Ecosystem Responses to Water Resource Developments in a Large Dryland River

2019

River Research & Apps

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The study and management of rivers have undergone a metamorphosis over the last four decades, transitioning from individual sub‐disciplines towards interdisciplinary approaches and an increased focus on viewing riverine landscapes as social‐ecological systems. Within this context, there is a growing emphasis on the need to take resilience‐based approaches to living with rivers in a sustainable way that maximises public security, infrastructure protection, and economic, ecological, and cultural benefits and values. The concept of viewing rivers as social‐ecological systems is gaining traction in science and management discourse; however, the idea is not new, and indigenous knowledge systems consistently place humans within the natural world. Integrating environmental knowledge, in its various forms, plays a key role in understanding issues and developing solutions for freshwater managers, especially in the context of rivers as social‐ecological systems. The 5th Biennial Symposium of the International Society for River Science conference, themed “Integrating Multiple Aquatic Values,” provided a forum for sharing environmental knowledge underpinning freshwater management critical for achieving multiple goals. The papers in this special issue highlight the fundamental properties of rivers as social‐ecological systems and the attempts to integrate multiple values concerned with rivers and their landscapes. From a series of case studies, a set of challenges and opportunities emerge that have the potential to further the management and research of rivers as social‐ecological systems and integrate multiple aquatic values. Key to this is acknowledging and respecting the value that indigenous worldviews and knowledge bring. We also echo the call of other authors that if the overall goals are that rivers, societies, and their interactions are to result in positive social and ecological outcomes for people and rivers, then integrating and respecting multiple values and knowledge systems will be required.

Section: Themes Of This Special Issuementioning

confidence: 99%

Integrating multiple aquatic values: Perspectives and a collaborative future for river science

Pingram

Price

2019

River Research & Apps

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“…Hydrological variability and spatial heterogeneity in physical character are primary abiotic drivers that define the landscape of these complex ecosystems (Stanford et al. , Delong and Thoms , Thoms and Delong ). The flow regime of rivers operates across multiple temporal scales, from seconds to centuries (Walker et al.…”

Section: Introductionmentioning

confidence: 99%

“…Collectively, hydrological variability and geomorphic heterogeneity influence the organization of food webs through increased primary production (Thoms et al. , Thoms and Delong ), immigration/emigration of prey and predators (Robertson et al. ), and retentive zones for autotrophs and organic matter (Petit et al.…”

Section: Introductionmentioning

confidence: 99%

“…Floodplain rivers are an excellent landscape for investigating ecosystem biocomplexity (Tockner et al 2010a). Hydrological variability and spatial heterogeneity in physical character are primary abiotic drivers that define the landscape of these complex ecosystems (Stanford et al 2005, Delong and Thoms 2016b, Thoms and Delong 2018. The flow regime of rivers operates across multiple temporal scales, from seconds to centuries (Walker et al 1995, Dollar et al 2007, and can be characterized by variation in magnitude, frequency, timing, duration, and rate of change (Richter et al 1996).…”

Section: Introductionmentioning

confidence: 99%

“…Greater spatial heterogeneity increases the diversity of niches present, resulting in a concomitant increase in species richness (e.g., Post 2002). Collectively, hydrological variability and geomorphic heterogeneity influence the organization of food webs through increased primary production (Thoms et al 2017, Thoms andDelong 2018), immigration/emigration of prey and predators (Robertson et al 2008), and retentive zones for autotrophs and organic matter (Petit et al 2017). Floodplain-river ecosystems, therefore, provide an excellent model for illustrating the interplay between the habitat template (hydrogeomorphology) and biocomplexity (Tockner et al 2010b).…”

Section: Introductionmentioning

confidence: 99%

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Interactive effects of hydrogeomorphology on fish community structure in a large floodplain river

Sorenson

2019

Ecosphere

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Biocomplexity is an emergent property of ecosystems that captures the interplay of structures and processes at multiple scales. These interactions can establish a dynamic habitat template that serves as a filter to define ecological organization across landscapes. Studies of biocomplexity in floodplain rivers typically focus on hydrological variability or geomorphic heterogeneity separately, with their interactions being an output rather than the direct focus of investigations. This study examines the interaction of hydrological variability and geomorphic heterogeneity across 25 off‐channel habitats (OCHs) of the Upper Mississippi River, USA. Questions posed were as follows: What are the interactive effects of hydrological variability and geomorphic heterogeneity shaping the physical habitat template of OCHs? and How does the organization of the physical habitat template influence fish community composition within OCHs? Three distinct OCH groups emerged from this study: where hydrological variability defined Group 1 (Lake group); Group 2 was organized via geomorphic heterogeneity (Backwater group); and a combination of hydrological and geomorphological variables defined Group 3 (Slackwater group). Thus, the differential interaction of hydrology and geomorphology defined the dynamic physical habitat template of OCHs in this riverine landscape. No significant difference between the association matrices of the hydrogeomorphic template and fish community composition for the 25 OCH sites was recorded. A priori grouping of fish into the three OCH groups revealed marked differences in fish community composition. A subset of hydrogeomorphic variables that defined the physical character of the OCHs acted as an environmental filter for the fish community composition of the three OCH groups. A conceptual model explaining hydrogeomorphic–ecological interactions across the OCHs of this floodplain river system is provided.

Human impacts on suspended sediment and turbidity in the River Murray, South Eastern Australia: Multiple lines of evidence

Rutherfurd

Kenyon

et al. 2020

River Research & Apps

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European settlement has led to increased loads of fine suspended sediment (SS) entering the River Murray, Australia's largest, and arguably, most important river. The River Murray's anthropogenic sediment history can be divided into four periods with varying source areas, sediment loads, and seasonal patterns. The Aboriginal period (before 1840) was characterized by clear water at summer low-flows in the River Murray and its southern tributaries, with more sediment coming from the northern catchment than the southern, and the Darling River being turbid at all flows. There is little evidence that Aboriginal burning resulted in any measurable increase in SS. SS loads peaked in the 1870s and 1880s (the gold and gully period, 1850-1930) as valley floors were incised by gullies (mostly in northern tributaries), and gold sluicing flushed huge amounts of sludge into southern tributaries. Sedimentation in wetlands and on floodplains increased by 2-10 times in this period, and the biota in wetlands switched from clear water to turbid water communities.In the hiatus period sediment supply from gullies and gold mining waned and low flow SS concentrations returned to low levels. Dam construction through the 1960s and 1970s (the regulation period, 1960 on) disconnected the River Murray from catchment derived sediment. Despite this, SS levels increased again: now largely derived from instream sources including bank erosion from long duration summer irrigation flows, the spread of bottom-feeding carp (Cyprinus carpio), and wave erosion from boats. Erosion switched from winter to summer dominated. Significant investment in securing water for the environment in the Murray-Darling Basin could be complemented by addressing inchannel sediment sources in the River Murray itself to reduce turbidity. Overall, European era SS concentrations remain relatively low with small sediment delivery to the ocean (0.1Mt per annum), despite high catchment erosion rates. This is due to poor sediment delivery efficiency through the low-gradient landscape.