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River Regulation (river + regulation)
Selected AbstractsThe responses of floodplain primary production to flood frequency and timingJOURNAL OF APPLIED ECOLOGY, Issue 1 2001A.I. Robertson Summary 1,River regulation and abstraction have dramatically altered the natural flow regime of many rivers world-wide, but experimental investigations of the biological effects are infrequent. In the mid-region of the Murray River, Australia, river regulation has reduced the frequency and duration of spring floods and increased the frequency of summer floods. We used controlled floods (treatments: no floods, spring floods, summer floods and spring + summer floods) to determine how the growth of river red gum Eucalyptus camaldulensis trees, aquatic macrophytes and biofilms varied with the seasonal timing and frequency of flooding. 2,After 6 years of controlled flooding, above-ground net production of wood by river red gum trees was equal and greatest in plots receiving spring + summer floods and summer floods (mean 496 g m,2 year,1). Production was significantly lower in plots receiving spring floods or no controlled floods, which had similar rates of production (mean 330 g m,2 year,1). 3,During 2 years of measurement in wetlands created by flooding, production and species richness of aquatic macrophyte were both greater in spring than in summer floods. The history of flood frequency at any experimental site did not affect macrophyte production or species richness. The aquatic macrophyte community in shallow regions of wetlands differed significantly with the seasonal timing of floods, but not flood frequency. 4,The accumulation of chlorophyll a and total mass of biofilm on wood surfaces in wetlands created by flooding were greater in spring (mean chlorophyll a, 0·88 µg cm,2; mean mass, 0·066 mg cm,2) than in summer floods (mean chlorophyll a, 0·09 µg cm,2; mean mass, 0·034 mg cm,2). The history of flood frequency at any experimental site did not affect accumulation of either the autotrophic or heterotrophic components of biofilms. 5,Spring flooding, while not as beneficial for tree growth, is critical for the growth of wetland macrophytes, the maintenance of macrophyte species richness, and favours better development of autotrophic biofilms. Maintenance of both the timber harvest and wetland conservation values of these floodplains will require the return of more natural flood flows in the spring period. Restoration of floodplain rivers requires a thorough understanding of the relationships between ecological functions and the natural flow regime. [source] Adaptive management of an environmental watering event to enhance native fish spawning and recruitmentFRESHWATER BIOLOGY, Issue 1 2010A. J. KING Summary 1. A common goal of many environmental flow regimes is to maintain and/or enhance the river's native fish community by increasing the occurrence of successful spawning and recruitment events. However, our understanding of the flow requirements of the early life history of fish is often limited, and hence predicting their response to specific managed flow events is difficult. To overcome this uncertainty requires the use of adaptive management principles in the design, implementation, monitoring and adjustment of environmental flow regimes. 2. The Barmah-Millewa Forest, a large river red gum forest on the Murray River floodplain, south-east Australia, contains a wide variety of ephemeral and permanent aquatic habitats suitable for fish. Flow regulation of the Murray River has significantly altered the natural flood regime of the Forest. In an attempt to alleviate some of the effects of river regulation, the Forest's water regime is highly managed using a variety of flow control structures and also receives targeted Environmental Water Allocations (EWA). In 2005, the largest environmental flow allocated to date in Australia was delivered at the Forest. 3. This study describes the adaptive management approach employed during the delivery of the 2005 EWA, which successfully achieved multiple ecological goals including enhanced native fish spawning and recruitment. Intensive monitoring of fish spawning and recruitment provided invaluable real-time and ongoing management input for optimising the delivery of environmental water to maximise ecological benefits at Barmah-Millewa Forest and other similar wetlands in the Murray-Darling Basin. 4. We discuss possible scenarios for the future application of environmental water and the need for environmental flow events and regimes to be conducted as rigorous, large-scale experiments within an adaptive management framework. [source] Denitrification in a hyporheic riparian zone controlled by river regulation in the Seine river basin (France)HYDROLOGICAL PROCESSES, Issue 5 2009F. Curie Abstract The purpose of this paper is to study denitrification and the conditions for its development in a hyporheic zone. The study site is the riparian zone of a former branch of the Seine River, where the river stage is kept almost constant during the year by hydraulic regulation. Hydrological and geochemical surveys were performed by monitoring four wells, ten shorter piezometers and the river over a 15-month period. The water fluxes originating from the chalky hillsides and the river converge in a zone parallel to the river that acts as a drainage flow path through the floodplain. The riparian zone between this flow path and the river shows an important depletion of nitrate during the summer and autumn period, which cannot be explained by a simple mixing of waters coming from the river and the chalky hillsides. It can be attributed to denitrification as it occurs when oxygen concentration is below 2 mg l,1, and goes along with a consumption of dissolved organic carbon and a decrease of redox potential. The river completely controls these hydro-geochemical conditions. It also keeps the wetness of the riparian zone almost constant, which allowed us to isolate the high temperatures in summer and autumn as an important triggering factor for denitrification through its influence on the reaction rate and oxygen deficits. We also found a small isotopic enrichment of nitrate, suggesting that denitrification occurs after diffusion of nitrate through the sediment and riparian zone matrix, which is consistent with the hyporheic functioning of the study site. Copyright © 2008 John Wiley & Sons, Ltd. [source] Groundwater,surface water interactions in a large semi-arid floodplain: implications for salinity managementHYDROLOGICAL PROCESSES, Issue 16 2005Sébastien Lamontagne Abstract Flow regulation and water diversion for irrigation have considerably impacted the exchange of surface water between the Murray River and its floodplains. However, the way in which river regulation has impacted groundwater,surface water interactions is not completely understood, especially in regards to the salinization and accompanying vegetation dieback currently occurring in many of the floodplains. Groundwater,surface water interactions were studied over a 2 year period in the riparian area of a large floodplain (Hattah,Kulkyne, Victoria) using a combination of piezometric surface monitoring and environmental tracers (Cl,, ,2H, and ,18O). Despite being located in a local and regional groundwater discharge zone, the Murray River is a losing stream under low flow conditions at Hattah,Kulkyne. The discharge zone for local groundwater, regional groundwater and bank recharge is in the floodplain within ,1 km of the river and is probably driven by high rates of transpiration by the riparian Eucalyptus camaldulensis woodland. Environmental tracers data suggest that the origin of groundwater is principally bank recharge in the riparian zone and a combination of diffuse rainfall recharge and localized floodwater recharge elsewhere in the floodplain. Although the Murray River was losing under low flows, bank discharge occurred during some flood recession periods. The way in which the water table responded to changes in river level was a function of the type of stream bank present, with point bars providing a better connection to the alluvial aquifer than the more common clay-lined banks. Understanding the spatial variability in the hydraulic connection with the river channel and in vertical recharge following inundations will be critical to design effective salinity remediation strategies for large semi-arid floodplains. Copyright © 2005 John Wiley & Sons, Ltd. [source] Responses of riparian plants to flooding in free-flowing and regulated boreal rivers: an experimental studyJOURNAL OF APPLIED ECOLOGY, Issue 6 2002M. E. Johansson Summary 1The long history of river regulation has resulted in extensively changed ecosystem structures and processes in rivers and their associated environments. This fact, together with changing climatic and hydrological conditions, has increased the need to recover the natural functions of rivers. To develop guidelines for river restoration, comparative ecological experiments at contrasting water-level regimes are needed. We compared growth and survival of transplanted individuals of four riparian plant species (Betula pubescens, Carex acuta, Filipendula ulmaria and Leontodon autumnalis) over 2 years on four free-flowing and four regulated riverbank sites in northern Sweden. The species were chosen as representatives of dominating life-forms and species traits on different elevations of the riverbanks. 2In Betula and Filipendula, mean proportional growth rates were significantly higher at free-flowing sites than at regulated sites, whereas no consistent differences between free-flowing and regulated sites were found in Carex and Leontodon. Differences among species were generally in accordance with natural distribution patterns along riverbank elevation gradients and with experimental evidence on flooding tolerance, although plants of all species survived and even showed positive growth rates on elevations below their natural range of occurrence. 3Partial least squares regression was used to relate plant performance (growth and survival) to duration, frequency and timing of flooding at the different sites. Flood duration and frequency typically reduced performance in all species and during all time periods, although to various degrees. Flood events early in the experiment determined the outcome to a high degree at all sites. Variables indicating a regulated regime were mostly negatively related to plant performance, whereas free-flowing regime variables were positively related to plant performance. 4We used two of the regression models generated from our data with an acceptably high predictive power to simulate a hypothetical re-regulation scenario in run-of-river impoundments. With an overall reduction in flooding duration and frequency of 50,75%, plant performance of Filipendula at low riverbank elevations showed predicted increases of about 20,30%, levelling off to zero at the highest elevations. Reductions in summer floods represented about one-third to half of this increase. 5We conclude that for a range of species individual plant performance is clearly reduced on banks of impoundments and storage reservoirs due to changes in the water-level regime. Furthermore, our model simulation suggests that rather substantial reductions of flood duration and frequency are needed to improve plant performance on riverbanks upstream from dams in impounded rivers. River restoration principles should, however, be based on a combination of experimental data on plant performance of individual species and observed long-term changes in plant communities of regulated rivers. Consequently, successful re-regulation schemes in boreal rivers should include both reductions of summer and winter floods as well as re-introduced spring floods. [source] The responses of floodplain primary production to flood frequency and timingJOURNAL OF APPLIED ECOLOGY, Issue 1 2001A.I. Robertson Summary 1,River regulation and abstraction have dramatically altered the natural flow regime of many rivers world-wide, but experimental investigations of the biological effects are infrequent. In the mid-region of the Murray River, Australia, river regulation has reduced the frequency and duration of spring floods and increased the frequency of summer floods. We used controlled floods (treatments: no floods, spring floods, summer floods and spring + summer floods) to determine how the growth of river red gum Eucalyptus camaldulensis trees, aquatic macrophytes and biofilms varied with the seasonal timing and frequency of flooding. 2,After 6 years of controlled flooding, above-ground net production of wood by river red gum trees was equal and greatest in plots receiving spring + summer floods and summer floods (mean 496 g m,2 year,1). Production was significantly lower in plots receiving spring floods or no controlled floods, which had similar rates of production (mean 330 g m,2 year,1). 3,During 2 years of measurement in wetlands created by flooding, production and species richness of aquatic macrophyte were both greater in spring than in summer floods. The history of flood frequency at any experimental site did not affect macrophyte production or species richness. The aquatic macrophyte community in shallow regions of wetlands differed significantly with the seasonal timing of floods, but not flood frequency. 4,The accumulation of chlorophyll a and total mass of biofilm on wood surfaces in wetlands created by flooding were greater in spring (mean chlorophyll a, 0·88 µg cm,2; mean mass, 0·066 mg cm,2) than in summer floods (mean chlorophyll a, 0·09 µg cm,2; mean mass, 0·034 mg cm,2). The history of flood frequency at any experimental site did not affect accumulation of either the autotrophic or heterotrophic components of biofilms. 5,Spring flooding, while not as beneficial for tree growth, is critical for the growth of wetland macrophytes, the maintenance of macrophyte species richness, and favours better development of autotrophic biofilms. Maintenance of both the timber harvest and wetland conservation values of these floodplains will require the return of more natural flood flows in the spring period. Restoration of floodplain rivers requires a thorough understanding of the relationships between ecological functions and the natural flow regime. [source] Integrating ecology with hydromorphology: a priority for river science and managementAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2009I.P. Vaughan Abstract 1.The assessment of links between ecology and physical habitat has become a major issue in river research and management. Key drivers include concerns about the conservation implications of human modifications (e.g. abstraction, climate change) and the explicit need to understand the ecological importance of hydromorphology as prescribed by the EU's Water Framework Directive. Efforts are focusing on the need to develop ,eco-hydromorphology' at the interface between ecology, hydrology and fluvial geomorphology. Here, the scope of this emerging field is defined, some research and development issues are suggested, and a path for development is sketched out. 2.In the short term, major research priorities are to use existing literature or data better to identify patterns among organisms, ecological functions and river hydromorphological character. Another early priority is to identify model systems or organisms to act as research foci. In the medium term, the investigation of pattern,processes linkages, spatial structuring, scaling relationships and system dynamics will advance mechanistic understanding. The effects of climate change, abstraction and river regulation, eco-hydromorphic resistance/resilience, and responses to environmental disturbances are likely to be management priorities. Large-scale catchment projects, in both rural and urban locations, should be promoted to concentrate collaborative efforts, to attract financial support and to raise the profile of eco-hydromorphology. 3.Eco-hydromorphological expertise is currently fragmented across the main contributory disciplines (ecology, hydrology, geomorphology, flood risk management, civil engineering), potentially restricting research and development. This is paradoxical given the shared vision across these fields for effective river management based on good science with social impact. A range of approaches is advocated to build sufficient, integrated capacity that will deliver science of real management value over the coming decades. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||