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Kate L Holland - One of the best experts on this subject based on the ideXlab platform.
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a review of groundwater surface water interactions in arid semi arid Wetlands and the consequences of salinity for Wetland Ecology
Ecohydrology, 2008Co-Authors: Ian Jolly, Kerryn Mcewan, Kate L HollandAbstract:In arid/semi-arid environments, where rainfall is seasonal, highly variable and significantly less than the evaporation rate, groundwater discharge can be a major component of the water and salt balance of a Wetland, and hence a major determinant of Wetland Ecology. Under natural conditions, Wetlands in arid/semi-arid zones occasionally experience periods of higher salinity as a consequence of the high evaporative conditions and the variability of inflows which provide dilution and flushing of the stored salt. However, due to the impacts of human population pressure and the associated changes in land use, surface water regulation, and water resource depletion, Wetlands in arid/semi-arid environments are now often experiencing extended periods of high salinity. This article reviews the current knowledge of the role that groundwater–surface water (GW–SW) interactions play in the Ecology of arid/semi-arid Wetlands. The key findings of the review are as follows: 1.GW–SW interactions in Wetlands are highly dynamic, both temporally and spatially. Groundwater that is low in salinity has a beneficial impact on Wetland Ecology which can be diminished in dry periods when groundwater levels, and hence, inflows to Wetlands are reduced or even cease. Conversely, if groundwater is saline, and inflows increase due to raised groundwater levels caused by factors such as land use change and river regulation, then this may have a detrimental impact on the Ecology of a Wetland and its surrounding areas. 2.GW–SW interactions in Wetlands are mostly controlled by factors such as differences in head between the Wetland surface water and groundwater, the local geomorphology of the Wetland (in particular, the texture and chemistry of the Wetland bed and banks), and the Wetland and groundwater flow geometry. The GW–SW regime can be broadly classified into three types of flow regimes: (i) recharge—Wetland loses surface water to the underlying aquifer; (ii) discharge—Wetland gains water from the underlying aquifer; or (iii) flow-through—Wetland gains water from the groundwater in some locations and loses it in others. However, it is important to note that individual Wetlands may temporally change from one type to another depending on how the surface water levels in the Wetland and the underlying groundwater levels change over time in response to climate, land use, and management. 3.The salinity in Wetlands of arid/semi-arid environments will vary naturally due to high evaporative conditions, sporadic rainfall, groundwater inflows, and freshening after rains or floods. However, Wetlands are often at particular risk of secondary salinity because their generally lower elevation in the landscape exposes them to increased saline groundwater inflows caused by rising water tables. Terminal Wetlands are potentially at higher risk than flow-through systems as there is no salt removal mechanism. 4.Secondary salinity can impact on Wetland biota through changes in both salinity and water regime, which result from the hydrological and hydrogeological changes associated with secondary salinity. Whilst there have been some detailed studies of these interactions for some Australian riparian tree species, the combined effects on aquatic biodiversity are only just beginning to be elucidated, and are therefore, a future research need. 5.Rainfall/flow-pulses, which are a well-recognized control on ecological function in arid/semi-arid areas, also play an important, though indirect, role through their impact on Wetland salinity. Freshwater pulses can be the primary means by which salt stored in both the water column and the underlying sediments are flushed from Wetlands. Conversely, increased runoff is also a commonly observed consequence of secondary salinity, and so, Wetlands can experience increased surface water inflows that are higher in salinity than under natural conditions. Moreover, changes in rainfall/flow-pulse regimes can have a significant impact on Wetland GW–SW interactions. It is possible that in some instances groundwater inflow to a Wetland may become so heavy that it could become a major component of the water balance, and hence, mask the role of natural pulsing regimes. However, if the groundwater is low in salinity, this may provide an ecological benefit in arid/semi-arid areas by assisting in maintaining water in Wetlands that become aquatic refugia between flow-pulses. 6.There has been almost no modelling of GW–SW interactions in arid/semi-arid Wetlands with respect to water fluxes, let alone salinity or Ecology. There is a clear need to develop modelling capabilities for the movement of salt to, from, and within Wetlands to provide temporal predictions of Wetland salinity which can be used to assess ecosystem outcomes. 7.There has been a concerted effort in Australia to collect and collate data on the salinity tolerance/sensitivity of freshwater aquatic biota and riparian vegetation. There are many shortcomings and knowledge gaps in these data, a fact recognized by many of the authors of this work. Particularly notable is that there is very little time-series data, which is a serious issue because Wetland salinities are often highly temporally variable. There is also a concern that many of the data are from very controlled laboratory experiments, which may not represent the highly variable and unpredictable conditions experienced in the field. In light of these, and many other shortcomings identified, our view is that the data currently available are a useful guide but must be used with some caution. Copyright © 2008 John Wiley & Sons, Ltd.
Luc Brendonck - One of the best experts on this subject based on the ideXlab platform.
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remote sensing and Wetland Ecology a south african case study
Sensors, 2008Co-Authors: Els De Roeck, Niko Verhoest, Okke Batelaan, Mtemi H Miya, Hans Lievens, A Thomas, Luc BrendonckAbstract:Remote sensing offers a cost efficient means for identifying and monitoring Wetlands over a large area and at different moments in time. In this study, we aim at providing ecologically relevant information on characteristics of temporary and permanent isolated open water Wetlands, obtained by standard techniques and relatively cheap imagery. The number, surface area, nearest distance, and dynamics of isolated temporary and permanent Wetlands were determined for the Western Cape, South Africa. Open water bodies (Wetlands) were mapped from seven Landsat images (acquired during 1987 – 2002) using supervised maximum likelihood classification. The number of Wetlands fluctuated over time. Most Wetlands were detected in the winter of 2000 and 2002, probably related to road constructions. Imagery acquired in summer contained fewer Wetlands than in winter. Most Wetlands identified from Landsat images were smaller than one hectare. The average distance to the nearest Wetland was larger in summer. In comparison to temporary Wetlands, fewer, but larger permanent Wetlands were detected. In addition, classification of non-vegetated Wetlands on an Envisat ASAR radar image (acquired in June 2005) was evaluated. The number of detected small Wetlands was lower for radar imagery than optical imagery (acquired in June 2002), probably because of deterioration of the spatial information content due the extensive pre-processing requirements of the radar image. Both optical and radar classifications allow to assess Wetland characteristics that potentially influence plant and animal metacommunity structure. Envisat imagery, however, was less suitable than Landsat imagery for the extraction of detailed ecological information, as only large Wetlands can be detected. This study has indicated that ecologically relevant data can be generated for the larger Wetlands through relatively cheap imagery and standard techniques, despite the relatively low resolution of Landsat and Envisat imagery. For the characterisation of very small Wetlands, high spatial resolution optical or radar images are needed. This study exemplifies the benefits of integrating remote sensing and Ecology and hence stimulates interdisciplinary research of isolated Wetlands.
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Integrating Remote Sensing and Wetland Ecology: a Case Study on South African Wetlands
2007 International Workshop on the Analysis of Multi-temporal Remote Sensing Images, 2007Co-Authors: Els De Roeck, Mtemi Miya, Niko Verhoest, Okke Batelaan, Luc BrendonckAbstract:Remote sensing is a valuable tool for Wetland Ecology and conservation. With this study, we aimed at providing relevant information on Wetland characteristics, obtained by standard techniques and relatively cheap optical imagery. The number, surface area, distance, and dynamics of temporary and permanent Wetlands were determined for the Western Cape, South Africa. These characteristics are important for the metacommunity structure of amphibians and invertebrates. Isolated open water Wetlands were classified by supervised maximum likelihood classification on seven Landsat images (1987 -2002). Imagery acquired in summer contained fewer Wetlands than those acquired in winter. The number of winter Wetlands showed an increasing trend over time, which was not significantly correlated with yearly rainfall. Most classified Wetlands were smaller than 1.5 ha. The distance to the nearest-Wetland was longer in winter. In comparison to temporary Wetlands, fewer, but on average larger permanent Wetlands were classified. The relatively high number of Wetlands is essential for local and migrating wading birds. The many small observed Wetlands could also serve as stepping-stones, important for species conservation. We conclude that through relatively cheap imagery and standard geographical information system (GIS) techniques, basic ecological data can be generated. However, the resolution of Landsat imagery is too low to detect small Wetlands. High accuracy images (such as IKONOS) would give more detailed results, but the high cost and the lack of long term data are at present restricting factors for their use by ecologists.
Richard Smardon - One of the best experts on this subject based on the ideXlab platform.
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Wetland Ecology principles and conservation second edition
Water, 2014Co-Authors: Richard SmardonAbstract:Abstract: This is a book review of Wetland Ecology Principles and Conservation, second edition, by Paul Keddy. This review focuses on the book’s content as it relates to Wetland sustainability for both science and management. Besides overall comments, comparisons are made with the first edition of the book and then very specific chapter-by-chapter relationships to Wetland sustainability are made to illustrate specific applications toward Wetland sustainability. Keywords: book review; Paul Keddy; sustainability; Wetland Ecology and management 1. Introduction and Book Organization This is a review of the second edition of this book and focuses specifically on its contribution to Wetland sustainability science and management. The other focus of this review is to compare it to other Wetland Ecology and management texts, such as Mitsch and Gosselink’s book “Wetlands”. The structure of the book is similar to the first edition but now has 14 chapters as opposed to the original 12, which was reviewed by Leopold in 2002 [1]. There is a slight reordering of the chapters as well as the addition of two chapters, but the structure is similar with early introductory chapters and building concepts related to Wetland science ending in chapters more focused on Wetland management. The other similar Wetland textbook is
Mike Acreman - One of the best experts on this subject based on the ideXlab platform.
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projecting impacts of climate change on hydrological conditions and biotic responses in a chalk valley riparian Wetland
Journal of Hydrology, 2016Co-Authors: Andrew House, Julian R Thompson, Mike AcremanAbstract:Projected changes in climate are likely to substantially impact Wetland hydrological conditions that will in turn have implications for Wetland Ecology. Assessing ecohydrological impacts of climate change requires models that can accurately simulate water levels at the fine-scale resolution to which species and communities respond. Hydrological conditions within the Lambourn Observatory at Boxford, Berkshire, UK were simulated using the physically based, distributed model MIKE SHE, calibrated to contemporary surface and groundwater levels. The site is a 10 ha lowland riparian Wetland where complex geological conditions and channel management exert strong influences on the hydrological regime. Projected changes in precipitation, potential evapotranspiration, channel discharge and groundwater level were derived from the UK Climate Projections 2009 ensemble of climate models for the 2080s under different scenarios. Hydrological impacts of climate change differ through the Wetland over short distances depending on the degree of groundwater/surface-water interaction. Discrete areas of groundwater upwelling are associated with an exaggerated response of water levels to climate change compared to non-upwelling areas. These are coincident with regions where a weathered chalk layer, which otherwise separates two main aquifers, is absent. Simulated water levels were linked to requirements of the MG8 plant community and Desmoulin’s whorl snail (Vertigo moulinsiana) for which the site is designated. Impacts on each are shown to differ spatially and in line with hydrological impacts. Differences in water level requirements for this vegetation community and single species highlight the need for separate management strategies in distinct areas of the Wetland.
Ian Jolly - One of the best experts on this subject based on the ideXlab platform.
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a review of groundwater surface water interactions in arid semi arid Wetlands and the consequences of salinity for Wetland Ecology
Ecohydrology, 2008Co-Authors: Ian Jolly, Kerryn Mcewan, Kate L HollandAbstract:In arid/semi-arid environments, where rainfall is seasonal, highly variable and significantly less than the evaporation rate, groundwater discharge can be a major component of the water and salt balance of a Wetland, and hence a major determinant of Wetland Ecology. Under natural conditions, Wetlands in arid/semi-arid zones occasionally experience periods of higher salinity as a consequence of the high evaporative conditions and the variability of inflows which provide dilution and flushing of the stored salt. However, due to the impacts of human population pressure and the associated changes in land use, surface water regulation, and water resource depletion, Wetlands in arid/semi-arid environments are now often experiencing extended periods of high salinity. This article reviews the current knowledge of the role that groundwater–surface water (GW–SW) interactions play in the Ecology of arid/semi-arid Wetlands. The key findings of the review are as follows: 1.GW–SW interactions in Wetlands are highly dynamic, both temporally and spatially. Groundwater that is low in salinity has a beneficial impact on Wetland Ecology which can be diminished in dry periods when groundwater levels, and hence, inflows to Wetlands are reduced or even cease. Conversely, if groundwater is saline, and inflows increase due to raised groundwater levels caused by factors such as land use change and river regulation, then this may have a detrimental impact on the Ecology of a Wetland and its surrounding areas. 2.GW–SW interactions in Wetlands are mostly controlled by factors such as differences in head between the Wetland surface water and groundwater, the local geomorphology of the Wetland (in particular, the texture and chemistry of the Wetland bed and banks), and the Wetland and groundwater flow geometry. The GW–SW regime can be broadly classified into three types of flow regimes: (i) recharge—Wetland loses surface water to the underlying aquifer; (ii) discharge—Wetland gains water from the underlying aquifer; or (iii) flow-through—Wetland gains water from the groundwater in some locations and loses it in others. However, it is important to note that individual Wetlands may temporally change from one type to another depending on how the surface water levels in the Wetland and the underlying groundwater levels change over time in response to climate, land use, and management. 3.The salinity in Wetlands of arid/semi-arid environments will vary naturally due to high evaporative conditions, sporadic rainfall, groundwater inflows, and freshening after rains or floods. However, Wetlands are often at particular risk of secondary salinity because their generally lower elevation in the landscape exposes them to increased saline groundwater inflows caused by rising water tables. Terminal Wetlands are potentially at higher risk than flow-through systems as there is no salt removal mechanism. 4.Secondary salinity can impact on Wetland biota through changes in both salinity and water regime, which result from the hydrological and hydrogeological changes associated with secondary salinity. Whilst there have been some detailed studies of these interactions for some Australian riparian tree species, the combined effects on aquatic biodiversity are only just beginning to be elucidated, and are therefore, a future research need. 5.Rainfall/flow-pulses, which are a well-recognized control on ecological function in arid/semi-arid areas, also play an important, though indirect, role through their impact on Wetland salinity. Freshwater pulses can be the primary means by which salt stored in both the water column and the underlying sediments are flushed from Wetlands. Conversely, increased runoff is also a commonly observed consequence of secondary salinity, and so, Wetlands can experience increased surface water inflows that are higher in salinity than under natural conditions. Moreover, changes in rainfall/flow-pulse regimes can have a significant impact on Wetland GW–SW interactions. It is possible that in some instances groundwater inflow to a Wetland may become so heavy that it could become a major component of the water balance, and hence, mask the role of natural pulsing regimes. However, if the groundwater is low in salinity, this may provide an ecological benefit in arid/semi-arid areas by assisting in maintaining water in Wetlands that become aquatic refugia between flow-pulses. 6.There has been almost no modelling of GW–SW interactions in arid/semi-arid Wetlands with respect to water fluxes, let alone salinity or Ecology. There is a clear need to develop modelling capabilities for the movement of salt to, from, and within Wetlands to provide temporal predictions of Wetland salinity which can be used to assess ecosystem outcomes. 7.There has been a concerted effort in Australia to collect and collate data on the salinity tolerance/sensitivity of freshwater aquatic biota and riparian vegetation. There are many shortcomings and knowledge gaps in these data, a fact recognized by many of the authors of this work. Particularly notable is that there is very little time-series data, which is a serious issue because Wetland salinities are often highly temporally variable. There is also a concern that many of the data are from very controlled laboratory experiments, which may not represent the highly variable and unpredictable conditions experienced in the field. In light of these, and many other shortcomings identified, our view is that the data currently available are a useful guide but must be used with some caution. Copyright © 2008 John Wiley & Sons, Ltd.
