This paper synthesises published literature on run-of-river hydropower, highlighting its potential to affect both the physical and ecological conditions of river systems. The paper considers the limited number of direct studies and reviews a wider literature on the two principal impacts of such schemes on river systems: the introduction or maintenance of in-channel barriers and water abstraction/flow regime alteration. We outline how river systems are likely to be impacted by such schemes and identify the key issues arising from their continued development. Potential mitigation approaches are highlighted and the areas of future research required to adequately address current knowledge gaps are identified.
This work demonstrates the effectiveness of the instantaneous frequency analysis in detecting a leaks and other features within the network. NHT and DQ allowed for the identification of the approximate location of leaks. The performance TEO is moderate, with Cepstrum being the worst performing method.
[1] An awareness of mixing processes is imperative in understanding the transport of pollutants in open channel flows, important for environmental impact studies. To date, controlled laboratory studies of the effects of vegetation on mixing processes have used simulated plants. This may neglect some of the important variables introduced by the presence of natural vegetation. In this study natural vegetation was planted within a laboratory channel, and a series of experiments quantifying velocity, turbulence, and longitudinal mixing were conducted over a time period sufficient to allow growth of the vegetation to impact on the mixing processes. In emergent conditions the results generally confirmed previous artificial vegetation and modeling studies, showing that vegetation reduces the magnitude of longitudinal shear dispersion. Additionally, measureable change in longitudinal mixing was observed primarily as a function of flow depth but also of plant age. Normalization using previously suggested parameter combinations failed to yield predictive trends. Submerged tests uniquely covered natural vegetation with a significant wake zone, and from this it was observed that longitudinal mixing is primarily a function of the degree of submergence. Overall, this paper presents a new data set quantifying the effects of natural vegetation on longitudinal mixing processes and illustrating deficiencies in previous understanding and predictive expressions based on idealized artificial vegetation.
[1] Prediction of the physical transport and mixing of pollutants or other soluble material is crucial for effective river management. Although well established methods exist which describe mixing processes in open channel flow, the presence of vegetation has a significant impact on mixing and few existing techniques account for this. To date, existing models which predict longitudinal dispersion coefficients in vegetated open channel flow have been derived and verified based on experiments conducted in simulated vegetation. This paper presents observations of longitudinal dispersion coefficients in a channel featuring living vegetation and tests against both an existing and a newly proposed model for longitudinal dispersion coefficient in submerged vegetated open channel flow. A model based on a mathematical technique of predicting dispersion in plain shear flow is shown to be capable of predicting longitudinal dispersion coefficients to within 20%.
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