Literatura académica sobre el tema "Intermittent streams"
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Artículos de revistas sobre el tema "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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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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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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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.
Tesis sobre el tema "Intermittent streams"
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Nhim, Tum. "Variability of intermittent headwater streams in boreal landscape : Influence of different discharge conditions". Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-183137.
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Dynamic expansions and contractions of stream networks can play an important role for hydrologic processes as they can connect different parts of the landscape to the stream channels. However, we know little about the temporal and spatial variations of stream networks during different flow and wetness conditions. This study focuses on the contraction and expansion of stream networks during different flow conditions in the boreal Krycklan catchment, located in Northern Sweden. The stream network and initiation points were extracted from a gridded digital elevation model (DEM) of 5-meter resolution, and then compared with the stream network initiation points (heads) observed during the spring flood (freshet) period in 2012. From the results of the study, it was clearly seen that the observed stream heads and the stream heads appearing in the stream network map extracted from DEM did not agree very well. 49% of the total observed stream heads (49) fell onto the low order stream branches and headwater streams derived from the DEM. Only few of them exactly matched the modeled stream heads. Moreover, the modeled stream network was much denser than the observed stream network, and so the simple raster based dynamic model developed could not well represent the dynamic stream network extension in the real system. Most headwater streams in the study catchment were man-made ditches, which were dug to drain water wetlands and to increase forest productivity. The majority of observed stream heads were formed by seepage from the saturated surrounding soils, while only a few of them were formed by saturation overland flow. On the other hand, the dynamic stream network derived from the DEM suggested that the number of streams of lower order and their lengths was sensitive to change in streamflow, especially during the high flow episode.
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Yu, Songyan. "Spatio-temporal dynamics and hydro-ecology of intermittent streams in eastern Australia". Thesis, Griffith University, 2019. http://hdl.handle.net/10072/389088.
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Intermittent streams that cease to flow for some period of most years are prevalent across global river networks. Their spatial extent is projected to increase in regions experiencing drying trends related to climate change and water extraction for human uses. Intermittent streams sustain biodiversity by hosting a unique combination of aquatic, amphibious, and terrestrial assemblages as a result of their wet and dry phases. Compared to perennial streams, the ecological values of intermittent streams are not well-appreciated or understood, and thus intermittent streams are less commonly incorporated into policy, management, and regulatory decisions. As research on intermittent streams is increasing, there have been strident calls for better recognition and protection of intermittent streams. This thesis aims to develop new methods to address some key issues related to spatio-temporal dynamics and hydro-ecology of intermittent streams, with a focus on eastern Australia.
River channel drying caused by intermittent stream flow is a widely-recognised factor shaping stream ecosystems. There is a strong need to quantify spatio-temporal variations in the hydrology of intermittent streams over broad spatial scales to inform ecological understanding and management. This is challenging because observational stream gauges are sparsely distributed and provide only point estimates of discharge. In this study, I developed models to simulate monthly discharge across river catchments. Due to the common issue of over-estimating low flows in discharge simulations, I also identified appropriate zero flow thresholds to mitigate this uncertainty. I quantified spatial and temporal patterns of flow intermittency for every stream segment within river networks of five major catchments in south-eastern Queensland (SEQ), eastern Australia. Results showed that the temporal dynamics of flow intermittency varied dramatically inter-annually over the period of 1900-2016, with the proportion of intermittent streams ranging in length from 3 % to nearly 100% of river networks, but there was no evidence of an increasing trend towards flow intermittency over this period. This approach to generating spatially explicit and catchment-wide estimates of streamflow intermittency can facilitate improved ecological understanding and management of intermittent streams.
Compared with monthly discharge simulations, daily discharge simulations can provide more detailed representation of the dynamic aspects of hydrological processes and potentially enables more ecologically relevant characterisation of hydrology. However, models of daily stream flow are more complex and often need to take river routing processes into account. I developed models to simulate daily stream flows for contiguous sub-catchments across entire river networks in two hydro-climatically distinctive regions (SEQ vs. the Tamar River
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catchment). I evaluated the models in terms of their ability to represent different ecologically important components of flow regime and quantified environmental correlates of differences in model accuracy within and between regions. The models showed generally good performance in both regions. However, average- and high flows were better predicted than low flows in SEQ because it is difficult to represent climate and hydrogeological processes influencing the low-flow part of the hydrograph. Spatial variation in flow characteristics revealed the highly dynamic nature of flow permanence in space and time, with intermittent flows affecting between 29% and 80% of the river network over the period of 1911-2017. I discuss the pros and cons of the applications of modelled monthly and daily flows, and conclude that the appropriate choice of modelling time step depends on the primary objectives of the research. The monthly time-step is suitable for quantifying ecologically relevant spatial and temporal variations in streamflow intermittency, but may be insufficient for studies aimed at quantifying ecological responses to short term flow events.
The hydrological variability of intermittent streams poses challenges for resident aquatic biota which require access to permanent surface water-bodies to persist during dry spells and to recolonise suitable habitats when flows resume. However, research to quantify the dynamics and environmental determinants of variation in surface water extent is usually conducted over limited spatial and/or temporal extents. One of the biggest barriers to this kind of research is the difficulty in obtaining observed data of surface water extent across river networks. In this study, I demonstrated a newly-developed field method for rapid surface water assessment, and then developed predictive models relating observed water extent to environmental attributes at 241 surveyed stream segments in SEQ. I used the models to predict daily variations in surface water dynamics throughout entire river networks over the past century, based on available long-term environmental attributes. Descriptors of surface water extent could be accurately modelled, with good internal and external validation performance. Long-term variations in surface water extent were highly dynamic through space and time, although the overall length of river networks with surface water remained relatively stable from year to year. This study provides valuable insights into the potential priority conservation areas for aquatic biota across the study region.
Systematic conservation prioritisation methods are increasingly being applied to freshwater ecosystems to identify candidate areas for ecosystem management and biodiversity protection. However, applications with emphasis on intermittent streams are scarce. The hydrological variability of intermittent streams means that the spatial distribution of dry season aquatic refuges within river networks and the temporal dynamics of hydrological connectivity between them are critical for the persistence of aquatic biodiversity. I developed a new approach to incorporating both surface water persistence and hydrological connectivity into systematic conservation prioritisation in intermittent streams. I also included multiple freshwater fish species distributions as explicit targets for habitat prioritisation, and incorporated estimates of their relative mobility to maximise potentially re-colonisable stream length from refuges. Compared with the situation without mobility, the inclusion of species mobility could significantly reduce the number of aquatic refuges required to meet the set conservation targets. High priority aquatic refuges were widely distributed across the study river networks, encompassing streams in various orders from main stems to headwaters. The research can help enhance both the resistance and resilience of freshwater biodiversity in intermittent stream ecosystems.
The thesis concludes with practical learnings from these modelling studies for intermittent stream research and management, namely, 1) that discharge simulations (monthly or daily) throughout river networks confirmed the prevalence of intermittent streams and revealed the highly dynamic nature of flow intermittency over space and time; 2) that spatial and temporal dynamics of surface water availability within stream reaches can be modelled through the combination of observed surface water extent with long-term environmental attributes; and 3) that systematic prioritisation of aquatic refuges by incorporating both surface water persistence and hydrological connectivity enables to efficiently meet conservation targets for species representation and cost-effective conservation management. The thesis also concludes with future challenges and directions for intermittent stream research.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
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McIntyre, Rebecca Elise Sinclair. "Soil biogeochemistry and flooding in intermittent streams of the semi-arid Pilbara region". University of Western Australia. School of Plant Biology, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0115.
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[Truncated abstract] Most of Australia, and large areas of many other continents, is drained by intermittent rivers and streams, however comparatively few biogeochemical studies have been completed for these systems. Intermittent, dryland streams are highly dynamic environments subject to unpredictable and sporadic flow. Natural disturbance from lengthy drought periods and sudden floods are typical for these systems. Without adequate baselines for natural disturbances, it is difficult to quantify other effects from anthropogenic disturbance such as dewatering, land clearing, and urbanisation, or climate change. This thesis presents work from a four-year study examining the biogeochemistry of nitrogen (N), phosphorus (P) and carbon (C) in soils and sediments of two intermittent streams (Barnett Creek and Pirraburdoo Creek) in the Pilbara region of north-west Australia. The Pilbara is an area of ancient geology and highly weathered environments that is undergoing rapid development yet is poorly understood from an ecological perspective. The principal objectives of this thesis were to determine: i) how flooding affects the spatiotemporal patterns of nutrients in intermittent stream landscapes; ii) the role of flooding in N and C mineralisation and microbial dynamics; and iii) the connections between benthic algae, microbes and nutrient availability in channel sediments. To address these objectives, three field studies and two incubation experiments were conducted. Field studies at Barnett Creek indicated that flooding reduced the spatial heterogeneity of available soil nutrients and microbes in the stream landscape, and that topography (relative elevation) in the stream landscape was of less importance in influencing nutrient and microbial patterns than flooding or landscape position. ... Field studies at Pirraburdoo Creek indicated that microbial biomass and activity increased in benthic algal mats during mat senescent stages, and decreased after flooding when mat biomass peaked. Benthic algae grew rapidly in gravel run environments after flooding, while declining in pools, and demonstrated moderate N limitation and strong P limitation. Pools had two to eight times greater NO3-N, three to five times more total N, and two to three times more labile P, OC and total C than either pools after flooding, or runs before or after flooding. Hence, the pools at Pirraburdoo Creek represented a local, interflood store of nutrients in otherwise nutrient-poor landscape, when connectivity to upstream reaches or upland environments was weak or non-existent. This thesis provides the first detailed analysis of soil and sediment biogeochemical responses to flooding for intermittent streams in the Pilbara region and for semi-arid Australia. Further pressing questions raised by this work include: What is the key pulse size and frequency for maintaining Pilbara riparian communities as well as soil microbial function? How do the spatio-temporal nutrient and microbial patterns observed persist over (i) multi-decadal scales, (ii) mega-spatial (larger landscape to regional) scales, (iii) different flood frequency-magnitude regimes, and (iv) different stream sizes? Stream biogeochemistry is a burgeoning field, and it is therefore reasonable to expect such existing gaps in knowledge may be addressed in the near future.
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Nicholas, Hillary Dianne. "Estimating Surface Water Presence and Infiltration for Intermittent Streams in the Semi-arid Southwest". Thesis, The University of Arizona, 2012. http://hdl.handle.net/10150/238891.
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Ephemeral streams with spatially and temporally variable flow are important ecological settings in semi-arid desert environments that until now have been poorly characterized. Our quantitative analysis explores how intermittent stream hydrology varies across geomorphic (mountain streams to desert washes) and climatic gradients (150-400 mm precipitation) in Southern Arizona. Stream channels were instrumented for the first time with a co-deployment of vertical profiles of subsurface temperature sensors, and electrical resistance (ER) sensors on the bed surface. HYDRUS 1-D was used to simulate vertical unsaturated flow, and differences along hydrologic, topographic, and climatic gradients were compared. Annual surface water presence varied < 1%-82% of the year, and reach-normalized infiltration water volumes were 20,000-2,500,000 m³/(km y). Surface water presence was correlated with geomorphic gradient, and infiltration volumes were correlated with surface water presence. This sensor co-deployment method has shown that ER sensors alone are necessary to estimate infiltration in semi-arid, poorly-sorted, coarse desert channels.
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McKenzie-Smith, Fiona Julie y n/a. "Habitat and Hydrological Variability in Sub-Tropical Upland Streams in South-East Queensland". Griffith University. Australian School of Environmental Studies, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030725.142256.
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Headwater streams are extremely vulnerable to the consequences of land-use change as they are tightly coupled with the surrounding landscape. Understanding the natural processes that influence the structure and function of these ecosystems will improve our understanding of how land-use change affects them. Benthic substratum habitat was investigated in a sub-tropical headwater stream by quantifying temporal change to sediment texture of surface sediments (less than 10cm), over four years. Hydrological characteristics were also surveyed in detail, as hydrological regime is a primary determinant of sediment transportation. Additionally, measures of hydro-geological features - hydraulic conductivity and groundwater depth were made in order to explore features of sediment habitat that extend beyond the sediment-water interface. Whilst the typical discharge pattern was one of intermittent base flows and infrequent, yet extreme flood events associated with monsoonal rain patterns, the study period also encompassed a drought and a one in hundred year flood. Rainfall and discharge did not necessarily reflect the actual conditions in the stream. Surface waters were persistent long after discharge ceased. On several occasions the stream bed was completely dry. Shallow groundwater was present at variable depths throughout the study period, being absent only at the height of the drought. The sediments were mainly gravels, sand and clay. Changes in sediment composition were observed for fine particulates (size categories less than 2mm). The grain size change in the finer sediment fractions was marked over time, although bedload movement was limited to a single high discharge event. In response to a low discharge regimen (drought), sediments characteristically showed non-normal distributions and were dominated by finer materials. High-energy discharge regimes (flood) were characterised by coarsening of sands and a diminished clay fraction. Particulate organic matter from sediments showed trends of build-up and decline with the high and low discharge regimes, respectively. Benthic habitats were described according to prevailing hydro-geological parameters. Faunas from sediment substratum samples were associated with identified habitat categories. The fauna reflected the habitat variability in terms of hydrological disturbance of the substratum structure and intermittency of discharge. An applied multivariate procedure was used to correlate temporally changing environmental parameters and faunal abundance data. Faunas were correlated with a group of variables dominated by either discharge variables or sediment textural parameters. Sediment characteristics that affect substratum quality and substratum preference at the micro-scale were investigated via hypotheses testing. A model of carbon loss was used to determine how long particulate organic matter could potentially sustain microbial activity under experimental conditions. An estimate of up to 200 days was determined from this laboratory experiment. Secondly, enriched carbon isotopes were used in a field-based experiment to establish a link between sediments and macrofauna. Enrichment via organic sediments was found for various detritivorous and carnivorous taxa. In the 'third' experiment, artificial treatments were applied to elucidate substratum preference. Fauna was offered the choice of variable quantities of clay and/or quality of organic matter. There were no significant preferences found for the different substratum treatments, although further investigation is needed and a different outcome from this method may be achieved under more benign field conditions than those encountered during this experiment. Finally, the study was set within a context of the primary features of scale. Climate and hydrological features, including linkages with the alluvial aquifer and terrestrial ecosystem, and their potential to change within 'ecological time' are perceived as critical to understanding the role of benthic sediment substratum.
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McKenzie-Smith, Fiona Julie. "Habitat and Hydrological Variability in Sub-Tropical Upland Streams in South-East Queensland". Thesis, Griffith University, 2003. http://hdl.handle.net/10072/366461.
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Headwater streams are extremely vulnerable to the consequences of land-use change as they are tightly coupled with the surrounding landscape. Understanding the natural processes that influence the structure and function of these ecosystems will improve our understanding of how land-use change affects them.
Benthic substratum habitat was investigated in a sub-tropical headwater stream by quantifying temporal change to sediment texture of surface sediments (less than 10cm), over four years. Hydrological characteristics were also surveyed in detail, as hydrological regime is a primary determinant of sediment transportation. Additionally, measures of hydro-geological features - hydraulic conductivity and groundwater depth were made in order to explore features of sediment habitat that extend beyond the sediment-water interface.
Whilst the typical discharge pattern was one of intermittent base flows and infrequent, yet extreme flood events associated with monsoonal rain patterns, the study period also encompassed a drought and a one in hundred year flood. Rainfall and discharge did not necessarily reflect the actual conditions in the stream. Surface waters were persistent long after discharge ceased. On several occasions the stream bed was completely dry. Shallow groundwater was present at variable depths throughout the study period, being absent only at the height of the drought.
The sediments were mainly gravels, sand and clay. Changes in sediment composition were observed for fine particulates (size categories less than 2mm). The grain size change in the finer sediment fractions was marked over time, although bedload movement was limited to a single high discharge event. In response to a low discharge regimen (drought), sediments characteristically showed non-normal distributions and were dominated by finer materials. High-energy discharge regimes (flood) were characterised by coarsening of sands and a diminished clay fraction. Particulate organic matter from sediments showed trends of build-up and decline with the high and low discharge regimes, respectively.
Benthic habitats were described according to prevailing hydro-geological parameters. Faunas from sediment substratum samples were associated with identified habitat categories. The fauna reflected the habitat variability in terms of hydrological disturbance of the substratum structure and intermittency of discharge. An applied multivariate procedure was used to correlate temporally changing environmental parameters and faunal abundance data. Faunas were correlated with a group of variables dominated by either discharge variables or sediment textural parameters.
Sediment characteristics that affect substratum quality and substratum preference at the micro-scale were investigated via hypotheses testing. A model of carbon loss was used to determine how long particulate organic matter could potentially sustain microbial activity under experimental conditions. An estimate of up to 200 days was determined from this laboratory experiment. Secondly, enriched carbon isotopes were used in a field-based experiment to establish a link between sediments and macrofauna. Enrichment via organic sediments was found for various detritivorous and carnivorous taxa. In the ‘third’ experiment, artificial treatments were applied to elucidate substratum preference. Fauna was offered the choice of variable quantities of clay and/or quality of organic matter. There were no significant preferences found for the different substratum treatments, although further investigation is needed and a different outcome from this method may be achieved under more benign field conditions than those encountered during this experiment.
Finally, the study was set within a context of the primary features of scale. Climate and hydrological features, including linkages with the alluvial aquifer and terrestrial ecosystem, and their potential to change within ‘ecological time’ are perceived as critical to understanding the role of benthic sediment substratum.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Australian School of Environmental Studies
Faculty of Environmental Sciences
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Creed, Cari K. "Identifying Controls on Patterns of Intermittent Streamflow in Three Streams of the American Southwest| A Geospatial Approach". Thesis, University of Louisiana at Lafayette, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10681171.
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Despite a rising interest in intermittent river systems, landscape influences on long-term wetting and drying patterns of streamflow are not well understood. There has been a significant increase in the presence of intermittent rivers worldwide due to climate change and subsequent increases in groundwater abstraction, and these effects are intensified in already arid regions such as the American Southwest. Consequently, the spatial extent of wet and dry reaches of Arizona’s Agua Fria River, Cienega Creek, and San Pedro River has been documented by citizen scientists for several years. Citizen science involves the use of trained members of the public for data collection, and the analysis of datasets produced from citizen science projects have become a huge asset to the scientific community. Here, we synthesize the most current data (1999–2016) to determine what stream and valley characteristics act as drivers for patterns of surface water flow. Geologic, geomorphic, and land cover characteristics of these rivers were analyzed via aerial imagery and Digital Elevation Models within ArcGIS 10.3 in conjunction with the Soil and Water Assessment Tool model. Principal Component Analysis was used in order to assess trends across sites. A set of landscape intermittency metrics was produced and then further analyzed using Multiple Linear Regression. We found that land cover had a significant (p-value < 0.01) positive correlation with reach average (i.e., the proportion of channel wet). Physical watershed and channel characteristics each had a negative correlation with both intermittency metrics (i.e., wet/dry status and reach average). However, their results were not significant to the 0.05 level. This study begins to shed light on the drivers of landscape intermittency patterns of desert streams and demonstrates the utility of citizen science in regard to the study of intermittent river systems.
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Belemtougri, Patindé Axel. "Compréhension et caractérisation de l'intermittence du réseau hydrographique en Afrique : développements méthodologiques et applications hydrologiques". Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS318.
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Les cours d’eau intermittents sont des cours d’eau qui cessent de couler à un moment donné dans l’espace et le temps. Cependant, la compréhension de la variabilité spatio-temporelle des cours d’eau intermittents ainsi que leur localisation précise dans le réseau hydrographique reste limitée en raison d’un manque de données (hydrométriques, hydrographiques, etc.…). Ces difficultés sont accentuées dans les régions à données limitées comme l’Afrique et cette thèse vise principalement à développer des approches méthodologiques qui s'appuient sur des modèles de forêts aléatoires (Random Forest) ainsi que des analyses statistiques pour caractériser la distribution spatiale des cours d’eau intermittents et mieux appréhender les mécanismes de contrôle de l’intermittence en Afrique afin de pallier les lacunes d’observations. D’abord, cette thèse s’est focalisée à l’échelle régionale au Burkina Faso où 49 stations de jaugeage des cours d’eau avec au minimum quatre ans de données sur la période 1955-1985 ont été examinées. Le nombre moyen de mois à débit nul par an ((Ndry) ̅) a été utilisé pour définir quatre classes croissantes d'intermittence du débit à savoir : permanent (0-1 mois à débit nul), faiblement intermittent (2-4), fortement intermittent (5-7), éphémère (8-12). Une analyse en composante principale (ACP) réalisée sur les 49 stations de jaugeages a montré que, bien que l’ordre de Strahler et la précipitation moyenne annuelle influencent la répartition géographique des différentes classes d’intermittence au Burkina Faso, la perméabilité moyenne et la surface amont des bassins versants expliquent principalement cette répartition. Cette étude suggère que la saisonnalité de la précipitation au Burkina Faso rend également saisonnier l’écoulement des cours d’eau à moins que les processus hydrogéologiques ne soient impliqués, notamment à travers la contribution des aquifères au débit de base pendant les périodes d’étiage. L’approche de prédiction par Random Forest a permis d’estimer sur le réseau hydrographique LCS que 83% de la longueur totale des cours d’eau au Burkina Faso sont intermittents contre 98% dans le réseau hydrographique nationale de référence (IGB-BNDT). Ensuite, à l’échelle de l’Afrique, 1125 stations de jaugeage avec au moins 4 ans de données sont examinées sur la période 1958-1991. Plusieurs modèles Random Forest ont été entrainés à relier les classes d’intermittence observée au droit des stations de jaugeage aux valeurs caractéristiques de 15 variables environnementales clés identifiées. L’indice d’aridité (P/ETP), la surface amont des bassins versants et l’évapotranspiration potentielle moyenne annuelle ont été identifiés comme les facteurs de contrôle les plus importants de l’intermittence à l’échelle continentale de l’Afrique. Cela se confirme d’autant plus que la majorité des stations classées intermittentes dans l’échantillon analysé ont des valeurs d’évapotranspiration potentielle moyenne annuelle qui sont supérieures à la précipitation moyenne annuelle (c.-à-d. indice d’aridité < 1). Cette étude prédit sur le réseau hydrographique LCS qu’en Afrique 44 % en longueur des cours d’eau sont permanents tandis que 56 % sont intermittents (9 % faiblement intermittents, 31 % fortement intermittents, 16 % éphémères). Les prédictions du modèle capturent en général la distribution spatiale de l’intermittence dans les réseaux hydrographiques nationaux de référence de l’Afrique du Sud, du Bénin, de Madagascar, du Mali et un peu moins au Burkina Faso. Enfin, cette thèse s’est appesantie sur les difficultés des réseaux hydrographiques globaux et continentaux à reproduire la variabilité spatiale de la densité de drainage observée sur les réseaux hydrographiques nationaux de référence des différents pays en Afrique. Une méthode simple pour extraire les cours d’eau des MNT (Modèle Numérique de Terrain) à partir de surface contributive (Amin) variable spatialement a été développéeIntermittent rivers are rivers that stop flowing at some point in space and time. However, the understanding of the spatio-temporal variability of intermittent rivers as well as their precise location in the hydrographic network remains limited due to a lack of data (hydrometric, hydrographic, etc..). These difficulties are accentuated in data-limited regions such as Africa and this thesis aims to develop methodological approaches that rely on Random Forest models and statistical analyses to characterize the spatial distribution of intermittent rivers and to better understand the controlling factors of intermittency in Africa in order to overcome the observation gaps. Firstly, this thesis focused on the regional scale in Burkina Faso where 49 stream gauging stations with at least four years of data over the period 1955-1985 were examined. The mean number of months with zero flow per year ((Ndry) ̅) was used as a predictor to define four increasing classes of flow intermittency namely: permanent (0-1 months with zero flow), weakly intermittent (2-4), highly intermittent (5-7), ephemeral (8-12). A principal component analysis (PCA) performed on 49 gauging stations showed that, although the Strahler order and the average annual precipitation influence the geographical distribution of the different intermittency classes in Burkina Faso, the average permeability and the upstream catchment area mainly explain this distribution. This study suggests that the seasonality of precipitation in Burkina Faso also makes streamflow seasonal regardless of mean annual precipitation unless hydrogeological processes are involved, notably through the contribution of aquifers to baseflow during low-flow periods. The Random Forest model estimated that 88% of the total length of the rivers in Burkina Faso are intermittent compared to 98% in the national reference hydrographic databases (IGB-BNDT). Secondly, at the African scale, 1125 gauging stations with at least 4 years of data are examined over the period 1958-1991. Several Random Forest models were trained to relate the classes of intermittency observed at the gauging stations to the characteristic values of the key environmental variables identified (15). This model calibration identified, in order of importance, the aridity index (P/ETP), upstream catchment area, and mean annual potential evapotranspiration as the most important controlling factors of intermittency at the continental scale in Africa. This is further confirmed by the fact that the majority of gauges stations classified as intermittent in the sample analyzed have mean annual potential evapotranspiration values that are higher than the mean annual precipitation (i.e, aridity index < 1). This study predicts that in Africa 44% of the river length is permanent while 56% is intermittent (9% weakly intermittent, 31% highly intermittent, 16% ephemeral). The model predictions generally capture the spatial distribution of intermittency in the national reference hydrographic database of South Africa, Benin, Madagascar, and Mali somewhat less so in Burkina Faso. Finally, this thesis focused on the difficulties of global and continental river networks to reproduce the spatial variability of the observed drainage density in the national reference hydrographic database of different countries in Africa. A simple method for extracting streams from DEM (Digital Elevation Model) with a spatially variable contributing area (Amin) was developed
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Bernal, Berenguer Susana. "Nitrogen storm responses in an intermittent Meditterranean stream". Doctoral thesis, Universitat de Barcelona, 2006. http://hdl.handle.net/10803/1436.
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The amount of dissolved inorganic nitrogen delivered to streams and groundwater has substantially increased in the last decades due to anthropogenic impacts. This fact has stimulated research on processes related to the nitrogen cycling in order to elucidate the ability of terrestrial and aquatic ecosystems in controlling nitrogen loads. Some of these studies pointed out during storms streamwater chemistry is significantly altered. However, because of the inherent difficulty of an extensive field experimental setting for dealing with episodic storms, studies focused on hydrological processes or stream solute dynamics during storms rely on a very limited number of events. Hydrobiogeochemical processes have been mainly studied in temperate experimental catchments and little attention has been paid to Mediterranean catchments. Recent studies have stressed the fragility of Mediterranean regions in front of the global change and because of that Mediterranean regions should become hot spots for present and future studies.The main goal of the present thesis was to study the variability of nutrient dynamics, in particular nitrogen, during stormflow in relation to baseflow conditions in Fuirosos, an intermittent stream draining a small Mediterranean catchment (Part I). As a secondary objective (Part II), solute dynamics in Fuirosos were compared with those measured at one of its main tributaries, the Grimola stream. Biotitic granodiorite was an important fraction of the Fuirosos catchment, whereas the Grimola catchment was underlain by leucogranite. The Fuirosos stream had an alluvial zone and it was flanked by a well developed riparian forest, whereas the Grimola stream had not a significant alluvial zone, neither a well developed riparian area. Thereby, the effect of (i) catchment size, (ii) lithology and (iii) the presence of an alluvial-riparian zone on stream hydrogrochemistry were assessed by comparing the Fuirosos and Grimola streams.
The Fuirosos Stream Watershed, a relatively undisturbed Mediterranean ecosystem that can not be considered a N-saturated catchment, leaks to the stream most of the nitrogen loss in the form of nitrate (57 %). This figure contrast with that reported for other pristine tropical and humid catchments where nitrogen export is mainly in the form of dissolved organic nitrogen. In particular, nitrate is mainly mobilized during stormflow conditions (from 52 % to 80 % of the annual yield). Contrastingly, most of the dissolved organic carbon export occurs during baseflow conditions (from 40 to 70 % of the annual yield). These results point to a decoupling between soil nitrification and nutrient uptake by biota, which brings about the leaking of nitrate to the stream. Hydrochemistry in this Mediterranean intermittent stream is highly variable within and in between years. The antecedent moisture conditions and the magnitude of storm events are key factors on shaping the hydrological responses to storm events. However, storm episodes that occur during similar climatological and hydrological conditions produce different streamwater chemistry depending upon the time of the year. This is so, mainly because of the influence of the summer drought period on streamwater chemistry. Both, the mixing model (EMMA) and the spectral analysis approaches, point out that groundwater is the most important contributor to stormflow in Fuirosos. Nonetheless, the EMMA approach emphasizes how stream water and nitrate sources vary throughout the year. Our results stress the importance of sampling storms during all seasons to draw general conclusions about watershed processes. The mixing model shows that nitrate is retained by biota in the Fuirosos alluvial zone only when streamflow is lower than 80 l/s. Above this threshold, the system is not efficient in retaining nitrate arriving from the catchment. This result might be keep on mind when establishing the importance of near- and in-stream processes for regulating catchment nitrate loads since a major fraction of the annual nitrate export usually occurs during stormflow conditions in many catchments. The spectral analysis also shows that the variability of stream nitrate concentrations is more damped in Fuirosos than in Grimola. This is attributed to the buffer effect that biota has on nitrate concentrations in the Fuirosos alluvial zone, which retards its delivery in relation to the Grimola catchment.
"Efecte de les pluges en la dinàmica del nitrogen en una riera intermitent i mediterrània"
La quantitat de nitrogen dissolt que arriba avui dia als nostres rius i aqüífers és substancialment major a la de fa un parell de dècades a resultes de l'activitat antròpica. Aquest fet ha estimulat força la recerca dels processos relacionats amb el ciclatge del nitrogen, amb la intenció d'esbrinar la capacitat que tenen els ecosistemas terrestres i aquàtics per controlar les càrregues de nitrat que els hi arriben. Alguns d'aquests estudis indiquen que durant les tempestes s'altera de forma substancial la química de l'aigua del riu. Això no obstant, la major part dels treballs realitzats es recolzen en un nombre limitat d'episodis, donada la dificultat inherent al mostreig intensiu de camp a l'hora d'estudiar les respostes hidrològiques i la dinàmica dels soluts durant les crescudes. Tradicionalment, la comunitat científica s'ha dedicat a l'estudi dels processos hidrobiogeoquímics de regions temperades i tropicals, i desafortunadament, les conques Mediterrànies no han estat objecte de la seva atenció. Estudis recents alerten de la fragilitat de les regions Mediterrànies enfront del canvi global, i per tant, urgeixen els estudis focalitzats en aquests ecosistemes.
El principal objectiu d'aquesta tesi ha estat l'estudi de la variabilitat de la dinàmica dels nutrients, en particular del nitrogen, durant les crescudes en relació a la seva dinàmica en condicions de cabal basal en una riera intermitent, Fuirosos, en una conca Mediterrània. La hidrologia i la dinàmica dels soluts a la riera de Fuirosos s'ha comparat amb les de la Grimola, un dels seus efluents més importants. Hi ha diferències litològiques notables entre les dues conques. A més la riera de Fuirosos té zona al.luvial i està flanquejada per un bosc de ribera ben desenvolupat, mentre que la riera de Grimola no té zona al.luvial ni tampoc una zona riberenca ben diferenciada. Per tant, els efectes de (i) la mida de la conca, (ii) la litologia, i (iii) la presència d'una zona al.luvial i riberenca sobre la hidrobiogeoquímica d'un riu, van poder ésser contrastats comparant les rieres de Fuirosos i Grimola. L'estudi es va realitzar al Parc Natural del Montnegre-Corredor al Vallès Oriental entre els anys 1998 i 2004.
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Sarremejane, R. (Romain). "Community assembly mechanisms in river networks:exploring the effect of connectivity and disturbances on the assembly of stream communities". Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526218632.
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Abstract Community assembly results from a combination of deterministic and stochastic mechanisms, whose relative effects can vary in response to environmental heterogeneity, connectivity, disturbance regimes and anthropogenic stressors. Understanding how community assembly mechanisms vary in response to environmental changes and connectivity is crucial for the management and conservation of river ecosystems. In this thesis, I tested the effects of connectivity and natural flow disturbances on riverine invertebrate communities by assessing assembly mechanism changes in response to (I) habitat connectivity, (II) seasonal flow intermittency and (III) inter–annual hydrological variability. I also conducted a field experiment to test for (IV) the effects of human–induced nutrient enrichment on community assembly of microorganisms (diatoms and aquatic fungi) and stream ecosystem functioning under different environmental settings. Invertebrate community assembly changed gradually with habitat connectivity. While limited dispersal resulted in higher community variability in the most isolated streams, mass effects caused community homogenization in the most connected ones. Natural and human induced disturbances lead to changes in the relative importance of deterministic and stochastic factors but often through different, or even opposite, mechanisms depending on the natural background of the ecosystem and organism type considered. For instance, seasonal drying and high–flow periods in intermittent Mediterranean rivers promoted deterministic and stochastic assembly processes respectively, whereas environmental sorting and stochastic processes respectively dominated during high and low flow years in boreal streams. Diatom and fungal communities responded differently to nutrient enrichment, with detrital processes and fungal communities responding more in naturally acidic than in circumneutral streams. The results of this thesis highlight the complexity of community assembly mechanisms: they tend to be highly context dependent and temporally variable. Therefore, stream bioassessment and conservation will benefit from explicitly incorporating connectivity and natural disturbance regimes. Assessing the interactive effects of connectivity and disturbances at the river network scale would provide a greater understanding of community assembly mechanisms and river ecosystem functioningTiivistelmä Eliöyhteisöjen koostumus heijastelee determinististen ja stokastisten mekanismien vuorovaikutusta. Niiden suhteellinen merkitys vaihtelee suhteessa yhteisöjen kytkeytyneisyyteen sekä luontaisiin ja ihmisen aiheuttamiin häiriöihin. Yhteisöjen säätelymekanismit vaihtelevat jokiverkoston eri osissa ja tietoa tästä vaihtelusta tarvitaan jokiekosysteemien hoidon kehittämiseksi. Tässä tutkielmassa testasin elinympäristöjen kytkeytyneisyyden ja luontaisten häiriöiden (virtaamavaihtelut) vaikutuksia jokien selkärangatonyhteisöihin. Suoritin myös kenttäkokeen, jossa testattiin ihmisen aiheuttaman rehevöitymisen vaikutuksia mikro–organismeihin (piilevät, mikrobit) ja ekosysteemitoimintoihin erilaisissa ympäristöoloissa (luontaisesti happamat vs. neutraalit purot). Selkärangattomien yhteisökoostumus muuttui asteittain jokiverkostossa. Yhteisökoostumuksen vaihtelu oli suurinta eristäytyneimmissä latvapuroissa, kun taas isommissa, uomaston keskivaiheilla sijaitsevissa koskissa voimakas levittäytyminen eri suunnista (ns. massatekijät) aiheutti yhteisöjen rakenteen homogenisoitumista. Kuivuusjaksot ja niitä seuraavat korkean virtaaman jaksot edistivät determinististen prosessien merkitystä Välimeren alueen joissa, kun taas boreaalisissa puroissa Pohjois–Suomessa äärevät virtaamaolot, erityisesti poikkeuksellisen kuivat kesät, edistivät satunnaismekanismien vaikutusta. Perustuottajat (piilevät) ja hajottajat (akvaattiset sienet) vastasivat eri tavoin ravinnelisäykseen. Sienten hajotustoiminta nopeutui ravinnelisäyksen myötä, mutta vain luontaisesti happamissa puroissa. Tämän opinnäytetyön tulokset korostavat yhteisön kokoonpanomekanismien monimutkaisuutta: ne ovat usein erittäin tilanneriippuvaisia ja ajallisesti vaihtelevia. Siksi jokien ekologisen tilan arvioinnissa tulisi huomioida tutkimuspaikkojen kytkeytyneisyys jokimaisemassa
Libros sobre el tema "Intermittent streams"
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DeLong, Lewis L. Estimating average dissolved-solids yield from basins drained by ephemeral and intermittent streams, Green River basin, Wyoming. Cheyenne, Wyo: Dept. of the Interior, U.S. Geological Survey, 1988.
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Vance, Linda K. Geographically isolated wetlands and intermittent/ephemeral streams in Montana: Extent, distribution, and function. Helena, Mont: Montana Natural Heritage Program, 2009.
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Vance, Linda K. Geographically isolated wetlands and intermittent/ephemeral streams in Montana: Extent, distribution, and function. Helena, Mont: Montana Natural Heritage Program, 2009.
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V, Zale Alexander, ed. The Physicochemistry, flora, and fauna of intermittent prairie streams: A review of the literature. Washington, D.C: U.S. Dept. of the Interior, Fish and Wildlife Service, Research and Development, 1989.
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Intermittent Rivers and Ephemeral Streams. Elsevier, 2017. http://dx.doi.org/10.1016/c2015-0-00459-2.
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Boulton, Andrew, Thibault Datry y Núria Bonada. Intermittent Rivers and Ephemeral Streams: Ecology and Management. Elsevier Science & Technology Books, 2017.
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Boulton, Andrew J., Thibault Datry y Núria Bonada. Intermittent Rivers and Ephemeral Streams: Ecology and Management. Elsevier Science & Technology Books, 2017.
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Library, The Law. Excess Spoil, Coal Mine Waste, and Buffers for Perennial and Intermittent Streams. Createspace Independent Publishing Platform, 2018.
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Vance, Linda K. Literature review: Hydrology-ecology relationships in Montana Prairie wetlands and intermittent/ephemeral streams. 2013.
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Lee, Yu Man. Amphibian communities and physical characteristics of intermittent streams in old-growth and young forest stands in western Oregon. 1997.
Buscar texto completoCapítulos de libros sobre el tema "Intermittent streams"
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del Campo, Rubén, Arnaud Foulquier, Gabriel Singer y Thibault Datry. "Plant Litter Decomposition in Intermittent Rivers and Ephemeral Streams". En The Ecology of Plant Litter Decomposition in Stream Ecosystems, 73–100. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-72854-0_5.
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Hanczewski, Sławomir y Maciej Stasiak. "Point-to-Group Blocking in 3-Stage Switching Networks with Multicast Traffic Streams". En Service Assurance with Partial and Intermittent Resources, 219–30. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-540-27767-5_22.
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Stanlake, G. J. y A. J. Landwer. "Rapid bioassessment of intermittent streams in the Upper Brazos River watershed". En Global Environmental Biotechnology, 559–65. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-017-1711-3_48.
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Perera, M. D. D., T. M. C. I. Madhushani y P. I. A. Gomes. "Importance of Leaving Intermittent Rivers and Ephemeral Streams (Ires) Untouched in a Sustainably Built Environment". En Lecture Notes in Civil Engineering, 887–97. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-3471-3_60.
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Hodda, Mike y Walter Traunspurger. "Nematodes from extreme and unusual freshwater habitats." En Ecology of freshwater nematodes, 109–50. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789243635.0004.
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Abstract This chapter discusses the ecology and biogeography of nematodes from freshwater environments that are extreme in temperature, chemical composition, variability, or isolation. Described and compared are the compositions of nematode faunas from hot or mineral springs, pools and bogs in polar regions, intermittent lakes or pools or streams, freshwater pools in bromeliads or tree hollows, stemflow, fresh groundwaters, and caves. Comparisons of the nematode faunas from these extreme habitats with those from more typical freshwater environments are also provided. Also discussed are nematodes with evolutionary affinities to freshwaters that are found in estuarine sediments along with nematodes from freshwaters with evolutionary affinities to otherwise marine taxa. The emphasis is on broad ecological patterns rather than on detailed species interactions with the various freshwater environments. Thus, the chapter focuses on genera or higher taxa rather than species.
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Branquinho, Cristina, Carla Gonzalez, Adelaide Clemente, Pedro Pinho y Otília Correia. "The Impact of the Rural Land-Use on the Ecological Integrity of the Intermittent Streams of the Mediterranean 2000 Natura Network". En Nitrogen Deposition, Critical Loads and Biodiversity, 229–41. Dordrecht: Springer Netherlands, 2014. http://dx.doi.org/10.1007/978-94-007-7939-6_25.
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Navarrete-Opazo, A., E. A. Dale y Gordon S. Mitchell. "Therapeutic Potential of Intermittent Hypoxia: Lessons from Respiratory Motor Plasticity". En Translational Research in Environmental and Occupational Stress, 31–42. New Delhi: Springer India, 2014. http://dx.doi.org/10.1007/978-81-322-1928-6_4.
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Serebrovskaya, T. V. "Lessons from a 20-Year Investigation of Intermittent Hypoxia: Principles and Practices". En Translational Research in Environmental and Occupational Stress, 267–74. New Delhi: Springer India, 2014. http://dx.doi.org/10.1007/978-81-322-1928-6_22.
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Pischik, Elena y Raili Kauppinen. "Potential Role of Oxidative Damage in Neurological Manifestations of Acute Intermittent Porphyria". En Oxidative Stress and Free Radical Damage in Neurology, 293–311. Totowa, NJ: Humana Press, 2010. http://dx.doi.org/10.1007/978-1-60327-514-9_16.
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Haw, R. C., J. K. Foss y J. F. Foss. "Vorticity Based Intermittency Measurements in a Single Stream Shear Layer". En Advances in Turbulence 2, 90–95. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-83822-4_15.
Texto completoActas de conferencias sobre el tema "Intermittent streams"
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Ninov, Plamen y Tzviatka Karagiozova. "MONITORING AND INVESTIGATION OF INTERMITTENT RIVERS IN BULGARIA". En XXVII Conference of the Danubian Countries on Hydrological Forecasting and Hydrological Bases of Water Management. Nika-Tsentr, 2020. http://dx.doi.org/10.15407/uhmi.conference.01.01.
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River flows could be defined according to their surface hydrologic stream duration as either perennial or temporary. Normally perennial streams flow throughout the year, while temporary streams lack surface flow for some periods of the year. Temporary streams are classified as intermittent or ephemeral. Intermittent streams flow in some periods as result of snowmelt and eventually elevated groundwater tables during the periods of increased precipitations. Intermittent streams are poorly represented in existing river monitoring programs in Bulgaria and seldom are objects of regular monitoring. Only in several gauging stations exist hydrological time series. Furthermore, intermittent and ephemeral streams are not adequately protected by current legislation and management strategies in Bulgaria and generally are neglected. The authors discuss the climatic, hydrological and soil conditions in different part of the country as the major factors determining their origin and distribution. Covering the whole territory of Bulgaria the authors identify four main types of intermittent streams as: 1) intermittent flows as result of Mediterranean climatic impact located in the southern part of the country; 2) sinking intermittent flows as result of specific geological and soil characteristics, 3) intermittent flows in large karst and loess areas and finally 4) the sinking flows in alluvium depositions mainly along the large mainstreams. Nevertheless, the limited number of gauging stations built up at these rivers some hydrological information is collected and statistical results are presented as duration curves of temporal rivers, hydrographs with seasonal characteristics etc. Intermittent streams have a hydrologic flow regime with very specific characteristics that place them as interact between land and water. Unfortunately, in Bulgaria there are poorly mapped, recognized, and protected but they have a critical influence on the ecological health of networks. There exists a strong need for new approaches to scientifically study, the structure and function of temporal streams. The construction of monitoring network for the regular registration of their hydrological regime is surely the first required step for their future detailed ingestions, use and protection.
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Warix, Sara R. y Sarah E. Godsey. "BASEFLOW CONTRIBUTION TO INTERMITTENT STREAMS IN A SEMI-ARID HEADWATER NETWORK". En GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-333934.
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Yildirim, Sinan, Kamer Kaya, Soner Aydin y Hakan Bugra Erentug. "Differentially Private Frequency Sketches for Intermittent Queries on Large Data Streams". En 2020 IEEE International Conference on Big Data (Big Data). IEEE, 2020. http://dx.doi.org/10.1109/bigdata50022.2020.9377786.
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Zdanowski, Sarah E. y Katie H. Costigan. "GEOMORPHIC CLASSIFICATION OF INTERMITTENT RIVERS AND EPHEMERAL STREAMS IN DIFFERENT ECOREGIONS OF THE CONTINENTAL UNITED STATES". En Joint 53rd Annual South-Central/53rd North-Central/71st Rocky Mtn GSA Section Meeting - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019sc-326577.
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Maharjan, Madan. "IMPACTS OF HIGH-FREQUENCY INTERMITTENT PUMPING ON GROUNDWATER AND SURFACE WATER INTERACTIONS ALONG THE REGULATED STREAMS". En Joint 69th Annual Southeastern / 55th Annual Northeastern GSA Section Meeting - 2020. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020se-344531.
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Riddell, Jill, Benjamin Rau y Christopher Russoniello. "LONG-TERM TEMPERATURE TRENDS IN INTERMITTENT HEADWATER STREAMS IN THE FERNOW EXPERIMENTAL FOREST, WEST VIRGINIA, USA". En GSA Connects 2023 Meeting in Pittsburgh, Pennsylvania. Geological Society of America, 2023. http://dx.doi.org/10.1130/abs/2023am-394690.
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Ferrante, Francesco, Frederic Gouaisbaut, Ricardo G. Sanfelice y Sophie Tarbouriech. "Observer-based control design for linear systems in the presence of limited measurement streams and intermittent input access". En 2015 American Control Conference (ACC). IEEE, 2015. http://dx.doi.org/10.1109/acc.2015.7172068.
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Tritthart, Michael, Daniel Wildt y Gabriele Weigelhofer. "A Model-Based Framework For The Estimation Of The Self-Purifying Capacity Of Intermittent Streams Under A Changing Climate". En Proceedings of the 39th IAHR World Congress From Snow to Sea. Spain: International Association for Hydro-Environment Engineering and Research (IAHR), 2022. http://dx.doi.org/10.3850/iahr-39wc252171192022585.
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Ferris, Gerald, Sarah Newton y Minh Ho. "Watercourse Crossing Program: 10 Years Performance". En ASME-ARPEL 2019 International Pipeline Geotechnical Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ipg2019-5314.
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Abstract Plains Midstream Canada (PMC) completes a watercourse crossing program as part of its overall integrity management program. The approximately 9,900 kilometers of operating and discontinued pipelines are evaluated within the watercourse crossing program. The pipelines are located throughout the Canadian Provinces of Alberta, Saskatchewan, Manitoba and Ontario. The terrain traversed ranges from relatively steep near the Rocky Mountains to extremely flat in northern Alberta and Southern Ontario. Since 2008, PMC’s systematic watercourse crossing program has evolved and now consists of approximately 5,000 individual watercourse crossings. The bankfull width of the watercourses ranges from less than 1 m for intermittent streams to more than 700 m at major rivers. The watercourse crossing program is subjected to a continuous improvement process, with a focus on key learnings from pipeline failures, free spans and exposure. This paper describes the results from the program over the last 10 years and highlights program improvements. In addition, data from a failure and three free spans on the pipelines now owned by PMC, but where the exposure, free span or failure occurred prior to PMC purchasing the pipelines were added to expand the available data for the key learnings.
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Vicedo, J., S. Vilmin, W. N. Dawes y A. M. Savill. "Intermittency Transport Modeling of Separated Flow Transition". En ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38719.
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An intermittency transport model is proposed for modeling separated-flow transition. The model is based on earlier work on prediction of attached flow bypass transition and is applied for the first time to model transition in a separation bubble at various degrees of free-stream turbulence. The model has been developed so that it takes into account the entrainment of the surrounding fluid. Experimental investigations suggest that it is this phenomena which ultimately determines the extent of the separation bubble. Transition onset is determined via a boundary layer correlation based on momentum thickness at the point of separation. The intermittent flow characteristic of the transition process is modeled via an intermittency transport equation. This accounts for both normal and streamwise variation of intermittency and hence models the entrainment of surrounding flow in a more accurate manner than alternative prescribed intermittency models. The model has been validated against the well established T3L semicircular leading edge flat plate test case for three different degrees of free-stream turbulence characteristic of turbomachinery blade applications.
Informes sobre el tema "Intermittent streams"
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Albright, Jeff, Kim Struthers, Lisa Baril, John Spence, Mark Brunson y Ken Hyde. Natural resource conditions at Glen Canyon National Recreation Area: Findings & management considerations for selected resources. National Park Service, abril de 2022. http://dx.doi.org/10.36967/nrr-2293112.
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Glen Canyon National Recreation Area (GLCA) encompasses more than 0.5 million ha (1.25 million ac) and extends over 322 km (200 mi) from its northern boundary in southern Utah to its southern boundary in northern Arizona. It is one of the most rugged, remote, and floristically diverse national parks on the Southern Colorado Plateau (Thomas et. al 2005) and has more than 4,900 km (3,045 mi) of waterways flowing through its eight Hydrologic Unit Code (HUC 8) watersheds. GLCA’s larger perennial rivers include the Colorado, Escalante, Dirty Devil, San Juan, and Paria, with smaller perennial and intermittent streams flowing into each of these rivers. After the creation of the Glen Canyon Dam, Lake Powell formed, covering 13% of the park’s total land area when full and the national recreation area attracts over 4 million visitors annually, and in 2019 GLCA ranked 19th highest in recreational visits out of all national parks. The National Park Service Natural Resource Condition Assessment Program selected GLCA to pilot its new NRCA project series. NRCA projects evaluate the best available science to provide park managers with reliable, actionable information pertaining to natural resource conditions in their park. For the park-selected focal study resources, this includes consideration of drivers and stressors known or suspected of influencing resource conditions; assessment of current conditions and trends for indicators of condition; and potential near-term and future activities or actions managers can consider, improving their knowledge and management of natural resources in parks. For focal resources that lack adequate data to assess current conditions, a gap analysis is provided (in lieu of a condition assessment) to highlight the present status of knowledge of the resource and to suggest useful indicators, data, and studies for further consideration and investigation. Park managers are encouraged to identify information needs and pose questions during the NRCA scoping process, with the understanding that information will be provided to help address those needs and answer those questions when possible. For a comprehensive list of GLCA managers’ questions and needs, please refer to Appendix A, Table A-1. The focus of GLCA’s NRCA study was the water-dependent resources—tinajas, springs & seeps, including water quality, riparian zone, amphibians, including the northern leopard frog (Lithobates pipiens), and small, native fishes—that are found off the mainstem Colorado River. Managers were interested in these particular environments and the natural resources that depend on them because they are less studied, and the habitats are “biodiversity hotspots” due to the intersection of complex desert and freshwater ecosystems in a region limited by water. The following summaries highlight the key findings of GLCA’s focal resource drivers and stressors (Chapter 2), states (Chapter 3), and manager responses (Chapter 4).
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Carpenter, Forrest. Understanding the Importance of Intermittently Fragmented Stream Habitat for Isolated Westslope Cutthroat Trout (Oncorhynchus clarki lewisi) in the Colville National Forest, Washington. Portland State University Library, enero de 2000. http://dx.doi.org/10.15760/etd.3295.
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Friedler, Eran y Karl G. Linden. Distributed UV LEDs for combined control of fouling of drip emitters and disinfection during irrigation with reclaimed wastewater effluent. Israel: United States-Israel Binational Agricultural Research and Development Fund, 2022. http://dx.doi.org/10.32747/2022.8134144.bard.
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Irrigating crops with reclaimed wastewater, replacing potable water, using drip irrigation has become more common as demands on water supplies have increased. Because of the quality characteristics of treated wastewater, the small size and geometry of drip emitters, and flow characteristics though the emitters, systems can become clogged for physical and biological reasons. Emitters clogging reduces flow and increases the variability of flows between emitters that can lead to crops water stress and thus reduce crop yield. Clogged systems require more energy or more labor- and chemical-intensive maintenance and cleaning, such as with chlorine. Ultraviolet (UV) irradiation, and specifically UV-C (200-300 nm) light emitting diodes (LEDs) have great promise for disinfection and biofouling prevention in irrigation water systems. LEDs are particularly well-suited for decentralized use in drip irrigation systems due to their small size, robust construction, low power requirements, long life, and intermittent operation capability. The main goal of this research was to study and develop UV-LED irradiation technology for reducing biofouling of drip irrigation fed by treated effluent, and to explore whether locating the UV-LEDs along the irrigation line as an integral part of the system could be advantageous.
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Yahav, Shlomo, John Brake y Orna Halevy. Pre-natal Epigenetic Adaptation to Improve Thermotolerance Acquisition and Performance of Fast-growing Meat-type Chickens. United States Department of Agriculture, septiembre de 2009. http://dx.doi.org/10.32747/2009.7592120.bard.
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: The necessity to improve broiler thermotolerance and performance led to the following hypothesis: (a) thethermoregulatory-response threshold for heat production can be altered by thermal manipulation (TM) during incubation so as to improve the acquisition of thermotolerance in the post-hatch broiler;and (b) TM during embryogenesis will improve myoblast proliferation during the embryonic and post-hatch periods with subsequent enhanced muscle growth and meat production. The original objectives of this study were as follow: 1. to assess the timing, temperature, duration, and turning frequency required for optimal TM during embryogenesis; 2. to evaluate the effect of TM during embryogenesis on thermoregulation (heat production and heat dissipation) during four phases: (1) embryogenesis, (2) at hatch, (3) during growth, and (4) during heat challenge near marketing age; 3. to investigate the stimulatory effect of thermotolerance on hormones that regulate thermogenesis and stress (T₄, T₃, corticosterone, glucagon); 4. to determine the effect of TM on performance (BW gain, feed intake, feed efficiency, carcass yield, breast muscle yield) of broiler chickens; and 5. to study the effect of TM during embryogenesis on skeletal muscle growth, including myoblast proliferation and fiber development, in the embryo and post-hatch chicks.This study has achieved all the original objectives. Only the plasma glucagon concentration (objective 3) was not measured as a result of technical obstacles. Background to the topic: Rapid growth rate has presented broiler chickens with seriousdifficulties when called upon to efficiently thermoregulate in hot environmental conditions. Being homeotherms, birds are able to maintain their body temperature (Tb) within a narrow range. An increase in Tb above the regulated range, as a result of exposure to environmental conditions and/or excessive metabolic heat production that often characterize broiler chickens, may lead to a potentially lethal cascade of irreversible thermoregulatory events. Exposure to temperature fluctuations during the perinatal period has been shown to lead to epigenetic temperature adaptation. The mechanism for this adaptation was based on the assumption that environmental factors, especially ambient temperature, have a strong influence on the determination of the “set-point” for physiological control systems during “critical developmental phases.” In order to sustain or even improve broiler performance, TM during the period of embryogenesis when satellite cell population normally expand should increase absolute pectoralis muscle weight in broilers post-hatch. Major conclusions: Intermittent TM (39.5°C for 12 h/day) during embryogenesis when the thyroid and adrenal axis was developing and maturing (E7 to E16 inclusive) had a long lasting thermoregulatory effect that improved thermotolerance of broiler chickens exposed to acute thermal stress at market age by lowering their functional Tb set point, thus lowering metabolic rate at hatch, improving sensible heat loss, and significantly decreasing the level of stress. Increased machine ventilation rate was required during TM so as to supply the oxygen required for the periods of increased embryonic development. Enhancing embryonic development was found to be accomplished by a combination of pre-incubation heating of embryos for 12 h at 30°C, followed by increasing incubation temperature to 38°C during the first 3 days of incubation. It was further facilitated by increasing turning frequency of the eggs to 48 or 96 times daily. TM during critical phases of muscle development in the late-term chick embryo (E16 to E18) for 3 or 6 hours (39.5°C) had an immediate stimulatory effect on myoblast proliferation that lasted for up to two weeks post-hatch; this was followed by increased hypertrophy at later ages. The various incubation temperatures and TM durations focused on the fine-tuning of muscle development and growth processes during late-term embryogenesis as well as in post-hatch chickens.
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Estimating average dissolved-solids yield from basins drained by ephemeral and intermittent streams, Green River basin, Wyoming. US Geological Survey, 1988. http://dx.doi.org/10.3133/wri874222.
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