. We modelled connectivity for a general representative woodland species using an interpatch dispersal distance and gap crossing threshold, and resistance from different land cover types. The gap crossing distance threshold was used to model movement between fine-scaled vegetation features. We compared the least-cost paths modelled with and without scattered trees.
Results
Our results show that by excluding scattered trees, least-cost paths across the cleared pasture landscape did not reflect the types of movement patterns typically observed from field studies, such as those associated with a foray-search strategy used by small and medium mammals and birds. The modelling also shows that the Karuah-Myall catchments are well connected and provide value to biodiversity beyond the catchment borders, by connecting coastal vegetation to the Great Eastern Ranges national wildlife corridor initiative.
Conclusion
Connectivity models that exclude fine-scale landscape features such as scattered trees and small, linear patches risk misrepresenting connectivity patterns. Models of regional-scale connectivity can be influenced by the presence or absence of even the smallest features, such as scattered trees.
Flow regulation is widely recognized as affecting fluvial processes and river ecosystems. Most impact assessments have focused on large dams and major water transfer schemes, so relatively little is ...known about the impacts of smaller dams, weirs and water diversions. This paper assesses sediment dynamics in an upland river (the Ehen, NW England) whose flows are regulated by a small weir and tributary diversion. The river is important ecologically due to the presence of the endangered freshwater pearl mussel Margaritifera margaritifera, a species known to be sensitive to sedimentary conditions. Fine sediment yield for the 300-m long study reach was estimated to be 0.057 t km⁻² year⁻¹, a very low value relative to other upland UK rivers. Mean in-channel storage of fine sediment was also low, estimated at an average of around 40 g m⁻². Although the study period was characterized by frequent high flow events, little movement of coarser bed material was observed. Data therefore indicate an extremely stable fluvial system within the study reach. The implication of this stability for pearl mussels is discussed.
Parkinson's disease is a degenerative disorder of the central nervous system, mainly affecting motor functions including the voice. The aetiology of dysphonia changes throughout the course of disease ...progression.
This study aimed to determine the laryngeal changes seen in early-, mid- and late-stage Parkinson's disease. Thirteen patients with Parkinson's disease are presented, representing the largest series of voice patients with Parkinson's disease seen in a voice clinic in the literature.
Age, gender, severity of handicap caused by voice disorder and possible associated reflux symptoms were examined.
Laryngeal function appeared to change gradually with progression of the disease, and may have been affected by the presence of pre-existing laryngeal pathology.
Laryngeal function in Parkinson's disease appears to go through a series of changes that may be helped by both therapeutic and surgical interventions. These patients should be treated within the confines of a voice clinic multidisciplinary model.
A major programme of dam building is underway in many of the world's tropical countries. This raises the question of whether existing research is sufficient to fully understand the impacts of dams on ...tropical river systems. This paper provides a systematic review of what is known about the impacts of dams on river flows, sediment dynamics and geomorphic processes in tropical rivers. The review was conducted using the SCOPUS® and Web of Science® databases, with papers analysed to look for temporal and geographic patterns in published work, assess the approaches used to help understand dam impacts, and assess the nature and magnitude of impacts on the flow regimes and geomorphology (‘hydromorphology’) of tropical rivers. As part of the review, a meta-analysis was used to compare key impacts across different climate regions. Although research on tropical rivers remains scarce, existing work is sufficient to allow us to draw some very broad, general conclusions about the nature of hydromorphic change: tropical dams have resulted in reductions in flow variability, lower flood peaks, reductions in sediment supply and loads, and complex geomorphic adjustments that include both channel incision and aggradation at different times and downstream distances. At this general level, impacts are consistent with those observed in other climate regions. However, studies are too few and variable in their focus to determine whether some of the more specific aspects of change observed in tropical rivers (e.g. time to reach a new, adjusted state, and downstream recovery distance) differ consistently from those in other regions. The review helps stress the need for research that incorporates before-after comparisons of flow and geomorphic conditions, and for the wider application of tools available now for assessing hydromorphic change. Very few studies have considered hydromorphic processes when designing flow operational policies for tropical dams.
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•A boom in dam building has been occuring in tropical rivers.•We identify a lack of work aimed at understanding the impacts of tropical dams on flows and fluvial processes.•A systematic search revealed 71 published papers dealing with hydromorphological impacts of dams on tropical rivers.•Most published papers focused on flow regime and sediment transport, with few dealing with geomorphology and flow hydraulics.•None of the published studies included development of functional flows designed to maintain hydromorphic integrity.
This paper presents the results of experiments in which a portable flume was used to manipulate hydraulic conditions and create bed load transport in a gravel bed river. Flume data are coupled with ...those from Helley‐Smith samples to assess bed load characteristics at shear stresses ranging from 5 to 60 N/m2. Experiments demonstrate that patches of fine sediment control both the intensity and duration of bed load under hydraulic conditions characteristic of the early stages of floods. The experiments allow quantifying bed load at the entrainment threshold, providing the first empirical evidence that marginal bed load transport can be attributed to the mobilization of sediments from patches. Bed load transport was recorded consistently once shear stress exceeded 5 N/m2. The experiments produced low bed load rates (<6 g/sm). Depletion of material in the patches occurred rapidly, with bed load rates and particle sizes decreasing after only 5 minutes. Combining flume and Helley‐Smith data for the study reach, a breakpoint in the relation between shear stress and bed load rate was calculated to be around 30 N/m2. This represents the transition between bed load transport phases: below the breakpoint, transport occurs at a low rate and is composed predominantly of fine sediment from patches, but above it, much higher rates occur from across the reach as a whole. Hydraulic conditions at the threshold are those which occur during small, frequent floods (25% bankfull, flow equaled or exceeded 15% of time). This indicates that sediment entrainment from patches of fine material is a frequent process and the threshold change between bed load phases occurs regularly.
Flow regulation is a major constraint on fish populations in many river systems. Current scientific understanding of the direct and indirect influence of hydrology on salmonids between spawning and ...emergence is reviewed and used to identify key knowledge gaps. The review emphasises difficulties in linking ecological response to physical process understanding and, conversely, the difficulties in applying detailed process understanding to large‐scale management. It is suggested that the lack of process understanding in the development of current environmental standards reflects differences in perspective, language and scale consideration between researchers and river managers. This presents considerable difficulties for the development of new and more defensible environmental standards. Although upscaling of process understanding should remain a focus for researchers, it is also necessary to acknowledge the ‘uniqueness of place’ and consequently that local data collection may frequently be required.
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