https://orcid.org/0000-0002-5018-0594
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Abstract
This article reviews current trends in interdisciplinary river research to argue that a “water bias” or tendency consider rivers as synonymous with water can hinder our understanding of rivers and consequently also their management. While water is central in defining rivers, contemporary scholarship across a wide spectrum of the natural sciences has expanded from an initial focus primarily interested in water to conceptualize rivers as a more complex set of ecological and physical processes that includes sediment, nutrients, microbial communities, flora and fauna. River research in the social sciences, however, almost exclusively considers rivers as hydrological processes, thus poorly reflecting these advances. We argue that overcoming this “water bias” is essential to both natural and social science research on rivers. Conceptualizing rivers as more than just water, combined with the tools of the social sciences, can generate more robust explanations of how rivers work socially and physically. This in turn can enable more effective river management in a time of rapid social, climatological, and ecological change, when acknowledging the “messy” nature of rivers and their politics and co-producing river knowledge are key to decision-making about rivers’ futures.
Citation: Demuth B, Parrinello G, Wohl E (2025) Rivers are messy: Beyond the water bias in research and management. PLOS Water 4(11): e0000447. https://doi.org/10.1371/journal.pwat.0000447
Editor: Cameron Holley, University of New South Wales, AUSTRALIA
Published: November 5, 2025
Copyright: © 2025 Demuth et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This work was supported by the Institute at Brown for Environment and Society ($3000 to BD) and Émergence(s) Grant, project SHIFTING SHORES, City of Paris ($2000, GP). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
1. Introduction
The last few decades have seen significant advances in interdisciplinary river studies across the natural and social science divide, along with calls for interdisciplinary collaborations from different communities [1–3]. New frameworks have emerged to provide conceptual and methodological structure to these collaborations, such as hydrosociality, social hydrology, and rivers as socio-ecological systems [4]. In a few cases, interdisciplinary collaborations have started to produce research results.
Current interdisciplinary research on rivers, however, remains hindered by a tendency to consider rivers as synonymous with water. While water is central in defining rivers, contemporary scholarship across a wide spectrum of the natural sciences has expanded from focusing primarily on water and begun to conceptualize rivers as a more complex set of ecological and physical processes that include sediment, nutrients, microbial communities, flora, and fauna. River research in the social sciences, however, almost exclusively considers rivers as hydrological processes, thus poorly reflecting these advances.
We argue that overcoming this “water bias” is essential to both natural and social science research on rivers. River research needs the social sciences, as they offer powerful tools to understand economic, social, and political drivers and consequences of riverine changes. Conceptualizing rivers as more than just water, combined with the tools of the social sciences, can generate more robust explanations of how rivers work socially and physically. It also highlights the “messy” nature of rivers and their politics, thus enabling more effective river management in a time of rapid social, climatological, and ecological change.
The article begins by briefly reviewing the contemporary understanding of rivers in the natural and social sciences and the extent to which these fields show a water bias. Section 2 traces the origins and consequences of the water bias on rivers and in research. Section 3 presents examples of research that integrates the social and natural sciences to move beyond the water bias and toward multi-scalar and multivariable understandings. Section 4 emphasizes the importance of acknowledging the “messy” nature of rivers and their politics in twenty-first century river management, and co-producing river knowledge as part of decision making.
2. The water bias in scholarship and management
2.1. Beyond the water bias: contemporary natural science understanding of rivers
Until the end of the 20th century, natural sciences focused on the role of water as a primary driver of river process and form. Although sediment and biota, especially woody vegetation, were acknowledged to influence rivers, these influences were more difficult to quantify than those associated with flowing water. The initial focus on water is reflected in conceptualizations such as hydraulic geometry [5], which used stream gauge records of discharge to develop quantitative relations between discharge and channel dimensions; the river continuum concept [6], which emphasized downstream changes in channel dimensions and ecological communities in response to downstream increases in discharge; and the natural flow regime [7], which emphasized characteristics of discharge (e.g., magnitude, frequency) as primary drivers of riverine biota. The idea of natural regimes governing riverine environments was subsequently expanded to include sediment [8] and large wood [9]. These additional regimes reflect the contemporary understanding of rivers as integrated biophysical systems driven by many more variables than simply water.
Natural scientists who investigate rivers include geologists, physical geographers, stream and riparian ecologists, and biogeochemists. Each individual brings their own disciplinary perspectives to this work, but the commonality is generally a recognition that conceptualizing a river involves four basic aspects. First, a river is not only the active channel, but also includes the adjacent floodplain and underlying hyporheic zone, as reflected in the phrases ‘river corridor’ or ‘riverscape’ [10,11]. This understanding recognizes the importance of varying levels of connectivity of materials and organisms in three dimensions (longitudinal, lateral, vertical) as an inherent property of natural rivers [12]. Second, a river exists within a broader biophysical spatial setting (e.g., watershed or catchment; e.g., [13]). This understanding recognizes connectivity and feedbacks between a particular river or segment of a river and the uplands and network of rivers contributing materials to that particular river. Materials in this context include water, solutes, sediment, and organic matter from fine particles to large wood. Third, a river is an ecosystem with a history. The ecosystem portion of this conceptualization recognizes multi-directional and nonlinear interactions between physical processes and biota [14] and feedbacks between processes and forms. The ‘history’ portion recognizes that the sequence of events matters in constraining ongoing adjustments and future configurations of the ecosystem [15]. Fourth, a river exists within a societal context [16]. This understanding recognizes that (i) the river corridor and the catchment reflect past human alterations of uplands and river corridors, (ii) few, if any, rivers have not been at least indirectly affected by human-induced changes (e.g., warming climate), and (iii) ongoing and future management of rivers is undertaken in a specific context of economic, political, and social conditions. Fig 1 reflects the natural science understanding of rivers as including diverse fundamental processes and functions beyond the downstream conveyance of water.
Schematic illustration of the characteristics of rivers beyond water. Central photo is the Amazon River. Inset photos, clockwise from top center, illustrate: carbon sequestration in floodplain soils; biodiversity (paddlefish and other fish species of the upper Mississippi River); subsurface water storage (a groundwater spring emerging from the Redwall Limestone in the Grand Canyon, Arizona); nutrient supply and biological uptake (aspen leaves decaying on the bed of a stream); habitat (backwater habitat upstream from a logjam); sediment storage (people walking across a sandbar in Grand Canyon); biomass (aquatic macroinvertebrate larva in cases attached to a boulder in a stream); and water quality (the calcium-rich waters of the Little Colorado River in Grand Canyon).
The conceptualization of a river summarized above reflects a relatively recent convergence among river-focused disciplines of fluvial geomorphology, stream and riparian ecology, and river biogeochemistry. This convergence, which has accelerated during the first decades of the 21st century, broadens individual disciplinary perspectives and facilitates the greater insight that can result from an integrative perspective of river natural science.
2.2. The water bias in scholarship on rivers and society
Social science scholarship has a long engagement with the ways people relate to rivers, from their cultural meanings to the politics of river management, the history of human adaptations to rivers and changes to river systems, and the production of knowledge about rivers. It would not be possible to do justice to the depth and breadth of this literature in a lengthy review, let alone in a few short paragraphs. We argue, however, that a broad trend of this scholarship is a focus on water processes to the detriment of other aspects of rivers.
Contemporary social science scholarship is diverse and includes specialists from disciplines such as political science, human geography, economics, history, sociology, and anthropology. The engagement of each of these disciplines with rivers varies, and so does the perspective from which each of them looks at rivers. Overall, however, they provide some general insights into the social, economic, and political causes and consequences of riverine changes. First, social scientists show how rivers are deeply embedded in modern economies. This begins with rivers’ role in two fundamental sectors, energy and food production, which depend directly and indirectly on water availability [17–19] be it for electricity production through hydropower plants, cooling thermoelectric and nuclear power facilities, irrigation, or flood security. Second, social science research shows how river governance and use are indissociable from conflicting interests and diverging values and understandings. Rivers are simultaneously subject to differing levels of government (local, regional, national, and intra-state for international rivers), each having different agendas. Multiple stakeholders (e.g., local communities, farmers, energy producers, industries, and cities) also have opposing interests in river use and governance. The values attached to rivers, as well as the understanding of rivers, are equally contested among social groups [20]. Rivers, in other words, are political and economic objects as much as physical and ecological ones. Third, social science scholars reveal that river transformation is linked to fundamental historical processes such as state formation, colonialism, and industrialization [21]. Water control was a source of political legitimacy for states and empires across epochs and continents [22–24]. Modern colonial empires sought to engineer rivers as conduits for commerce and engines of agricultural intensification [25,26]. The development of industrial economies depended equally on using rivers as “sinks” for toxic byproducts [27] as well as sources of energy [28]. Today’s rivers cannot be understood without considering the legacies and path dependencies that result from these processes.
While rich and diverse, social science scholarship has predominantly focused on rivers as hydrological flows. Scholarship on river basin governance has mostly investigated decisions concerning water distribution and use (including pollution) at the subnational, national, or international levels. Scholarship in river economics has typically addressed the interdependencies among economic sectors stemming from shared water resources.
Historiography on rivers has predominantly focused on the alteration of hydrological flows through dams, levees, and canals, or water pollution by industries and cities. Even when they move beyond the water bias, for instance, by incorporating sediment [29,30] social science approaches rarely look at the complexity of rivers as they emerge from the more recent literature in the natural sciences [31].
3. The water bias in river management
3.1. The development of the water bias in river management
The reduction of rivers to water has played an important role in river use and management. Human interventions on river processes and flows have a millenary history, from the use of polders in China to channelization for flood control and irrigation by the Inka Empire in the Andes [21]. However, the scale of river changes intensified in the nineteenth and twentieth centuries, as nation-states sought to reduce flooding and channel movement and to use the water in rivers to facilitate agriculture, urbanization, electricity generation, navigation, and waste disposal.
European colonialism—the expansion of European presence and political control outside Europe beginning at scale in the fifteenth century—also played a major role in altering rivers. European empires considered rivers to be strategic arteries for commerce and territorial control and sought to facilitate this function by dredging their beds and straightening their channels. In places like south-east Asia, European empires also enrolled rivers in projects of agricultural intensification, building dams and diverting water to irrigate fields [25]. River transformation for navigation, agriculture, and industry was also important to countries that did not fall under European control, such as Japan, China, and the early Ottoman Empire, as well as African and Asian countries that obtained their independence in the 1950s and 1960s. So-called postcolonial states embraced river engineering, seen as a way to consolidate their independence and increase the wellbeing of their citizens [26].
This “command and control” approach [e.g., 32] focused on hard engineering to control and distribute water. It was not automatic or without alternatives. In mid-nineteenth-century France and Italy, for example, a spate of disastrous river floods—likely linked to the Little Ice Age—was accompanied by a debate on flood control. While artificial levees had been in use for centuries, river experts and state engineers began to argue for new policies, from upstream land management to the removal of levees altogether, on the grounds they were ineffective and rivers should be able to expand on the floodplain [33]. Advocates countered that the economic interests dependent on levees were too important, leaving no choice but to maintain levees [34]. By the late nineteenth century, state authorities effectively closed the debate by committing to unprecedented financial and technical investments to reinforce and expand levees [35].
During the twentieth century, the river basin or watershed became the privileged scale to achieve command and control, to assert colonial and neocolonial forms of power, and harmonize rivers’ multiple economic functions, and maximize the social benefits of water through hydropower and other projects [36], along with the quantification of water resources [37] This water-centric understanding of rivers sublimated the importance of sediments, biota (excepting in some cases economically important fish species), and the ecological role of flooding—not to mention spiritual or non-instrumental understandings of rivers.
Objections to large projects were often based on more expansive understandings of rivers, sometimes successfully. Before the development of fossil fuels in Alaska, many considered water, particularly as hydropower, to be one of the state’s most important resources. In the 1950s, the U.S. Army Corps of Engineers proposed damming the Yukon, Alaska’s largest river. The project would flood the Yukon Flats, an area roughly the size of Lake Erie, and submerge seven Alaska Native villages. The dam initially had federal support, including from President John F. Kennedy, and many boosters in the state, who saw such development as an integral to progress and the river as a malleable body of water that could be changed without significant downsides. Alaska Native leaders organized a statewide and then national campaign against the dam, drawing on their knowledge of the river to assert the project’s potential ecological damage and elision of Indigenous rights. A key part of their argument focused on the river as more than just water, emphasizing the critical nesting habitat for waterfowl in the Yukon Flats, the social importance of timber along the river, and how arresting salmon migration at the dam site would withhold their nutrients from reaching more than a thousand miles of river. Alaska Native organizing to protect the Yukon became critical in a larger movement for land claims with the federal government, and the basis for coalition-building beyond Alaska. By the mid-1960s, national environmental groups like the Sierra Club, bird hunters’ associations, and some in the U.S. Fish and Wildlife Service joined in opposition, citing these social and environmental consequences. Debate over the dam continued until President Jimmy Carter designated the proposed flood zone a national monument in 1985 (Fig 2).
U.S. Army Corps of Engineers rendering of the Rampart Dam, Alaska. Committee on the Environment and Public Works (Government Publishing Office, Washington, D.C. 1979): 47. [public domain].
While such historical examples show that engineering rivers primarily for their water resources is not inevitable, the water bias has become a global norm in management, with the result of homogenizing and simplifying river flows, processes, and morphology [38–40].
3.2. Consequences of the water bias in river management
A major consequence of the water bias is that rivers are partitioned into their component parts, causing linked factors to be treated as separate or rendered invisible.
Many rivers have experienced multiple ecological and physical alterations, often as the unintended consequence of water engineering and use, or due to actions that were excluded from the purview of river management approaches that focused only on water and the river channel. Examples of unintended consequences include the alteration of sediment cascades due to hydropower and irrigation dams [41] and the reduction of the nitrogen uptake capacity of rivers caused by floodplain reclamation through levees [42]. Actions often excluded from the purview of river management include pesticide and fertilizer use in agriculture; plastic, nuclear, and other pollution; and the introduction or the extirpation of species, both aquatic and terrestrial.
These changes can be additive. Flow regulation and consumptive water use can cumulatively prevent rivers from reaching the ocean (e.g., Indus, Colorado, Huang He Rivers). Substantial loss of carbon storage in the floodplains of large rivers stems from multiple human alterations. For example, in addition to dams, sediment cascades can be altered by upland land cover increase (e.g., deforestation, agriculture) or decrease (e.g., urbanization); by aggregate mining that removes sediment from river corridors; flow diversions that alter the ability of river channels to move sediment; and river engineering that either reduces the mobility of sediment (e.g., bank stabilization) or removes sediment from a river (e.g., dredging). Looking both at and beyond water shows how several or all of these factors aggregate to change rivers.
Alterations to rivers directly or indirectly resulting from the water bias are now evident in most rivers of the world as shown in Fig 3, with detrimental effects on aquatic and terrestrial ecosystems as well as human activities that depend on rivers.
Map designed by John Wyatt Greenlee using the following map layers: https://www.cia.gov/the-world-factbook/static/47d9018542b378ee53f7e78001f9cf29/world_phy_03102025.pdf; https://upload.wikimedia.org/wikipedia/commons/6/6a/CIA_WorldFactBook-Political_world.pdf; https://en.wikipedia.org/wiki/File:Winkel_triple_projection_SW.jpg#/media/File:Winkel_triple_projection_SW.jpg.
4. Understanding river change beyond the water bias
Explaining complex, cumulative riverine transformations requires the insights and methods of both the natural and social sciences. This section offers cases that do so. We have selected the case studies below among the most well-documented ones in both the natural and the social sciences. The wealth of multidisciplinary research on these cases allows us to showcase the benefits of integrating a broad understanding of riverine processes beyond the water bias with complex explanations of social change. Each case study looks at both small-scale indirect causes and large-scale direct changes to river forms and processes, to expand the definition of a river to include, but not be limited to, water.
4.1. Causes and consequences of ignoring nutrient cycling in rivers
4.1.1. State expansion, trophic webs, and river change.
Trophic cascades occur when predators limit the density or behavior of their prey in a manner that enhances the survival of organisms lower in the food web. Alteration of trophic levels in a terrestrial ecosystem can influence river ecosystems when terrestrial organisms use river corridors. The most well-documented example comes from Yellowstone National Park in the United States; it is also a case tied to U.S. colonization west of the Mississippi and later, settler-agriculture focused policies in the 19th and 20th centuries.
Historically, Yellowstone elk herds faced predation from wolves and the region’s Indigenous peoples. Colonial policies following the expansion of U.S. territory in the later nineteenth century changed predation. Across the U.S. West, the federal expropriation of Indigenous land for settler agriculture led to the near extermination of large wild mammals and their replacement with domestic stock. National parks like Yellowstone, founded in 1872, were intended to preserve elk, bison, and other game. Indigenous residents were expelled from the park and hunting restricted [43]. Outside the park, federal policy eliminated wolves by the 1930s to protect settler livestock. Wolf extermination facilitated elk population increases, particularly within park boundaries where competition from domestic animals was absent and human predation limited to targeted culls after the 1930s [44].
Elk can heavily browse willows (Salix spp.) in river corridors, causing stunting or dieback of willows. Loss of willows can reduce the resistance of streambanks to erosion, as well as limiting habitat for beaver (Castor canadensis). In Yellowstone, these changes transformed river corridors from beaver meadows with high water tables, abundant floodplain wetlands, densely vegetated willow carrs, and interconnecting channels, to the alternate state of elk grasslands with lowered water table, minimal surface water, and woody vegetation, as well as a single, incised channel [45]. Here, combining a social and natural science perspective shows how federal policies that were not focused on rivers, but were intended to expand U.S. sovereignty through settled agriculture—with select regions set aside for conservation— substantially altered Yellowstone’s trophic relationships and regional hydrology.
4.1.2. The Gulf of Mexico dead zone.
Each summer, excess nitrogen causes a large hypoxic zone to form in the Gulf of Mexico. The primary cause is the application of inorganic nitrogen fertilizers thousands of miles away on farmland in the Upper Midwestern portion of the Mississippi drainage [46]. The use of inorganic nitrogen is itself the result of intensified agricultural production following the Second World War, a shift in political economy that has also seen global supply chains consolidate into a limited number of agribusiness corporations [47]. Regulating nitrogen fertilizers is now politically complex due to agribusiness lobbying power and, within the United States, the hesitancy of presidential candidates to change agricultural policy in part due to the early presidential primary in Iowa [48].
The source point, however, is only part of the explanation. The ecological and physical condition of the river corridor is also critical to understanding the causes of excess nitrogen in coastal waters. Microbial communities that live in wet riparian areas play a crucial role in processing nitrogen inputs. In the case of the Mississippi River, wet riparian areas have shrunk, beginning with fur trade pressure on beaver (Castor spp.) in the eighteenth century. Beavers create systems of dams and canals that retain surface and subsurface water, solutes, sediment, and organic matter. This facilitates resilience to floods, droughts, and wildfires; enhances uptake of nutrients; and substantially enhances biomass and biodiversity among a diverse array of organisms that use or inhabit river corridors [49]. Extensive trapping of beavers along the Mississippi and its tributaries from the early colonial period onward has transformed the ecosystems of small to medium-sized channels and the larger floodplain [50].
Wet riparian zones shrunk considerably again in the twentieth century, primarily due to the Army Corps of Engineers’ federal levees program. Standardizing river flow for transportation and flood control, while making floodplain land available for agriculture and urbanization, has drastically limited the ability of the river corridor to absorb and process nitrogen inputs coming from upstream leading to the sediment plumes visible in Fig 4. Extensive nearshore “dead zones” caused by excess nitrates appear across the world, including the Chesapeake Bay, the Baltic Sea and the Black Sea [51].
The Mississippi River watershed drains 1.245 million square miles, including all or parts of 31 U.S. states and two Canadian provinces. This map illustrates how runoff from farms (green areas) and cities (red areas) drains into the Mississippi River, delivering nutrients into the Gulf of Mexico and fueling the annual hypoxic zone. Credit: NOAA.
4.2. Sediment starvation in river management
4.2.1. Land loss in the Mississippi delta.
Sediment cascades describe the movement of mineral sediment and adsorbed materials from source areas into depositional environments such as river floodplains or the seafloor. Rivers form a primary conduit for the transport of sediment from terrestrial to marine environments and the sediment substantially influences river ecosystem processes and forms as it moves through or is stored within river corridors. Changing sediment transport has wide-ranging consequences. Engineering on the Mississippi River, for example, has caused significant land loss in the river delta, a process that has been accelerating since the late twentieth century as tributary dams prevented sediments from entering the main stem and stabilized banks on the lower river decreased erosion, starving the deltaic coast of the material necessary to sustain growth.
By the late twentieth century, land loss became a major political problem and, combined with sea level rise, is dramatically affecting coastal communities that are increasingly vulnerable to storm surges and displacement [52]. This land loss is the direct consequence of river engineering that focused only on water and certain functions of the river—energy production, flood control, and transportation—to the detriment of its geomorphic functions. Similar dynamics have led to subsidence elsewhere in the world, including the Mekong [53], as well as the disappearance of sandy beaches due to reduced riverine inputs of sand [54].
The acknowledgment of the shortcomings of past management approaches in the Mississippi led the Army Corps of Engineers to design and implement the Mid-Barataria Sediment Diversion, aimed at letting the river flood part of the delta and thus deposit sediment to counter subsidence and erosion. Although more attentive to the necessity of sediment than past management, this approach still ignores social and political implications, as proved by the conflict with disenfranchised African American communities living in the area now regularly flooded by the new sediment diversion [55].
4.2.2. Sediments and near-shore fisheries in Egypt.
Sediment loss has also affected the Nile River and its delta as a result of the Aswan High Dam, completed in 1970 and designed to store water for year-round irrigation, electricity generation, and to streamline the flow of the lower Nile. Preceded by a smaller dam in 1902 [56], the High Dam was first conceived under British colonial rule, but built under the authority of the post-colonial government of General Nasser with the Soviet Union’s assistance. It was a crowning achievement of Nasser’s rule, who made the dam a symbolic and material demonstration of Egypt’s newfound political and economic independence from colonial powers. The energy generated by the dam would power infrastructural modernization and industrialization, while year-round irrigation enabled by the dam would sustain the growth of agricultural productivity [57]. The dam, however, also stored the sediment that the Nile carries, especially from the Ethiopian plateau. Sediment and nutrients from the upper Nile played a major role in maintaining soil fertility in the highly cultivated river corridor and were essential to the progradation and nutrient resources of the delta. The first attempt at damming the Nile, made by the British in 1902, had already reduced the amount of sediment reaching the delta and caused a visible increase in coastal erosion by the 1950s. The High Dam, by capturing a much larger proportion of Nile sediment fluxes, has had a more significant impact on the delta, which is now menaced by submergence [58]. The consequences on the delta were well known at the time. However, the political significance of the dam as a symbol of postcolonial independence and prosperity encouraged the Egyptian government to pursue its completion and hide official evidence of potential harm to the delta [59].
Completion of the High Dam also caused a collapse of the coastal Mediterranean fisheries off the Nile Delta, although the fishery has recovered since the mid-1980s as artificial fertilizer and sewage outflows from Egypt have increased [60]. The recovery, however, is partly produced by ‘fishing down’ the marine food web [61]. Analogous fluctuations in nearshore commercial fisheries have occurred in the Black Sea.
4.3. Research beyond the water bias
These examples focus on nutrient cycling and sedimentation, but research that looks beyond the water bias can also include, among other examples, the loss of biomass and biodiversity in river and riparian ecosystems, or changes to river processes that reduce resilience to floods, droughts, and wildfires. Critical to this research is the integration of social and natural science, while taking an expansive approach to research questions. In the social sciences, this can require looking beyond sources typically associated with rivers (e.g., accounting for agricultural and forestry policy broadly rather than irrigation policy alone) and paying attention to a range of approaches to living with rivers, including ideas that were proposed as alternatives to the water bias. In the natural sciences, this requires continuing and expanding the integrative approach outlined above. In any kind of research, the elements of what a river is can include a wide range of variables—to name a few, electoral dynamics, agricultural policies, forest use, species distribution, sedimentation, and climate changes. The result is scholarship in which river processes are not reduced to water processes, and river politics are not limited to water distribution and control, showing the messiness and dynamism of rivers at scales from the microbial to the global.
5. Moving beyond the water bias in river relationships
Viewing and managing rivers as if they are synonymous with water is both intellectually and practically an act of simplification, reducing complex and interrelated social and ecological processes to a single if important variable. Managing rivers with this goal has compromised the full range of river functions for many rivers globally, as rivers need to flood, move and shrink; carry driftwood and sediment; provide habitat for and be shaped by animals and plants; and play a fundamental role in nutrient cycling, delta creation, and marine ecosystems (Figs 5 and 6). We are calling this variability and indeterminacy at a range of scales and functions messiness.
When a river is regarded only as water, societal emphasis may be on resources and hazards, as illustrated by the inset photos around the central photo of Starved Rock Dam on the Illinois River in Illinois.
When we move beyond the water bias, rivers are perceived to exist within broader contexts involving physical (water, sediment), chemical (pesticides, nutrients, contaminants), and biological (introduced species, extinctions) influences from the greater environment, as well as societal (regulations, elections) controls.
Managing rivers primarily for their water might appear to make them tidy and predictable but often has the result of making riverine systems less stable or resilient. Messiness denied in the short term can compound into substantial issues over time. For many rivers, the varied impacts of climate change will only exacerbate such consequences, due to shifts in rainfall, stronger storm surges, changes in species density and range, and other factors [62]. The climatological and ecological context of the twenty-first century needs forms of management that allow rivers to function as more than channels of water.
At least five approaches based in a growing recognition of the problems stemming from traditional river management are moving in this direction. These approaches include creating environmental flows [63] that restore key aspects of the natural flow regime [7] by modifying dam operations or purchasing reserved water rights for environmental applications [64]. The longest-running and best documented example of the effects of environmental flows comes from the Colorado River in the Grand Canyon of Arizona, USA, where ongoing monitoring of the physical and biological effects of experimental high flow releases from Glen Canyon Dam have been used to adjust the timing, magnitude, and duration of these flow releases [e.g., 65]. Second, removing dams [66] and other flow regulation structures such as diversions can be used to restore longitudinal connectivity for water, solutes, sediment, and organisms. Dam removal has been highly successful in some rivers such as the Elwha River in Washington, USA [e.g., 67], but dam removal can also be problematic because of (i) continuing need for dam-related services such as hydropower or water storage [68], (ii) the presence of contaminated sediments in the dam’s reservoir [69], or (iii) the ability of the dam to limit movement of introduced aquatic organisms that may threaten native freshwater ecosystems [70].
A third approach that goes beyond traditional river management involves restoring space within river corridors for biophysical adjustments to fluctuating flows. This is known by various names, including room for rivers, accommodation space, and freedom space [71]. The idea is that, rather than trying to rigidly control river form, as in traditional approaches, at least some of the historical river corridor will be allowed to adjust to continual changes in water and sediment moving downstream. Examples of using this approach to river restoration include levee setbacks on the White River in Washington, USA [72] and the Bear River in California, USA [73]. A fourth approach designed to improve on traditional river management involves employing process- rather than form-based restoration of river corridors. The intent behind this approach is to consider ecological functions rather than just channel morphology and to allow processes such as water and sediment fluxes to drive ongoing adjustments in the river corridor [74,75]. Examples come from the Provo River in Utah, USA and the Congost River in Catalonia, Spain. On the Provo River, levee removal, construction of a new meandering and multithread channel planform, reconnection of the river to historic secondary channels, and reestablishment of channel-floodplain connectivity were designed to reestablish historic habitat diversity and connectivity [76]. On the Congost River, removal of engineering structures such as bank stabilization facilitated more natural river adjustment to fluctuating inputs via lateral channel migration and development of bedforms, all of which improved water quality biodiversity relative to unrestored reaches [77].
Finally, managing uplands to influence the water, sediment, and other materials entering rivers, such as via afforestation [78] represents a more integrative approach to managing rivers than has been traditional. Examples come from grazed uplands in the UK in which the planting of trees in shelter belts or buffer strips is used to reduce peak runoff from hillslopes [e.g., 79] and restored peatlands in the UK [80]. Achieving the more integrative, comprehensive river management envisioned in these approaches requires allowing rivers to function at a greater range of scales—allowing rivers to be messier in space and across time—with attention to the full range of riverine components.
Such process-focused river management is not politically straightforward. Even changing rivers’ forms is complex, as infrastructures like dams create the baseline experience of the landscape that people build their lives around, leading to culturally and politically fraught uncertainties. Altering channelization can impact what land is open to farming or construction. Managing rivers so their full range of processes can function has the potential to be still more intricate, as it expands the arenas in which decisions about rivers emerge—from narrow if often still contested decisions around form changes (e.g., removing levees) to issues as varied as the number of beavers in a landscape to the chemical composition of the car tires that, when used, create runoff toxic to salmon. Genuine tradeoffs can exist, as when diminishing hydroelectric capacity with dam removal can require using more fossil fuels. Making choices that allow river processes to operate beyond water will not be identical for every river system or its associated political, economic, and social contexts.
The water bias in scholarly and management discussions downplays tensions and reinforces hierarchies of knowledge. This can make river management appear to be a fairly constrained set of decisions about rivers’ most economically useful components, like water. But, the politics of living with rivers have always been complicated. As the examples above from Europe and Alaska show, people have long recognized and valued rivers for processes and functions beyond water and held reservations about managing rivers only for their water. As the Yukon River example indicates, when such knowledge is brought to bear on rivers, decisions that allow full function can result.
Arguments like those Alaska Native communities made for the Yukon River seventy years ago have grown to include calls for incorporating Indigenous ontologies into river care and decolonial research methods, particularly concepts of relationality rather than top-down management [81,82]. Researchers and community workers have used the One Health model to incorporate sociocultural values, land management, and pollution monitoring [83]. New legal tools, including designating rivers as persons or as having intrinsic rights, have become a global movement, often emerging from Indigenous understandings of rivers as agentic as in New Zealand and Columbia, or blend spiritual and western legal forms as in India [84,85]. In Ecuador, the rights of nature are now part of the national constitution, a legal status that has successfully prevented mining from destroying the headwaters of the La Plata River via a legal argument that linked river health and wholeness to the presence of cloud forests—an explicit articulation of rivers as agents made of more than water [86]. While the recent implementation of these laws means their full impacts are not yet clear, and some—as with the case of the Ganges in India—are not always tied to enforcement, they expand how and by whom rivers are defined significantly.
What this indicates is that management of rivers needs to be informed by the continued expansion and democratization of knowledge about rivers, and its incorporation into decisions made about how communities live with them. In addition to bringing social and natural science perspectives together, co-producing knowledge about rivers with practitioners, Indigenous knowledge-holders, local communities, and managers of both water and non-water aspects of rivers would allow alternative understandings—ones often ignored or overwritten by the water bias—to inform river-specific decisions. Allowing rivers the full mess that comes with functionality involves political and epistemic mess as well. Both river research and river management should strive to provide access to people with interests and knowledge formed through relationships with a wide range of riverine processes.
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