River Regime

11 Key excerpts on "River Regime"

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  eBook - ePub

  Introduction to Physical Hydrology

  • Richard J. Chorley(Author)
  • 2019(Publication Date)
  • Taylor & Francis

    (Publisher)

  10.I. River Regimes

  ROBERT P. BECKINSALE

  School of Geography, Oxford University

  The regime of a river may be defined as the variations in its discharge. In its widest sense the regime involves all occurrences and is portrayed by a curve based on continuous or hourly observations. Such curves, however, present complicated problems of analysis and for some purposes the discharge variations are better expressed by graphs of mean monthly flow. When used for critical purposes, such as the delimitation of hydrological regions, the ideal seasonal regime hydrograph (station-model) would show additionally, for each month and for the year as a whole:

  1.  the mean flow; 2.  the mean maxima and minima; and 3.  the absolute maximum and minimum.

  It would also be helpful to insert (not as a curve) the absolute daily maximum and minimum recorded during the period.

  However, for general comparative purposes and for global classifications the monthly means seem adequate and, indeed, such simple data is still not available for large areas. On this broad scale comparison is facilitated by expressing the mean monthly value either as a ratio of the mean monthly flow for the year (taken as 1) (as in figs. 10.I.5 and 10.I.6 ), or as a percentage of the mean annual flow (taken as 100) (as in figs. 10.I.2 and 10.I.3 ). If the actual quantities are stated as one of the ordinates this method does not lose much in practical utility, particularly if the mean annual total flow is also stated somewhere on the regime hydrograph. Only by insisting on actual quantity as well as on comparative ratios will the possibilities of inter-regional water exchanges be kept constantly before civil engineers and planners.

  1. Factors controlling River Regimes

  Seasonal variations in the natural runoff of a drainage basin depend primarily on the relationships between climate, vegetation, soils and rock structure, basin morphometry, and hydraulic geometry. Of these only rock structure and, to a lesser extent, basin size can be strictly independent of climate. It should be stressed that the features of basin morphometry and hydraulic geometry are only of direct relevance to the seasonal regimes of large river basins.

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  Riverine Ecosystem Management: Science for Governing Towards a Sustainable Future (Volume 8.0)

  • Stefan Schmutz, Jan Sendzimir(Authors)
  • 2018(Publication Date)
  • Springer Open

    (Publisher)

  Chapter 4 River Hydrology, Flow Alteration, and Environmental Flow Bernhard Zeiringer, Carina Seliger, Franz Greimel, and Stefan Schmutz “ The water runs the river. ” This chapter focuses on the river fl ow as the fundamental process determining the size, shape, structure, and dynamics of riverine ecosystems. We brie fl y introduce hydrological regimes as key characteristics of river fl ow. Hydrological regimes are then linked to habitats and biotic communities. The effects of fl ow regulation as a result of human activities such as water abstraction (irrigation and hydropower), river channelization, land use, and climate change are demon-strated. Finally, methods to assess the environmental fl ow, the fl ow that is needed to maintain the ecological integrity, are described, and examples of successful fl ow restoration presented. 4.1 The Water Cycle and Hydrological Regimes In temperate zones water received via precipitation is either stored in ice and snow during winter or in fi ltrates into the groundwater and is released into rivers during summer. Water cycles through stages of evaporation, water storage in the atmo-sphere, precipitation, (sub)surface runoff, and storage in the ocean. The water cycle and climatic conditions form the boundary conditions for the hydrological regimes that de fi ne distinct seasonal and daily fl ow patterns. High altitude rivers receive water mainly from glacial melt during summer with distinct diurnal melting peaks following air temperature warm-up ( glacial regime ) (Fig. 4.1 ). At lower elevations snow melting in spring causes seasonal peaks ( nival regime ), while periods of high fl ow and fl oods due to rainfall can occur at any time of the year ( pluvial regime ).

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  Friend Report Flow Regimes from International experimental and network data

  • (Author)
  • 1997(Publication Date)
  • Irstea

    (Publisher)

  Unstable and relatively unstable regimes are found in the low zones where the flows are of the rainfall-snowmelt origin and when during some winters with much snow the earlier snowmelt in the spring time is not synchronous with the rainfall period (which is usually April-June).

  6 Conclusions

  ● The significant variation in altitude of a zone or catchment subject to the influence of a particular climate leads to a differentiation of several micro-types of flow regimes. If a certain zone is found under the control of the intersection of many atmospheric circulation the micro-regime is a result of their combination with the altitude influence.

  ● An appropriate index of the stability of a particular flow regime is the total entropy of the occurrence of the characteristics discriminating a flow pattern.

  Stability of river flow regimes

  Stabilité des regimes d’ecoulements en rivières

  I.Krasovskaia, L.Gottschalk

  1 Introduction

  A flow regime describes the average seasonal behaviour of river flow. This characteristic of river runoff is important for sustainable environmental management and in particular for rational use of water resources. An inherent characteristic of a flow regime is its stability, i.e. regularity of the seasonal pattern. This pattern can demonstrate more or less similar temporal distribution of periods with high and low flow during each individual year, i.e. a stable regime, or it can alternate between a couple of different patterns during individual years, i.e. an unstable regime. Seasonality of river flow is by tradition described on the basis of long-term average values, which tell nothing about the stability of the flow regime. Meanwhile, flow stability represents an important environmental constraint for many aquatic species and operational water management schemes rely upon certain stability of seasonal flow patterns.

  Being the product of climatic and physiographic conditions in a basin, river flow regimes reflect the character of these two factors. Natural or man-induced changes in basin’s environment and climate are therefore inevitably followed by changes in river flow regimes and their stability. An objective river flow regime classification, having among its discriminating criteria also stability of seasonal flow patterns, expressed in quantitative terms, offers a reference frame, necessary to follow these changes in time and to be able to predict a future character of flow regimes. The aspect of variation of river flow regimes in time added a new temporal dimension to the, by tradition, static description of seasonal flow patterns. This new temporal dimension necessitates frequent updating of the flow regime classification, which with regard to large data sets is hardly feasible, unless it is computer-performed.

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  Environmental Flows

  Saving Rivers in the Third Millennium

  • Angela Arthington(Author)
  • 2012(Publication Date)
  • University of California Press

    (Publisher)

  Understanding historical and recent temporal patterns of flow, temperature, and other environmental drivers is central to the development of river management and environmental flow strategies (Petts and Amoros 1996). Appreciation of the dynamic nature of river flows in spatial dimensions and over different times scales was one of the ideas that sparked the next conceptual development. THE NATURAL FLOW REGIME PARADIGM The overriding importance of dynamic flow patterns in streams and rivers is captured in the Natural Flow Regime Paradigm (Poff et al. 1997), which states that “the integrity of flowing water systems depends on their natural dynamic character” and “streamflow, which is strongly correlated with many critical physicochemical characteristics of rivers, such as water temperature, channel geomorphology and habitat diver-sity, can be considered a ‘master variable’ . . . that limits the distribution and abundance of riverine species and regulates the ecological integrity r i v E r E c ol o g y a n d p r i nc i p l E s 55 of flowing waters.” One of the main ideas in this paradigm is that “nat-urally variable flows create and maintain the dynamics of in-channel and floodplain conditions and habitats that are essential to aquatic and riparian species” and that the “predictable diversity of in-channel and floodplain habitat types has promoted the evolution of species that exploit the habitat mosaic created and maintained by hydrologic vari-ability” (Poff et al. 1997). Adaptation of riverine species to this envi-ronmental dynamism “allows aquatic and floodplain species to persist in the face of seemingly harsh conditions, such as floods and droughts, that regularly destroy and re-create habitat elements” (Poff et al. 1997). A river’s flow regime can be described in terms of five flow facets: the magnitude, frequency, duration, timing, and rate of change of flows (see Chapter 2).

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  Large Rivers

  Geomorphology and Management

  • Avijit Gupta(Author)
  • 2008(Publication Date)
  • Wiley

    (Publisher)

  Geomorphology , 71: 126–138. Thoms, M.C., Beyer, P. and Rogers, K.H. (2006) Variability, complexity and diversity – the geomorphology of river ecosystems in dryland regions. In: The Ecology of Desert The Murray-Darling Basin 607 Rivers (R.T. Kingsford, Ed.). Cambridge University Press, Cambridge, 47–75. Thorp, J.H., Thoms, M.C. and Delong, M.D. (2007) The River Ecosystem Synthesis . Elsevier (in press). Townsend, C.R. and Hildrew, A.G. (1994) Species traits in rela-tion to a habitat templet for river systems. Freshwater Biology , 31: 265–275. Van Niekerk, A.W., Heritage, G.L. and Moon, B.P. (1995) River classification for management: the geomorphology of the Sabie River in the eastern Transvaal. South African Geographical Journal , 77: 68–76. Wiens J.A. (1989) Spatial scaling in ecology. Functional Ecology , 3: 385–397. 29 Climatic and Anthropogenic Impacts on Water and Sediment Discharges from the Yangtze River (Changjiang), 1950–2005 Kehui Xu 1 , John D. Milliman 1 , Zuosheng Yang 2 and Hui Xu 3 1 School of Marine Science, College of William & Mary, Gloucester Point, VA 23062, USA 2 College of Marine Geosciences / Key Lab of Submarine Science and Exploration Technology, Ministry of Education, Ocean University of China, Qingdao 266003, People’s Republic of China 3 Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, People’s Republic of China Large Rivers: Geomorphology and Management , Edited by A. Gupta © 2007 John Wiley & Sons, Ltd 29.1 INTRODUCTION Rivers form the major links between land and ocean through their transfer of water and sediment. Fluvial dis-charges to the oceans, however, are unevenly distributed in both space and time, in large part influenced by both climatic (e.g. precipitation) and anthropogenic (e.g. dam construction) forcings.

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  Intermittent Rivers and Ephemeral Streams

  Ecology and Management

  • Thibault Datry, Núria Bonada, Andrew J. Boulton(Authors)
  • 2017(Publication Date)
  • Academic Press

    (Publisher)

  Chapter 2.1

  Geomorphology and Sediment Regimes of Intermittent Rivers and Ephemeral Streams

  Kristin L. Jaeger* ; Nicholas A. Sutfin† ; Stephen Tooth‡ ; Katerina Michaelides§ , ¶ ; Michael Singer¶ , **     

  * USGS Washington Water Science Center, Tacoma, WA, United States† Los Alamos National Laboratory, Los Alamos, NM, United States‡ Aberystwyth University, Aberystwyth, Wales, United Kingdom§ University of Bristol, Bristol, United Kingdom¶ Earth Research Institute, University of California Santa Barbara, Santa Barbara, CA, United States** Cardiff University, Cardiff, United Kingdom

  Abstract

  The geomorphology and sediment regimes of intermittent rivers and ephemeral streams (IRES) are extremely diverse, owing in large part to the substantial spatiotemporal variability of the associated hydrological regimes. We describe the geomorphological character and sediment transport processes along IRES within the context of four geomorphological zones—upland, piedmont, lowland, and floodout—to illustrate the underpinning longitudinal trends of sediment production, transfer, and deposition that exist at the landscape scale. Many geomorphological features of IRES tend to be spatially discontinuous as a result of extended no or low-flow conditions that are punctuated by high-magnitude flood events. Diversity of geomorphology and sediment regimes both within and between the four geomorphological zones therefore promotes ecological processes and patterns in IRES that can be very distinct from perennial river systems.

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  Environmental Sedimentology

  • Chris Perry, Kevin Taylor, Chris Perry, Kevin Taylor(Authors)
  • 2009(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  This chapter summarizes, updates and builds on this work, and, specifically, highlights the ever increasing effects of anthropogenic activity on sedimentation in rivers. 3.1.1 Definition and classification of fluvial environments, and relevance to environmental sedimentology The word ‘fluvial’ pertains to a stream or river, the existence, growing or living in or about a stream or river, or something that is produced by a river (Bates & Jackson 1980). Fluvial environ-ments occur on every continent on Earth and in every climatic zone (Fig. 3.1), and thus are often classified according to climate, with arid, semi-arid, temperate (cool), temperate (Mediterranean) and tropical types known (e.g. Jansen & Painter 1974). Rivers are also classified by their flow regimes, with perennial (flowing every year, throughout the year), intermittent (flow for only part of a year, every year, usually during or after a wet season) and ephemeral (occasional flow) types defined. Intermittent and ephemeral rivers often occur in Mediterranean or tropical environments, whereas perennial rivers occur in temperate regions. ‘Fluvial sediments’ are those sediments that consist of material transported by, suspended in, or laid down by a stream (Bates & Jackson 1980). They are important sources of nutrients, contaminants and other solid materials to downstream fluvial, estuarine and coastal envir-onments. Millions of tonnes of sediment are trans-ported annually to oceans (Table 3.1), with the 76 KAREN HUDSON -EDWARDS amounts determined by climate (precipitation), topography, vegetation cover, land-use, and the susceptibility of the underlying rocks, soils or other unconsolidated materials to physical, chem-ical and biological weathering. A river system is, by definition, the system of connected river channels in a drainage (catchment) basin (Bridge 2003). The system contains a large number of features, but the two most important are its channels and floodplains (Fig. 3.2).

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  Geomorphology and River Management

  Applications of the River Styles Framework

  • Gary J. Brierley, Kirstie A. Fryirs(Authors)
  • 2013(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  In recent decades there has been a shift in the way river change is perceived and tackled in river rehabilitation practice. The river engineering paradigm that emerged during the industrial revolution viewed nature to provide boundless resources to be conquered and utilized by human endeavor. Wherever rivers could be readily exploited by society through measures to control, divert, channelize, or dam them, they generally were. Management practices reflected human desires for simple, efficient, and predictable systems that enhanced prospects for economic development. Rivers were viewed as conduits with which to maximize the conveyance of water, sediments, and environmental “waste products” through uniform, stable, hydraulically smooth channels. Despite, or maybe because of, the profound changes to river character that have taken place following human disturbance, management efforts emphasized the need for “stable” rivers. Principles of regime theory, originally devised by hydraulic engineers as part of canal design specifications, were applied to create uniform channels with a prescribed hydraulic regime (the classic trapezoidal channel). Roughness elements such as riparian vegetation and woody debris were considered to produce messy, complex, and irregular channels, creating uncertainty and reducing predictability in what was ostensibly a “controlled” environment (Williams, 2001).

  When ecological impacts became so pronounced that societal alarm was raised, the engineering mind-set engendered a sense that problems could be rectified using the next variant of technological development (technofix). Reactive management practices were applied to maintain and protect infrastructure, navigation, and flood protection/ mitigation networks. However, in endeavors to stabilize channels, many engineering practices accentuated their instability (e.g., Leeks et al., 1988; Bravard et al., 1997). Imposing a stable channel through “training,” “improvement,” or “stabilization” techniques, or “normalized” flow regimes, will not result in sustainable or healthy river systems. Indeed, planning for “mean” conditions is unsympathetic to the natural range of biotic and geomorphic process activity. In many ways, the inherent variability of river behavior and responses to disturbance drives the functioning of aquatic ecosystems. Instability is a key attribute of many systems. Suppression of the natural tendency of rivers to adjust limits the capacity of systems to self-heal. Anything that compromises the ecological integrity of river systems leaves society worse off in financial, cultural, social, and environmental terms.

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  The Rivers Handbook

  Hydrological and Ecological Principles

  • Peter P. Calow, Geoffrey E. Petts, Peter P. Calow, Geoffrey E. Petts(Authors)
  • 2009(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  242 Modelling: Forecasting and Prediction equilibrium is most closely approached and the tendency to change is least. This condition may be regarded as the integrated effect of all varying conditions over a long period of time. Unfortunately, there is no universally agreed method of determining the dominant discharge. In a recent study a number of the different definitions proposed for dominant discharge were compared on data from large gravel rivers in Alberta. The data set was not extensive so it is difficult to be dogmatic about the results, but the best predicted expressions were those based on flow frequency. The discharge which is exceeded 0.6% of the time gave the best predictions (White et al 1986). Design of physical models As part of an investigation for a water intake for an irrigation scheme a mobile·bed model was designed of the Sabi River} a large sand river in Zimbabwe. The river channel was in regime and the physical model was designed on the basis that the model channel must also be in regime (White 1982). The resulting model successfully repro- duced the behaviour of the prototype. Assessment of morphological changes in rivers An investigation was carried out into the impact of a proposed dam at Condo on the Sabi River. One of the effects of the dam would be to alter the distribution of flows in the river downstream. By determining how the dominant discharge would be changed the effect that this would have on the river morphology was assessed using regime theory (Hydraulics Research 1982). 12.4 PLAN FORM OF RIVERS Although the plan shapc of rivers displays a continuous variation of form it has traditionally been classified into the three broad categories of straight, meandered or braided. The division into the three categories is in part arbitrary as it is difficult to distinguish between a straight channel and a meandering channel of low sinuosity and not everybody agrees on what constitutes a mean- dering or braided channel.

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  River, Coastal and Estuarine Morphodynamics: RCEM 2007, Two Volume Set

  Proceedings of the 5th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, Enschede, NL, 17-21 September 2007

  • C. Marjolein Dohmen-Janssen, Suzanne J.M.H. Hulscher(Authors)
  • 2019(Publication Date)
  • CRC Press

    (Publisher)

  Regime modelling of morphology J.R. Spearman HR Wallingford ABSTRACT: Estuary morphology studies often adopt an approach, commonly termed Expert Geomorpho-logical Assessment (EGA), based around the use of empirical or simple analytical relationships, aided by broad rules of thumb and expert judgement. In a recent research project funded by the Department of the Environment, Food and Rural Affairs in the UK the tools for assessing the future evolution of estuary morphology have been reviewed and formalised. As part of this review the use of Regime Theory was considered, a tool often used in EGA. In simple terms this approach adopts some characteristic relationship between hydrodynamics and estuary morphology, such as tidal prism and cross-section area, and uses this simple formula to describe estuary equilibrium. The validity of this approach is explored. By considering how flow parameters will change as a result of anthropogenic intervention, or as a result of natural processes, it is possible to use Regime Theory to make an assessment of how the morphology will evolve as a result. Perturbation analysis indicates that the use of Regime Theory, when combined iteratively with a flow model, approximates to long term sediment transport, providing certain conditions are satisfied. However, the form of the resultant characteristic regime relationship resulting from the perturbation analysis is different to those commonly used in the literature and demonstrates the importance of sediment supply to the nature of estuary equilibrium. The consequences of this result are discussed in the context of the evolution of muddy estuaries. The differences in the nature of evolution of muddy estuaries and sandy estuaries are discussed.

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  River Dynamics

  Geomorphology to Support Management

  • Bruce L. Rhoads(Author)
  • 2020(Publication Date)
  • Cambridge University Press

    (Publisher)

  388 River Dynamics and Management on water and sediment fluxes occurs at the watershed scale. Human disturbance may produce flux boundary conditions for the transformed style that differ from the undisturbed, or reference, flux boundary conditions for this style. In this case, management may be directed at mitigating the effects of these disturbed flux boundary conditions or at reestab- lishing the reference flux boundary conditions. In other cases, slow recovery may gradually return the disturbed system to its predisturbance style (Rathburn et al., 2013), but recovery times may greatly exceed ordinary manage- ment timescales, which are usually only on the order of several decades. In such evolving river systems, long-term management may have to be directed at reference conditions that are moving targets (Brierley and Fryirs, 2016). 16.6 What Is the Role of Geomorphology in Implementation of Management Strategies? Besides providing useful information and analysis for developing appropriate management strategies to address problems related to river dynamics, fluvial geomorphology can contribute directly to implementation of these strategies. A variety of management strategies are possible, ranging from doing nothing to undertaking various forms of restora- tion, naturalization, mitigation, or even creation. Except in the case of doing nothing, existing river forms and processes usually are actively reconfigured to achieve more desirable conditions. Implementation of such strategies involves the formulation of environmental designs so that input from the applied design science of fluvial geomorphology becomes highly relevant at this stage of management. Although scientific and technical information, including geomorpho- logical information, usually is taken into account in implementing management strategies, decisions about implementation also involve social, political, economic, and aesthetic considerations.

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