ArticlePublisher preview available

The Irrigation Effect: How River Regulation Can Promote Some Riparian Vegetation

Authors:
Karen Gill at University of Lethbridge
Karen Gill
Lori Goater at University of Lethbridge
Lori Goater
Jeffrey H. Braatne
Jeffrey H. Braatne
Jeffrey H. Braatne
  • This person is not on ResearchGate, or hasn't claimed this research yet.
Stewart Rood at University of Lethbridge
Stewart Rood
Read publisher preview
Download citation
To read the full-text of this research, you can request a copy directly from the authors.

Abstract and Figures

River regulation impacts riparian ecosystems by altering the hydrogeomorphic conditions that support streamside vegetation. Obligate riparian plants are often negatively impacted since they are ecological specialists with particular instream flow requirements. Conversely, facultative riparian plants are generalists and may be less vulnerable to river regulation, and could benefit from augmented flows that reduce drought stress during hot and dry periods. To consider this ‘irrigation effect’ we studied the facultative shrub, netleaf hackberry (Celtis reticulata), the predominant riparian plant along the Hells Canyon corridor of the Snake River, Idaho, USA, where dams produce hydropeaking, diurnal flow variation. Inventories of 235 cross-sectional transects revealed that hackberry was uncommon upstream from the reservoirs, sparse along the reservoir with seasonal draw-down and common along two reservoirs with stabilized water levels. Along the Snake River downstream, hackberry occurred in fairly continuous, dense bands along the high water line. In contrast, hackberry was sparsely scattered along the free-flowing Salmon River, where sandbar willow (Salix exigua), an obligate riparian shrub, was abundant. Below the confluence of the Snake and Salmon rivers, the abundance and distribution of hackberry were intermediate between the two upstream reaches. Thus, river regulation apparently benefited hackberry along the Snake River through Hells Canyon, probably due to diurnal pulsing that wets the riparian margin. We predict similar benefits for some other facultative riparian plants along other regulated rivers with hydropeaking during warm and dry intervals. To analyze the ecological impacts of hydropeaking we recommend assessing daily maxima, as well as daily mean river flows.
Figures - available from: Environmental Management
This content is subject to copyright. Terms and conditions apply.
A preview of this full-text is provided by Springer Nature.
Learn more
Content available from Environmental Management
This content is subject to copyright. Terms and conditions apply.
Environmental Management (2018) 61:650–660
https://doi.org/10.1007/s00267-017-0991-4
The Irrigation Effect: How River Regulation Can Promote Some
Riparian Vegetation
Karen M. Gill1●Lori A. Goater1●Jeffrey H. Braatne2●Stewart B. Rood 1
Received: 11 June 2017 / Accepted: 29 December 2017 / Published online: 11 January 2018
© Springer Science+Business Media, LLC, part of Springer Nature 2018
Abstract
River regulation impacts riparian ecosystems by altering the hydrogeomorphic conditions that support streamside vegetation.
Obligate riparian plants are often negatively impacted since they are ecological specialists with particular instream flow
requirements. Conversely, facultative riparian plants are generalists and may be less vulnerable to river regulation, and could
benefit from augmented flows that reduce drought stress during hot and dry periods. To consider this ‘irrigation effect’we
studied the facultative shrub, netleaf hackberry (Celtis reticulata), the predominant riparian plant along the Hells Canyon
corridor of the Snake River, Idaho, USA, where dams produce hydropeaking, diurnal flow variation. Inventories of 235
cross-sectional transects revealed that hackberry was uncommon upstream from the reservoirs, sparse along the reservoir
with seasonal draw-down and common along two reservoirs with stabilized water levels. Along the Snake River
downstream, hackberry occurred in fairly continuous, dense bands along the high water line. In contrast, hackberry was
sparsely scattered along the free-flowing Salmon River, where sandbar willow (Salix exigua), an obligate riparian shrub, was
abundant. Below the confluence of the Snake and Salmon rivers, the abundance and distribution of hackberry were
intermediate between the two upstream reaches. Thus, river regulation apparently benefited hackberry along the Snake River
through Hells Canyon, probably due to diurnal pulsing that wets the riparian margin. We predict similar benefits for some
other facultative riparian plants along other regulated rivers with hydropeaking during warm and dry intervals. To analyze
the ecological impacts of hydropeaking we recommend assessing daily maxima, as well as daily mean river flows.
Keywords Celtis reticulata ●Hells canyon ●Hydropeaking ●Salmon river ●Snake river
Introduction
River damming and flow regulation have altered many
riparian ecosystems, resulting in woodland decline,
encroachment from upland vegetation, invasion of intro-
duced species, and changes in population structure, suc-
cessional pathways, and community composition (Naiman
et al. 2005). The responses often depend on the nature of
hydrologic alteration, how streamflow magnitude, timing,
frequency, duration, and rate of change have been modified
(Richter et al. 1996). For example, water withdrawal and
storage for irrigation have reduced spring and summer flows
and caused woodland decline along some rivers in the North
American western prairies (Rood and Mahoney 1990).
Attenuated peak flows for flood control has resulted in
woodland expansion and channel narrowing along other
rivers in western North America (Johnson 1994; Dixon and
Johnson 1999; Merritt and Cooper 2000; Tiedemann and
Rood 2015). One common aspect of flow alteration that has
been recognized to impact fish and aquatic ecosystems but
has had limited investigation relative to riparian vegetation
is ‘hydropeaking’(Bejarano et al. 2017). This represents
diurnal flow pulsing associated with peak power demand,
resulting in daily water level fluctuations of up to several
meters. Dam operations for hydroelectric power generation
often produce outflows that are highly variable on short
time scales and studies of aquatic species including fish and
invertebrates have shown that rapid variation in physical
conditions can displace ecological specialists with general-
ists, which can better tolerate the artificial flow regime
(Jones 2014).
*Stewart B. Rood
rood@uleth.ca
1Department of Biological Sciences, University of Lethbridge,
Lethbridge, AB, Canada
2Department of Fish, Wildlife and Range Resources, University of
Idaho, Moscow, ID, USA
1234567890();,:
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... On the other hand, some authors point out that the species richness and floristic composition of transformed and untransformed sections of river valleys are similar, with differences mainly involving area cover by certain species (Aguiar, Ferreira & Moreira, 2001;Caffrey, Monahan & Tierney, 2006). The effect of river regulation on vegetation has been repeatedly investigated (Merrit & Cooper, 2000;Sankey et al., 2015;Kui et al., 2017;Picco et al., 2017;Gill et al., 2018), but fewer works show the impact of interactions within previously transformed river sections (Henry & Amoros, 1996;Kaenel & Uehlinger, 1998;Baattrup-Pedersen, Larsen & Riis, 2002). ...
Effects of dredging on the vegetation in a small lowland river
Article
Full-text available
  • Jan 2019
Background. Conventional river engineering operations have a substantial influence on the fluvial ecosystem. Regulation and channelization generally reduce the physical heterogeneity of river beds and banks and the heterogeneity of habitats. They determine the character, diversity and species richness of plant communities. The effect of river regulation on vegetation has been repeatedly investigated, but few studies have been conducted within reaches of previously regulated rivers. The aim of this work is to expand and current knowledge about the impact of dredging on the vegetation of a regulated section of a lowland river. Materials & Methods. The study included pre-dredging (1 year before) and post-dredging surveys (results 1 and 2 years after dredging). The vegetation was analysed in terms of species composition, origin of species, life forms, distribution of Grime's life strategies, and selected ecological factors. The Shannon-Wiener biodiversity index (H) and evenness were also analysed in each year of the study. The impact of dredging on the vascular flora was assessed by 'before-after-control-impact' (BACI) analysis. Results. The number of species and biodiversity as measured by the Shannon-Wiener index (H) increased in the analysed section of the river valley. However, enrichment of the flora was observed only on the floodplain, on the surface of the deposited dredging material, while the number of species in the river channel decreased, as dredging of the river bed and levelling of the banks had markedly reduced habitat diversity. Although species richness in the second year after the dredging approached the values recorded before the intervention, the absence of particularly species or phytocenoses associated with shallow river banks and sandbars was still observed. The change in habitat conditions and the destruction of the vegetation cover during the dredging enabled penetration by numerous previously unrecorded alien species of plants and apophytes. There was a perceptible increase in the role of therophytes in the flora. It is worth noting that the number of alien species and therophytes declined significantly in the second year after the dredging. Analysis of the proportions of species representing various life strategies showed that previously unrecorded species with the type R (ruderal) life strategy had appeared, representing by pioneer species occurring in frequently disturbed habitats. There was also a marked increase in the share of species representing the mixed C-R (competitive-ruderal) strategy, occurring in habitats with low levels of stress, whose competitive abilities are limited by repeated disturbances. By the second year after the dredging, however, these changes were largely no longer observed. Conclusions. Through appropriate maintenance of the regulated river, it can be rapidly recolonized by vegetation after the procedure, but it may lead to the loss of some species and phytocoenoses.
View
Impacts of hydropeaking: A systematic review
Article
Full-text available
  • Dec 2023
  • SCI TOTAL ENVIRON
Hydropower is commonly considered a renewable energy source. Nevertheless, this does not imply an absence of impacts on the riverine ecosystem, the extent of which is expected to increase in the coming years due to the energy transition from fossil fuels to renewable sources and for the climate change. A common consequence of hydroelectric power generation is hydropeaking, which causes rapid and frequent fluctuations in the water flow downstream of hydropower plants. The review incorporates 155 relevant studies published up until November 2023 and follows a systematic review method, Preferred Reporting Items for Systematic Reviews and Meta- Analyses (PRISMA), which is a multi-stage systematic procedure for the identification and selection of research documents. The selected studies highlighted several prominent impacts of hydropeaking on aquatic environments. The primary effects include alterations in flow patterns, modification of water temperature, changes in sediment dynamics and fluctuations in dissolved gas levels. These alterations have been found to affect various aspects of aquatic ecosystems, including fish growth, behavior, reproductive success, habitat, and migration patterns, and benthic macroinvertebrate communities. Furthermore, hydropeaking can also lead to habitat fragmentation, erosion, and loss of riparian vegetation, thereby impacting terrestrial ecosystems that depend on the aquatic environment. Despite the body of literature reviewed, several knowledge gaps were identified, underscoring the need for further research. There is limited understanding of the long-term ecological consequences of hydropeaking and its cumulative effects on aquatic ecosystems. Additionally, there is lack of consensus regarding the quantification of ecosystem services, economic impact, soil moisture content, and weighted usable area due to flow fluctuation and global evolution of energy production from renewable energy sources. Addressing the identified research gaps is crucial for achieving a balance between energy production and the conservation of freshwater ecosystems in the context of a rapidly changing global climate.
View
Hydrogeomorphic Effects of Reservoirs, Dams, and Diversions
Chapter
  • Jan 2021
Reservoirs, dams, and diversions are vital for securing water supplies, producing hydroelectric power, and controlling floods. However, the changes they impose on the fluvial processes of downstream rivers, mainly reflecting reduced sediment loads and lower flood magnitudes, can be dramatic. A ‘typical’ model of channel response with bed degradation immediately below a dam and channel narrowing farther downstream shows complex variations at the reach scale and between rivers. Complete readjustment can take hundreds of years so that many reaches show sequences of transient states. The factors influencing such complex channel changes in space and time are examined and management/restoration options, including dam removal, are discussed.
View
The effects of hydropeaking on riverine plants: a review
Article
Full-text available
  • Aug 2017
  • BIOL REV
Hydropeaking refers to frequent, rapid and short-term fluctuations in water flow and water levels downstream and upstream of hydropower stations. Such fluctuations are becoming increasingly common worldwide and are known to have far-reaching effects on riverine vegetation. Novel hydrology caused by hydropeaking has no natural correspondence in freshwater systems, and hence few species have adaptations to all its aspects. Here, we review the literature on hydropeaking effects on riverine plants and define the state of the information on this human alteration of riverine ecosystems. We focus on riparian plants, but also draw on information from aquatic plant species, which exhibit a wide variety of adaptations to inundation and associated processes. Riparian plants face both physiological and physical constraints because of the shifts between submergence and drainage, and erosion of substrates. At the population level, hydropeaking may favour dispersal within, but not between, reservoirs, but may hamper germination, establishment, growth and reproduction. At the community level, strong filtering towards easily dispersed, flexible, flood-tolerant and amphibious plants is expected, although few species share these traits. Hence, most riparian plant species are expected to disappear or be pushed towards the upper boundaries of the regulated river margin. Future research should examine more closely global variation in hydropeaking effects, including other taxonomic groups of species and the diversity of hydropeaking regimes. There is also a need for studies focusing on identifying the boundaries within which hydropeaking could operate without impairing plant life.
View
View
View
Riparian vegetation and channel change in response to river regulation: A comparative study of regulated and unregulated streams in the Green River Basin, USA
Article
  • Nov 2000
The effects of river damming on geomorphic processes and riparian vegetation were evaluated through Field studies along the regulated Green River and the free-flowing Yampa River in northwestern Colorado, USA. GIS analysis of historical photographs, hydrologic and sediment records, and measurement of channel planform indicate that fluvial processes and riparian vegetation of the two meandering stream reaches examined were similar prior to regulation which began in 1962. Riparian plant species composition and canopy coverage were measured during 1994 in 36, 0.01 ha plots along each the Green River in Browns Park and the Yampa River in Deerlodge Park. Detrended correspondence analysis (DCA) of the vegetation data indicates distinctive vegetation differences between Browns Park and Deerlodge Park. Canonical correspondence analysis (CCA) indicates that plant community composition is controlled largely by fluvial processes at Deerlodge Park, but that soil chemical rather than flow related factors play a more important role in structuring plant communities in Browns Park. Vegetation patterns reflect a dichotomy in moisture conditions across the floodplain on the Green River in Browns Park: marshes with anaerobic soils supporting wetland species (Salix exigua, Eleocharis palustris, Schoenoplectus pungens, and Juncus nodosus) and terraces having xeric soil conditions and supporting communities dominated by desert species (Seriphidium tridentatum, Sarcobatus vermiculatus, and Sporobolus airoides). In contrast, vegetation along the Yampa River is characterized by a continuum of species distributed along a gradual environmental gradient from the active channel (ruderal species such as Xanthium struminarium and early successional species such as S. exigua, Populus deltoides subsp. wislizsenii, and Tamarix ramossissima) to high floodplain surfaces characterized by Populus forests and meadow communities. GIS analyses indicate that the channel form at Browns Park has undergone a complex series of morphologic changes since regulation began, while the channel at Deerlodge Park has remained in a state of relative quasi-equilibrium with discharge and sediment regimes. The Green River has undergone three stages of channel change which have involved the transformation of the historically deep, meandering Green River to a shallow, braided channel over the 37 years since construction of Flaming Gorge Dam. The probable long-term effects of channel and hydrologic changes at Browns Park include the eventual replacement of Populus-dominated riparian forest by drought tolerant desert shrublands, and the enlargement of in-channel fluvial marshes. Copyright (C) 2000 John Wiley & Sons, Ltd.
View
Increasing River Flow Expands Riparian Habitat: Influences of Flow Augmentation on Channel Form, Riparian Vegetation and Birds Along the Little Bow River, Alberta
Article
  • Mar 2016
With river regulation, water withdrawal is common, reducing instream flows. The opposite alteration, flow augmentation, is less common and could reveal a mechanistic coordination between flow regime, channel form, and riparian ecosystems. The Little Bow River, a naturally intermittent prairie stream in Southern Alberta, has experienced flow augmentation since the late 1890s, and the Little Bow/Highwood Project of 2004 enabled a tripling of diversion flows from 2.9 to 8.5 m3/s. We investigated the subsequent responses by assessing the channel form and riparian vegetation based on aerial photographs taken in 2000 versus 2010, and riparian birds were assessed between 2005 and 2013 to investigate associations with riparian vegetation. Following recent flow augmentation, the mean channel width increased from 12.2 to 13.5 m, while sinuosity was relatively unchanged. Streamside zones with true willows (especially Salix exigua and Salix bebbiana) increased from 7 to 11% of the river corridor, and the facultative riparian wolf willow (Elaeagnus commutata) zones increased from 16 to 20%, while grassy zones decreased from 64 to 52%. Avian species richness and Shannon–Wiener index increased, while species evenness was relatively unaltered, suggesting an increase of rarer bird species in response to the increased habitat structure and diversity following the expansion of riparian shrubs and woodland. This study revealed responses to the recent flow augmentation over the first decade of implementation, and alterations following flow augmentation would likely continue for decades until the river and riparian zones adjust to the new flow regime. Copyright
View
Renewable Energy Sources and Climate Change Mitigation: Special Report of the Intergovernmental Panel on Climate Change
Article
  • Dec 2011
This Intergovernmental Panel on Climate Change Special Report (IPCC-SRREN) assesses the potential role of renewable energy in the mitigation of climate change. It covers the six most important renewable energy sources - bioenergy, solar, geothermal, hydropower, ocean and wind energy - as well as their integration into present and future energy systems. It considers the environmental and social consequences associated with the deployment of these technologies, and presents strategies to overcome technical as well as non-technical obstacles to their application and diffusion. SRREN brings a broad spectrum of technology-specific experts together with scientists studying energy systems as a whole. Prepared following strict IPCC procedures, it presents an impartial assessment of the current state of knowledge: it is policy relevant but not policy prescriptive. SRREN is an invaluable assessment of the potential role of renewable energy for the mitigation of climate change for policymakers, the private sector, and academic researchers.
View
Flood dependency of cottonwood establishment along the Missouri River, Montana, USA
Article
  • May 1997
Flow variability plays a central role in structuring the physical environment of riverine ecosystems. However, natural variability in flows along many rivers has been modified by water management activities. We quantified the relationship between flow and establishment of the dominant tree (plains cottonwood, Populus deltoides subsp. monilifera) along one of the least hydrologically altered alluvial reaches of the Missouri River: Coal Banks Landing to Landusky, Montana. Our purpose was to refine our understanding of how local fluvial geomorphic processes condition the relationship between flow regime and cottonwood recruitment. We determined date and elevation of tree establishment and related this information to historical peak stage and discharge over a 112-yr hydrologic record. Of the excavated trees, 72% were established in the year of a flow >1400 m3/s (recurrence interval of 9.3 yr) or in the following 2 yr. Flows of this magnitude or greater create the necessary bare, moist establishment sites at an elevation high enough to allow cottonwoods to survive subsequent floods and ice jams. Almost all cottonwoods that have survived the most recent flood (1978) were established >1.2 m above the lower limit of perennial vegetation (active channel shelf). Most younger individuals were established between 0 and 1.2 m, and are unlikely to survive over the long term. Protection of riparian cottonwood forest along this National Wild and Scenic section of the Missouri River depends upon maintaining the historical magnitude, frequency, and duration of floods > 1400 m3/s. Here, a relatively narrow valley constrains lateral channel movement that could otherwise facilitate cottonwood recruitment at lower flows. Effective management of flows to promote or maintain cottonwood recruitment requires an understanding of locally dominant fluvial geomorphic processes.
View
Equations for potential annual direct incident radiation and heat load
Article
  • Aug 2002
  • J VEG SCI
Estimation of potential annual direct incident radiation has traditionally required numerical integration with simulation models. As an alternative, we present convenient equations for use in spreadsheet, GIS, and database applications. Input variables are latitude, slope, and aspect. The equations apply to 0-60degrees north latitude, slopes from 0-90degrees, and all aspects. By transforming aspect, the equations can also be applied as an index of heat load, symmetrical about a northeast to southwest axis.
View
Riparia: Ecology, Conservation and Management of Streamside Communities
Book
  • Jan 2005
Publisher Summary This chapter describes the various geomorphic and hydrologic processes such as catchments that influence riparian system development and maintenance. Catchments are areas of the land surface in which all the runoff drains to a single point on a stream or river channel, and are bounded by drainage divides; catchments have been known to range from hundreds of square meters in size to millions of square kilometers. Catchment drainage networks may have dendritic, palmate dendritic, or trellised forms, depending on the nature of underlying geology. These networks vary in drainage density and gradient, which affect riparia by impacting flood intensity and stream power, respectively. The most basic geomorphic processes in catchments are erosion, transport, and deposition. These processes operate across all time and space scales but vary in relative importance along drainage networks. Erosive processes dominate headwater regions, whereas deposition processes dominate the bottom of catchments draining to the ocean or into enclosed basins. Transport dominates in the mid-reaches of river systems. Erosion scours and eliminates riparian habitats and occurs when the shear stress imposed by flowing water exceeds the shear strength of the material over which it flows. The dominant forms of erosion include down-cutting and lateral movement of channels and scouring of channels and floodplains. Hydrologic processes strongly influence riparian habitats as the transport medium for sediments, but the presence or absence of water by itself is also an important control on riparian form and function. Flooding is a key process that distributes surface water to riparian environments and sets up gradients that drive surface water-groundwater exchanges. Four characteristics of floods, which are especially important to riparian and floodplain ecosystems are magnitude, frequency, timing, and duration.
View
Light Requirements of Acacia smallii and Celtis laevigata in Relation to Secondary Succession on Floodplains of South Texas
Article
  • Jan 1986
Acacia smallii, a legume, is a pioneer woody species in secondary succession of floodplain forests of S Texas, where Celtis laevigata is the climax forest dominant. Variable light regimes, under greenhouse conditions, showed that A. smallii had its maximum growth in the highest irradiance and decreased growth occurred with decreased irradiance. Celtis laevigata showed no significant differences in growth between the two highest irradiances used. Interspecific comparisons based on percent of maximum growth indicated C. laevigata had a significantly higher percentage of maximum growth in lower light treatments, whereas A. smallii had a significantly higher percentage of maximum growth in the highest light treatment. Acacia smallii is a heliophyte, while C. laevigata is a sciophyte. Loss of A. smallii in mature communities is probably due to inability of its seedlings to survive in the shaded environment of a mature forest community.
View