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1
Higgisson, William, Dianne Gleeson, Linda Broadhurst, and Fiona Dyer. "Genetic diversity and gene flow patterns in two riverine plant species with contrasting life-history traits and distributions across a large inland floodplain." Australian Journal of Botany 68, no. 5 (2020): 384. http://dx.doi.org/10.1071/bt20074.
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Gene flow is a key evolutionary driver of spatial genetic structure, reflecting demographic processes and dispersal mechanisms. Understanding how genetic structure is maintained across a landscape can assist in setting conservation objectives. In Australia, floodplains naturally experience highly variable flooding regimes that structure the vegetation communities. Flooding plays an important role, connecting communities on floodplains and enabling dispersal via hydrochory. Water resource development has changed the lateral-connectivity of floodplain-river systems. One possible consequence of these changes is reduced physical and subsequent genetic connections. This study aimed to identify and compare the population structure and dispersal patterns of tangled lignum (Duma florulenta) and river cooba (Acacia stenophylla) across a large inland floodplain using a landscape genetics approach. Both species are widespread throughout flood prone areas of arid and semiarid Australia. Tangled lignum occurs on floodplains while river cooba occurs along rivers. Leaves were collected from 144 tangled lignum plants across 10 sites and 84 river cooba plants across 6 sites, on the floodplain of the lower and mid Lachlan River, and the Murrumbidgee River, NSW. DNA was extracted and genotyped using DArTseq platforms (double digest RADseq). Genetic diversity was compared with floodplain-river connection frequency, and genetic distance (FST) was compared with river distance, geographic distance and floodplain-river connection frequency between sites. Genetic similarity increased with increasing floodplain-river connection frequency in tangled lignum but not in river cooba. In tangled lignum, sites that experience more frequent flooding had greater genetic diversity and were more genetically homogenous. There was also an isolation by distance effect where increasing geographic distance correlated with increasing genetic differentiation in tangled lignum, but not in river cooba. The distribution of river cooba along rivers facilitates regular dispersal of seeds via hydrochory regardless of river level, while the dispersal of seeds of tangled lignum between patches is dependent on flooding events. The genetic impact of water resource development may be greater for species which occur on floodplains compared with species along river channels.
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Thomas, David H. L. "Artisanal Fishing and Environmental Change in a Nigerian Floodplain Wetland." Environmental Conservation 22, no. 2 (1995): 117–26. http://dx.doi.org/10.1017/s037689290001016x.
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Floodplain wetlands are of major importance in semi-arid Africa, providing agricultural, livestock, forestry, and fisheries, products as well as many other goods and services. Through a case-study of a floodplain wetland in northern Nigeria, it is demonstrated that the factors determining the characteristics of floodplain fishermen, defined in terms of how they fish, where they fish, and when they fish, are spatially and temporally very complex and may best be analysed within a simple systems framework.Despite the important values and functions that floodplains provide, many have been degraded owing to the construction of dams within their catchments. Studies of the social and economic impact of these developments tend to have adopted an ‘ecosystem’ approach to analysis that conceals the socio-economic complexity of the floodplain. However, if proposals to manage the water resources of river basins effectively are to be successfully implemented, it will be essential to understand the complexity of socioeconomic relations of floodplain users and their interaction with the environment. In conclusion, there is a need for much more detailed socio-economic studies that explore the ways in which floodplain inhabitants use the system in space and time.
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Zellman, Kristine L., Piret Plink-Björklund, and Henry C. Fricke. "Testing hypotheses on signatures of precipitation variability in the river and floodplain deposits of the Paleogene San Juan Basin, New Mexico, U.S.A." Journal of Sedimentary Research 90, no. 12 (February 18, 2021): 1770–801. http://dx.doi.org/10.2110/jsr.2020.75.
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ABSTRACTMuch progress has been made in recent years towards a set of recognition criteria for river discharge variability in river channel deposits, and thus sedimentary proxies for precipitation variability. Despite this progress, there is currently no consensus on how different styles of discharge variability are reflected in river sedimentary records, and whether variable-discharge river records from different climate types can be distinguished. Herein, river discharge and precipitation variability in the Paleogene is investigated using associations between river channel and floodplain deposits across the Paleocene–Eocene boundary from the Paleocene upper Nacimiento Formation and the early Eocene San Jose Formation in the San Juan Basin, New Mexico, USA.The succession is identified as deposits of variable-discharge river systems based on shared channel-deposit characteristics with modern and ancient variable-discharge river systems and the proposed facies models, in addition to alternations of poorly drained and well-drained floodplain deposits and/or slickensides indicating alternating wet–dry cycles. A long-term stratigraphic trend toward increasingly well-drained floodplain deposits is also observed and hypothesized to indicate successively more arid conditions from the Paleocene into the early Eocene. Comparisons with modern rivers from various climate zones suggest a long-term shift from a monsoonal climate in the Paleocene, to a fluctuating subhumid climate, ultimately leading to semiarid to arid conditions in the early Eocene. These observations suggest that floodplain deposits may be a better indicator of ambient climate, whereas channel deposits are records for frequency and magnitude of high-intensity precipitation events. Therefore, the existing facies models for variable-discharge rivers that consider only channel facies may not capture critical information needed to make accurate interpretations of paleoclimatic conditions. This study also adds to a growing body of evidence from geologic records of mid-latitude Paleogene river systems suggesting increases in the magnitude or variability of river discharge coinciding with established climate perturbations.
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Vilizzi, Lorenzo, Leigh A. Thwaites, Benjamin B. Smith, Jason M. Nicol, and Chris P. Madden. "Ecological effects of common carp (Cyprinus carpio) in a semi-arid floodplain wetland." Marine and Freshwater Research 65, no. 9 (2014): 802. http://dx.doi.org/10.1071/mf13163.
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Common carp, Cyprinus carpio, is a highly invasive fish species across freshwater systems of south-eastern Australia, and especially in semi-arid floodplain wetlands. However, multi-component, large-scale experimental studies on carp effects on such ecosystems are scarce. This is in spite of demands to prioritise management and control of carp for the rehabilitation of habitats across the Murray–Darling Basin. A 2-year, large-scale field experiment in a terminal wetland of the lower River Murray (South Australia) evaluated the effects of free-ranging carp on water transparency, aquatic macrophytes (biomass and cover), zooplankton density, benthic invertebrates (density, richness and diversity) as well as native fish. Within 1 year since artificial inundation, transparency sharply decreased and this was accompanied by a decrease in aquatic macrophyte biomass and cover, a fluctuation in zooplankton density, and a decrease in benthic invertebrate richness and diversity. Also, the decreases in transparency and benthic invertebrate richness were significantly related to carp biomass, which averaged 68.0 kg ha–1 and induced a shift from clear- to turbid-water state. Following a flood event, increased connectivity caused carp to further access the newly inundated areas.
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Sheldon, Fran, Stuart E. Bunn, Jane M. Hughes, Angela H. Arthington, Stephen R. Balcombe, and Christine S. Fellows. "Ecological roles and threats to aquatic refugia in arid landscapes: dryland river waterholes." Marine and Freshwater Research 61, no. 8 (2010): 885. http://dx.doi.org/10.1071/mf09239.
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Dryland rivers are renowned for their periods of ‘boom’ related to the episodic floods that extend over vast floodplains and fuel incredible production, and periods of ‘bust’ where the extensive channel network is restricted to the permanent refugial waterholes. Many of these river systems are unregulated by dams but are under increasing pressure, especially from water abstraction and overland flow interception for agriculture and mining. Although some aquatic organisms with desiccation-resistant life stages can utilise ephemeral floodplain habitats, the larger river waterholes represent the only permanent aquatic habitat during extended periods of low or no flow. These waterholes act as aquatic refugia in an otherwise terrestrial landscape. Variable patterns of connection and disconnection in space and time are a fundamental driver of diversity and function in these dryland river systems, and are vital for dispersal and the maintenance of diverse populations, generate the spatial and temporal variability in assemblage structure for a range of different organisms and fuel the productivity that sustains higher trophic levels. Changes to natural patterns of connection and disconnection of refugial waterholes, owing to water-resource development or climate change, will threaten their persistence and diminish their functional capacity to act as aquatic refugia.
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Campbell, Cherie Joy, Fiona Linda Freestone, Richard P. Duncan, Will Higgisson, and Sascha Jade Healy. "The more the merrier: using environmental flows to improve floodplain vegetation condition." Marine and Freshwater Research 72, no. 8 (2021): 1185. http://dx.doi.org/10.1071/mf20303.
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Environmental flows are increasingly being used to restore degraded floodplain vegetation; however, the type of flow regime required for recovery to healthy condition can vary depending on the extent of degradation before restoration. Regulation of the River Murray has affected floodplain ecosystems at many locations, including Bottle Bend Reserve, in south-western New South Wales, Australia. Within Bottle Bend Reserve, tangled lignum (Duma florulenta) dominates sections of the higher floodplain elevations. Lignum is an important and widely distributed Australian shrub occurring in arid and semiarid river systems within the Murray–Darling and Lake Eyre Basins. In an effort to restore floodplain vegetation, three environmental flows were delivered to Bottle Bend Reserve between 2013 and 2016. Flows varied in magnitude, leading to a mosaic of different regimes across the area. Condition surveys were undertaken over 1 year, namely, before, during and after delivery of the September 2016 environmental flow. This study found that the greatest response occurred in lignum plants with no recent environmental water, although lignum plants with one or two recent environmental flows still responded relative to the control. Lignum was in a better condition at sites that received more environmental flows, demonstrating the value of increased frequency of flows in recovering vegetation health.
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T. Kingsford, Richard, Rachael F. Thomas, and Alison L. Curtin. "Conservation of wetlands in the Paroo and Warrego River catchments in arid Australia." Pacific Conservation Biology 7, no. 1 (2001): 21. http://dx.doi.org/10.1071/pc010021.
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Irrigation proposals to divert water from the Paroo and Warrego Rivers in arid Australia will affect their aquatic ecosystems. These two are the last of 26 major rivers in the Murray-Darling Basin without large dams and diversions. Knowledge of the extent of their biodiversity value is critical to assessing likely impacts. During the 1990 flood, 1.73 million ha of wetlands, or 12.5% of the land surface of the Paroo and Warrego River catchments, were flooded. Flooded wetland area in the respective catchments was 781 330 ha and 890 534 ha. Most of the wetland area (97%) was floodplain, with 37 freshwater lakes (>50 ha) occupying 2.5% of the wetland area and 177 salt lakes covering 0.8%. A high diversity and abundance of biota depend on these wetlands. Only 7% of the wetland area, all in the Paroo catchment, is in conservation reserves. New South Wales has a high proportion of the wetland area on the Paroo (60%) and a substantial proportion of the wetland area on the Warrego River (23%). Queensland, the upstream state, will influence the ecology of the entire catchment areas of both river systems through its proposed water management plan. Any resulting extraction practices will have detrimental ecological consequences within a decade. Conservation of wetlands is usually site-focused and reflects a paradigm of conservation based on reservation of parcels of land. However, wetlands are dependent on water that is seldom adequately protected. Intergovernment co-operation should protect the entire catchment of the Paroo River from major diversions and stop further development on the Warrego River. This would do more for the conservation of wetlands than the formal reservation of small parts of their catchments.
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Gleason, C. J., L. C. Smith, D. C. Finnegan, A. L. LeWinter, L. H. Pitcher, and V. W. Chu. "Technical Note: Semi-automated classification of time-lapse RGB imagery for a remote Greenlandic river." Hydrology and Earth System Sciences Discussions 12, no. 1 (January 29, 2015): 1311–27. http://dx.doi.org/10.5194/hessd-12-1311-2015.
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Abstract. River systems in remote environments are often challenging to monitor and understand where traditional gauging apparatus are difficult to install or where safety concerns prohibit field measurements. In such cases, remote sensing, especially terrestrial time lapse imaging platforms, offer a means to better understand these fluvial systems. One such environment is found at the proglacial Isortoq River in southwest Greenland, a river with a constantly shifting floodplain and remote Arctic location that make gauging and in situ measurements all but impossible. In order to derive relevant hydraulic parameters for this river, two RGB cameras were installed in July of 2011, and these cameras collected over 10 000 half hourly time-lapse images of the river by September of 2012. Existing approaches for extracting hydraulic parameters from RGB imagery require manual or supervised classification of images into water and non-water areas, a task that was impractical for the volume of data in this study. As such, automated image filters were developed that removed images with environmental obstacles (e.g. shadows, sun glint, snow) from the processing stream. Further image filtering was accomplished via a novel automated histogram similarity filtering process. This similarity filtering allowed successful (mean accuracy 79.6%) supervised classification of filtered images from training data collected from just 10% of those images. Effective width, a hydraulic parameter highly correlated with discharge in braided rivers, was extracted from these classified images, producing a hydrograph proxy for the Isortoq River between 2011 and 2012. This hydrograph proxy shows agreement with historic flooding observed in other parts of Greenland in July 2012 and offers promise that the imaging platform and processing methodology presented here will be useful for future monitoring studies of remote rivers.
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Gleason, C. J., L. C. Smith, D. C. Finnegan, A. L. LeWinter, L. H. Pitcher, and V. W. Chu. "Technical Note: Semi-automated effective width extraction from time-lapse RGB imagery of a remote, braided Greenlandic river." Hydrology and Earth System Sciences 19, no. 6 (June 26, 2015): 2963–69. http://dx.doi.org/10.5194/hess-19-2963-2015.
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Abstract. River systems in remote environments are often challenging to monitor and understand where traditional gauging apparatus are difficult to install or where safety concerns prohibit field measurements. In such cases, remote sensing, especially terrestrial time-lapse imaging platforms, offer a means to better understand these fluvial systems. One such environment is found at the proglacial Isortoq River in southwestern Greenland, a river with a constantly shifting floodplain and remote Arctic location that make gauging and in situ measurements all but impossible. In order to derive relevant hydraulic parameters for this river, two true color (RGB) cameras were installed in July 2011, and these cameras collected over 10 000 half hourly time-lapse images of the river by September of 2012. Existing approaches for extracting hydraulic parameters from RGB imagery require manual or supervised classification of images into water and non-water areas, a task that was impractical for the volume of data in this study. As such, automated image filters were developed that removed images with environmental obstacles (e.g., shadows, sun glint, snow) from the processing stream. Further image filtering was accomplished via a novel automated histogram similarity filtering process. This similarity filtering allowed successful (mean accuracy 79.6 %) supervised classification of filtered images from training data collected from just 10 % of those images. Effective width, a hydraulic parameter highly correlated with discharge in braided rivers, was extracted from these classified images, producing a hydrograph proxy for the Isortoq River between 2011 and 2012. This hydrograph proxy shows agreement with historic flooding observed in other parts of Greenland in July 2012 and offers promise that the imaging platform and processing methodology presented here will be useful for future monitoring studies of remote rivers.
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Fenner, Aaron L., Chris R. Pavey, and C. Michael Bull. "Behavioural observations and use of burrow systems by an endangered Australian arid-zone lizard, Slater's skink (Liopholis slateri)." Australian Journal of Zoology 60, no. 2 (2012): 127. http://dx.doi.org/10.1071/zo12047.
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The endangered Slater’s skink (Liopholis slateri) is restricted to the river floodplain habitat of central Australia. It is an obligate burrower and creates complex, multientrance burrow systems in the mound of soil that builds up around the base of some shrubs and small trees. We provide detailed information about the behaviour and use of the burrow systems by Slater’s skink. The behaviour of lizards remained consistent over the four months (October–January) of the study, and lizards performed almost all of their daily activities around their burrow/mound systems. Lizards also showed signs of sociality, as pairs of lizards were observed to share occupancy of single burrow systems over extended periods, and demonstrated a high level of tolerance to conspecifics. This study emphasises the importance of the burrow systems for the daily life of this lizard and suggests that conservation measures should focus on ensuring that the lizards have a reliable supply of stable and suitable burrows in their preferred habitat.
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Lamsdell, James C., Linda Lagebro, Gregory D. Edgecombe, Graham E. Budd, and Pierre Gueriau. "Stylonurine eurypterids from the Strud locality (Upper Devonian, Belgium): new insights into the ecology of freshwater sea scorpions." Geological Magazine 156, no. 10 (January 30, 2019): 1708–14. http://dx.doi.org/10.1017/s0016756818000936.
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AbstractThe Upper Famennian (Upper Devonian) Strud locality has yielded very abundant and diversified flora as well as vertebrate and arthropod faunas. The arthropod fauna, mostly recovered from fine shales deposited in a calm, confined floodplain habitat including temporary pools, has delivered a putative insect and various crustaceans including eumalacostracans and notostracan, spinicaudatan and anostracan branchiopods. Here we present the Strud eurypterids, consisting of semi-articulated juvenile specimens assigned to Hardieopteridae recovered from the pool and floodplain deposits, as well as larger isolated fragments of potential adults recovered from stratigraphically lower, coarser dark sandy layers indicative of a higher-energy fluvial environment. The Strud fossils strongly suggest that, as proposed for some Carboniferous eurypterids, juvenile freshwater eurypterids inhabited sheltered nursery pools and migrated to higher-energy river systems as they matured.
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Stave, J., G. Oba, and N. C. Stenseth. "Temporal changes in woody-plant use and the ekwar indigenous tree management system along the Turkwel River, Kenya." Environmental Conservation 28, no. 2 (June 2001): 150–59. http://dx.doi.org/10.1017/s0376892901000157.
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Indigenous systems of management for regulating extraction of non-timber forest products (NTFP) have not been well documented in arid zone grazing lands. Conservation projects have therefore lacked information on customary rights to trees, while they have enforced systems of tree resource management that often conflicted with the indigenous system. This study focused on the indigenous tree tenure system of the Turkana pastoralists called ekwar (plural ngikwarin). The indigenous tree management system in 15.4 km2 of the Turkwel River floodplain woodlands near Lodwar, Kenya was investigated. The study began in 1990 after impoundment of the Turkwel Gorge Dam. In 1990 and 1998, Turkana pastoralists were interviewed about the ekwar. In individual ngikwarin woody cover, wood volume and woody-plant density were measured, and wood extraction assessed in terms of stems and twigs removed by the pastoralists and the urban population of Lodwar. Intensity of charcoal burning was assessed in terms of the density of earthen kilns, and livestock impact in terms of browsing frequency on woody plants. Potential Acacia tortilis litter production was estimated and an ekwar quality index developed to describe woodland productivity conditions. Tree produce was shared with and leased to friends and relatives. Woody cover showed no significant changes, while woody-plant density and volume declined, over the 8-year period. The Turkana usually do not cut live trees, but use dead trees and dry tree-parts for making charcoal. Increased kiln density and increased extraction of tree-parts were considered to be indicative of increased pressure on the riverine woodlands. Livestock browsing did not seem to contribute to woodland degradation. However, decline in woody-plant density and volume might have contributed to the reduction of litter production of A. tortilis. Trends in woodlands in the floodplain might be associated with damming of the Turkwel River and local anthropogenic pressures. Also, the ekwar system of tree tenure seemed to be threatened by the official forestry policy that it be ignored. Incorporating the ekwar system into the forestry conservation policy may achieve sustainable use and improve conservation of the Turkwel River floodplain woodlands.
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Choy, S. C., C. B. Thomson, and J. C. Marshall. "Ecological condition of central Australian arid-zone rivers." Water Science and Technology 45, no. 11 (June 1, 2002): 225–32. http://dx.doi.org/10.2166/wst.2002.0399.
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Australian arid-zone rivers are known to be ecologically variable and go through “boom and bust” cycles based on highly variable and unpredictable flow regimes. They are facing increasing pressure from land and water resources development and, whilst they are considered to be still in relatively good condition, no studies have yet been carried out to verify this. Such baseline studies are crucial if we are to assess any ecological changes in response to development and management interventions. The ecological condition of four of these endorheic rivers (Georgina, Diamantina, Cooper-Thomson and Bulloo) flowing into the Lake Eyre and Bulloo Basins in central Australia was assessed using several criteria (level of human influence, habitat condition, water chemistry and aquatic macroinvertebrate composition). Using criteria based on the level of human influence, most of the sites were assessed to be relatively unimpacted (reference) condition. The most discernible and widespread impact was riparian and bank damage by stock access. However, the level of this impact was considered to be only moderate. Most aquatic macroinvertebrates found in the area are considered to be opportunistic and tolerant of a wide range of environmental conditions, but with their life histories known to be linked to flow conditions. Their trophic guild was dominated by collectors and predators. The AusRivAS modelled observed to expected values of macroinvertebrate composition indicated that there were differences in ecological condition between sites (e.g. different waterholes) and between times (e.g. seasons and years). Overall, 75% of sites were assessed to be good condition with the remainder being mildly impaired. Water chemistry of the sites was characterised by high spatial and temporal variability with low conductivity and alkaline pH, relatively high turbidity, total nitrogen and total phosphorus, and wide-ranging dissolved oxygen. Given the high variability in water quality and ecological condition within a catchment, there was little evidence of any overall difference in these factors between the catchments. However, given that the hydrology of each river system is distinctly different, one might expect some differences in ecological structure and function at finer scale. Periods of hydrological isolation (eg. to allow natural dryouts) as well as the maintenance of natural connectivity (eg. instream, overbank and floodplain wetting) are both necessary for the maintenance of ecological integrity of these systems.
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Broich, M., A. Huete, M. G. Tulbure, X. Ma, Q. Xin, M. Paget, N. Restrepo-Coupe, K. Davies, R. Devadas, and A. Held. "Land surface phenological response to decadal climate variability across Australia using satellite remote sensing." Biogeosciences 11, no. 18 (September 29, 2014): 5181–98. http://dx.doi.org/10.5194/bg-11-5181-2014.
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Abstract. Land surface phenological cycles of vegetation greening and browning are influenced by variability in climatic forcing. Quantitative spatial information on phenological cycles and their variability is important for agricultural applications, wildfire fuel accumulation, land management, land surface modeling, and climate change studies. Most phenology studies have focused on temperature-driven Northern Hemisphere systems, where phenology shows annually recurring patterns. However, precipitation-driven non-annual phenology of arid and semi-arid systems (i.e., drylands) received much less attention, despite the fact that they cover more than 30% of the global land surface. Here, we focused on Australia, a continent with one of the most variable rainfall climates in the world and vast areas of dryland systems, where a detailed phenological investigation and a characterization of the relationship between phenology and climate variability are missing. To fill this knowledge gap, we developed an algorithm to characterize phenological cycles, and analyzed geographic and climate-driven variability in phenology from 2000 to 2013, which included extreme drought and wet years. We linked derived phenological metrics to rainfall and the Southern Oscillation Index (SOI). We conducted a continent-wide investigation and a more detailed investigation over the Murray–Darling Basin (MDB), the primary agricultural area and largest river catchment of Australia. Results showed high inter- and intra-annual variability in phenological cycles across Australia. The peak of phenological cycles occurred not only during the austral summer, but also at any time of the year, and their timing varied by more than a month in the interior of the continent. The magnitude of the phenological cycle peak and the integrated greenness were most significantly correlated with monthly SOI within the preceding 12 months. Correlation patterns occurred primarily over northeastern Australia and within the MDB, predominantly over natural land cover and particularly in floodplain and wetland areas. Integrated greenness of the phenological cycles (surrogate of vegetation productivity) showed positive anomalies of more than 2 standard deviations over most of eastern Australia in 2009–2010, which coincided with the transition from the El Niño-induced decadal droughts to flooding caused by La Niña.
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Broich, M., A. Huete, M. G. Tulbure, X. Ma, Q. Xin, M. Paget, N. Restrepo-Coupe, K. Davies, R. Devadas, and A. Held. "Land surface phenological response to decadal climate variability across Australia using satellite remote sensing." Biogeosciences Discussions 11, no. 5 (May 28, 2014): 7685–719. http://dx.doi.org/10.5194/bgd-11-7685-2014.
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Abstract. Land surface phenological cycles of vegetation greening and browning are influenced by variability in climatic forcing. Quantitative information on phenological cycles and their variability is important for agricultural applications, wildfire fuel accumulation, land management, land surface modeling, and climate change studies. Most phenology studies have focused on temperature-driven Northern Hemisphere systems, where phenology shows annually reoccurring patterns. Yet, precipitation-driven non-annual phenology of arid and semi-arid systems (i.e. drylands) received much less attention, despite the fact that they cover more than 30% of the global land surface. Here we focused on Australia, the driest inhabited continent with one of the most variable rainfall climates in the world and vast areas of dryland systems. Detailed and internally consistent studies investigating phenological cycles and their response to climate variability across the entire continent designed specifically for Australian dryland conditions are missing. To fill this knowledge gap and to advance phenological research, we used existing methods more effectively to study geographic and climate-driven variability in phenology over Australia. We linked derived phenological metrics with rainfall and the Southern Oscillation Index (SOI). We based our analysis on Enhanced Vegetation Index (EVI) data from the MODerate Resolution Imaging Spectroradiometer (MODIS) from 2000 to 2013, which included extreme drought and wet years. We conducted a continent-wide investigation of the link between phenology and climate variability and a more detailed investigation over the Murray–Darling Basin (MDB), the primary agricultural area and largest river catchment of Australia. Results showed high inter- and intra-annual variability in phenological cycles. Phenological cycle peaks occurred not only during the austral summer but at any time of the year, and their timing varied by more than a month in the interior of the continent. The phenological cycle peak magnitude and integrated greenness were most significantly correlated with monthly SOI within the preceding 12 months. Correlation patterns occurred primarily over north-eastern Australia and within the MDB predominantly over natural land cover and particularly in floodplain and wetland areas. Integrated greenness of the phenological cycles (surrogate of productivity) showed positive anomalies of more than two standard deviations over most of eastern Australia in 2009–2010, which coincided with the transition between the El Niño induced decadal droughts to flooding caused by La Niña. The quantified spatial-temporal variability in phenology across Australia in response to climate variability presented here provides important information for land management and climate change studies and applications.
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Stover, Jiana, Edward Keller, Tom Dudley, and Eddy Langendoen. "Fluvial Geomorphology, Root Distribution, and Tensile Strength of the Invasive Giant Reed, Arundo Donax and Its Role on Stream Bank Stability in the Santa Clara River, Southern California." Geosciences 8, no. 8 (August 14, 2018): 304. http://dx.doi.org/10.3390/geosciences8080304.
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Arundo donax (giant reed) is a large, perennial grass that invades semi-arid riparian systems where it competes with native vegetation and modifies channel geomorphology. For the Santa Clara River, CA, changes in channel width and intensity of braiding over several decades are linked in part to high flow events that remove A. donax. Nevertheless, the area of A. donax at the two study sites increased fivefold over a period of 28 years at one site and fourfold over 15 years at the second site. Effects of A. donax on bank stability are compared to those of a common native riparian tree—Salix laevigata (red willow)—at two sites on the banks and floodplain of the Santa Clara River. There is a significant difference of root density of A. donax compared to S. laevigata and the latter has a higher number of roots per unit area at nearly all depths of the soil profile. Tensile root strength for S. laevigata (for roots of 1–6 mm in diameter) is about five times stronger than for A. donax and adds twice the apparent cohesion to weakly cohesive bank materials than does A. donax (8.6 kPa compared to 3.3 kPa, respectively). Modeling of bank stability for banks of variable height suggests that S. laevigata, as compared to A. donax, increases the factor of safety (FS) by ~60% for banks 1 m high, ~55% for banks 2 m high and ~40% for banks 3 m high. For 3 m high banks, the FS for banks with A. donax is <1. This has geomorphic significance because, in the case of A. donax growing near the water line of alluvial banks, the upper 10–20 cm has a hard, resistant near-surface layer overlying more erodible banks just below the near-surface rhizomal layer. Such banks may be easily undercut during high flow events, resulting in overhanging blocks of soil and A. donax that slump and collapse into the active channel, facilitating lateral bank erosion. Therefore, there is a decrease in the lateral stability of channels if the mixed riparian forest is converted to dominance by A. donax.
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Alaghmand, S., S. Beecham, and A. Hassanli. "Impacts of groundwater extraction on salinization risk in a semi-arid floodplain." Natural Hazards and Earth System Sciences 13, no. 12 (December 23, 2013): 3405–18. http://dx.doi.org/10.5194/nhess-13-3405-2013.
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Abstract. In the lower River Murray in Australia, a combination of a reduction in the frequency, duration and magnitude of natural floods, rising saline water tables in floodplains, and excessive evapotranspiration have led to an irrigation-induced groundwater mound forcing the naturally saline groundwater onto the floodplain. It is during the attenuation phase of floods that these large salt accumulations are likely to be mobilised and discharged into the river. This has been highlighted as the most significant risk in the Murray–Darling Basin and the South Australian Government and catchment management authorities have subsequently developed salt interception schemes (SIS). The aim of these schemes is to reduce the hydraulic gradient that drives the regional saline groundwater towards the River Murray. This paper investigates the interactions between a river (River Murray in South Australia) and a saline semi-arid floodplain (Clark's floodplain) that is significantly influenced by groundwater lowering due to a particular SIS. The results confirm that groundwater extraction maintains a lower water table and a higher amount of fresh river water flux to the saline floodplain aquifer. In terms of salinity, this may lead to less solute stored in the floodplain aquifer. This occurs through three mechanisms, namely extraction of the solute mass from the system, reducing the saline groundwater flux from the highland to the floodplain and changing the floodplain groundwater regime from a losing to a gaining one. It is shown that groundwater extraction is able to remove some of the solute stored in the unsaturated zone and this can mitigate the floodplain salinity risk. A conceptual model of the impact of groundwater extraction on floodplain salinization has been developed.
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Souter, Nicholas J., Todd Wallace, Mark Walter, and Richard Watts. "Raising river level to improve the condition of a semi-arid floodplain forest." Ecohydrology 7, no. 2 (January 4, 2013): 334–44. http://dx.doi.org/10.1002/eco.1351.
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Smith, Rhiannon, and Nick Reid. "Carbon storage value of native vegetation on a subhumid–semi-arid floodplain." Crop and Pasture Science 64, no. 12 (2013): 1209. http://dx.doi.org/10.1071/cp13075.
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The protection of carbon (C) stores in the form of remnant native vegetation and soils is crucial for minimising C emissions entering the atmosphere. This study estimated C storage in soils, woody vegetation, dead standing vegetation, coarse woody debris, herbaceous vegetation, litter and roots in plant communities commonly encountered on cotton farms. River red gum was the most valuable vegetation type for C storage, having up to 4.5% C content in the surface (0–5 cm) soil, a total-site C store of 216 ± 28 t ha–1 (mean ± s.e.) and a maximum value of 396.4 t C ha–1. Grasslands were the least C-dense, with 36.4 ± 3.72 t C ha–1. The greatest proportion of C in river red gum sites was in standing woody biomass, but in all other vegetation types and especially grasslands, the top 0–30 cm of the soil was the most C-rich component. Aboveground woody vegetation determined total-site C sequestration, as it strongly influenced all other C-storing components, including soil C. This study illustrates the value of native vegetation and the soil beneath for storing large amounts of C. There is a case for rewarding farmers for maintaining and enhancing remnant vegetation to avoid vegetation degradation and loss of existing C stores.
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Colloff, Matthew J., and Darren S. Baldwin. "Resilience of floodplain ecosystems in a semi-arid environment." Rangeland Journal 32, no. 3 (2010): 305. http://dx.doi.org/10.1071/rj10015.
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Implicit to loss of ecosystem resilience is that systems can shift from one stable state to another as a result of disturbance. We present a conceptual model of ecosystem resilience of floodplains and wetlands in semi-arid environments like those of the Murray–Darling Basin. The model is based on a single state characterised by fluctuating wet and dry phases driven by episodic floods and droughts. It might appear that such a single state is inherently unstable, but stability, and the measure of resilience, is conferred by the capacity of floodplains and wetlands to undergo drought and yet return to a functioning wet phase following inundation as well as to undergo flooding and return to the dry phase following flood recession. Floodplains and wetlands are driven by strong, periodic abiotic disturbances and their ecosystem functions and biogeochemical processes are highly rate-limited, spatiotemporally variable and driven by relatively species-poor assemblages of plants and animals adapted to withstand drought and flooding. Extreme drying due to climatic change and over-allocation of water resources represents the primary mechanism via which resilience is lost.
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Ogden, Ralph, and Martin Thoms. "The importance of inundation to floodplain soil fertility in a large semi-arid river." SIL Proceedings, 1922-2010 28, no. 2 (July 2002): 744–49. http://dx.doi.org/10.1080/03680770.2001.11901813.
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Alaghmand, S., S. Beecham, I. D. Jolly, K. L. Holland, J. A. Woods, and A. Hassanli. "Modelling the impacts of river stage manipulation on a complex river-floodplain system in a semi-arid region." Environmental Modelling & Software 59 (September 2014): 109–26. http://dx.doi.org/10.1016/j.envsoft.2014.05.013.
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Alaghmand, S., S. Beecham, and A. Hassanli. "Fully integrated physically-based numerical modelling of impacts of groundwater extraction on surface and irrigation-induced groundwater interactions: case study Lower River Murray, Australia." Natural Hazards and Earth System Sciences Discussions 1, no. 4 (July 26, 2013): 3577–624. http://dx.doi.org/10.5194/nhessd-1-3577-2013.
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Abstract. Combination of reduction in the frequency, duration and magnitude of natural floods, rising saline water-table in floodplains and excessive evapotranspiration have led to an irrigation-induced groundwater mound forced the naturally saline groundwater onto the floodplain in the Lower River Murray. It is during the attenuation phase of floods that these large salt accumulations are likely to be mobilised and will discharge into the river. The Independent Audit Group for Salinity highlighted this as the most significant risk in the Murray–Darling Basin. South Australian government and catchment management authorities have developed salt interception schemes (SIS). This is to pump the highly saline groundwater from the floodplain aquifer to evaporation basins in order to reduce the hydraulic gradient that drives the regional saline groundwater towards the River Murray. This paper investigates the interactions between a river (River Murray in South Australia) and a saline semi-arid floodplain (Clarks Floodplain) significantly influenced by groundwater lowering (Bookpurnong SIS). Results confirm that groundwater extraction maintain a lower water-table and more fresh river water flux to the saline floodplain aquifer. In term of salinity, this may lead to less amount of solute stored in the floodplain aquifer. This occurs through two mechanisms; extracting some of the solute mass from the system and changing the floodplain groundwater regime from a losing to gaining one. Finally, it is shown that groundwater extraction is able to remove some amount of solute stored in the unsaturated zone and mitigate the floodplain salinity risk.
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Thoms, M., and P. Cullen. "The Impact of Irrigation Withdrawals on Inland River Systems." Rangeland Journal 20, no. 2 (1998): 226. http://dx.doi.org/10.1071/rj9980226.
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Responsible decision making about water extractions in arid and semi-arid areas requires a good understanding of both the physical and biological character of these systems. The intrinsic variability of these systems is an important ecosystem control. Ecological concepts and water management practices developed in temperate areas are inappropriate to these erratic and highly pulsed systems. Key words: Water resource development, environmental flows, environmental impact, management paradigms
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TOOTH, S., T. S. McCARTHY, P. J. HANCOX, D. BRANDT, K. BUCKLEY, E. NORTJE, and S. McQUADE. "THE GEOMORPHOLOGY OF THE NYL RIVER AND FLOODPLAIN IN THE SEMI-ARID NORTHERN PROVINCE, SOUTH AFRICA." South African Geographical Journal 84, no. 2 (September 2002): 226–37. http://dx.doi.org/10.1080/03736245.2002.9713774.
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González, Eduardo, Etienne Muller, Belinda Gallardo, Francisco Antonio Comín, and María González-Sanchis. "Factors controlling litter production in a large Mediterranean river floodplain forest." Canadian Journal of Forest Research 40, no. 9 (September 2010): 1698–709. http://dx.doi.org/10.1139/x10-102.
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Although litter production is an essential floodplain forest function, the drivers and their relative importance remain largely unknown, especially in semi-arid rivers. The influence of forest structure, flooding regime, soil conditions, and litterfall chemistry (a total of 17 variables) on spatial variability of litter production within the Middle Ebro River floodplain forests (northeastern Spain) was examined by monitoring litterfall in 12 forest plots in 2007. Linear mixed effects (LME) models, using stem density (SD), river distance (RD) (or soil total organic C (TOC)), and soil total P (TP) as independent predictors, explained 51% of the variance in litter production, while an alternative LME model using SD and P use efficiency (P-NUE) explained 40%. In particular, litter increased with SD and TP and decreased with RD, P-NUE, and TOC. Based on these results, P limitation appears to be controlling litter production in a rather dry hydrological regime. We hypothesized that a deficient sediment input at the plot scale (especially in the outer floodplain), with flood quality (overbank flooding, ground-water seepage, ponding) being a greater determinant than quantity (flood duration, water table levels), might ultimately be responsible for the spatial variability observed in litter production.
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Alaghmand, S., S. Beecham, J. A. Woods, K. L. Holland, I. D. Jolly, A. Hassanli, and H. Nouri. "Quantifying the impacts of artificial flooding as a salt interception measure on a river-floodplain interaction in a semi-arid saline floodplain." Environmental Modelling & Software 79 (May 2016): 167–83. http://dx.doi.org/10.1016/j.envsoft.2016.02.006.
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Cockayne, B. J., D. Sternberg, D. W. Schmarr, A. W. Duguid, and R. Mathwin. "Lake Eyre golden perch (Macquaria sp.) spawning and recruitment is enhanced by flow events in the hydrologically variable rivers of Lake Eyre Basin, Australia." Marine and Freshwater Research 66, no. 9 (2015): 822. http://dx.doi.org/10.1071/mf14242.
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Understanding the links between fish recruitment and riverine flows is integral for setting priorities for river-management strategies, particularly in hydrologically variable and unpredictable arid and semi-arid zone rivers. In the present study, we used daily and annual otolith age estimates to identify relationships between riverine flow and spawning and recruitment of Lake Eyre golden perch (Macquaria sp.); an endemic fish of the Lake Eyre Basin, central Australia. We found a close association between Lake Eyre golden perch spawning and periods of increased river flow, with most of spawning occurring 0–35 days after the start of these flow events. Spawning occurred throughout the year but was commonly observed during the first flow events proceeding consecutive months of no-flow when water temperatures exceeded 26°C. Spawning was not dependent on floodplain inundation, with most spawning occurring during within-channel flow events. Annual average year-class strength was related to the number of flow events per year, but not total annual discharge, or the number of low-flow days per year. These results highlight the importance of natural within-channel flow patterns to Lake Eyre golden perch spawning and recruitment and demonstrate the importance of maintaining the natural flow regime of Australia’s arid- and semi-arid-zone rivers.
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Baldwin, Darren S., Warren L. Paul, Jessica S. Wilson, Tara Pitman, Gavin N. Rees, and Annaleise R. Klein. "Changes in soil carbon in response to flooding of the floodplain of a semi-arid lowland river." Freshwater Science 34, no. 2 (June 2015): 431–39. http://dx.doi.org/10.1086/681009.
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Ringrose, Susan, Wilma Matheson, Mary Seely, Lin Cassidy, Stephan Coetzee, and Thebe Kemosidile. "Aspects of floodplain deposition in semi-arid ephemeral rivers, examples from the Kuiseb river valley, central Namibia." Transactions of the Royal Society of South Africa 69, no. 3 (September 2, 2014): 187–93. http://dx.doi.org/10.1080/0035919x.2014.953623.
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Northcott, Krista, Douglas C. Andersen, and David J. Cooper. "The influence of river regulation and land use on floodplain forest regeneration in the semi-arid upper Colorado River Basin, USA." River Research and Applications 23, no. 6 (2007): 565–77. http://dx.doi.org/10.1002/rra.1007.
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Mvandaba, Vuyelwa, Denis Hughes, Evison Kapangaziwiri, Jean-Marc Mwenge Kahinda, and Nadia Oosthuizen. "Modelling of channel transmission loss processes in semi-arid catchments of southern Africa using the Pitman Model." Proceedings of the International Association of Hydrological Sciences 378 (May 29, 2018): 17–22. http://dx.doi.org/10.5194/piahs-378-17-2018.
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Abstract. Water availability is one of the major societal issues facing the world. The ability to understand and quantify the impact of key hydrological processes, on the availability of water resources, is therefore integral to ensuring equitable and sustainable resource management. Channel transmission losses are an “under-researched” hydrological process that affects resource availability in many semi-arid regions such as the Limpopo River Basin in southern Africa, where the loss processes amount to approximately 30 % of the water balance. To improve the understanding of these loss processes and test the capability of modelling routines, three approaches using the Pitman model are applied to selected alluvial aquifer environments. The three approaches are an explicit transmission loss function, the use of a wetland function to represent channel-floodplain storage exchanges and the use of a “dummy” reservoir to represent floodplain storage and evapotranspiration losses. Results indicate that all three approaches are able to simulate channel transmission losses with differing impacts on the regional flows. A determination of which method best represents the channel transmission losses process requires further testing in a study area that has reliable observed historical records.
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Domenech, S., F. Espejo, A. Ollero, and M. Sánchez-Fabre. "Recent floods in the Middle Ebro River, Spain: hydrometeorological aspects and floodplain management." Hydrology and Earth System Sciences Discussions 6, no. 5 (September 17, 2009): 5937–76. http://dx.doi.org/10.5194/hessd-6-5937-2009.
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Abstract. The Ebro River has the largest Mediterranean basin in the Iberian Peninsula and the third one by surface among those of the Mediterranean Sea. The middle stretch of this river is especially interesting because it constitutes a very economically important axis of population in a semi-arid environment context. Flooding processes are common in the Middle Ebro River, but the combination among decrease of discharges, dam construction and expansion and reinforcement of defences created an unusually quiet period as regards flooding events during the last quarter of the previous century. Nevertheless, with the turn of the century it seems that the Middle Ebro River has entered into new dynamics, with bigger and more frequent floods, the appearance of which has changed its seasonal nature. The most relevant examples are those of February 2003 and March–April 2007. The present paper examines these recent trends and discusses their possible causes from the points of view of hydro-meteorology, flood management through the use of reservoirs, and floodplain management. The consequences of recent floods in the Middle Ebro River have reopened the debate about possible risk management measures.
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Thorburn, PJ, LJ Mensforth, and GR Walker. "Reliance of creek-side river red gums on creek water." Marine and Freshwater Research 45, no. 8 (1994): 1439. http://dx.doi.org/10.1071/mf9941439.
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Measurements of naturally occurring stable isotopes of hydrogen (2H) and oxygen (18O) were used to determine the importance of creek waters to river red gums (Eucalyptus camaldulensis Dehnh., Myrtaceae) on the banks of creeks in the semi-arid and saline Chowilla floodplain region of South Australia. The 2H and 18O concentrations of water sampled from trees were significantly different from those of the creek water, indicating that, generally, trees were not obtaining all their water from the creek. This was found even in trees overlying highly saline groundwater. Thus, saline groundwater and/or soil water were important water sources for the trees studied. The results indicated that the water relations of these trees are complex, and the trees may be less affected by changes in creek flow and/or salinity than was previously anticipated.
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Annys, Sofie, Tesfaalem Ghebreyohannes, and Jan Nyssen. "Impact of Hydropower Dam Operation and Management on Downstream Hydrogeomorphology in Semi-Arid Environments (Tekeze, Northern Ethiopia)." Water 12, no. 8 (August 8, 2020): 2237. http://dx.doi.org/10.3390/w12082237.
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Due to renewed interest in hydropower dams in the face of climate change, it is important to assess dam operations and management in combination with downstream impacts on rivers in (semi-)arid environments. In this study, the impacts of the Tekeze hydropower dam on downstream hydrology and river morphology were investigated, including impacts under normal and extreme reservoir operation conditions. Field observations, in-depth interviews, repeat terrestrial photographs, multi-year high-resolution satellite images, daily reservoir water levels and data on hourly to daily energy production were collected and studied. The results show that high flows (Q5) have declined (with factor 5), low flows (Q95) have increased (with factor 27), seasonal flow patterns have smoothened, river beds have incised (up to 4 m) and locally aggraded near tributary confluences. The active river bed has narrowed by 31%, which was accelerated by the gradual emergence of Tamarix nilotica and fruit plantations. A new post-dam equilibrium had been reached until it was disrupted by the 2018 emergency release, caused by reservoir management and above-normal reservoir inflow, and causing extensive erosion and agricultural losses downstream. Increased floodplain occupation for irrigated agriculture consequently provides an additional argument for reservoir operation optimization to avoid future risks for riparian communities.
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Filipe, A. F., I. G. Cowx, and M. J. Collares-Pereira. "Spatial modelling of freshwater fish in semi-arid river systems: a tool for conservation." River Research and Applications 18, no. 2 (2002): 123–36. http://dx.doi.org/10.1002/rra.638.
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Aguiar, Francisca C., Maria Teresa Ferreira, and António Albuquerque. "Patterns of exotic and native plant species richness and cover along a semi-arid Iberian river and across its floodplain." Plant Ecology 184, no. 2 (November 24, 2005): 189–202. http://dx.doi.org/10.1007/s11258-005-9064-5.
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Alaghmand, S., S. Beecham, J. A. Woods, K. L. Holland, I. D. Jolly, A. Hassanli, and H. Nouri. "Injection of fresh river water into a saline floodplain aquifer as a salt interception measure in a semi-arid environment." Ecological Engineering 75 (February 2015): 308–22. http://dx.doi.org/10.1016/j.ecoleng.2014.11.014.
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Toledo, Cristian Epifanio, Emanuelly De Moura Silva Almeida, Alexandre Vicente Lopes Neto, Thályta Lharyssa Gonçalves Rodrigues Gonçalves Rodrigues Silva, and Filipe Augusto Rodrigues Santos. "Water loss in transit in an intermittent river in brazilian semi-arid." REVISTA AGRO@MBIENTE ON-LINE 12, no. 3 (October 29, 2018): 177. http://dx.doi.org/10.18227/1982-8470ragro.v12i3.5090.
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Riverwater often comes into contact with the underground flow in aquifers. When this contact
occurs, the river and aquifer are considered to be hydraulically connected. In recent decades, there has
been great interest in trying to to improve understanding of the interactions occuring between superficial and
subterranean water systems. A variety of analytical solutions have been proposed to describe the interaction of
confined and free aquifers with adjacent rivers, including the quantification of the decrease of river flow along
its course. The objective of the current study was to calibrate and validate a loss-in-transit flow model for rivers,
and to evaluate the minimum flow that still permits connectivity between water sources in the Alto Jaguaribe
basin. The methodology used was based on the equation of continuity and mass balance along the study river.
A modified Araújo and Ribeiro equation showed strong applicability to loss-in-transit generation, with a mean
loss in transit of 3.6% km-1, and a Nash and Sutcliffe Efficiency value of 0.29. On the other hand, the classbased
loss of upstream flow generated 4 classes with a mean of 2.6% km-1 and showed great improvement,
reaching an NSE of 0.74 - high efficiency. Minimum flows were below the regular flow recorded by the Ceará
Secretariat of Water Resources, showing that the ability exists in the region hydrological connectivity between
reservoirs in the Alto Jaguaribe basin and for alluvial aquifers to be recharged.
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Cantonati, Poikane, Pringle, Stevens, Turak, Heino, Richardson, et al. "Characteristics, Main Impacts, and Stewardship of Natural and Artificial Freshwater Environments: Consequences for Biodiversity Conservation." Water 12, no. 1 (January 16, 2020): 260. http://dx.doi.org/10.3390/w12010260.
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In this overview (introductory article to a special issue including 14 papers), we consider all main types of natural and artificial inland freshwater habitas (fwh). For each type, we identify the main biodiversity patterns and ecological features, human impacts on the system and environmental issues, and discuss ways to use this information to improve stewardship. Examples of selected key biodiversity/ecological features (habitat type): narrow endemics, sensitive (groundwater and GDEs); crenobionts, LIHRes (springs); unidirectional flow, nutrient spiraling (streams); naturally turbid, floodplains, large-bodied species (large rivers); depth-variation in benthic communities (lakes); endemism and diversity (ancient lakes); threatened, sensitive species (oxbow lakes, SWE); diverse, reduced littoral (reservoirs); cold-adapted species (Boreal and Arctic fwh); endemism, depauperate (Antarctic fwh); flood pulse, intermittent wetlands, biggest river basins (tropical fwh); variable hydrologic regime—periods of drying, flash floods (arid-climate fwh). Selected impacts: eutrophication and other pollution, hydrologic modifications, overexploitation, habitat destruction, invasive species, salinization. Climate change is a threat multiplier, and it is important to quantify resistance, resilience, and recovery to assess the strategic role of the different types of freshwater ecosystems and their value for biodiversity conservation. Effective conservation solutions are dependent on an understanding of connectivity between different freshwater ecosystems (including related terrestrial, coastal and marine systems).
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Medley, Kimberly E. "Patterns of forest diversity along the Tana River, Kenya." Journal of Tropical Ecology 8, no. 4 (November 1992): 353–71. http://dx.doi.org/10.1017/s0266467400006684.
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ABSTRACTTropical forest vegetation occurs within a narrow corridor along the semi-arid lower floodplain of the Tana River, Kenya. An inventory of the woody flora and ecological study of 12 forest areas in the Tana River National Primate Reserve (TRNPR) describe the composition and structure of this riverine forest ecosystem and identify patterns of regional and local diversity. Only 175 species in 49 families are recorded in the woody flora, but the geographic affinities of 98 species are from four major floristic regions in Africa: Zanzibar-Inhambane (31%), Somalia-Masai (16%), Guinea-Congolian (12%), and Zambezian (1%). Ten species are rare and/or disjunct. Forests have a disturbed physiognomy characterized by a low mean height (14.4 m), high species importance attributable to a few trees, low density (409 ha−1) and coverage (23.1 m2 ha−1) of trees > 10 cm dbh, and an abundance of palms and lianes. Changes along the river in sediment deposition and hydrology explain the high diversity of landforms and corresponding forest types in the TRNPR vicinity, but the absence of trees which are most important near Bura, Acacia elalior, and near Wema, Barringtonia racemosa, suggests that the regional diversity of the ecosystem is inadequately protected. Preservation of key resources, such as the endangered primates, should be coupled with protection of the forest heterogeneity that characterizes this dynamic landscape.
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Ogilvie, Andrew, Jean-Christophe Poussin, Jean-Claude Bader, Didier Martin, Gora Ndiaye, and Djiby Dia. "Improved understanding of the Senegal floodplain socio-hydrosystems with multi-scalar earth observations." Proceedings of the International Association of Hydrological Sciences 383 (September 16, 2020): 255–60. http://dx.doi.org/10.5194/piahs-383-255-2020.
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Abstract. In semi-arid regions, the annual floods of alluvial plains, wetlands and lakes provide essential services to millions of farmers, livestock holders and fishers. The scale, number and dispersion of these water bodies limit however their hydrological understanding, whose complexity is exacerbated by the mutual interactions between water and society. Rising availability of high spatial and temporal resolution remote sensing imagery provide novel opportunities to improve the understanding of the hydrology of multiple water bodies and of their ability to support local livelihoods. Multi-scalar interdisciplinary research combining remote sensing, in situ observations, hydrological modelling and farmer interviews was developed to investigate multiple socio-hydrosystems in the Senegal floodplain. Surface water monitoring with MNDWI on multi-spectral imagery (Landsat 5, 7, 8 and Sentinel-2A) is used to identify intra-annual and inter-annual variations in water availability. Validation against field monitoring (R2=0.88) and photointerpretation of drone imagery highlights the benefits of Sentinel's increased resolution to monitor floods of minor surface area and duration and improve the representation of hysteresis in floodplains. Integrated into forthcoming river basin modelling, these results can help simulate the influence of upstream changes on the hydrology and associated services of these complex socio-hydrosystems and improve watershed management.
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Morwood, M. J. "The prehistory of Aboriginal landuse on the upper Flinders River, North Queensland Highlands." Queensland Archaeological Research 7 (January 1, 1990): 3–56. http://dx.doi.org/10.25120/qar.7.1990.126.
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A general theme in Australian prehistory is the development of the distinctive social, economic and technological systems observed in recent Aboriginal societies. Research has demonstrated significant change in the Australian archaeological sequence and general trends of such are shared by numerous regions. Most that have been investigated indicate low density occupation during the Pleistocene and early Holocene with significant increases in site numbers, increased artefact discard rates and dissemination of new technologies and artefact types in mid-to-late Holocene times (e.g. Lourandos 1985). On the other hand, each region has a unique prehistory, range of material evidence and research potential. Our knowledge of Holocene developments in aboriginal subsistence systems, for instance, is largely based upon the history of cycad exploitation in the central Queensland Highlands (Beaton 1982), the appearance of seed grindstones in arid and semi-arid zones (Smith 1986) and evidence for increased emphasis on small-bodied animals in N.E. New South Wales and S.E. Queensland (McBryde 1977:233; Morwood 1987:347).
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Abd-Elaty, Ismail, Hala M. Ghanayem, Martina Zeleňáková, Peter Mésároš, and Osama K. Saleh. "Numerical Investigation for Riverbank Filtration Sustainability Considering Climatic Changes in Arid and Semi-Arid Regions; Case Study of RBF Site at Embaba, Nile Delta, Egypt." Sustainability 13, no. 4 (February 10, 2021): 1897. http://dx.doi.org/10.3390/su13041897.
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Changes in riverine hydrography and reduced aquifer recharge due to projected climate changes in arid and semi-arid regions are the main issues of water supply, especially in the Nile Delta, Egypt. Continuous degradation results from reduced Nile water flow, poor management of groundwater extraction, and human activities throughout the Nile’s course and drainage channels. Contamination of this water with heavy metals and dissolved organic solids reduces the quality of this water, which increases the price of treatment. River Bank Filtration (RBF) is a water treatment technology used for improving the quality of drinking water taken from polluted rivers where abstraction wells are installed on the banks. This study was applied to the RBF site at Embaba, Nile Delta, Egypt using the numerical code MT3D. The study was simulated and calibrated for the current situation and number of scenarios to investigate the effect of climatic changes on RBF sustainability. Four scenarios were simulated to identify and estimate the RBF portion and the total water travel time from the river to the wells. The first scenario involves a reduction in river stages, the second a decrease in aquifer recharge, the third a combination of the first two scenarios, and the fourth scenario combines scenarios 1, 2, and 3. The results indicate that the RBF portion decreased from 67.42% in the base case to 35.46% and 64.99% with a reduction in river stage by 75% from the base case and a decrease in aquifer recharge from 182.50 (base case) to 50 mm per year, respectively. Moreover, the RBF portion increased to reach 87.75% with a reduction in the General Head Boundary of 75% from the base case, while the combination of the three scenarios decreased the RBF portion to 67.24%. Finally, the water supply systems in arid and semi-arid regions should be extended by installing and operating RBF facilities to manage the negative effects of climatic change through reduction in river stages and aquifer recharge, and increasing abstraction due to overpopulation.
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Wang, Shilin, Xinyu Yan, Dong Wang, Imran Ahammad Siddique, Ji Chen, Qi Xu, Cancan Zhao, Leyun Yang, Yuan Miao, and Shijie Han. "Soil Microbial Community Based on PLFA Profiles in an Age Sequence of Pomegranate Plantation in the Middle Yellow River Floodplain." Diversity 13, no. 9 (August 27, 2021): 408. http://dx.doi.org/10.3390/d13090408.
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Pomegranate (Punica granatum L.) is one of the most important fruit trees in semi-arid land. Previous studies were primarily focused on soil microbial community composition under different pomegranate plantation managements. However, soil microbial community composition under long-term pomegranate plantation has rarely been studied. We investigated pomegranate plantation along with an age sequence (i.e., 1, 3, 5, and 10 years after pomegranate plantation; abbreviated by P1, P3, P5, P10, respectively) in the Middle Yellow River floodplain. Our objectives were to address (1) variations of soil physicochemical properties and (2) changes in soil microbial community composition and the influential factors. The results demonstrated that the soil water content of pomegranate plantation decreased with the increase of pomegranate plantation stand age. Specifically, dissolved organic carbon, ammonium, and available phosphorus increased significantly with stand age both at 0–10- and 10–20-cm soil depths. The P10 had the highest microbial phospholipid fatty acid (PLFA) profiles, including fungi, bacteria, Gram-positive bacteria, Gram-negative bacteria, and arbuscular mycorrhizal fungi. The ratio of fungal PLFAs to bacterial PLFAs increased and the ratio of Gram-positive to Gram-negative bacterial PLFAs decreased along the pomegranate plantation stand age. Dissolved organic carbon was the most important influential factor among the studied variables, which explained 42.2% variation of soil microbial community. In summary, the long-term plantation of pomegranate elevated soil microbial biomass and altered microbial community composition.
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Castino, F., B. Bookhagen, and A. de la Torre. "Atmospheric dynamics of extreme discharge events from 1979 to 2016 in the southern Central Andes." Climate Dynamics 55, no. 11-12 (September 16, 2020): 3485–505. http://dx.doi.org/10.1007/s00382-020-05458-1.
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Abstract During the South-American Monsoon season, deep convective systems occur at the eastern flank of the Central Andes leading to heavy rainfall and flooding. We investigate the large- and meso-scale atmospheric dynamics associated with extreme discharge events (> 99.9th percentile) observed in two major river catchments meridionally stretching from humid to semi-arid conditions in the southern Central Andes. Based on daily gauge time series and ERA-Interim reanalysis, we made the following three key observations: (1) for the period 1940–2016 daily discharge exhibits more pronounced variability in the southern, semi-arid than in the northern, humid catchments. This is due to a smaller ratio of discharge magnitudes between intermediate (0.2 year return period) and rare events (20 year return period) in the semi-arid compared to the humid areas; (2) The climatological composites of the 40 largest discharge events showed characteristic atmospheric features of cold surges based on 5-day time-lagged sequences of geopotential height at different levels in the troposphere; (3) A subjective classification revealed that 80% of the 40 largest discharge events are mainly associated with the north-northeastward migration of frontal systems and 2/3 of these are cold fronts, i.e. cold surges. This work highlights the importance of cold surges and their related atmospheric processes for the generation of heavy rainfall events and floods in the southern Central Andes.
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Heritage, G., S. Tooth, N. Entwistle, and D. Milan. "Long-term flood controls on semi-arid river form: evidence from the Sabie and Olifants rivers, eastern South Africa." Proceedings of the International Association of Hydrological Sciences 367 (March 3, 2015): 141–46. http://dx.doi.org/10.5194/piahs-367-141-2015.
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Abstract. Rivers in the Kruger National Park, eastern South Africa, are characterised by bedrock-influenced "macrochannels" containing variable alluvial thicknesses and riparian vegetation assemblages. Evidence from the Sabie and Olifants rivers suggests that flows up to moderate floods (<3500 m3 s−1) tend to result in net alluviation, with sediments gradually covering the underlying bedrock. More extreme floods strip alluvium and erode bedrock, effectively exerting the primary control over long-term river morphologic development. On the Olifants River, post-flood aerial LIDAR imagery reveals that the 2012 extreme flood (~14000 m3 s−1) resulted in extensive stripping of stored alluvial sediment, exposing and eroding the underlying weathered bedrock. On the Sabie River, preliminary optically stimulated luminescence ages for remnant alluvium are all less than 1000 years, highlighting typical timescales of sediment storage. Together, these results suggest that while periods of general alluviation occur on these systems, long-term river development results from extreme flood-generated bedrock erosion.
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de Ceballos, B. S. O., H. Oliveira, C. M. B. S. Meira, A. Konig, A. O. Guimarães, and J. T. de Souza. "River water quality improvement by natural and constructed wetland systems in the tropical semi-arid region of Northeastern Brazil." Water Science and Technology 44, no. 11-12 (December 1, 2001): 599–605. http://dx.doi.org/10.2166/wst.2001.0886.
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The efficiencies of a natural Typha spp wetland (Wn) formed on a river bed and its effluent treatment in a constructed wetland (Wc, subsurface horizontal flow) were investigated in northeastern Brazil (Paraiba State). The Wc system (12 tanks with stone gravel, 4.13 m2, 0.22 m3, 20 Typha spp rhizomes. m-2 each, with 38, 29, and 19 mm.d-1 hydraulic loadings, and 5, 7, and 10 days HRT) was fed daily with effluent from a Wn. Wn removal presented the highest values after Typha spp were cut during the 5th week. Removal values were (1st and 2nd periods or before and after cutting): 75% and 81% BOD5; 10-53% total phosphorus; 13%-55% ammonia; 89%-91% FC; 90-96% coliphages and bacteriophages. Wc removals increased with time with best results on 10d HRT. Removals were also higher in the 2nd period: 74%-78% BOD5; 58%-82% ammonia; 90% FC; 94-98% FS; and 92%-96% coliphages and bacteriophages. Despite the high remaining values of FC (1.4×104 CFU/100 ml) and FX (4×103 CFU/100 ml), the removals were satisfactory and HRT dependent, suggesting a gradual optimization of the system with time. The Wc exhibited good efficiency for improving water quality from polluted river.
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Alaghmand, Sina, Simon Beecham, and Ali Hassanli. "Impacts of Vegetation Cover on Surface-Groundwater Flows and Solute Interactions in a Semi-Arid Saline Floodplain: A Case Study of the Lower Murray River, Australia." Environmental Processes 1, no. 1 (March 2014): 59–71. http://dx.doi.org/10.1007/s40710-014-0003-0.
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Slaughter, Andrew R., and Sukhmani K. Mantel. "Water quality modelling of an impacted semi-arid catchment using flow data from the WEAP model." Proceedings of the International Association of Hydrological Sciences 377 (April 16, 2018): 25–33. http://dx.doi.org/10.5194/piahs-377-25-2018.
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Abstract. The continuous decline in water quality in many regions is forcing a shift from quantity-based water resources management to a greater emphasis on water quality management. Water quality models can act as invaluable tools as they facilitate a conceptual understanding of processes affecting water quality and can be used to investigate the water quality consequences of management scenarios. In South Africa, the Water Quality Systems Assessment Model (WQSAM) was developed as a management-focussed water quality model that is relatively simple to be able to utilise the small amount of available observed data. Importantly, WQSAM explicitly links to systems (yield) models routinely used in water resources management in South Africa by using their flow output to drive water quality simulations. Although WQSAM has been shown to be able to represent the variability of water quality in South African rivers, its focus on management from a South African perspective limits its use to within southern African regions for which specific systems model setups exist. Facilitating the use of WQSAM within catchments outside of southern Africa and within catchments for which these systems model setups to not exist would require WQSAM to be able to link to a simple-to-use and internationally-applied systems model. One such systems model is the Water Evaluation and Planning (WEAP) model, which incorporates a rainfall-runoff component (natural hydrology), and reservoir storage, return flows and abstractions (systems modelling), but within which water quality modelling facilities are rudimentary. The aims of the current study were therefore to: (1) adapt the WQSAM model to be able to use as input the flow outputs of the WEAP model and; (2) provide an initial assessment of how successful this linkage was by application of the WEAP and WQSAM models to the Buffalo River for historical conditions; a small, semi-arid and impacted catchment in the Eastern Cape of South Africa. The simulations of the two models were compared to the available observed data, with the initial focus within WQSAM on a simulation of instream total dissolved solids (TDS) and nutrient concentrations. The WEAP model was able to adequately simulate flow in the Buffalo River catchment, with consideration of human inputs and outputs. WQSAM was adapted to successfully take as input the flow output of the WEAP model, and the simulations of nutrients by WQSAM provided a good representation of the variability of observed nutrient concentrations in the catchment. This study showed that the WQSAM model is able to accept flow inputs from the WEAP model, and that this approach is able to provide satisfactory estimates of both flow and water quality for a small, semi-arid and impacted catchment. It is hoped that this research will encourage the application of WQSAM to an increased number of catchments within southern Africa and beyond.