1,721,018 research outputs found
Guidance on Environmental Flows - Integrating E-flow Science with Fluvial Geomorphology to Maintain Ecosystem Services
Full text linkFluvial systems provide a wide range of necessary services for human society to thrive on. These are the so-called ecosystem services: food, drinking water, natural flood mitigation, energy and so forth. Such services are linked to an appropriate level of functionality of fluvial processes, which can be accounted for in terms of ecological objectives. These ecological objectives in watercourses can be reached only if appropriate flow and sediment regimes and related quality of channel morphology are guaranteed. The establishment and maintenance of such flow regimes, namely environmental flows (e-flows), is therefore an essential element in preserving riverine ecosystems and the services they provide, and should be included as a constraint in water resource assessment and in national legislative frameworks. It is well established that e-flows refer to the typical seasonal and interannual variability of the natural flow regime, and not only to the minimum amount of water (low flows) to be maintained in a river. In addition to this pure hydrological assessment of natural flow variability, there is also the necessity to link e-flow definition to the related hydromorphological processes and local ecological objectives of a river. This guidance therefore presents a methodology (based on knowledge and literature on river system processes) to consider hydrological and morphological aspects in defining e-flows for environmental river management. The report has been produced within the context of an agreement between the WMO Commission for Hydrology and the Italian National Institute for Environmental Protection and Research (ISPRA), to cooperate in the implementation of activities related to managing river flows and maintaining services offered to human society and ecosystems. The research can be contextualized inside the implementation of the WMO Hydrology and Water Resources programme
Manuale tecnico-operativo per la modellazione e la valutazione dell’integrità dell’habitat fluviale
Full text linkIl presente Manuale descrive la modellazione e la valutazione dell’integrità dell’habitat fluviale utilizzando l’approccio a meso-scala e la metodologia denominata “MesoHABSIM – Mesohabitat Simulation Model”. Tale metodologia, adattata per il contesto italiano, si inserisce nel più ampio “Sistema di Valutazione Idromorfologica, Analsi e Monitoraggio dei corsi d’acqua – IDRAIM” (ISPRA, MLG N° 131/2016). In particolare, la metodologia MesoHABSIM è integrata con il “Sistema di Rilevamento e Classificazione delle Unità Morfologiche dei corsi d’acqua – SUM” (ISPRA, MLG N° 132/2016) per costituire uno strumento atto a descrivere la variabilità spazio-temporale degli habitat fluviali disponibili per la fauna, in funzione della portata defluente e della morfologia del corso d’acqua. La metodologia descritta nel presente manuale è inoltre in accordo con quanto riportato nelle linee guida in tema di “ecological flows” (e-flows) dell’Unione Europea (“Ecological flows in the implementation of the Water Framework Directive”, European Commission, Guidance N° 31, 2015), in cui viene menzionata come strumento idoneo alla valutazione dell’habitat fluviale e utilizzata in due casi studio (casi studio #6 e #8 della guida). Viene infine presentato nel manuale l’Indice di integrità dell’Habitat (IH) e riportati i passi procedurali per la sua applicazione
A novel unsupervised method for assessing mesoscale river habitat structure and suitability from 2D hydraulic models in gravel-bed rivers
Full text linkApplication of mesoscale habitat models in gravel-bed rivers is increasingly common for a variety of purposes, from ecological flow design, impact assessment and conservation programmes. Integration with 2D hydraulic modelling offers the potential for broader applicability of mesoscale habitat models, extending applications to larger streams and nonwadable flow conditions, when on-the-ground and in-stream surveys are challenging or even prohibitive. In this work, a novel fully unsupervised procedure that allows the segmentation of the river channel area at a given flow condition at a scale that is consistent with the mesoscale is presented. Further, it defines an objective methodology to choose segmentation parameters and thus an optimal segmentation, based on intrinsic spatial properties of the resulting regions. Segmentation parameters are objectively selected by minimising a Global Score, which is based on three metrics representing intrasegment homogeneity, intersegment heterogeneity and an optimal range of segment numbers based on an empirically defined mesoscale. Applications of the model are tested on two reaches of the multithread Mareta and meandering Aurino Rivers in South Tyrol (NE, Italy). Model outcomes are compared with ground mesohabitat surveys, and habitat suitability is then assessed for three fish species (marble trout, grayling and European bullhead). A high level of agreement is found when comparing model- and survey-based habitat suitability estimates, with an overall value of (Formula presented.). The proposed approach shows potential for application of the mesohabitat concept for large gravel-bed rivers and nonwadable flow conditions. By allowing habitat estimates at flow ranges that could not be surveyed in-stream, the approach facilitates applicability of mesoscale habitat models to nonwadable conditions and large streams. The workflow is river-independent and fully unsupervised, as it does not require calibration or subjective choices of segmentation parameters. Significance statement. Quantifying suitable habitat for riverine fauna is increasingly used for ecological flows assessment, with the use of mesoscale habitat modelling approaches becoming more common in the past few decades. Existing mesoscale habitat modelling approaches often rely on field surveys, which, however, become prohibitive at nonwadable flow conditions and in large streams. Here we develop and test against field data a fully unsupervised approach able to extract mesohabitats and their hydraulic characteristics from the outputs of 2D hydraulic models. Compared with existing approaches, our approach allows an automated segmentation of the wetted reach into mesoscale units through the implementation of an unsupervised optimality step in which optimal segmentation parameters are defined, and a final mesohabitat mosaic is selected. The methodology makes it easier to expand the applicability of mesoscale habitat modelling to a broader range of river sizes and conditions
Success of a low-sloping rack for improving downstream passage of silver eels at a hydroelectric plant
No full textThe European eel (Anguilla anguilla) is a critically endangered species, and one major threat is the survival of silver eels migrating downstream towards the sea from lake and river rearing areas. During this migration, many eels are impinged and die on intake racks, or are injured or killed when passing through turbines. Intake racks at a hydroelectric plant were modified to avoid impingement and to collect eels without injury; high mortality on both racks and in turbines was previously documented. Modifications consisted of reducing the rack gap width from 20 to 18 mm, decreasing the rack slope from 63 to 35 degrees, increasing the rack surface area by 58% and installing six openings in the rack leading to traps. Downstream passage conditions for silver eels at the hydroelectric plant were significantly improved, reducing mortality from >70% at the old steep 20 mm racks to <10% at the modified 18 mm rack collection facility. No tagged eels were impinged and killed on the racks, and 80% entered the collection facility. Survival can probably be improved even more, as the individuals that passed the facility most likely escaped through holes in the traps. Moreover, injured untagged eels were still encountered at the modified racks, illustrating the need for rehabilitative measures to be implemented at all obstacles between the main eel rearing areas and the sea
The Influence of Soil Characteristics in Low Flows Regionalization
No full textProblem statement: For the purpose of low flows regionalization, relevant issue for water resources management like environmental flows requirements definition, this study focused on the controls on the seasonal and spatial variability of q95 (i.e., the specific discharge that was exceeded on 95% of all the time) with particular reference to the role of soil characteristics, that, like soil infiltration rate, aquifers recharge, evapotranspiration and topography, usually play a relevant role in low flows seasonality and occurrence within a river. Approach: Piemonte and Valle d'Aosta Regions (North-Western Italy) were the investigated study area (30,027 km2) where 41 catchments were analyzed with the aim of robust regression models enabling the transfer of hydrological information from gauged to un-gauged sites. Results: The regionalization method consisted of multiple regression models between low flows and catchment characteristics. Twenty-five catchment descriptors were used, checking their relative influence with the multi-regressive procedure and a special attention was devoted to the selection of significant soil characteristics in the regionalization process. Seasonality indices were used to classify catchments into two sub-regions and separate multiple regressions was performed by checking the prediction performance with cross-validation. Also a global regression was fitted out but it yielded a lower performance. In the study domain land use, topography and Thornthwaite moisture index demonstrated to be the most significant variables in order to represent relationships between catchment soil characteristics and low flows regime. Conclusion/Recommendations: Results obtained in this study were comparable with other regionalization studies carried out in Austria and Switzerland. The interpretation of the identified regression models provided, at local scale, new tools for water management and environmental flows requirements and, from a wider point of view, useful insights into the general comprehension of low flows processes
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
COST-EFFECTIVENESS OF SOIL AND WATER CONSERVATION MEASURES ON THE CATCHMENT SEDIMENT BUDGET-THE LAABA WATERSHED CASE STUDY, BURKINA FASO
No full textIn the Sahelian region, the high precipitation intensity and the daily rainfall extreme values are currently the main cause of soil erosion and land degradation. In addition, solid transport often leads to reservoir siltation and reduction of the amount of water available for agriculture. To cope with these issues, Soil and Water Conservation (SWC) measures have been regularly employed in the Sahelian area. However, a proper cost-effectiveness analysis of the impact of SWC interventions on the catchment sediment budget normally requires quantitative surveys on erosion and sedimentation processes. Where data for calibration and validation of models are scarce, an overall methodology to evaluate the economical sustainability of a proposed intervention can be of paramount importance. The study herein proposed aims to assess the monetary sustainability of SWC measures in limiting the reservoir siltation of the Laaba dam (Yatenga District, Northern Burkina Faso). In particular, the catchment sediment budget was estimated by means of morphological and pedologic parameters and dam sedimentation rates; a cost-effectiveness analysis was then performed to assess the economic sustainability of a possible SWC intervention. The proposed methodology showed interesting potentials for land and water management in Burkina Faso, particularly when data and financial resources are limited and where the application of detailed process-based models is not possible
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
Low Flows Regionalization in North-Western Italy
No full textPrediction of low flows in ungauged catchments is needed in many branches of water resources management, including water availability and river ecology studies. In this paper we analyze the regional variability of q95, i.e., the specific discharge that is exceeded 95% of the time, in North-Western Italy (Piemonte and Valle d'Aosta Regions). Multiple regressions with morphoclimatic catchment characteristics are applied in subregions obtained through four classification methods: Seasonality Indices (SI), Classification and Regression Trees (CRT), Residual Pattern Approach (RPA) and Weighted Cluster Analysis (WCA). All the classification methods separate the South-Eastern Apennine-Mediterranean area from the rest of the study domain (the Alps mountain range), even if they use different criteria to carry out this division (e.g., the percentage of forest, seasonality of low flows, combination of several parameters). In the Apennine-Mediterranean part of the area, low flows occur in summer with a long period of drought and are mainly due to dry climate, moderate snowpack storage and high evapotranspiration. In Alpine catchments low flows occur in winter and vary according to precipitation, elevation, interactions with aquifers and land cover. Within the Alpine mountain range the CRT algorithm identifies a number of small high-elevation catchments in which the intense drought period during winter has the soil freezing processes as the driving force. From a statistical point of view, the CRT model outperforms the models obtained by the other classification techniques in terms of explained variance (69%). Because of this, and given the meaningful hydrological interpretation of the results, we use the CRT model for the regionalization of q95 in Piemonte and Valle d'Aosta. Lastly, as operational procedure for future low flow regionalization studies, we suggest that more classification methods should be applied to assist the critical analysis of the result
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