Artículos de revistas: "Intermittent streams"

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Poff, N. LeRoy y J. V. Ward. "Implications of Streamflow Variability and Predictability for Lotic Community Structure: A Regional Analysis of Streamflow Patterns". Canadian Journal of Fisheries and Aquatic Sciences 46, n.º 10 (1 de octubre de 1989): 1805–18. http://dx.doi.org/10.1139/f89-228.

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Long-term discharge records (17–81 yr) of 78 streams from across the continental United States were analyzed to develop a general quantitative characterization of streamflow variability and predictability. Based on (1) overall flow variability, (2) flood regime patterns, and (3) extent of intermittency, 11 summary statistics were derived from the entire record for each stream. Using a nonhierarchical clustering technique, nine stream types were identified: harsh intermittent, intermittent flashy, intermittent runoff, perennial flashy, perennial runoff, snowmelt, snow + rain, winter rain, and mesic groundwater. Stream groups separated primarily on combined measures of intermittency, flood frequency, flood predictability, and overall flow predictability, and they showed reasonable geographic affiliation. A conceptual model that incorporates the nine stream clusters in a hierarchical structure is presented. Also, the positions of the 78 streams in a continuous three-dimensional flow space illustrate the wide range of ecologically important hydrologic variability that can constrain ecological and evolutionary processes in streams. Long-term daily streamflow records are a rich source of information with which to evaluate temporal and spatial patterns of lotic environments across many physiographic and ecographic regions. Relative positions of streams in flow space provide a conceptual framework for evaluating a priori the relative importance of abiotic and biotic factors in regulating population and community processes and patterns.

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Stanish, Lee F., Tyler J. Kohler, Rhea M. M. Esposito, Breana L. Simmons, Uffe N. Nielsen, Diana H. Wall, Diana R. Nemergut y Diane M. McKnight. "Extreme streams: flow intermittency as a control on diatom communities in meltwater streams in the McMurdo Dry Valleys, Antarctica1This article is derived from a special session entitled “A New Hydrology: Inflow Effects on Ecosystem Form and Functioning” that took place at the February 2011 ASLO Aquatic Sciences conference in San Juan, Puerto Rico." Canadian Journal of Fisheries and Aquatic Sciences 69, n.º 8 (agosto de 2012): 1405–19. http://dx.doi.org/10.1139/f2012-022.

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In the McMurdo Dry Valleys of Antarctica, stream biota is limited by the brief availability of liquid water. The benthic microbial mats harbor diatoms that have adapted to hydrologic stresses, including numerous endemic species. We found a strong relationship between diatom community composition and flow intermittency in a data set including seven streams that spanned a gradient in flow intermittency. In particular, two genera represented by numerous endemic species in Dry Valley habitats, Hantzschia and Luticola , had high abundances in moderately and highly intermittent streams, respectively. The Shannon Index of diversity was greatest in streams with intermediate flow intermittency, with lower diversity in more stable streams resulting from lower evenness, and lower diversity in highly intermittent streams resulting from lower richness. These results indicate that multiple metrics of biodiversity may be useful in assessing the response of diatom communities to changing hydrologic regime. We propose that flow intermittency acts as a species filter that increases habitat heterogeneity in Dry Valley streams and may allow endemic species to persist. Future Antarctic warming may alter diatom community composition and habitats that act as refugia for desiccation-tolerant taxa.

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Larsen, Noah E., Richard M. Simkins, Jeff S. Wesner, R. Cary Tuckfield y Mark C. Belk. "Species-Specific Abundance Response of Montane Stream Fishes to Drought-Induced Variation in Streamflow". Water 14, n.º 16 (10 de agosto de 2022): 2467. http://dx.doi.org/10.3390/w14162467.

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Climate change projections in the western United States suggest that snowpack levels and winter precipitation will decline, but mean annual precipitation levels will remain unchanged. Mountain streams that once saw a constant source of water from snowpack will begin to see large seasonal variation in flow. Increased stream intermittency will create significant conservation risks for fish species; however, few studies have examined the abundance responses of fish in high elevation streams to the shift from perennial to intermittent flow. To determine the effects of stream intermittency on fish abundance in a montane stream, we quantified changes in abundance for five species over a five-year period that exhibited extreme variation in streamflow. Responses varied by species and life stage, suggesting that the shift from perennial to intermittent flow will cause significant declines in abundance for some species. Northern leatherside chub may experience large decreases in their range as the availability of perennial streams decreases. The study of drought effects on fish abundance will be crucial to the conservation of biodiversity in montane regions of the world.

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4

Price, Karen, Arlene Suski, Joanna McGarvie, Barbara Beasley y John S. Richardson. "Communities of aquatic insects of old-growth and clearcut coastal headwater streams of varying flow persistence". Canadian Journal of Forest Research 33, n.º 8 (1 de agosto de 2003): 1416–32. http://dx.doi.org/10.1139/x03-089.

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Headwater streams, varying in flow persistence from ephemeral to intermittent to perennial, provide the tightest coupling between water and land, yet they often receive the least protection during forest management. We described communities of aquatic insects in perennial, intermittent, and ephemeral channels surrounded by old-growth forest and 4- to 8-year-old clearcuts in Clayoquot Sound, British Columbia, to determine whether temporary streams have unique aquatic communities and to examine the short-term impacts of harvesting. We measured flow persistence, stream size, canopy cover, organic detritus, and algal biomass in 19 streams. We sampled aquatic invertebrates with a combination of emergence cages and kicknet samples. Temporary and old-growth streams had more organic detritus and a higher abundance of shredders. Perennial and clearcut streams had a higher abundance of some algal grazers, but not higher algal biomass. Insect richness was similar in intermittent and perennial streams of each seral stage but lower in ephemeral streams. Intermittent streams contained four taxa not found in the other stream classes; perennial and ephemeral streams had none. Communities of aquatic insects differed between streams surrounded by clearcuts and old growth, and varied with continuity of flow.

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Piano, Elena, Alberto Doretto, Elisa Falasco, Laura Gruppuso, Francesca Bona y Stefano Fenoglio. "Flow intermittency negatively affects three phylogenetically related shredder stoneflies by reducing CPOM availability in recently intermittent Alpine streams in SW-Italian Alps". Hydrobiologia 847, n.º 19 (12 de septiembre de 2020): 4049–61. http://dx.doi.org/10.1007/s10750-020-04399-4.

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Abstract Several Alpine streams are currently facing recurrent summer drying events with detrimental consequences on stream detritivores, i.e., shredders, due to negative effects via changes the organic matter (CPOM) availability. We examined the ecological requirements of three phylogenetically related shredder genera belonging to the family of Nemouridae (Plecoptera), namely Nemoura, Protonemura and Amphinemura, in 14 Alpine streams recently facing recurrent summer flow intermittency events. We evaluated the overlap among their ecological niches measured in terms of hydraulic stress, substrate composition, changes in CPOM availability and competition with other shredder taxa (i.e., presence of individuals of other shredders) and we examined potential changes in their ecological niches between permanent and intermittent sites. The ecological niches of Protonemura and Amphinemura overlap broadly, but not with Nemoura, suggesting only partial potential competition. The reduced CPOM availability decreased the individual abundance of the three genera in intermittent sites, where they consistently preferred microhabitats with high CPOM availability and low competition with other shredder taxa, possibly due to food limitation. Overall, our results emphasize how the negative effect of flow intermittency on shredders in Alpine streams is mainly due to the decrease in CPOM availability, with consequent potential bottom up effects on stream ecosystem functionality.

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Kaplan, Nils Hinrich, Theresa Blume y Markus Weiler. "Event controls on intermittent streamflow in a temperate climate". Hydrology and Earth System Sciences 26, n.º 10 (23 de mayo de 2022): 2671–96. http://dx.doi.org/10.5194/hess-26-2671-2022.

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Abstract. Intermittent streams represent a substantial part of the total stream network, and their occurrence is expected to increase due to climate change. Thus, it is of high relevance to provide detailed information on the temporal and spatial controls of streamflow intermittency to support management decisions. This study presents an event-based analysis of streamflow responses in intermittent streams in a mesoscale catchment with a temperate climate. Based on the streamflow responses, precipitation events were classified into flow or no-flow classes. Response controls like precipitation, soil moisture, and temperature were used as predictors in a random forest model to identify the temporally changing factors that explain streamflow intermittency at the event scale. Soil moisture was the most important predictor, but the predictor importance varied with the geology in the catchment. Streamflow responses in the slate geology were controlled by soil moisture in the shallow and deep soil layers, while streamflow in the marl geology was primarily controlled by soil moisture in the upper soil layer. Streamflow responses in catchments underlain by both marl and sandstone were dependent on soil moisture, whereas streamflow in the only catchment with a pure sandstone geology depended on precipitation characteristics. In all slate and marl catchments, streamflow intermittency also varied with soil temperature, which is probably a proxy for seasonal changes in evapotranspiration and an indicator of freezing conditions. Our findings underline the importance of using high temporal resolution data and tailored event definitions that account for the fast changes between flow/no flow in intermittent streams to identify streamflow controls at the event scale.

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Clarke, Amber, Ralph Mac Nally, Nick Bond y P. S. Lake. "Flow permanence affects aquatic macroinvertebrate diversity and community structure in three headwater streams in a forested catchment". Canadian Journal of Fisheries and Aquatic Sciences 67, n.º 10 (octubre de 2010): 1649–57. http://dx.doi.org/10.1139/f10-087.

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Drying can be a common disturbance affecting macroinvertebrate communities in headwater streams. Whether intermittent and ephemeral streams have a lower diversity and (or) unique assemblage structure relative to physically similar and nearby perennial streams is still debated. We investigated changes in the diversity and assemblage composition of aquatic macroinvertebrates occupying debris dams in three headwater streams with a gradient of flow permanence (perennial, intermittent, and ephemeral) during a dry period in the austral summer of 2007 and a wet period in the spring of 2008. In the dry period, mean taxon richness and abundance in debris dams were lower in the intermittent and ephemeral streams than in the perennial stream, and the length of time without connected surface flow appeared to produce different patterns in community composition. However, during the wet period, mean taxon richness, abundance, and community composition of macroinvertebrates were very similar among the three streams. Hierarchical Bayesian modeling showed evidence for a strong effect of permanence on taxon richness, abundance, and evenness within debris dams. Taxa from the perennial stream were extremely efficient at colonizing seasonally dry nearby streams. Differences in assemblage structure between these temporary and permanent headwater streams may only arise seasonally and also appear related to flow permanence.

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8

Robson, Belinda J. "Role of residual biofilm in the recolonization of rocky intermittent streams by benthic algae". Marine and Freshwater Research 51, n.º 7 (2000): 725. http://dx.doi.org/10.1071/mf00012.

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Human use of stream flow for water supply may increase the duration and/or frequency of dry periods in intermittent streams, but there is little information on the effect of this change on in-stream flora or fauna. To predict the effects of dry periods on stream biota, it is necessary to understand the relative roles of various sources of recolonization. A transplant experiment was used to test the hypothesis that the dry residual algal biofilm on stones in intermittent streams is an important source of algal growth when the streams are re-wetted. Two sites were chosen, one on each of two intermittent streams in south-eastern Australia. Rocks at the sites differed in the amount of naturally occurring residual biofilm on them. Forty rocks were transplanted between the sites and counts of algal densities were made from samples taken one and five weeks after flow recommenced. At one of the sites, where the biofilm was dominated by Cyanobacteria, dry residual biofilm strongly influenced the developing algal community at both one and five weeks after flow recommenced. At the other site the influence of dry biofilm was limited after five weeks, implying that other sources of algal recolonization were influential there.

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9

Chester, E. T. y B. J. Robson. "Do recolonisation processes in intermittent streams have sustained effects on benthic algal density and assemblage composition?" Marine and Freshwater Research 65, n.º 9 (2014): 784. http://dx.doi.org/10.1071/mf13239.

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When intermittent streams flow, benthic algae develop from both colonising propagules and regrowing dried biofilm. We aimed to determine whether colonisation processes influence algal densities and taxonomic composition beyond the period immediately following commencement of winter flows, and whether regulation modifies those processes, in the Victoria Range, Australia. Stones were placed in two unregulated streams, and upstream and downstream of weirs in three regulated streams, after dry biofilm was removed. Epilithic algae on treatment and control stones were collected after winter flows (12 weeks). Treatment effects were still apparent in one (unregulated) stream, but not in the other streams. Algal assemblages and densities upstream and downstream of weirs differed, but there was no systematic pattern among streams. In intermittent headwater streams, recolonisation processes may influence algal assemblages until spring; but in most streams, the duration of influence will be shorter, depending on the assemblage composition in regrowth and refuges, which is also shaped by conditions during the previous flow season. If the effects of regulation depend on how idiosyncratic flow regimes and assemblage compositions influence recolonisation, they may be difficult to predict. Similarly, recovery trajectories for stream communities after drought will differ among streams, depending on whether biofilm can develop during potentially short seasonal flows.

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Bruno, Maria Cristina, Alberto Doretto, Fulvio Boano, Luca Ridolfi y Stefano Fenoglio. "Role of the Hyporheic Zone in Increasing the Resilience of Mountain Streams Facing Intermittency". Water 12, n.º 7 (17 de julio de 2020): 2034. http://dx.doi.org/10.3390/w12072034.

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We investigated the impact of intermittence in previously-perennial Alpine stream reaches, targeting the role of the hyporheic zone in increasing the resilience of these aquatic systems. We selected a perennial and an intermittent site in a reach of the Po River (North-Western Italy). We installed piezometers reaching −1 m (permanent and intermittent site), and −3 m (intermittent site) and monitored three supraseasonal droughts over a period of three years. We classified the hyporheic fauna into three categories of increasing affinity to life in the hyporheic (stygoxene, stygophile, stygobite), and used communities composition, abundance, beta-diversity and functional groups: (1) to compare assemblages at the same depth but with different hydrological characteristics, as well as assemblages from two depths at the intermittent site, and (2) to assess how the connection with surface water and the direction of the vertical aquifer flow determined the faunistic assemblages. Different taxonomic groups responded differently to intermittence, the hyporheic zone acted as a refuge increasing the resilience of the system, but resilience decreased with increasing degree of affinity to hyporheic life. Disentangling the effects of intermittence on the different faunistic component in the hyporheic zone can help guiding effective protection and restoration measures of river systems with temporary reaches.

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Tzoraki, Ourania. "Operating Small Hydropower Plants in Greece under Intermittent Flow Uncertainty: The Case of Tsiknias River (Lesvos)". Challenges 11, n.º 2 (3 de agosto de 2020): 17. http://dx.doi.org/10.3390/challe11020017.

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In arid and semi-arid parts of the world, river exploitation is intensive, involving water storage for irrigation or hydropower generation. In Greece, 100 small hydropower plants (SHPs) take advantage of less than 10% of the hydropower potential of low flow streams (<2 m3/s), a very small amount in relation to the 70% of the European Union. The energy policy of complete decarbonization of the country by 2023 on a national scale opens the road for new investments in SHP projects, especially in intermittent-flow streams of the Greek islands. Simulated flows by the Modello Idrologico SemiDistribuito in continuo (MISDc model) are used to construct the annual flow duration curve (FDC) to study and assess the hydropower potential of an intermittent stream (Tsiknias river, Lesvos, Greece). For Tsiknias River, but also for six other intermittent-flow rivers of Crete island, the capacity factor (CF), which represents the mean annual power of the hydropower plant, should remain >75% to exploit the river’s potential. The FDC and CF are essential in designing SHP projects in intermittent-flow streams with long no-flow periods. The development of public participatory approaches and a closer cooperation among policy makers and stakeholders should work to promote hydropower exploitation and accelerate licensing procedures.

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Wigington, PJ, JL Ebersole, ME Colvin, SG Leibowitz, B. Miller, B. Hansen, HR Lavigne et al. "Coho salmon dependence on intermittent streams". Frontiers in Ecology and the Environment 4, n.º 10 (diciembre de 2006): 513–18. http://dx.doi.org/10.1890/1540-9295(2006)4[513:csdois]2.0.co;2.

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Zhou, Zibo, Ian Cartwright y Uwe Morgenstern. "Sources and mean transit times of stream water in an intermittent river system: the upper Wimmera River, southeast Australia". Hydrology and Earth System Sciences 26, n.º 17 (9 de septiembre de 2022): 4497–513. http://dx.doi.org/10.5194/hess-26-4497-2022.

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Abstract. Determining the mean transit times (MTTs) and water sources in catchments at different flow conditions helps better understand river functioning, and manage river health and water resources. Despite being common in a range of environments, the MTTs and water sources in intermittent streams are much less well understood compared to perennial streams. Major ion geochemistry, stable isotopes, 14C, and 3H were used in this study to identify water sources and MTTs of the periodically intermittent upper Wimmera River from southeast Australia at different flow conditions, including zero-flow periods. The disconnected pool waters during the zero-flow period in the summer months of 2019 had 3H activities of 0.64 to 3.29 TU. These and the variations in total dissolved solids and stable isotopes imply that these pools contained a mixture of older groundwater and younger stream water impacted by evaporation. 3H activities during the high-flow period in July 2019 were 1.85 to 3.00 TU, yielding MTTs of up to 17 years. The 3H activities at moderate and low-flow conditions in September and November 2019 ranged from 2.26 to 2.88 TU, implying MTTs of 1.6 to 7.8 years. Regional groundwater near the Wimmera River had 3H activities of < 0.02 to 0.45 TU and 14C activities of 57 to 103 pMC, and was not recharged by the river at high flows. The Wimmera River and other intermittent streams in southeast Australia are sustained by younger catchment waters from relatively small near-river stores than comparable perennial streams, which have older deeper regional groundwater inputs. This results in these intermittent streams being more susceptible to short-term changes in climate and necessitates the protection of near-river corridors to maintain the health of the riverine systems.

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Olson, Deanna H. y George Weaver. "Vertebrate Assemblages Associated with Headwater Hydrology in Western Oregon Managed Forests". Forest Science 53, n.º 2 (1 de abril de 2007): 343–55. http://dx.doi.org/10.1093/forestscience/53.2.343.

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Abstract We characterized headwater stream habitats, fish and amphibian fauna, in and along 106 headwater stream reaches at 12 study sites within managed forest stands 40 to 70 years old in western Oregon. Headwater stream types in our sample included perennial, spatially intermittent, and dry reaches. We captured 454 fish of three species groups and 1,796 amphibians of 12 species. Using canonical correlation, nonmetric multidimensional scaling ordination, and generalized linear models, we identified species and assemblages associated with reach hydrologic type (e.g., perennial, intermittent, dry), stream size, gradient, and substrate composition. Our findings of torrent salamander (Rhyacotriton species) occurrences in spatially intermittent streams, and patchy and infrequent occurrences of Cottus fish (sculpins) and coastal tailed frogs (Ascaphus truei Stejneger) suggests these taxa warrant consideration during headwater management for retention of locally distinct biotic resources.

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Beaufort, Aurélien, Nicolas Lamouroux, Hervé Pella, Thibault Datry y Eric Sauquet. "Extrapolating regional probability of drying of headwater streams using discrete observations and gauging networks". Hydrology and Earth System Sciences 22, n.º 5 (24 de mayo de 2018): 3033–51. http://dx.doi.org/10.5194/hess-22-3033-2018.

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Abstract. Headwater streams represent a substantial proportion of river systems and many of them have intermittent flows due to their upstream position in the network. These intermittent rivers and ephemeral streams have recently seen a marked increase in interest, especially to assess the impact of drying on aquatic ecosystems. The objective of this paper is to quantify how discrete (in space and time) field observations of flow intermittence help to extrapolate over time the daily probability of drying (defined at the regional scale). Two empirical models based on linear or logistic regressions have been developed to predict the daily probability of intermittence at the regional scale across France. Explanatory variables were derived from available daily discharge and groundwater-level data of a dense gauging/piezometer network, and models were calibrated using discrete series of field observations of flow intermittence. The robustness of the models was tested using an independent, dense regional dataset of intermittence observations and observations of the year 2017 excluded from the calibration. The resulting models were used to extrapolate the daily regional probability of drying in France: (i) over the period 2011–2017 to identify the regions most affected by flow intermittence; (ii) over the period 1989–2017, using a reduced input dataset, to analyse temporal variability of flow intermittence at the national level. The two empirical regression models performed equally well between 2011 and 2017. The accuracy of predictions depended on the number of continuous gauging/piezometer stations and intermittence observations available to calibrate the regressions. Regions with the highest performance were located in sedimentary plains, where the monitoring network was dense and where the regional probability of drying was the highest. Conversely, the worst performances were obtained in mountainous regions. Finally, temporal projections (1989–2016) suggested the highest probabilities of intermittence (> 35 %) in 1989–1991, 2003 and 2005. A high density of intermittence observations improved the information provided by gauging stations and piezometers to extrapolate the temporal variability of intermittent rivers and ephemeral streams.

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Rutkowska, Agnieszka, Silvia Kohnová, Kazimierz Banasik y Jan Szolgay. "Flow characteristics of intermittent rivers in Slovakia". Annals of Warsaw University of Life Sciences – SGGW. Land Reclamation 50, n.º 3 (1 de septiembre de 2018): 215–27. http://dx.doi.org/10.2478/sggw-2018-0017.

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Abstract Flow characteristics of intermittent rivers in Slovakia. Intermittent rivers are rivers that cease to fl ow, i.e. temporary, ephemeral, seasonal, and episodic rivers. Analysis of hydrological regime of such rivers is pivotal in assessment of water resources because changes in fl ow characteristics of such rivers may affect neighboring catchments or the entire region through changes in water supply reservoirs such as lakes, wetlands and mosses. Recently, an increasing number of intermittent rivers and ephemeral streams (IRES) and an elongation of the zero- -fl ow events has been observed in Europe due to climatic changes and anthropogenic influence. Intermittent rives in Slovakia were studied in the paper using statistical methods. The characteristics of the zero-fl ow period, of duration of the longest annual zero-fl ow event and of timing of such events were derived. The circular statistics were helpful in recognition of the dates of occurrence of such events. The comparative analysis between catchments was performed. The variability in precipitation and evapotranspiration and the increasing temperature were identified as the possible drivers of the fl ow intermittence in these catchments. The research was performed within the COST Action SMIRES (Science and Management of Intermittent Rivers & Ephemeral Streams).

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Yu, Songyan, Hong Xuan Do, Albert I. J. M. van Dijk, Nick R. Bond, Peirong Lin y Mark J. Kennard. "Evaluating a landscape-scale daily water balance model to support spatially continuous representation of flow intermittency throughout stream networks". Hydrology and Earth System Sciences 24, n.º 11 (12 de noviembre de 2020): 5279–95. http://dx.doi.org/10.5194/hess-24-5279-2020.

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Abstract. There is a growing interest globally in the spatial distribution and temporal dynamics of intermittently flowing streams and rivers, and how this varies in relation to climatic and other environmental factors. However, biases in the distribution of stream gauges may give a misleading impression of spatial-temporal variations in streamflow intermittency within river networks. Here, we developed an approach to quantify catchment-wide streamflow intermittency over long time frames and in a spatially explicit manner, using readily accessible and spatially contiguous daily runoff data from a national-scale water balance model. We examined the ability of the water balance model to simulate streamflow in two hydro-climatically distinctive (subtropical and temperate) regions in Australia, with a particular focus on low-flow simulations. We also evaluated the effect of model time step (daily vs. monthly) on flow intermittency estimation to inform future model selection. The water balance model showed better performance in the temperate region characterised by steady baseflow than in the subtropical region with flashy hydrographs and frequent cease-to-flow periods. The model tended to overestimate low-flow magnitude mainly due to overestimation of gains (e.g. groundwater release to baseflow) during low-flow periods. Modelled patterns of flow intermittency revealed highly dynamic behaviour in space and time, with cease-to-flow events affecting between 29 and 80 % of the river network over the period of 1911–2016, using a daily streamflow model. The daily flow model did not perform better than the monthly flow model in quantifying flow intermittency at a monthly time step, and model selection should depend on the intended application of the model outputs. Our general approach to quantifying spatio-temporal patterns of flow intermittency is transferable to other parts of the world, and it can inform hydro-ecological understanding and management of intermittent streams where limited gauging data are available.

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Death, Russell G. "Spatial patterns in lotic invertebrate community composition: is substrate disturbance actually important?" Canadian Journal of Fisheries and Aquatic Sciences 60, n.º 5 (1 de mayo de 2003): 603–11. http://dx.doi.org/10.1139/f03-052.

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Twenty-five forest streams were sampled in August 1994 in Te Urewera National Park, New Zealand, to examine the effect of substrate disturbance on invertebrate community structure. Stream size, flow permanence, and riparian cover were more influential than substrate disturbance in affecting invertebrate composition. Three community types were distinguishable based on these three factors: small (<1 m wide), intermittent streams were dominated by Chironomidae; larger (1215 m wide), open streams were dominated by Chironomidae, Plecoptera, and Ephemeroptera; and intermediate-sized (110 m wide) streams with continuous riparian cover were dominated by mayflies and caddisflies. Periphyton biomass was negatively affected by substrate disturbance but not to the same degree as reported by others studying unshaded streams. This may explain why the influence of substrate disturbance on community composition was less than that of stream size, flow permanence, and riparian cover. The key effect of substrate disturbance on postdisturbance community composition in these light-limited New Zealand streams appears to be the removal of animals rather than food loss. Thus, differences between communities that experience high flows and those that do not are far less than they might be in unshaded streams in which the food base is more severely affected by substrate disturbance.

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Foltz, David A., Clarissa N. Damis, Nicole M. Sadecky, Cynthia L. Cyprych y Zachary J. Loughman. "The crayfish of Tomlinson Run State Park, Hancock County, West Virginia, USA". Freshwater Crayfish 22, n.º 1 (31 de diciembre de 2016): 1–8. http://dx.doi.org/10.5869/fc.2016.v22-1.1.

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Abstract In 2015, a survey of Tomlinson Run State Park (TRSP) located in Hancock County, West Virginia USA was completed. Thirty stations, each 100m long, were randomly selected using ArcGIS for both intermittent and perennial stream reaches. Sites were sampled by performing ten seine hauls at each randomly selected station and scored using an Ohio EPA Qualitative Habitat Evaluation Index (QHEI) to obtain qualitative habitat data. Ponds and impoundments were trapped for crayfish using baited crayfish/minnow traps. Burrows found in wetlands and seeps were excavated to determine TRSP burrowing crayfish species composition. In total, 471 crayfish of four species (Cambarus carinirostris, Cambarus monongalensis, Cambarus robustus and Orconectes obscurus) were collected. A statistically significant correlation existed between QHEI score and CPUE for C. carinirostris on intermittent streams. Cambarus monongalensis was the sole burrowing species encountered while C. carinirostris was only collected from intermittent stations (CPUE = 0.12). O. obscurus was the most common species collected from perennial streams (CPUE = 0.95) while Cambarus robustus was the rarest species (CPUE = 0.09) encountered in Tomlinson Run State Park. The crayfish fauna of TRSP is typical for the Upper Ohio River Valley, and at the present time, all species appear stable.

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Shavers, E. y L. Stanislawski. "STREAMS DO WORK: MEASURING THE WORK OF LOW-ORDER STREAMS ON THE LANDSCAPE USING POINT CLOUDS". ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-4 (19 de septiembre de 2018): 573–78. http://dx.doi.org/10.5194/isprs-archives-xlii-4-573-2018.

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<p><strong>Abstract.</strong> The mutable nature of low-order streams makes regular updating of surface water maps necessary for accurate representation. Low-order streams make up roughly half the streams in the conterminous United States by length, and small inaccuracies in stream head location can result in significant error in stream reach, order, and density. Reliable maps of stream features are vital for hydrologic modeling, ecosystem research, and boundary monitoring. High resolution digital elevation models derived from lidar data have shown promise in low order stream modeling yet forested high relief landscapes and low relief agricultural areas remain challenging. Here we present early results from research analyzing lidar point clouds to identify features and patterns that may be used in low-order stream identification and classification in challenging geographic conditions. This work has identified characteristics derived from point clouds that correlate with the presence of streams and stream heads and show promise for mapping small streams. In low topographic relief agricultural areas, cross sections collected at regular intervals along drainage channels extracted as 3D lines show a significant jump in value and variance of profile curvature standard deviation at stream heads. In high relief areas, observations show potential for stream mapping by identifying trends in riparian zone structure. Lidar return point density from riparian vegetation under 30 feet tall dips in the vicinity of intermittent stream heads. Also seen is an increase in point density above 60 feet downstream of stream heads. The trends found here likely reflect a change in vegetation structure relative to the presence of streams.</p>

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Loganathan, G. V., P. Mattejat, C. Y. Kuo y M. H. Diskin. "Frequency Analysis of Low Flows: Hypothetical Distribution Methods and a Physically Based Approach". Hydrology Research 17, n.º 3 (1 de junio de 1986): 129–50. http://dx.doi.org/10.2166/nh.1986.0009.

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A mixed log Pearson type III distribution, a double bounded probability density function, partial duration series and a physically based approach are analyzed for frequency estimates of low flows. The mixed log Pearson III involves a point probability mass at zero for intermittent streams. The double bounded probability distribution has lower and upper bounds with a point mass at the lower bound. Two approaches are used in partial duration series i) truncation, and ii) censoring which represent curtailing of the population and the sample respectively. The parameters are estimated by maximum likelihood procedure. Considering low flows as part of the recession limb of stream flow hydrographs a physically based approach is formulated. By using the exponential decay of stream recessions and considering the initial recession flows, recession durations, and recharge due to incoming storms as statistically independent random variables, a first order random coefficient Markov model for initial recession flows is formed. The resulting steady state probability distribution for initial recession flows is combined with the probability distribution of the exponential decay to obtain the probabilities of low flow events. The methods are applied to both perennial and intermittent streams.

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22

Wang, Xin, Xuanhao Fan, Yuxin Wang, Honghong Wu y Lei Zhang. "Effect of intermittent structures on the spectral index of the magnetic field in the slow solar wind". Annales Geophysicae 41, n.º 1 (28 de marzo de 2023): 129–45. http://dx.doi.org/10.5194/angeo-41-129-2023.

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Abstract. Intermittent structures are ubiquitous in the solar wind turbulence, and they can significantly affect the power spectral index (which reflects the cascading process of the turbulence) of magnetic field fluctuations. However, to date, an analytical relationship between the intermittency level and the magnetic spectral index has not been shown. Here, we present the continuous variation in the magnetic spectral index in the inertial range as a function of the intermittency level. Using the measurements from the Wind spacecraft, we find 42 272 intervals with different levels of intermittency and with a duration of 5–6 min from 46 slow-wind streams between 2005 and 2013. Among them, each of the intermittent intervals is composed of one dominant intermittent structure and background turbulent fluctuations. For each interval, a magnetic spectral index αB is determined for the Fourier spectrum of the magnetic field fluctuations in the inertial range between 0.01 and 0.3 Hz. A parameter Imax, which corresponds to the maximum of the trace of the partial variance increments of the intermittent structure, is introduced as an indicator of the intermittency level. Our statistical result shows that, as Imax increases from 0 to 20, the magnetic spectrum becomes gradually steeper and the magnetic spectral index αB decreases from −1.63 to −2.01. Accordingly, for the first time, an empirical relation is established between αB and Imax: αB=0.4exp⁡(-Imax/5)-2.02. The result will help us to uncover more details about the contributions of the intermittent structures to the magnetic power spectra and, furthermore, about the physical nature of the energy cascade taking place in the solar wind. It will also help to improve turbulence theories that contain intermittent structures.

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23

Falasco, Elisa, Elena Piano y Francesca Bona. "Suggestions for diatom-based monitoring in intermittent streams". Knowledge & Management of Aquatic Ecosystems, n.º 417 (2016): 38. http://dx.doi.org/10.1051/kmae/2016025.

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24

Azarnivand, Ali, Matteo Camporese, Sina Alaghmand y Edoardo Daly. "Modeling hydrological impacts of afforestation on intermittent streams". Science of The Total Environment 728 (agosto de 2020): 138748. http://dx.doi.org/10.1016/j.scitotenv.2020.138748.

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25

Seidman, Victoria M. y Cynthia J. Zabel. "BAT ACTIVITY ALONG INTERMITTENT STREAMS IN NORTHWESTERN CALIFORNIA". Journal of Mammalogy 82, n.º 3 (2001): 738. http://dx.doi.org/10.1644/1545-1542(2001)082<0738:baaisi>2.0.co;2.

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26

Seidman, V. M. y C. J. Zabel. "Bat Activity along Intermittent Streams in Northwestern California". Journal of Mammalogy 82, n.º 3 (17 de agosto de 2001): 738–47. http://dx.doi.org/10.1093/jmammal/82.3.738.

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27

Aksoy, Hafzullah y Mehmet�ik Bayazit. "A model for daily flows of intermittent streams". Hydrological Processes 14, n.º 10 (2000): 1725–44. http://dx.doi.org/10.1002/1099-1085(200007)14:10<1725::aid-hyp108>3.0.co;2-l.

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28

Robson, Belinda J. y Ty G. Matthews. "Drought refuges affect algal recolonization in intermittent streams". River Research and Applications 20, n.º 7 (diciembre de 2004): 753–63. http://dx.doi.org/10.1002/rra.789.

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29

Latterell, Joshua J., Robert J. Naiman, Brian R. Fransen y Peter A. Bisson. "Physical constraints on trout (Oncorhynchus spp.) distribution in the Cascade Mountains: a comparison of logged and unlogged streams". Canadian Journal of Fisheries and Aquatic Sciences 60, n.º 8 (1 de agosto de 2003): 1007–17. http://dx.doi.org/10.1139/f03-088.

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The upstream extent of coastal cutthroat (Oncorhynchus clarki clarki) and rainbow (Oncorhynchus mykiss) trout distribution in logged and unlogged streams of the western Cascade Mountains appears to be primarily constrained by steep channel gradient and sparse pool habitat. Narrow or intermittent wetted channels are also important constraints in logged drainages. The upstream extent of trout distribution appears to be resilient to the combined impacts of historic and current forest management activities, in the absence of impassable road culverts. The probability of trout presence decreased with channel gradient and increased with pool abundance in both logged and unlogged streams, as indicated by logistic regression analysis of physical stream attributes flanking the trout distribution limit in 37 logged and 21 unlogged streams. Reductions in wetted channel width reduced the likelihood of trout presence in logged streams. Logistic regression models fit to data from logged drainages generated accurate predictions of trout presence or absence when applied to data from unlogged drainages. The pervasive extent of native trout in the channel networks of the Cascade Mountains emphasizes the ecological importance of small streams in watershed planning.

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30

Guo, Hongrong, Fuzhong Wu, Xiaoyue Zhang, Wentao Wei, Ling Zhu, Ruobing Wu y Dingyi Wang. "Effects of Habitat Differences on Microbial Communities during Litter Decomposing in a Subtropical Forest". Forests 13, n.º 6 (13 de junio de 2022): 919. http://dx.doi.org/10.3390/f13060919.

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The differences between aquatic and terrestrial habitats could change microbial community composition and regulate litter decomposition in a subtropical forest, but the linkage remains uncertain. Using microbial phospholipid fatty acids (PLFAs), the litter decomposition associated with microbial organisms was monitored to characterize the differences of microbial communities in the forest floor, headwater stream, and intermittent stream. Habitat type did not significantly affect the concentrations of total PLFA. However, microbial community composition (fungi, G+ bacteria, and eukaryote) was significantly affected by the microenvironment among habitats. Compared with which in headwater stream, more individual PLFAs were identified in the natural forest floor and the intermittent stream during the whole decomposition period. The differences in individual PLFA concentrations were reflected in the forest floor and aquatic system in the early stage of litter decomposition, but they mainly reflected in the headwater stream and the intermittent stream in the later stage of litter decomposition. We linked the relationships between microbial community and litter decomposition and found that communities of decomposers drive differences in litter decomposition rate among habitats. Intriguingly, the microbial community showed the greatest correlation with the decomposition rate of litter in streams. These findings could contribute to the understanding of habitats difference on the microbial community during litter decomposition.

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31

ERZINGER, FELICITAS, BJÖRN ROTTER, NICOLAS KREZDORN y STEFFEN U. PAULS. "Gene expression profiling in the aquatic caddisfly larvae Micropterna lateralis (Insecta: Trichoptera) in relation to stream drying". Zoosymposia 14, n.º 1 (15 de julio de 2019): 54–58. http://dx.doi.org/10.11646/zoosymposia.14.1.7.

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Aquatic ecosystems can be either permanently wet or be subject to seasonal or intermittent drying. Insect species inhabiting temporally dry streams have evolved behavioural, morphological and/or life history traits to ensure their persistence. The limnephilid caddisfly Micropterna lateralis (Stephens 1837) has a life cycle that is tailored to the temporal dynamics of periodically dry streams where adults usually hatch before drought commences. Their aquatic larvae are, however, also able to survive stream drying, but the mechanisms driving this survival ability have not been studied to date. We conducted an experiment to simulate drying conditions, using samples from a M. laterialis population taken from an intermittent stream in the Spessart Mountains of the central German highlands. The experiment simulated three hydrological conditions: wet, moist and dry. In a first test of our system we compared gene expression profiles of three individuals (one per condition) using Illumina-based Massive Analysis of cDNA Ends MACE-Seq. Our first results show large differences in gene expression between the studied phases with many genes exhibiting gradual up- or down-regulation across the three experimental hydrological conditions. Under drought stress, up-regulation was primarily found in genes controlling production and mobilization of desiccation protectants, mainly sugars, whereas down-regulated genes were related to cuticle organisation and lipid metabolism. These preliminary results give valuable insights into genetic and physiological responses of aquatic insects to stream drying.

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32

Chafiq, Mohamed, Janine Gibert y Cécile Claret. "Interactions among sediments, organic matter, and microbial activity in the hyporheic zone of an intermittent stream". Canadian Journal of Fisheries and Aquatic Sciences 56, n.º 3 (1 de marzo de 1999): 487–95. http://dx.doi.org/10.1139/f98-208.

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Interactions between surface and subsurface water in intermittent streams are poorly understood. We predicted that surface discharge patterns would influence retention and transport of fine sediments and particulate organic matter in a first-order intermittent stream, which in turn would affect microbial activity at different depths in the sediment. We measured sediments, dissolved and particulate organic carbon, and microbial and bacterial biomass and activity at three depths (surface and 20 and 40 cm) over a period spanning low and high flows at five stations on an intermittent stream. Discharge influenced physicochemical and sediment characteristics at the upstream stations with coarse substratum. In the finer sediments of the lower reaches, an active hyporheic microbial assemblage primarily governed sediment and organic dynamics. With decreasing discharge and increasing retention of fine sediments and particulate organic carbon, greater microbial hydrolytic activity in bed-sediments occurred downstream. Dissolved oxygen, organic carbon, fine sediments, microbial biomass, hydrolytic activity, and bacterial biomass declined with depth, and changed over time, apparently in response to varying discharge. We conclude that discharge and substratum particle size may interact to control organic dynamics and hyporheic microbial activity in a 1st order stream.

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33

Lockaby, B. G., R. Governo, B. Rummer y C. Colson. "Silvicultural Management Within Streamside Management Zones of Intermittent Streams: Effects on Decomposition, Productivity, Nutrient Cycling, and Channel Vegetation". Southern Journal of Applied Forestry 28, n.º 4 (1 de noviembre de 2004): 211–24. http://dx.doi.org/10.1093/sjaf/28.4.211.

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Abstract The purpose of this watershed study on three intermittent streams was to evaluate responses ofriparian processes to three streamside management zone (SMZ) treatments; no harvest, clearcut, and partial harvest(50% basal area removal). Riparian response variables measured included litterfall, leaf litter decomposition, understory vegetation, soil temperature and water chemistry. However, due to drought conditions, insufficient water chemistry data were collected to support quantitative assessment of treatment effects. Comparisons of mass loss rates (k) indicated that decomposition on the control treatment was the most rapid. Understory vegetation surveys showed statistically greater mass of forbs and grasses within the clearcut SMZ. Results suggest that no harvest or a partial harvest within SMZs along intermittent streams are preferable because these treatments maintain carbon inputs to streams. South. J. Appl. For. 28(4): 211–224.

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34

Řezníčková, Pavla, Lenka Tajmrová, Petr Pařil y Světlana Zahrádková. "Effects of drought on the composition and structure of benthic macroinvertebrate assemblages – a case study". Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 61, n.º 6 (2013): 1853–65. http://dx.doi.org/10.11118/actaun201361061853.

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Natural drying up of streams is not common in Central Europe. Nevertheless, the recurrent drying up of small streams in last decades has shown an urgent need to pay attention to the impact of global climate change. This strong disturbance influences conditions in streams markedly and causes changes in the taxonomical and functional structure of biota. The aim of the study was to compare aquatic macroinvertebrate assemblages of one intermittent and one permanent brook in South Moravia. The study was carried out in two stretches with otherwise comparable environmental parameters. Lower densities of macroinvertebrates were found at the intermittent site the difference was statistically significant. The number of taxa and diversity were significantly higher at the permanent site. Functional structure of the assemblages also varied. The shares of rheobionts, grazers and predators differed.

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35

Lakel, William A., Wallace M. Aust, M. Chad Bolding, C. Andrew Dolloff, Patrick Keyser y Robert Feldt. "Sediment Trapping by Streamside Management Zones of Various Widths after Forest Harvest and Site Preparation". Forest Science 56, n.º 6 (1 de diciembre de 2010): 541–51. http://dx.doi.org/10.1093/forestscience/56.6.541.

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Abstract Recommended widths for streamside management zones (SMZs) for sediment protection vary. The objectives of this study were to compare the effects of SMZ widths and thinning levels on sediment moving through SMZs. Four SMZ treatments were installed within 16 harvested watersheds where intermittent streams graded into small perennial streams. Sites were clearcut, prescribed burned, and planted with loblolly pine (Pinus taeda L.). Treatments were 30.4-, 15.2-, and 7.6-m-wide SMZs without thinning and 15.2-m-wide SMZs with thinning. Three to seven treatments replicated within four blocks created a randomized incomplete block design. Erosion rates from watersheds and sediment trapping within SMZ treatments were monitored with modeling and sediment pins. A second study evaluated 24 subwatersheds within eight watersheds. Three subwatersheds were located within each watershed so sediment traps collected inputs into SMZs from harvest site-prepared areas, firelines, or at streams. SMZ treatments had no significant differences regarding sediment trapping. All SMZs widths were generally effective in trapping sediment. Within the 16 intermittent-perennial watersheds and 24 ephemeral subwatersheds, erosion to sediment delivery ratios from harvests ranged from 3 to 14%. For ephemeral stream subwatersheds, firelines adjacent to SMZs contributed 14% of total sediment. Sediment trap data collected within SMZs indicated that 97% of watershed erosion was trapped before reaching streams. In three subwatersheds, sediment penetrated SMZs due to channelized flow from failed or inadequate water controls on roads and firelines. Results support the common recommendation for SMZ widths of 15.2 m in which partial harvests may occur and emphasize the importance of implementation of best management practices for roads and firelines.

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36

George, Melvin R., Royce E. Larsen, Neil K. McDougald Kenneth W. Tate, John D. Gerlach y Kenneth O. Fulgham. "Influence of Grazing on Channel Morphology of Intermittent Streams". Journal of Range Management 55, n.º 6 (noviembre de 2002): 551. http://dx.doi.org/10.2307/4003998.

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37

BOULTON, A. J. y P. S. LAKE. "The ecology of two intermittent streams in Victoria, Australia." Freshwater Biology 27, n.º 1 (febrero de 1992): 99–121. http://dx.doi.org/10.1111/j.1365-2427.1992.tb00527.x.

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38

BOULTON, A. J. y P. S. LAKE. "The ecology of two intermittent streams in Victoria, Australia." Freshwater Biology 27, n.º 1 (febrero de 1992): 123–38. http://dx.doi.org/10.1111/j.1365-2427.1992.tb00528.x.

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39

Schiller, D., T. Datry, R. Corti, A. Foulquier, K. Tockner, R. Marcé, G. García‐Baquero et al. "Sediment Respiration Pulses in Intermittent Rivers and Ephemeral Streams". Global Biogeochemical Cycles 33, n.º 10 (octubre de 2019): 1251–63. http://dx.doi.org/10.1029/2019gb006276.

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40

Rodrigues, Sara, Bárbara Xavier, Sandra Nogueira y Sara C. Antunes. "Intermittent Rivers as a Challenge for Freshwater Ecosystems Quality Evaluation: A Study Case in the Ribeira de Silveirinhos, Portugal". Water 15, n.º 1 (21 de diciembre de 2022): 17. http://dx.doi.org/10.3390/w15010017.

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Intermittent rivers and streams are aquatic ecosystems that lose hydrological connectivity during drought periods. Anthropogenic pressures combined with climate change accelerate the spatial and temporal intermittency of these ecosystems, promoting alterations in ecology and ecosystem functions. This study aimed to assess the ecological status of Ribeira de Silveirinhos, located in the municipalities of Valongo and Gondomar (north of Portugal), using the metrics described in the Water Framework Directive. Thus, five sampling sites were selected along Ribeira de Silveirinhos. Sampling was done in three different periods, spring of 2019 and 2020, and autumn of 2019. At each site, physical and chemical water parameters were measured, and the benthic macroinvertebrates community was characterized. Physical and chemical parameters showed low pH values at upstream sites (where the dry phase occurs and is surrounded by Eucalyptus monoculture) and high concentrations of phosphorus at the downstream sites (subjected to several anthropogenic activities, iron waters, and agriculture). The macroinvertebrate community revealed low values of specific abundance and richness, especially during the dry period. Sensitive taxa (Ephemeroptera, Plecoptera, and Trichoptera) were negatively correlated with flow intermittency. Results showed that Ribeira de Silveirinhos is classified between “poor” and “moderate” in terms of ecological status. Intermittent streams are undervalued, so their protection is at risk. Thus, it is important to consider the specific ecological functioning of these ecosystems and to adjust the planning and management models in order to guarantee ecological quality and conservation processes.

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41

Karim, G. A., A. Hanafi y S. A. Mehta. "Volatilization and Ignition of Oil Sand Samples During Intermittent Exposure to Hot Low-Velocity Air Streams". Journal of Energy Resources Technology 111, n.º 2 (1 de junio de 1989): 104–9. http://dx.doi.org/10.1115/1.3231404.

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The behavior of small oil sand samples was monitored experimentally when subjected repeatedly to low-velocity heated air streams, with either prompt quenching or slow cooling of the samples to their initial temperatures between these exposures. The stream temperature was either in the range of 300°C to 500°C in air or at higher temperatures of up to 760°C, while being exposed to the products of combustion of very lean hydrogen-air mixtures. This was done in relation to understanding better the associated processes in some in-situ recovery trials where stoppage of the combustion front and/or the flow of the injected fluids can occur. A variety of multi-exposure-cooling schemes was considered and their effects on the extent of volatilization and ignition established. Comparison to the corresponding behavior of similar samples under uninterrupted exposure to the heated streams was made throughout.

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42

Delucchi, Carla M. "Comparison of community structure among streams with different temporal flow regimes". Canadian Journal of Zoology 66, n.º 3 (1 de marzo de 1988): 579–86. http://dx.doi.org/10.1139/z88-085.

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A study was conducted in four streams in the same watershed in New York to determine whether the benthic invertebrate community structure varied among streams with different temporal flow regimes. Timed kick samples were taken from 13 riffles and 4 pools once a month from June to November 1982. Riffle sites were classified according to temporal flow regime as permanent, intermittent (dry for less than 3 months), or dry (dry for over 3 months), and varied in size as a function of discharge. Ordination analysis (detrended correspondence analysis) showed that the structure of the benthic invertebrate communities in these streams was related not only to riffle permanence, but also to other abiotic and biotic parameters. Differences in community structure were greater between adjacent pools and riffles than between temporary and permanent riffles. Stream size, seasonal changes in taxa, how recently the riffle had dried, and the length of the dry period contributed to differences in community structure among riffles. It appears that differences in community structure between permanent and temporary riffles are minimized by generalized adaptations of stream benthos, such as high rates of migration, drought-resistant eggs, and the tendency to take refuge in the hyporheic zone.

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43

Closs, GP. "Feeding of Galaxias olidus (Guenther) (Pisces: Galaxiidae) in an intermittent Australian stream". Marine and Freshwater Research 45, n.º 2 (1994): 227. http://dx.doi.org/10.1071/mf9940227.

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Patterns of feeding in the mountain galaxiid (Galaxias olidus) were examined at dawn and dusk during low flow in April and high flow in September in an intermittent stream. During April (low flow), feeding rates were relatively low and aperiodic, whereas in September (high flow), the fish were clearly feeding diurnally at a relatively high rate. These results suggest that feeding in G. olidus in intermittent streams may vary on a daily and seasonal basis, possibly as a consequence of changes in light availability and stream flow. Light determines the ability of fish to find their prey, and seasonal changes in flow may determine the availability of prey (i.e. drifting invertebrates). This pattern suggests that the predatory impact of drift-feeding fish, such as G. olidus, is likely to be considerably less during low-flow periods when drifting invertebrates are not available than during high-flow periods when such prey may be abundant.

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44

Bernal, S. y F. Sabater. "Changes in discharge and solute dynamics between a hillslope and a valley-bottom intermittent streams". Hydrology and Earth System Sciences Discussions 8, n.º 5 (27 de octubre de 2011): 9505–36. http://dx.doi.org/10.5194/hessd-8-9505-2011.

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Abstract. We investigated differences on stream water flux as well as on chloride, carbon and nitrogen dynamics between two semiarid nested catchments, one at the hillslope and the other one at the valley-bottom. The two streams were intermittent, yet only the valley-bottom stream was embraced by a riparian forest and a well-developed alluvium with highly conductive coarse sediments. We found that stream water flux decreased by more than 40% from the hillslope to the valley-bottom during hydrological transition periods (from dry-to-wet and from wet-to-dry conditions), coinciding with periods when stream-to-aquifer fluxes prevailed. During the hydrological transition period, stream export of chloride, nitrate, and dissolved organic carbon decreased 34–97% between the hillslope and the valley-bottom catchments. There was a strong correlation between monthly differences in stream discharge and in stream Cl− export between the two catchments. In contrast, monthly differences in stream export for bio-reactive solutes were only partially explained by stream discharge. In annual terms, stream nitrate export from the valley-bottom catchment (0.32 ± 0.12 kg N ha−1 yr−1 – average ± standard deviation) was 30–50% lower than from the hillslope catchment (0.56 ± 0.32 kg N ha−1 yr−1). Although the riparian forest could be an extra source of organic matter to the valley-bottom stream, the annual export of dissolved organic carbon was similar between the two catchments (1.8 ± 1 kg C ha−1 yr−1). Our results suggested that stream hydrology was a strong driver of stream solute export during the hydrological transition period, and that hydrological retention in the alluvial zone could contribute to reduce stream water and solute export under semiarid conditions in the valley-bottom stream.

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45

Duncan, William W., Kathleen M. Bowers y John R. Frisch. "Missing Compensation: A Study of Compensatory Mitigation and Fish Passage in Georgia". Journal of Fish and Wildlife Management 9, n.º 1 (14 de febrero de 2018): 132–43. http://dx.doi.org/10.3996/022016-jfwm-017.

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Abstract Thousands of permit applications are filed annually with the U.S. Army Corp of Engineers, requiring significant review efforts to ensure that applications conform to regulations, and that proposed activities avoid, minimize, and compensate for stream and wetland impacts. However, the effectiveness of this approach remains uncertain. We evaluated the effectiveness of those regulatory efforts using newly installed stream–road crossings as a case study because crossings are pervasive on the landscape and many U.S. Army Corp of Engineers jurisdictions have requirements that are aimed at minimizing crossing-induced impacts to fish passage. Specifically, we assessed whether requirements intended to facilitate fish passage were implemented, whether requirements resulted in fish-passable stream–road crossings, and whether the amount of construction-related stream impact that was authorized by permits corresponded to the amount of compensation that was required. Our analysis is devoted solely to stream–road crossings in Georgia that are permitted under nationwide permits, the permit type commonly used to authorize activities in streams throughout the United States. We found that no new crossings conformed entirely to the requirements intended to avoid and minimize impacts to fish passage. The measured total stream impact length in this study was 46.0% higher than the amount of impact proposed in permit applications for perennial streams, and 23.7% higher for intermittent and ephemeral streams. Only 30.6% of the perennial stream length affected in this study received compensation for impacts even though 90.9% of impacts qualified. Collectively, these results indicate that regulations and mitigation policies are not having their intended effects of providing fish passage or preventing net loss of streams in Georgia as required under the Clean Water Act. We recommend that decision makers undertake a more geographically comprehensive evaluation of stream impacts that are authorized by permits to thoroughly evaluate regulatory effectiveness and impacts to fish passage.

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46

Driver, Lucas J. y David J. Hoeinghaus. "Spatiotemporal dynamics of intermittent stream fish metacommunities in response to prolonged drought and reconnectivity". Marine and Freshwater Research 67, n.º 11 (2016): 1667. http://dx.doi.org/10.1071/mf15072.

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Hydrological regimes are primary drivers of community structure and dynamics in streams with strong seasonal or annual flood and drought cycles. In the current study, we investigated the dynamics of fish metacommunities in two intermittent streams (Hickory Creek and Clear Creek) in north Texas, USA, by examining changes in diversity, abundance, assemblage structure and temporal stability associated with prolonged seasonal drought and reconnectivity. Diversity (α and γ), abundance and stability increased with initial isolation during summer drought but dramatically declined as drought or drying persisted through the winter (November–December). During post-drought reconnectivity in Hickory Creek, diversity and abundance increased and approached pre-drought levels. Abundance and body size varied greatly among species and indicated species-specific responses (i.e. mortality, recruitment, dispersal) to hydrologic fragmentation and connectivity. Ultimately, assemblage structures were significantly altered by drought in Hickory and Clear creeks, and despite a trend towards recovery in Hickory Creek, assemblages did not fully recover during the present study. Intermittent-stream fishes may be generally adapted to natural drought dynamics; however, climate change and human-mediated habitat alterations may result in prolonged and intensified drought conditions that exceed many species mechanisms of resistance or resilience having potentially large impacts on biodiversity across spatial and temporal scales.

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47

Sroczyńska, K., F. Leitão, I. Maximo y P. Range. "Independent effects of habitat and stream typology on macroinvertebrate communities in Mediterranean-type intermittent streams". Limnetica 38, n.º 2 (15 de julio de 2019): 535–53. http://dx.doi.org/10.23818/limn.38.31.

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Levick, Lainie, Samantha Hammer, Russell Lyon, Joel Murray, Amy Birtwistle, Phillip Guertin, David Goodrich, Brian Bledsoe y Melinda Laituri. "An ecohydrological stream type classification of intermittent and ephemeral streams in the southwestern United States". Journal of Arid Environments 155 (agosto de 2018): 16–35. http://dx.doi.org/10.1016/j.jaridenv.2018.01.006.

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Kaplan, Nils Hinrich, Ernestine Sohrt, Theresa Blume y Markus Weiler. "Monitoring ephemeral, intermittent and perennial streamflow: a dataset from 182 sites in the Attert catchment, Luxembourg". Earth System Science Data 11, n.º 3 (4 de septiembre de 2019): 1363–74. http://dx.doi.org/10.5194/essd-11-1363-2019.

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Abstract. The temporal and spatial dynamics of streamflow presence and absence is considered vital information to many hydrological and ecological studies. Measuring the duration of active streamflow and dry periods in the channel allows us to classify the degree of intermittency of streams. We used different sensing techniques including time-lapse imagery, electric conductivity and stage measurements to generate a combined dataset of presence and absence of streamflow within various nested sub-catchments in the Attert catchment, Luxembourg. The first sites of observation were established in 2013 and successively extended to a total number of 182 in 2016 as part of the project Catchments As Organized Systems (CAOS). Temporal resolution ranged from 5 to 15 min intervals. Each single dataset was carefully processed and quality controlled before the time interval was homogenised to 30 min. The dataset provides valuable information of the dynamics of a meso-scale stream network in space and time. This can be used to test and evaluate hydrologic models but also for the assessment of the intermittent stream ecosystem in the Attert basin. The dataset presented in this paper is available at the online repository of the German Research Center for Geosciences (GFZ, https://doi.org/10.5880/FIDGEO.2019.010, Kaplan et al., 2019).

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Gruppuso, Laura, Alberto Doretto, Elisa Falasco, Stefano Fenoglio, Michele Freppaz, Mark Eric Benbow y Francesca Bona. "Flow Intermittency Affects Leaf Decomposition and Benthic Consumer Communities of Alpine Streams: A Case Study along the Po River". Water 14, n.º 2 (16 de enero de 2022): 258. http://dx.doi.org/10.3390/w14020258.

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Streams and rivers are becoming increasingly intermittent in Alpine regions due to the global climate change and related increases of local water abstractions, making it fundamental to investigate the occurrence of supraseasonal drying events and their correlated effects. We aimed to investigate leaf litter decomposition, the C:N ratio of the litter, and changes in associated macroinvertebrate communities in three reaches of the Po River: One upstream, consistently perennial, a perennial mid-reach with high hydrological variability, and an intermittent downstream reach. We placed leaf litter bags of two leaf types—chestnut and oak; both showed comparable decomposition rates, but the remaining litter mass was different and was attributed to the C:N ratio and palatability. Furthermore, (1) in perennial reaches, leaf litter decomposed faster than in the intermittent ones; (2) in intermittent reaches, the C:N ratio showed a decreasing trend in both leaf types, indicating that drying affected the nitrogen consumption, therefore the conditioning phase; (3) associated macroinvertebrate communities were richer and more stable in perennial reaches, where a higher richness and abundance of EPT taxa and shredders was observed. Our results suggest that the variations in the hydrology of mountain streams caused by global climate change could significantly impact on functional processes and biodiversity of benthic communities.

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