Connectivity through allochthony: Reciprocal links between adjacent aquatic and terrestrial ecosystems in South Africa
- Richoux, Nicole B, Moyo, Sydney, Chari, Lenin D, Bergamino, Leandro, Carassou, Laure, Dalu, Tatenda, Hean, Jeff W, Sikutshwa, Likho, Gininda, Simphiwe, Magoro, Mandla, Perhar, Gurbir, Ni, Felicity, Villet, Martin H, Whitfield, Alan K, Parker, Daniel M, Froneman, P William, Arhonditsis, George, Craig, Adrian J F K
- Authors: Richoux, Nicole B , Moyo, Sydney , Chari, Lenin D , Bergamino, Leandro , Carassou, Laure , Dalu, Tatenda , Hean, Jeff W , Sikutshwa, Likho , Gininda, Simphiwe , Magoro, Mandla , Perhar, Gurbir , Ni, Felicity , Villet, Martin H , Whitfield, Alan K , Parker, Daniel M , Froneman, P William , Arhonditsis, George , Craig, Adrian J F K
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438363 , vital:73454 , ISBN 978-1-4312-0679-7 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2186-1-15.pdf
- Description: An important aspect of the dynamics of nutrients and pollutants in natural systems is captured in the concept of allochthony, founded on the observation that nutrients and energy in a variety of forms are transferred between adjacent habitats, com-munities and ecosystems that are not routinely considered as connected. Different forms of nutrients and energy move across the conceptual boundaries of habitats via organisms’ activities or physical processes such as wind or water currents, and these transfers can represent important food subsidies. Such cross-partition ecolog-ical subsidies can augment the nutritional condition, biomass and biodiversity of communities, particularly where local production (or autochthony) alone may be inadequate to support local food webs. Furthermore, organic subsidies can influ-ence population dynamics, community interactions and ecosystem processes, and can represent dominant flux inputs in ecosystem budgets. Our intention was to ex-plore organic nutrient fluxes in relation to a primarily lotic (i.e. flowing) aquatic sys-tem at the scale of a hydrological catchment.
- Full Text:
- Authors: Richoux, Nicole B , Moyo, Sydney , Chari, Lenin D , Bergamino, Leandro , Carassou, Laure , Dalu, Tatenda , Hean, Jeff W , Sikutshwa, Likho , Gininda, Simphiwe , Magoro, Mandla , Perhar, Gurbir , Ni, Felicity , Villet, Martin H , Whitfield, Alan K , Parker, Daniel M , Froneman, P William , Arhonditsis, George , Craig, Adrian J F K
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438363 , vital:73454 , ISBN 978-1-4312-0679-7 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2186-1-15.pdf
- Description: An important aspect of the dynamics of nutrients and pollutants in natural systems is captured in the concept of allochthony, founded on the observation that nutrients and energy in a variety of forms are transferred between adjacent habitats, com-munities and ecosystems that are not routinely considered as connected. Different forms of nutrients and energy move across the conceptual boundaries of habitats via organisms’ activities or physical processes such as wind or water currents, and these transfers can represent important food subsidies. Such cross-partition ecolog-ical subsidies can augment the nutritional condition, biomass and biodiversity of communities, particularly where local production (or autochthony) alone may be inadequate to support local food webs. Furthermore, organic subsidies can influ-ence population dynamics, community interactions and ecosystem processes, and can represent dominant flux inputs in ecosystem budgets. Our intention was to ex-plore organic nutrient fluxes in relation to a primarily lotic (i.e. flowing) aquatic sys-tem at the scale of a hydrological catchment.
- Full Text:
Implementing uncertainty analysis in water resources assessment and planning
- Hughes, Denis A, Mohobane, T, Mallory, S
- Authors: Hughes, Denis A , Mohobane, T , Mallory, S
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438281 , vital:73448 , ISBN 978-1-4312-0629-2 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2056-1-14.pdf
- Description: The main objective of the project was to contribute to the incorporation of uncer-tainty assessments in practical water resource decision-making in South Africa. There are three main components to this objective. The first is the quantification of realistic levels of uncertainty that are as low as possible given the available infor-mation (reducing uncertainty). The second is the availability of tools to implement uncertainty analysis across the broad spectrum of data analysis and modelling plat-forms that form part of practical water resources assessment (including hydrologi-cal and water resources yield models). The third relates to the issue of using uncer-tain information in the process of making decisions about the design, development or operation of water resources systems. The latter includes social, political and economic uncertainties as well as the hydrological uncertainties that are directly addressed in this report. None of these are independent and all are associated with the fundamental issue that all of the role players should understand the key con-cepts of uncertainty and that virtually all of the information we use to make deci-sions is uncertain. One of the major challenges in this project as well as the previous WRC-supported project on uncertainty methods, was the lack of understanding of some of the key issues, or a lack of appreciation of the importance of uncertainty in all water resources decision-making.
- Full Text:
- Authors: Hughes, Denis A , Mohobane, T , Mallory, S
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438281 , vital:73448 , ISBN 978-1-4312-0629-2 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2056-1-14.pdf
- Description: The main objective of the project was to contribute to the incorporation of uncer-tainty assessments in practical water resource decision-making in South Africa. There are three main components to this objective. The first is the quantification of realistic levels of uncertainty that are as low as possible given the available infor-mation (reducing uncertainty). The second is the availability of tools to implement uncertainty analysis across the broad spectrum of data analysis and modelling plat-forms that form part of practical water resources assessment (including hydrologi-cal and water resources yield models). The third relates to the issue of using uncer-tain information in the process of making decisions about the design, development or operation of water resources systems. The latter includes social, political and economic uncertainties as well as the hydrological uncertainties that are directly addressed in this report. None of these are independent and all are associated with the fundamental issue that all of the role players should understand the key con-cepts of uncertainty and that virtually all of the information we use to make deci-sions is uncertain. One of the major challenges in this project as well as the previous WRC-supported project on uncertainty methods, was the lack of understanding of some of the key issues, or a lack of appreciation of the importance of uncertainty in all water resources decision-making.
- Full Text:
Towards assessing impacts of alien plant infestations on river systems in the Southern Cape using cost-benefit analyses
- Rivers-Moore, Nick A, Dallas, Helen, Barendse, Jaco, de Moor, Ferdy C
- Authors: Rivers-Moore, Nick A , Dallas, Helen , Barendse, Jaco , de Moor, Ferdy C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438336 , vital:73452 , ISBN 978-1-4312-0661-2 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2264.pdf
- Description: Ecosystem resilience is key to the provision of dependable ecosystem goods and services, and it is generally accepted that ecosystem diversity helps to maintain sys-tem resilience. It is therefore reasonable to postulate that changes to the variables that drive species patterns will result in changes to ecosystem community structure and consequently negatively impact on system resilience. Alien vegetation in the riparian zone can impact on water temperatures, flow patterns, degree of shading, channel modification, and changes to natural sediment loads. Climate change is likely to exacerbate the problem both directly through its amplification of thermal extremes in aquatic systems, and indirectly through its impacts on dispersal patterns of alien invasive vegetation.
- Full Text:
- Authors: Rivers-Moore, Nick A , Dallas, Helen , Barendse, Jaco , de Moor, Ferdy C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438336 , vital:73452 , ISBN 978-1-4312-0661-2 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2264.pdf
- Description: Ecosystem resilience is key to the provision of dependable ecosystem goods and services, and it is generally accepted that ecosystem diversity helps to maintain sys-tem resilience. It is therefore reasonable to postulate that changes to the variables that drive species patterns will result in changes to ecosystem community structure and consequently negatively impact on system resilience. Alien vegetation in the riparian zone can impact on water temperatures, flow patterns, degree of shading, channel modification, and changes to natural sediment loads. Climate change is likely to exacerbate the problem both directly through its amplification of thermal extremes in aquatic systems, and indirectly through its impacts on dispersal patterns of alien invasive vegetation.
- Full Text:
Understanding and modelling surface water-groundwater interactions
- Tanner, Jane L, Hughes, Denis A
- Authors: Tanner, Jane L , Hughes, Denis A
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438220 , vital:73444 , ISBN 978-1-4312-0630-8 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2056%20-2-14.pdf
- Description: The main objective of the total project was to contribute to the incorpo-ration of uncertainty assessments in practical water resource decision making in South Africa. The companion report addresses more general issues of uncertainty and hydrological modelling, while this report con-centrates on the uncertainties in both understanding and modelling the interactions between surface water and groundwater. Since groundwa-ter routines were added into the widely used Pitman model in the early 2000s by both Prof Hughes and Mr Karim Sami, the approaches have come under a great deal of criticism mainly from the geohydrological community of specialists within South Africa. Arguably, a great deal of this criticism is based on misunderstandings of the intention of adding groundwater routines into an existing surface water model. It was stated quite clearly at the time that this approach was not seen as a replace-ment for existing detailed numerical approaches to groundwater model-ling. The intention was to create a scientific and practical tool that could be used to simulate the complete hydrological cycle at the catchment scale so that integrated water resources decision making could be better supported.
- Full Text:
- Authors: Tanner, Jane L , Hughes, Denis A
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438220 , vital:73444 , ISBN 978-1-4312-0630-8 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2056%20-2-14.pdf
- Description: The main objective of the total project was to contribute to the incorpo-ration of uncertainty assessments in practical water resource decision making in South Africa. The companion report addresses more general issues of uncertainty and hydrological modelling, while this report con-centrates on the uncertainties in both understanding and modelling the interactions between surface water and groundwater. Since groundwa-ter routines were added into the widely used Pitman model in the early 2000s by both Prof Hughes and Mr Karim Sami, the approaches have come under a great deal of criticism mainly from the geohydrological community of specialists within South Africa. Arguably, a great deal of this criticism is based on misunderstandings of the intention of adding groundwater routines into an existing surface water model. It was stated quite clearly at the time that this approach was not seen as a replace-ment for existing detailed numerical approaches to groundwater model-ling. The intention was to create a scientific and practical tool that could be used to simulate the complete hydrological cycle at the catchment scale so that integrated water resources decision making could be better supported.
- Full Text:
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