Artykuły w czasopismach: „Dryland rivers”

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Parsons, Melissa, i Mark Southwell. "Flooding and geomorphology influence the persistence of the invasive annual herb Noogoora burr (Xanthium occidentale Bertol.) in the riparian zone of the dryland Darling River, Australia". Rangeland Journal 37, nr 5 (2015): 433. http://dx.doi.org/10.1071/rj14116.

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The relationship between flooding, and the establishment and persistence of exotic species, is not well understood in highly variable dryland rivers. Increased moisture associated with floods is likely to stimulate establishment and growth of exotic plants, but floods may also act as a stress to exotic plants if floods last for weeks to months. This study examined how physical drivers of dryland rivers – flood inundation and geomorphology – influence the persistence of Xanthium occidentale Bertol. in the dryland Darling River, Australia. The distribution of X. occidentale was associated with flood-related moisture subsidy, moderated by channel geomorphology. Dead stalks and burrs on the ground occurred above the 8-m height of the previous flood. Adult and juvenile plants occurred below 8 m corresponding to smaller flood events. Flatter geomorphic units (floodplains and benches) contained more plants and burrs, whereas steeper geomorphic units (banks) did not retain burrs, limiting plant abundance. Flooding is not a stress to X. occidentale. A glasshouse experiment showed that flood durations of up to 40 days had minimal effect on the germination, survival and growth of X. occidentale burrs, seeds or seedlings. Weed management strategies for X. occidentale in dryland rivers could be enhanced by targeting periods following flooding when moisture availability is increased on the flatter geomorphic units in the river channel.

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Sandercock, P. J., J. M. Hooke i J. M. Mant. "Vegetation in dryland river channels and its interaction with fluvial processes". Progress in Physical Geography: Earth and Environment 31, nr 2 (kwiecień 2007): 107–29. http://dx.doi.org/10.1177/0309133307076106.

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Vegetation forms a major component of the channel environment of dryland rivers in Mediterranean Europe yet the interactions between vegetation and fluvial processes in dryland river channels have received relatively little attention. Characteristic of dryland channels is a degree of complexity and irregularity in morphology coupled with abrupt changes in patterns of riparian vegetation along their course. This is in contrast to more temperate and humid channels, which show strong downstream trends in morphology and a regularity in the distribution of vegetation across the valley floor. The general effect of vegetation in these channels appears to be to enhance the processes of sedimentation and increase resistance to erosion. However, at high stress levels vegetation may be removed. The limited work that has been undertaken indicates that there is considerable variability in the effect that vegetation has on channel processes, depending on both the magnitude of the flow and characteristics of the vegetation, such as their distribution and positioning within the channel and factors such as plant flexibility, cross-sectional area (blockage ratio), number of stems. Studies of sediment connectivity are beginning to yield new insights into the dynamics of dryland rivers, and in particular the role of vegetation in reducing the connectivity of sediment transfers downstream. Detailed surveying at monitored sites such as is being carried out within the EU-funded project RECONDES is required to study the interactions between vegetation, sediment and flow in dryland rivers of the Mediterranean region.

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Burford, Michele A., Andrew J. Cook, Christine S. Fellows, Stephen R. Balcombe i Stuart E. Bunn. "Sources of carbon fuelling production in an arid floodplain river". Marine and Freshwater Research 59, nr 3 (2008): 224. http://dx.doi.org/10.1071/mf07159.

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Dryland rivers are characterised by highly pulsed and unpredictable flow, and support a diverse biota. The present study examined the contribution of floodplain sources to the productivity of a disconnected dryland river; that is a waterhole, after a major overland flood event. Rate measures of productivity were combined with stable isotope and biomass data on the food web in the waterhole and floodplain. The present study estimated that 50% of the fish carbon in the waterhole after flooding was derived from floodplain food sources. In the few months after retraction of the river to isolated waterholes, the large biomass of fish concentrated from the flooding decreased by 80%, most likely as a result of starvation. Based on the development of a carbon budget for the waterhole, mass mortality is hypothesised to be the cause of the high rates of heterotrophic production in the waterhole. The present study suggests that floodplain inputs are important for fuelling short-term production in waterholes, but via an unconventional pathway; that is, fish mortality. The episodic nature of flooding in dryland rivers means that changes in flow regimes, such as water regulation or abstraction, will reduce flooding and hence floodplain subsidies to the river. This is likely to have significant impacts on river productivity.

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Costa, A. C., A. Bronstert i J. C. de Araújo. "A channel transmission losses model for different dryland rivers". Hydrology and Earth System Sciences 16, nr 4 (3.04.2012): 1111–35. http://dx.doi.org/10.5194/hess-16-1111-2012.

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Abstract. Channel transmission losses in drylands take place normally in extensive alluvial channels or streambeds underlain by fractured rocks. They can play an important role in streamflow rates, groundwater recharge, freshwater supply and channel-associated ecosystems. We aim to develop a process-oriented, semi-distributed channel transmission losses model, using process formulations which are suitable for data-scarce dryland environments and applicable to both hydraulically disconnected losing streams and hydraulically connected losing(/gaining) streams. This approach should be able to cover a large variation in climate and hydro-geologic controls, which are typically found in dryland regions of the Earth. Our model was first evaluated for a losing/gaining, hydraulically connected 30 km reach of the Middle Jaguaribe River (MJR), Ceará, Brazil, which drains a catchment area of 20 000 km2. Secondly, we applied it to a small losing, hydraulically disconnected 1.5 km channel reach in the Walnut Gulch Experimental Watershed (WGEW), Arizona, USA. The model was able to predict reliably the streamflow volume and peak for both case studies without using any parameter calibration procedure. We have shown that the evaluation of the hypotheses on the dominant hydrological processes was fundamental for reducing structural model uncertainties and improving the streamflow prediction. For instance, in the case of the large river reach (MJR), it was shown that both lateral stream-aquifer water fluxes and groundwater flow in the underlying alluvium parallel to the river course are necessary to predict streamflow volume and channel transmission losses, the former process being more relevant than the latter. Regarding model uncertainty, it was shown that the approaches, which were applied for the unsaturated zone processes (highly nonlinear with elaborate numerical solutions), are much more sensitive to parameter variability than those approaches which were used for the saturated zone (mathematically simple water budgeting in aquifer columns, including backwater effects). In case of the MJR-application, we have seen that structural uncertainties due to the limited knowledge of the subsurface saturated system interactions (i.e. groundwater coupling with channel water; possible groundwater flow parallel to the river) were more relevant than those related to the subsurface parameter variability. In case of the WEGW application we have seen that the non-linearity involved in the unsaturated flow processes in disconnected dryland river systems (controlled by the unsaturated zone) generally contain far more model uncertainties than do connected systems controlled by the saturated flow. Therefore, the degree of aridity of a dryland river may be an indicator of potential model uncertainty and subsequent attainable predictability of the system.

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Balcombe, Stephen R., Angela H. Arthington, Neal D. Foster, Martin C. Thoms, Glenn G. Wilson i Stuart E. Bunn. "Fish assemblages of an Australian dryland river: abundance, assemblage structure and recruitment patterns in the Warrego River, Murray - Darling Basin". Marine and Freshwater Research 57, nr 6 (2006): 619. http://dx.doi.org/10.1071/mf06025.

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Fish in dryland rivers must cope with extreme variability in hydrology, temperature and other environmental factors that ultimately have a major influence on their patterns of distribution and abundance at the landscape scale. Given that fish persist in these systems under conditions of high environmental variability, dryland rivers represent ideal systems to investigate the processes contributing to and sustaining fish biodiversity and recruitment in variable environments. Hence, spatial and temporal variation in fish assemblage structure was examined in 15 waterholes of the Warrego River between October 2001 and May 2003. Fish assemblages in isolated waterholes were differentiated at the end of the dry 2001 winter but were relatively similar following high summer flows in January 2002 as a consequence of high hydrological connectivity among waterholes. Small, shallow waterholes supported more species and higher abundances than large-deep waterholes. Large, deep waterholes provided important refuge for large-bodied fish species such as adult yellowbelly, Macquaria ambigua, and the eel-tailed catfish, Tandanus tandanus. Recruitment patterns of bony bream (Nematalosa erebi), Hyrtl’s tandan (Neosilurus hyrtlii) and yellowbelly were associated with high flow events and backwater inundation; however recruitment of yellowbelly and bony bream was also evident following a zero-flow period. Departures from typical flood-induced seasonal spawning patterns may reflect opportunistic spawning behaviours appropriate to the erratic patterns of flooding and dry spells in dryland rivers.

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Costelloe, J. F., J. R. W. Reid, J. C. Pritchard, J. T. Puckridge, V. E. Bailey i P. J. Hudson. "Are alien fish disadvantaged by extremely variable flow regimes in arid-zone rivers?" Marine and Freshwater Research 61, nr 8 (2010): 857. http://dx.doi.org/10.1071/mf09090.

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The proliferation of alien fish in dryland rivers potentially obstructs the maintenance of river health. Modified flow regimes are hypothesised to facilitate invasions by alien fish but in unregulated dryland rivers, large floods provide a recruitment advantage for native over alien species whereas droughts favour alien species. We tested these hypotheses by using data from a 3-year study (2000–2003) of fish populations in the unmodified rivers of the Lake Eyre Basin (LEB) of Australia. Results from a lower reach of Cooper Creek were compared with those of an earlier study (1986–1992). During both periods, large floods occurred, with return periods ranging from >1 in 5 to >1 in 25 years. In the lower Cooper, decreases in the abundance of alien species relative to native species, and dramatic increases in recruitment of native species, were observed during a 1–3-year period following large floods. In two other rivers in 2000–2003, there was no statistically significant change in the already low abundances of alien species. We suggest that the naturally variable hydrological regimes and native-dominant fish assemblages of the unregulated LEB rivers afford some resistance to the establishment and proliferation of alien fish through flood and drought conditions.

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Tooth, Stephen, i Gerald C. Nanson. "EQUILIBRIUM AND NONEQUILIBRIUM CONDITIONS IN DRYLAND RIVERS". Physical Geography 21, nr 3 (maj 2000): 183–211. http://dx.doi.org/10.1080/02723646.2000.10642705.

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FELLOWS, CHRISTINE S., STUART E. BUNN, FRAN SHELDON i NERIDA J. BEARD. "Benthic metabolism in two turbid dryland rivers". Freshwater Biology 54, nr 2 (luty 2009): 236–53. http://dx.doi.org/10.1111/j.1365-2427.2008.02104.x.

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Costa, A. C., A. Bronstert i J. C. de Araújo. "A channel transmission losses model for different dryland rivers". Hydrology and Earth System Sciences Discussions 8, nr 5 (4.10.2011): 8903–62. http://dx.doi.org/10.5194/hessd-8-8903-2011.

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Abstract. Channel transmission losses in drylands take place normally in extensive alluvial channels or streambeds underlain by fractured rocks. They can play an important role in flood prediction, groundwater recharge, freshwater supply and channel-associated ecosystems. We aim to develop a semi-distributed channel transmission losses model, a coupling of formulations which are more suitable for data-scarce dryland environments, applicable for both hydraulically disconnected losing streams and hydraulically connected losing(/gaining) streams. Hence, this approach should be able to cover a large variation in climate and hydro-geologic controls, which are typically found in dryland regions of the world. Traditionally, channel transmission losses models have been developed for site specific conditions. Our model was firstly evaluated for a losing/gaining, hydraulically connected 30 km reach of the Jaguaribe River, Ceará, Brazil, which controls a catchment area of 20 000 km2. Secondly, we applied it to a small losing, hydraulically disconnected 1.5 km channel reach in the Walnut Gulch Experimental Watershed (WGEW), Arizona, USA. The model based on the perceptual hydrological models of the reaches was able to predict reliably the stream flow for the both case studies. For the larger river reach, the evaluation of the hypotheses on the dominant hydrological processes was fundamental for reducing structural model uncertainties and improving the stream flow prediction, showing that both lateral stream-aquifer water fluxes and groundwater flow in the underlying alluvium parallel to the river course are necessary to predict stream flow and channel transmission losses, the former process being more relevant than the latter. The sensitivity analysis showed that even if the parameters can "potentially" produce large flow exchanges between model units in the saturated part of the modelling, large flow exchanges do not happen because they are restricted by the actual hydraulic gradient between the model units. Moreover, the saturated-part-based parameters (active in the larger river) produced much smaller variation in the sensitivity coefficient than those (active in the smaller river) which drive the unsaturated part of the channel transmission losses model.

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Wan, Wenhua, Hang Zheng, Yueyi Liu, Jianshi Zhao, Yingqi Fan i Hongbo Fan. "Ecological Compensation Mechanism in a Trans-Provincial River Basin: A Hydrological/Water-Quality Modeling-Based Analysis". Water 14, nr 16 (18.08.2022): 2542. http://dx.doi.org/10.3390/w14162542.

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Ecological compensation is an important economic means of water pollution control and quality management, especially for trans-regional rivers with unbalanced economic and social development between upstream and downstream. The Tangbai River Basin (TRB), a watershed crossing Henan province and Hubei province, China, forms one of the nation’s most productive agricultural regions. The TRB has been exposed to high doses of fertilizers for a long time. This study simulates hydrologic and nutrient cycling in the TRB using Soil and Water Assessment Tool (SWAT) with limited data available. The results indicate that dryland fields, which constitute 62% of the basin area, produce 80% of total nitrogen (TN) and 85% of total phosphorus (TP) yields of the whole river basin. The water quality of river sections at the provincial boundary shows that only 29% of the time from 2000 to 2019 met the Class III standard regarding TN and TP concentrations, and the concentrations in the spring flood season are approximately three times the mean in the non-flood season. The Grain for Green ecological restoration measure in Henan province shows that restoration of non-flat drylands can reduce nutrient loads at trans-provincial sections by 3.5 times compared to that of slope-independent drylands; however, the water quality compliance rate remains similar. The value of ecological compensation can also vary widely depending on different quantitative criteria. The SWAT-based pollutant quantification method adopted in this study could have implications for ecological compensation in trans-regional rivers.

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Fischer, Viktoria. "The deposition of bronzes at Swiss lakeshore settlements: new investigations". Antiquity 85, nr 330 (listopad 2011): 1298–311. http://dx.doi.org/10.1017/s0003598x00062062.

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The famous lakeside sites of Switzerland have long been known for their pile dwellings and their massive quantities of Late Bronze Age metalwork. On the most recent excavations, the bronzes have been mapped in situ, allowing comparison with assemblages from dryland sites and rivers, as well as providing a context for the nineteenth-century collections. The pile dwellings emerge as special places where depositions of selected bronze objects in groups or as single discards, comparable to those usually found in dryland deposits or in rivers, accumulated in the shallow water during a unique 250-year spell of ritual practice.

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Puckridge, J. T., K. F. Walker i J. F. Costelloe. "Hydrological persistence and the ecology of dryland rivers". Regulated Rivers: Research & Management 16, nr 5 (2000): 385–402. http://dx.doi.org/10.1002/1099-1646(200009/10)16:5<385::aid-rrr592>3.0.co;2-w.

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Puckridge, J. T., F. Sheldon, K. F. Walker i A. J. Boulton. "Flow variability and the ecology of large rivers". Marine and Freshwater Research 49, nr 1 (1998): 55. http://dx.doi.org/10.1071/mf94161.

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Ecological processes in large rivers are controlled by their flow variability. However, it is difficult to find measures of hydrological variability that characterize groups of rivers and can also be used to generate hypotheses about their ecology. Multivariate analyses of the hydrographs of 52 rivers worldwide revealed distinctive patterns of flow variability that were often correlated with climate. For example, there were groups of rivers that corresponded broadly with ‘tropical’ and ‘dryland’ climates. However, some rivers from continental climates occupy both extremes of this range, illustrating the limitations of simple classification. Individual rivers and groups of rivers may also have different hydrographic ‘signatures’, and attempts to combine measures of hydrological variability into indices mask biologically significant information. This paper identifies 11 relatively independent measures of hydrological variability that help categorize river types and are each associated with aspects of fish biology. Ways are suggested by which the Flood Pulse Concept can be expanded to encompass hydrological variability and accommodate differences among groups of rivers from different climatic regions. Such recognition of the complex role of hydrological variability enhances the value of the concept for river conservation, management and restoration.

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Leigh, Catherine, Fran Sheldon, Richard T. Kingsford i Angela H. Arthington. "Sequential floods drive 'booms' and wetland persistence in dryland rivers: a synthesis". Marine and Freshwater Research 61, nr 8 (2010): 896. http://dx.doi.org/10.1071/mf10106.

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Flow is a key driver regulating processes and diversity in river systems across a range of temporal and spatial scales. In dryland rivers, variability in the timing and scale of floods has specific ecological significance, playing a major role in sustaining biotic diversity across the river-floodplain mosaic. However, longitudinal effects of floods are equally important, delivering water downstream through channels and wetland complexes. Interaction among spatially distributed wetlands, their connecting channel and floodplain geomorphology and the temporally variable flow events not only creates the spatial complexity in dryland rivers but also determines temporal persistence of wetlands. These act as hydrological ‘sponges’, absorbing water from upstream and needing to fill before releasing water downstream. Sequential high flow events are essential for the ecological persistence of riverine wetlands and the transmission of flows further downstream through the channel network. These flood sequences maintain aquatic refugia and drive booms in productivity sustaining aquatic and terrestrial biota over large spatial and temporal scales. Disrupting the sequence, with modified flow regimes and water removal for diversion (e.g. irrigation), significantly reduces the opportunity for wetland replenishment. As a result, the benefits of sequential flooding to the wetland ‘sponges’ and their biotic communities will be lost.

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Marshall, Jonathan C., Joanna J. Blessing, Sara E. Clifford, Kate M. Hodges, Peter M. Negus i Alisha L. Steward. "Ecological impacts of invasive carp in Australian dryland rivers". Aquatic Conservation: Marine and Freshwater Ecosystems 29, nr 11 (4.09.2019): 1870–89. http://dx.doi.org/10.1002/aqc.3206.

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Sheldon, Fran, i Christine S. Fellows. "Water quality in two Australian dryland rivers: spatial and temporal variability and the role of flow". Marine and Freshwater Research 61, nr 8 (2010): 864. http://dx.doi.org/10.1071/mf09289.

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Water quality, along with hydrology, plays an important role in the spatial and temporal dynamics of a range of ecological patterns and processes in large rivers and is also often a key component of river health assessments. Geology and land use are significant drivers of water quality during flow periods while during periods of no-flow, local-scale factors such as evaporation, groundwater influence and the concentration and precipitation of compounds are important. This study explored the water quality changes in two Australian dryland rivers, the Cooper Creek (Lake Eyre Basin) and the Warrego River (Murray–Darling Basin), across different hydrological phases over several years. Water quality varied both spatially and temporally; the greatest spatial variability occurred during the no-flow phase, with temporal changes driven by flow. Concentrations of major anions and cations also varied spatially and temporally, with an overall cation dominance of calcium and magnesium and an anion dominance of bicarbonate. This bicarbonate dominance contrasts with previous data from inland lentic systems where sodium chloride was found to dominate. Such extreme spatial and temporal variability hampers successful derivation of water quality guidelines for these variable rivers and suggests such guidelines would need to be developed with respect to ‘flow phase’.

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Fellows, C. S., M. L. Wos, P. C. Pollard i S. E. Bunn. "Ecosystem metabolism in a dryland river waterhole". Marine and Freshwater Research 58, nr 3 (2007): 250. http://dx.doi.org/10.1071/mf06142.

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Little is known about ecosystem processes in dryland rivers, despite the global distribution of these systems. Those in Australia are characterised by long periods of no flow in which they persist for many months as series of isolated, often turbid, waterholes. We assessed benthic and pelagic primary production, respiration, and bacterial production in one of these waterholes to determine the metabolic balance of the waterhole and resolve the relative importance of autochthonous and allochthonous sources of organic carbon. Despite a photic zone depth of only 0.25 m, three lines of evidence suggested that autochthonous sources of organic carbon were important for fuelling bacterial production under no-flow conditions: the metabolic balance of the waterhole was not indicative of large allochthonous inputs; rates of gross primary production were great enough to meet a substantial fraction of estimated bacterial carbon demand; and pathways for allochthonous carbon to enter the waterhole were limited. These results suggest that models of lake metabolism based on temperate ecosystems can be expanded to include dryland river waterholes, which group with eutrophic lakes owing to their high levels of inorganic nutrients, low allochthonous inputs and autotrophic metabolic balance.

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Agoramoorthy, Govindasamy, i Minna J. Hsu. "Small dams revive dry rivers and mitigate local climate change in India’s drylands". International Journal of Climate Change Strategies and Management 8, nr 2 (21.03.2016): 271–85. http://dx.doi.org/10.1108/ijccsm-12-2014-0141.

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Purpose – This study aims to assess how small check dams built across rivers in India’s drylands can revitalize rivers during dry season and mitigate local climate change consequences. The surface- and groundwater resources are increasingly under pressure throughout India. The imminent climate change consequences will further aggravate the crisis and this paper has addressed this difficult issue. Design/methodology/approach – This study was conducted in India’s dryland districts, namely, Dahod in Gujarat and Jhalawar and Banswara in Rajasthan state, to assess the impacts of small dams. Data on dams, sustainability, groundwater levels and benefits to farmers were systematically collected to analyze advantages offered by check dams with reference to climate change mitigation. Findings – The study shows that 356 check dams built during 1990-2012 across the tribal drylands of India, with a cost of USD 17 million, benefited over one million people from farming communities. The dams also increased groundwater levels in villages, revived rivers during dry season and increased forest growth along rivers, ultimately mitigating local climate change-imposed negative consequences. Research limitations/implications – Data on small dams are limited in India, as public have no access to such data because the work is done mainly by local contractors. Practical implications – The check dams, the role of which is highlighted here, are simple, eco-friendly and cost-effective. If it is adopted across the vast drylands of India and elsewhere, it has the potential to increase agricultural output; guarantee food security; enhance groundwater resources; and, above all, mitigate local climate change consequences. Social implications – If check dams are built in large numbers across India, it has the potential to increase agricultural output; guarantee food security; enhance groundwater resources; and, above all, mitigate climate change. Originality/value – The highlighted results and discussion will guide scientists, politicians and policymakers to make informed decisions to combat India ’ s future climate change consequences.

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Lang, S. C., T. H. D. Payenberg, M. R. W. Reilly, T. Hicks, J. Benson i J. Kassan. "MODERN ANALOGUES FOR DRYLAND SANDY FLUVIAL-LACUSTRINE DELTAS AND TERMINAL SPLAY RESERVOIRS". APPEA Journal 44, nr 1 (2004): 329. http://dx.doi.org/10.1071/aj03012.

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Ephemeral sandy fluvial-lacustrine deltas and terminal splays associated with dryland depositional environments are important reservoirs in many basins around the world, in both pericratonic and intracratonic settings (Triassic of Algeria; Triassic of the North Sea; and Pliocene of the Caspian Sea). Research on modern depositional analogues from dryland basins offers insights into these types of reservoirs. Australia’s modern Lake Eyre Basin, an arid to hyper-arid, low-accommodation intracratonic basin in central Australia, provides an ideal natural laboratory.This paper highlights field observations of modern, sand-prone, reservoir analogues from the Neales River and Umbum Creek, on the western fringe of Lake Eyre, including unique aerial observations of sedimentation from a rare flood event in an ephemeral fluvial system. These rivers flow irregularly in a dryland setting, but are prone to flash flooding and highly variable discharge that moves large volumes of sediment over a few hours or days. Although there are variations in sediment type and discharge, similarities exist with the key reservoir elements common to most modern and ancient dryland fluvial-lacustrine systems.Distinctive elements include fluvial point bar and associated overbank deposits, distributive avulsion channels and down-dip terminal splays, either on the floodplain or onto the playa lake fringe. The terminal splays are formed, where there is not a pre-existing standing body of water, during rapidly decelerating flows with high-flow regime, transitional to low-flow regime conditions. Typical structures include parallel lamination, convex-upward parallel lamination, climbing ripples and small-scale 2D and 3D dunes. Flow interference with in-channel and floodplain vegetation is an important sediment-trapping mechanism with reservoir quality implications. Aeolian deflation is also significant as it causes the removal of fine-grained sediments during dry periods. The main controls on sediment preservation include the overall low-accommodation setting and rare major lake-filling events controlled by flooding out-of-phase with flows down the western rivers. Depositional products are either high-net-to gross fluvial- terminal splay sheet sands or lower net-to-gross fluvial- terminal splay-lacustrine delta sand sheets or stringers.

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North, C. P., G. C. Nanson i S. D. Fagan. "Recognition of the Sedimentary Architecture of Dryland Anabranching (Anastomosing) Rivers". Journal of Sedimentary Research 77, nr 11 (1.11.2007): 925–38. http://dx.doi.org/10.2110/jsr.2007.089.

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Walker, Keith F. "Jim Puckridge: a pioneer in the ecology of dryland rivers". Marine and Freshwater Research 61, nr 8 (2010): 829. http://dx.doi.org/10.1071/mf10133.

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Holland, Aleicia, Paul J. McInerney, Michael E. Shackleton, Gavin N. Rees, Nick R. Bond i Ewen Silvester. "Dissolved organic matter and metabolic dynamics in dryland lowland rivers". Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 229 (marzec 2020): 117871. http://dx.doi.org/10.1016/j.saa.2019.117871.

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McGregor, Glenn B., Jonathan C. Marshall i Martin C. Thoms. "Spatial and temporal variation in algal-assemblage structure in isolated dryland river waterholes, Cooper Creek and Warrego River, Australia". Marine and Freshwater Research 57, nr 4 (2006): 453. http://dx.doi.org/10.1071/mf05128.

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The scale at which algal biodiversity is partitioned across the landscape, and the biophysical processes and biotic interactions which shape these communities in dryland river refugia was studied on two occasions from 30 sites in two Australian dryland rivers. Despite the waterholes studied having characteristically high levels of abiogenic turbidity, a total of 186 planktonic microalgae, 253 benthic diatom and 62 macroalgal species were recorded. The phytoplankton communities were dominated by flagellated cryptophytes, euglenophytes and chlorophytes, the diatom communities by cosmopolitan taxa known to tolerate wide environmental conditions, and the macroalgal communities by filamentous cyanobacteria. All algal communities showed significant differences between catchments and sampling times, with a suite of between 5 and 12 taxa responsible for ~50% of the observed change. In general, algal assemblage patterns were poorly correlated with the measured environmental variables. Phytoplankton and diatom assemblage patterns were weakly correlated with several waterhole geomorphic measures, whereas macroalgal assemblage patterns showed some association with variability in ionic concentration.

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Sheldon, Fran, Stuart E. Bunn, Jane M. Hughes, Angela H. Arthington, Stephen R. Balcombe i Christine S. Fellows. "Ecological roles and threats to aquatic refugia in arid landscapes: dryland river waterholes". Marine and Freshwater Research 61, nr 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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Amos, Kathryn, Carley Goodwin i Angel Soria. "Incised valleys in marginal-lacustrine depositional environments: a new reservoir analogue from Lake Eyre, central Australia". APPEA Journal 52, nr 1 (2012): 513. http://dx.doi.org/10.1071/aj11040.

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Incised-valley fill deposits can form important hydrocarbon reservoirs and provide pathways for hydrocarbon migration. Incised-valleys formed in marginal-marine environments are well described, however, marginal-lacustrine incised-valleys have been the focus of extremely few investigations and are poorly understood. This paper provides a new description of incised-fluvial systems that are presently constructing terminal deposits in embayments around the shoreline of Lake Eyre, central Australia. It is anticipated that better awareness of such deposits will assist in the recognition of these depositional environments in the rock record, which should be useful for exploration purposes and for the generation of improved models for continental dryland fluvial-lacustrine reservoir deposits. A classification of all significant river mouth deposits around Lake Eyre (width >300 m; n = 104), from topographic map and satellite image data, found that 54% are incised-valleys presently accreting a terminal deposit in a shoreline embayment (playa lake estuary). The depositional elements of three incised-valley systems have been mapped using satellite imagery in a GIS platform, from which element geometries are described. Controls on incised-valley formation are investigated by comparing these observations with evidence for past lake highstands and neotectonics and observations from satellite images, geological map data, and digital elevation model data. The terminal splay deposits of rivers around Lake Eyre are well-used analogues for dryland reservoirs; however, the focus has been on deposits accreting directly onto the playa. It is likely the incised-valleys and terminal deposits in the embayments described here will be of interest to companies exploring in, and producing from, ancient drylands and other lacustrine depositional environments.

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Borrok, David M., i Mark A. Engle. "The role of climate in increasing salt loads in dryland rivers". Journal of Arid Environments 111 (grudzień 2014): 7–13. http://dx.doi.org/10.1016/j.jaridenv.2014.07.001.

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Tooth, Stephen. "Process, form and change in dryland rivers: a review of recent research". Earth-Science Reviews 51, nr 1-4 (sierpień 2000): 67–107. http://dx.doi.org/10.1016/s0012-8252(00)00014-3.

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Bunn, Stuart E., Martin C. Thoms, Stephen K. Hamilton i Samantha J. Capon. "Flow variability in dryland rivers: boom, bust and the bits in between". River Research and Applications 22, nr 2 (2006): 179–86. http://dx.doi.org/10.1002/rra.904.

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Higgisson, William, Linda Broadhurst, Foyez Shams, Bernd Gruber i Fiona Dyer. "Reproductive Strategies and Population Genetic Structure in Two Dryland River Floodplain Plants, Marsilea drummondii and Eleocharis acuta". Genes 13, nr 9 (23.08.2022): 1506. http://dx.doi.org/10.3390/genes13091506.

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Aquatic plants share a range of convergent reproductive strategies, such as the ability to reproduce both sexually and asexually through vegetative growth. In dryland river systems, floodplain inundation is infrequent and irregular, and wetlands consist of discrete and unstable habitat patches. In these systems, life history strategies such as long-distance dispersal, seed longevity, self-fertilisation, and reproduction from vegetative propagules are important strategies that allow plants to persist. Using two aquatic plants, Marsilea drummondii and Eleocharis acuta, we investigated the proportions of sexual and asexual reproduction and self-fertilisation by employing next-generation sequencing approaches, and we used this information to understand the population genetic structure of a large inland floodplain in western New South Wales (NSW), Australia. Asexual vegetative reproduction and self-fertilisation were more common in M. drummondii, but both species used sexual reproduction as the main mode of reproduction. This resulted in a highly differentiated genetic structure between wetlands and a similar genetic structure within wetlands. The similarity in genetic structure was influenced by the wetland in the two species, highlighting the influence of the floodplain landscape and hydrology on structuring population genetic structure. The high levels of genetic variation among wetlands and the low variation within wetlands suggests that dispersal and pollination occur within close proximity and that gene flow is restricted. This suggests a reliance on locally sourced (persistent) seed, rather than asexual (clonal) reproduction or recolonisation via dispersal, for the population maintenance of plants in dryland rivers. This highlights the importance of floodplain inundation to promote seed germination, establishment, and reproduction in dryland regions.

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Burford, M. A., A. T. Revill, D. W. Palmer, L. Clementson, B. J. Robson i I. T. Webster. "River regulation alters drivers of primary productivity along a tropical river-estuary system". Marine and Freshwater Research 62, nr 2 (2011): 141. http://dx.doi.org/10.1071/mf10224.

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Worldwide, rivers continue to be dammed to supply water for humans. The resulting regulation of downstream flow impacts on biogeochemical and physical processes, potentially affecting river and estuarine productivity. Our study tested the hypothesis that primary production in the downstream freshwater reaches of a dammed river was less limited by light and nutrients relative to downstream estuarine primary production. In a tropical dryland Australian river estuary, we found that water-column primary productivity was highest at freshwater sites that had lowest light attenuation. Nitrogen may also have limited primary productivity. Below the freshwater zone was a region of macrotidal mixing with high concentrations of suspended soil particles, nutrients and chlorophyll a, and lower but variable primary productivity rates. Light controlled productivity, but the algal cells may also have been osmotically stressed due to increasing salinity. Further downstream in the estuary, primary productivity was lower than the freshwater reaches and light and nutrient availability appear to be a factor. Therefore the reduced magnitude of peak-flow events due to flow regulation, and the resulting decrease in nutrient export, is likely to be negatively impacting estuarine primary production. This has implications for future development of dams where rivers have highly seasonal flow.

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Arthington, Angela H., Julian D. Olden, Stephen R. Balcombe i Martin C. Thoms. "Multi-scale environmental factors explain fish losses and refuge quality in drying waterholes of Cooper Creek, an Australian arid-zone river". Marine and Freshwater Research 61, nr 8 (2010): 842. http://dx.doi.org/10.1071/mf09096.

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Many rivers experience intermittent flows naturally or as a consequence of water abstraction. Climate change is likely to exacerbate flow variability such that dry spells may become more common. It is important to understand the ecological consequences of flow intermittency and habitat fragmentation in rivers, and to identify and protect habitat patches that provide refugia for aquatic biota. This paper explores environmental factors influencing dry season fish losses from isolated waterbodies in Cooper Creek, an unregulated arid-zone river in the Lake Eyre Basin, Australia. Multivariate ordination techniques and classification and regression trees (CART) were used to decompose species–environment relationships into a hierarchically structured data set, and to determine factors explaining changes in fish assemblage structure and species losses over a single dry season. Canonical correspondence analysis (CCA) explained 74% of fish assemblage change in terms of waterhole morphology (wetted perimeter, depth), habitat structure (bench development, off-take channels), waterhole quality (eroded banks, gross primary production), the size of surrounding floodplains and the relative isolation of waterholes. Classification trees for endemic and restricted species reaffirmed the importance of these waterhole and floodplain variables as drivers of fish losses. The CCA and CART models offer valuable tools for identification of refugia in Cooper Creek and, possibly, other dryland rivers.

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Robertson, Alistar I., Adrienne Burns i Terry J. Hillman. "Scale-dependent lateral exchanges of organic carbon in a dryland river during a high-flow experiment". Marine and Freshwater Research 67, nr 9 (2016): 1293. http://dx.doi.org/10.1071/mf15371.

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We estimated the magnitude and direction of exchanges of particulate organic carbon (POC) and dissolved organic carbon (DOC) between the river and four floodplain wetlands (billabongs) and a 140-km reach of riverbank and floodplain of the Murrumbidgee River during a managed high-flow experiment. There was a net transport of organic carbon from the river to billabongs during connection, ranging from 87 to 525kg POC per billabong or from 1.4 to 5.7g POC m–2 of billabong sediment surface area and from 36 to 4357kg DOC, or from 0.4 to 29.8g DOC m–2. At the whole-reach scale, there was a net loss of 754Mg POC from the river channel to riverbank and floodplain and a net input of 821Mg DOC to the river channel. This DOC input, which was small relative to the total organic carbon in transit, was likely to have contributed significantly to oxidative processes in the river. The DOC entering the river was derived from litter and soils in riverbank habitats or from abraded biofilms in the river channel. The results support an extended flood-pulse concept that includes in-channel flow pulses as important elements in the biogeochemistry of dryland rivers. Piggybacking dam releases on tributary flows to deliver in-channel flows delivers significant benefit for riverine organic-matter cycles.

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Ielpi, Alessandro, i Mathieu G. A. Lapôtre. "Linking sediment flux to river migration in arid landscapes through mass balance". Journal of Sedimentary Research 92, nr 8 (22.08.2022): 695–703. http://dx.doi.org/10.2110/jsr.2022.118.

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ABSTRACT Lateral migration is a key process shaping sinuous rivers and controlling sediment exchange with floodplains. The rate at which channels migrate is affected by bend curvature, bank erodibility, and sediment supply. The relationship between migration rate and sediment supply is poorly understood in dryland regions, where direct measurements are scarce. Here we propose a simple mass-balance model to estimate the sediment flux of ephemeral streams in North America's Great Basin and establish a comparison with timelapse photogrammetric data of lateral migration. The model takes into consideration variables such as long-term hillslope erosion, transient sediment storage in intra-catchment lowlands, and sediment bypass to depocenters. Our results point to first-order similarities in how sediment supply drives channel migration across diverse hydro-climatic regimes. However, we find that, for a given sediment supply and channel width, and despite their ephemeral discharge, dryland streams with minimal bank vegetation migrate about three times faster than humid-climate, vegetated ones. This difference in migration pace likely results from the compound effect of bank erodibility and bend geometry. Our model sheds new light on the driving mechanisms of channel mobility in dryland streams and may find application in assessing the sediment budgets of ungauged streams, reservoir trapping, and morphodynamic adjustments in stressed watersheds.

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Balcombe, S. R., A. H. Arthington i D. Sternberg. "FISH BODY CONDITION AND RECRUITMENT RESPONSES TO ANTECEDENT FLOWS IN DRYLAND RIVERS ARE SPECIES AND RIVER SPECIFIC". River Research and Applications 30, nr 10 (7.08.2014): 1257–68. http://dx.doi.org/10.1002/rra.2797.

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Henares, S., M. E. Donselaar i L. Caracciolo. "Depositional controls on sediment properties in dryland rivers: Influence on near-surface diagenesis". Earth-Science Reviews 208 (wrzesień 2020): 103297. http://dx.doi.org/10.1016/j.earscirev.2020.103297.

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Bino, Gilad, Kate Brandis, Richard T. Kingsford i John Porter. "Waterbird synchrony across Australia's highly variable dryland rivers – Risks and opportunities for conservation". Biological Conservation 243 (marzec 2020): 108497. http://dx.doi.org/10.1016/j.biocon.2020.108497.

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Sheldon, Fran. "Incorporating Natural Variability into the Assessment of Ecological Health in Australian Dryland Rivers". Hydrobiologia 552, nr 1 (grudzień 2005): 45–56. http://dx.doi.org/10.1007/s10750-005-1504-7.

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Heritage, George, Neil Entwistle, David Milan i Stephen Tooth. "Quantifying and contextualising cyclone-driven, extreme flood magnitudes in bedrock-influenced dryland rivers". Advances in Water Resources 123 (styczeń 2019): 145–59. http://dx.doi.org/10.1016/j.advwatres.2018.11.006.

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Kingsford, Richard T., Andrew J. Boulton i Jim T. Puckridge. "Challenges in managing dryland rivers crossing political boundaries: lessons from Cooper Creek and the Paroo River, central Australia". Aquatic Conservation: Marine and Freshwater Ecosystems 8, nr 3 (maj 1998): 361–78. http://dx.doi.org/10.1002/(sici)1099-0755(199805/06)8:3<361::aid-aqc294>3.0.co;2-v.

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Grenfell, S., i M. Grenfell. "Characterising the late Quaternary facies stratigraphy of floodplains in South Africa". South African Journal of Geology 124, nr 4 (1.12.2021): 963–76. http://dx.doi.org/10.25131/sajg.124.0056.

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Abstract South African river floodplains and their alluvial deposits reflect a diversity of geological and geographical drivers. We use a genetic geomorphic classification system originally developed for dryland wetlands to characterise geomorphic processes and potential successions of sedimentary fill for South African floodplains. Using case studies from the literature, we consider differences between alluvial rivers and mixed bedrock-alluvial rivers in the context of macro-scale geomorphic setting, and evaluate the impact of the setting on floodplain persistence and potential as a palaeo-environmental archive. Sedimentary facies associations represented in South African floodplains, including lateral and oblique accretion, channel, channel infill, levee vertical accretion, floodplain vertical accretion and debris flow deposits, are also evaluated. Floodplains of South Africa’s interior are typically mixed bedrock-alluvial as channel beds are set upon or close to bedrock and sediment thickness is limited. By contrast some floodplains in tectonic basin settings have sediment deposits exceeding 30 m in thickness. The resulting rivers are alluvial, and thus able to adjust their width, depth and slope to accommodate changes in discharge and sediment supply. Similarly, coastal floodplain rivers are alluvial due to downcutting during the last glacial maximum and subsequent sedimentary infilling as sea levels rose. When considering the potential of floodplains as palaeoarchives of environmental change, two considerations emerge. First, floodplain stratigraphy is not a response to a single variable due to complex process-form feedbacks. Rather, floodplain stratigraphy is an outcome of both autogenic and allogenic processes. Second, most South African floodplains are zones of sediment recycling, and as such, preservation potential is typically low. Thus, although floodplain settings of the interior may be a few million years old, the sediment within them may be only thousands to tens of thousands of years old. Our review indicates that research has historically focused on meandering river and mixed bedrock-alluvial anabranching river floodplains, while understanding of other floodplain sub-types remains limited.

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Rogosch, Jane S., i Julian D. Olden. "Dynamic contributions of intermittent and perennial streams to fish beta diversity in dryland rivers". Journal of Biogeography 46, nr 10 (5.08.2019): 2311–22. http://dx.doi.org/10.1111/jbi.13673.

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Sheldon, Fran, i Martin C. Thoms. "Relationships between flow variability and macroinvertebrate assemblage composition: data from four Australian dryland rivers". River Research and Applications 22, nr 2 (2006): 219–38. http://dx.doi.org/10.1002/rra.907.

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Dean, D. J., i D. J. Topping. "Geomorphic change and biogeomorphic feedbacks in a dryland river: The Little Colorado River, Arizona, USA". GSA Bulletin 131, nr 11-12 (24.04.2019): 1920–42. http://dx.doi.org/10.1130/b35047.1.

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Abstract The Little Colorado River in Arizona, United States, has undergone substantial geomorphic change since the late 1800s and early 1900s, consisting of sediment accumulation following an earlier period of likely widespread sediment evacuation. We analyzed hydrologic and geomorphic data at different spatial and temporal scales to determine the primary mechanisms responsible for these changes, and to provide context for periods of sediment evacuation and accumulation in other rivers. Peak-flow magnitude has progressively declined since the 1920s despite the occurrence of four alternating periods of high and low total annual flow. Largely coincident with this hydrologic change, the channel has narrowed between 72% and 88% in some reaches since the 1930s, with increases in sinuosity in wide alluvial valleys causing ∼21%–32% reductions in channel slope. Dense stands of vegetation colonized, and thus stabilized, the newly deposited floodplains. Although large, long-duration floods caused some channel widening, these floods have been too infrequent to offset the progressive narrowing. Channel narrowing, increases in sinuosity, decreases in slope, and increases in vegetative roughness appear to have caused biogeomorphic feedbacks, thereby exacerbating sediment deposition, disrupting flood conveyance, and contributing to decreases in peak-flow magnitude and in sediment transport. The progressive increase in water development in parts of the basin has also likely contributed to progressive declines in peak flow. These results show that biogeomorphic feedback processes combined with human water development may be as important as, if not more important than, changes in climate in driving hydrologic, geomorphic, and sediment-load change in dryland river environments.

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Sheldon, Fran, Martin C. Thoms, Oliver Berry i Jim Puckridge. "Using disaster to prevent catastrophe: referencing the impacts of flow changes in large dryland rivers". Regulated Rivers: Research & Management 16, nr 5 (2000): 403–20. http://dx.doi.org/10.1002/1099-1646(200009/10)16:5<403::aid-rrr593>3.0.co;2-3.

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Bateman, Heather L., Sidney B. Riddle i Erin S. Cubley. "Using Bioacoustics to Examine Vocal Phenology of Neotropical Migratory Birds on a Wild and Scenic River in Arizona". Birds 2, nr 3 (2.08.2021): 261–74. http://dx.doi.org/10.3390/birds2030019.

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Passive acoustic recorders have been used successfully as automated survey tools to detect terrestrial wildlife. However, few studies have monitored Neotropical migratory bird use of riparian forest habitat using this technology. Within dryland ecosystems, the forests along rivers support high bird diversity. Many bird species of conservation concern require these floodplain forest habitats for foraging, migration stop-overs, and breeding. Few studies have explored the use of acoustic records in riverine systems designated for conservation for their natural resource value via the Wild and Scenic Rivers Act in the USA. Using acoustic recorders, we document vocal activity of four riparian-obligate species (Bell’s Vireo, Vireo bellii; Summer Tanager, Piranga rubra; Yellow Warbler, Setophaga petechial; and Yellow-billed Cuckoo, Coccyzus americanus) to determine species occurrence along a Wild and Scenic River. We established three study reaches along the perennial Lower Verde River, in the Sonoran Desert of central Arizona, USA. Nine acoustic recorders were used over the period of 80–120 days during the summer of 2018. We measured vegetation composition and structure in 100 m2 plots paired with acoustic recorders. Visualizing vocal activity showed that three species were calling and singing at each reach; whereas, one species, the cuckoo, had fewer recordings and occurred later in the summer. We demonstrate the utility of acoustic monitoring even when applied to rare birds in complex riparian habitats. This information is important for land management and conservation efforts concerning these species of interest and identifying important habitat features in Southwestern US riparian woodlands.

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Devianti, Fachruddin, Eva Purwati, Dewi Sartika Thamren i Agustami Sitorus. "Application of Geographic Information Systems and Sediment Routing Methods in Sediment Mapping in Krueng Jreu Sub-Watershed, Aceh Province, Indonesia". International Journal of Sustainable Development and Planning 16, nr 7 (30.11.2021): 1253–61. http://dx.doi.org/10.18280/ijsdp.160706.

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Land management in the Krueng Jreu sub-watershed (Aceh Province, Indonesia) that did not follow soil and water conservation methods encouraged erosion. This can lead to silting of rivers or irrigation canals due to sediment deposition. Limited tools were the main reason for the infrequent measurement and mapping of these sediments in watersheds. Therefore, this study aims to conduct sedimentary mapping using GIS techniques combined with the sediment routing method to successfully produce a map of sediment assessment criteria for the Krueng Jreu sub-watershed area from 2010 to 2019. Rainfall and spatial data from the Krueng Jreu sub-watershed were analyzed to obtain several parameters of surface runoff, peak discharge, erodibility, slope, the value of ground cover, and land management. The results show that the Krueng Jreu sub-watershed was included in the wet climate type. The type of land use classification of savanna accounted for the most significant runoff, and land use type of open soil gave the smallest runoff. The maximum erosion found in the secondary dryland forest type land classification. It was known that the type of secondary dryland forest land use was the most significant contributor to sediment occurrence in the Krueng Jreu sub-watershed area.

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Sheldon, F., i M. C. Thoms. "In-channel geomorphic complexity: The key to the dynamics of organic matter in large dryland rivers?" Geomorphology 77, nr 3-4 (lipiec 2006): 270–85. http://dx.doi.org/10.1016/j.geomorph.2006.01.027.

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Boys, Craig A., i Martin C. Thoms. "A Large-scale, Hierarchical Approach for Assessing Habitat Associations of Fish Assemblages in Large Dryland Rivers". Hydrobiologia 572, nr 1 (5.04.2006): 11–31. http://dx.doi.org/10.1007/s10750-005-0004-0.

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Tobin, NF. "Presence of deoxynivalenol in Australian wheat and triticale dash New South Wales Northern Rivers region, 1983". Australian Journal of Experimental Agriculture 28, nr 1 (1988): 107. http://dx.doi.org/10.1071/ea9880107.

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Of 12 wheat samples from crops affected by head blight (caused by Fusarium graminearum) at harvest in the Northern Rivers region of New South Wales in November 1983, 11 contained up to 6.7 mg kg-1 (mean 1.8 mg kg-1) of the trichothecene mycotoxin, deoxynivalenol (DON, also known as vomitoxin). Grain feeds responsible for feed refusal and vomiting in a piggery in the region were found to contain up to 3.7 mg kg-1 of the toxin. Two triticale samples contained 9 and 11mg kg-1 of DON, but 2 barley samples were negative. A wide range of other wheat samples, principally representative of the New South Wales dryland wheat belt, were all, with 1 exception. found free of DON. Since DON can be produced in times of wet harvest, maximum limits for contamination of grains are recommended.

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Vélez-Agudelo, Camilo, i Marcela A. Espinosa. "Benthic diatoms in relation to environmental factors in an allochthonous river from Patagonia, Argentina". Marine and Freshwater Research 72, nr 9 (2021): 1340. http://dx.doi.org/10.1071/mf20249.

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Natural and human pressures increasingly threatening the biodiversity and water resources of dryland rivers. Fluvial environments of Patagonia harbour high diatom diversity, but their management value is overlooked. The aim of this study is to explore the diatom distribution in surface sediments of the Chubut River and evaluate their relationship with environmental variables. In total, 243 diatom taxa were identified in 16 littoral zone sites. The physical and chemical variables independently explained the variance in diatom data, whereas sediment texture had a low influence. Conductivity, major ions (HCO3–, Cl–, SO42–, Na+, K+, Ca2+ and Mg2+) and pH were the main environmental drivers explaining the diatom composition. As the highlighted variables increased near the mouth, so did the relative abundances of marine–brackish taxa such as Amphora copulatoides, Sarcophagodes alfred-wegeneri, Nitzschia fonticola and Tryblionella apiculata. Meanwhile, the presence of high pollution-tolerant diatoms can be put forward to explain the river health deterioration towards downstream areas. The marine–brackish taxa found at freshwater sites reflect a weak tidal influence in the estuary compared with other coastal systems of Patagonia. This study provides valuable information to test the hypothesis on the ecological status of aquatic resources and the potential effects of climatic and hydrological changes in the area.

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