Status and trends in EFlows in southern Africa

Brown, Catherine; Campher, Dirk; King, Jackie

doi:10.1111/1477-8947.12190

Cited by 15 publications

(6 citation statements)

References 46 publications

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“…While the choice of which model to use may depend on a number of factors (including user preference and experience), it is clearly important that the model includes components that simulate all the main anthropogenic impacts, including large dams and smaller farm dams [16,17]. Many countries of southern Africa have some form of policy and legislation that regulates water use to ensure a defined level of protection for aquatic ecosystems, and methods have been developed to undertake the necessary assessments [41][42][43] and generate information that is compatible with integrated water resources yield models [44,45]. The lower part of the diagram represents the main decision-making part of the whole process where various scenarios can be considered in the context of the requirements and attitudes of the full range of stakeholders.…”

Section: Managing and Mitigating Impacts 41 Various Integrated Approa...mentioning

confidence: 99%

Farm Dams in Southern Africa: Balancing Environmental and Socio-Economic Sustainability

Mantel,

Hughes

2023

Environmental Sciences

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The proliferation and extent of small dams is a significant issue for water resources management. South Africa has an extensive spatial database of farm dams; however, uncertainties remain when estimating the water volume held, although satellite-based techniques offer some means of measurement. This chapter compares various datasets on the occurrence of farm dams in southern Africa and summarises the research on their impacts. Correlations between high-density of small dams and the decline of macroinvertebrate communities, resulting from compromised water quality and low flows, have been established in South Africa. Despite this, the assessment of the cumulative impact of farm dams on riverine ecosystems proves complex due to various uncertainties. The degree of impact varies by dam type, with off-channel dams exhibiting a lower influence on connectivity and sediment dynamics. Efforts to manage and mitigate the effects of small dams is being addressed through a variety of integrated approaches, including: a spatial cost-benefit framework, a model that incorporates different value systems with equitable allocation criteria, and agent-based modelling. The viability of these techniques is dependent upon securing agreement among stakeholders. The chapter concludes with some recommendations for the ways forward.

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Section: Managing and Mitigating Impacts 41 Various Integrated Approa...mentioning

confidence: 99%

Farm Dams in Southern Africa: Balancing Environmental and Socio-Economic Sustainability

Mantel,

Hughes

2023

Environmental Sciences

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“…Establishing robust methods for trade-offs between competing values is an important step towards establishing a consensus around desired outcomes. Brown et al [114,115] describe two approaches to determining desired outcomes-prescriptive vs. scenario based. In a prescriptive approach, there is an agreed level of ecological condition that must be maintained, and a flow regime is prescribed to support this.…”

Section: Establishing Expectation and Desired Conditionsmentioning

confidence: 99%

Advancing the Science of Environmental Flow Management for Protection of Temporarily Closed Estuaries and Coastal Lagoons

Stein

Gee

Adams

et al. 2021

Water

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The science needed to inform management of environmental flows to temporarily closed estuaries and coastal lagoons is decades behind the state of knowledge for rivers and large embayments. These globally ubiquitous small systems, which are often seasonally closed to the ocean’s influence, are under particular threat associated with hydrologic alteration because of changes in atershed land use, water use practices, and climate change. Managing environmental flows in these systems is complicated by their tight coupling with watershed processes, variable states because of intermittently closing mouths, and reliance on regional scale sediment transport and littoral processes. Here we synthesize our current understanding of ecohydrology in temporarily closed estuaries (TCEs) and coastal lagoons and propose a prioritized research agenda aimed at advancing understanding of ecological responses to altered flow regimes in TCEs. Key research needs include agreeing on a consistent typology, improving models that couple watershed and ocean forcing at appropriate spatial and temporal scales, quantifying stress–response relationships associated with hydrologic alteration, improving tools to establish desired conditions that account for climate change and consider cultural/indigenous objectives, improving tools to measure ecosystem function and social/cultural values, and developing monitoring and adaptive management programs that can inform environmental flow management in consideration of other stressors and across different habitat types. Coordinated global efforts to address the identified research gaps can help guide management actions aimed at reducing or mitigating potential impacts of hydrologic alteration and climate change through informed management of freshwater inflows.

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“…These EFlows support human cultures, economies, sustainable livelihoods, and well-being [28]. EFlow requirements were seldom considered in water resource planning and management [29][30][31][32][33] until methods were developed for estuaries in South Africa, Australia, and the USA (CA and TX) [33,34]. EFlow requirements have also been described for Mediterranean coastal ecosystems, such as the Ebro Delta, where anthropogenic pressures are magnified by the natural hydrological variability of aquatic ecosystems [35,36].…”

Section: Eflow Studies In South Africamentioning

confidence: 99%

“…This necessitates a holistic catchment-to-coast management approach that requires collaboration across government departments and sectors (Figure 12b). The Integrated Water Resource Management (IWRM) process captures some of this complexity and EFlows are an important component [30]. Estuaries are subjected to multiple pressures, e.g., artificial breaching and biological invasions [7], and need to be assessed as part of an estuary EFlow assessment to ensure that desired state objectives are achievable.…”

Section: Principle 10: Catchment To Coast Integrated Management Appromentioning

confidence: 99%

Ten Principles to Determine Environmental Flow Requirements for Temporarily Closed Estuaries

Adams

Niekerk

2020

Water

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Temporarily closed estuaries require seasonal opening to tidal flows to maintain normal ecological processes. Each estuary has specific environmental flow (EFlow) requirements based on the relationship between freshwater inflow, coastal dynamics, rate of sandbar formation, and the open/closed state of the mouth. Key abiotic processes and ecosystem services linked to mouth state were highlighted. We reviewed completed EFlow requirement studies for temporarily closed estuaries in South Africa and found that the formulation of these requirements should consider the timing and magnitude of flows in relation to the morphology of an estuary, its mouth structure, catchment size, and climate. We identified ten key principles that could be adapted to similar systems in equivalent climatic settings. Principle 1 recognizes that each estuary is unique in terms of its EFlow requirements because size, scale, and sensitivity of core elements to freshwater inflow are specific for each system; EFlows cannot be extrapolated from one estuary to another. Principle 2 highlights the importance of baseflows in keeping an estuary mouth open because a small reduction in flow can cause the mouth to close and alter essential ecological processes. Principle 3 outlines the role of floods in resetting natural processes by flushing out large volumes of sediment and establishing the equilibrium between erosion and sedimentation. Principle 4 emphasizes the need for open mouth conditions to allow regular tidal flushing that maintains water quality through reducing retention times and preventing the onset of eutrophic conditions. Principle 5 advises artificial breaching to be practiced with caution because execution at low water levels encourages sedimentation that reduces the scouring effect of flushing. Principle 6 holds that elevated inflow volumes from wastewater treatment works or agricultural return flows can increase the frequency of mouth opening and cause ecological instability. Principle 7 states that water released from dams to supply the environmental flow cannot mimic the natural flow regime. Principle 8 specifies the need for short- and long-term data to increase the confidence levels of EFlow assessments, with data to be collected during the open and closed mouth states. Principle 9 advocates the implementation of a monitoring program to track the achievement of EFlow objectives as part of a strategic adaptive management cycle. Finally, Principle 10 recommends the adoption of a holistic catchment-to-coast management approach underpinned by collaboration with regulatory authorities and stakeholders across a range of sectors. These principles can be used to guide the formulation and management of EFlows, an essential strategy that links the maintenance of estuarine ecological integrity with social well-being.

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Status and trends in EFlows in southern Africa

Cited by 15 publications

References 46 publications

Farm Dams in Southern Africa: Balancing Environmental and Socio-Economic Sustainability

Farm Dams in Southern Africa: Balancing Environmental and Socio-Economic Sustainability

Advancing the Science of Environmental Flow Management for Protection of Temporarily Closed Estuaries and Coastal Lagoons

Ten Principles to Determine Environmental Flow Requirements for Temporarily Closed Estuaries

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