Graham Jewitt

Bio: Graham Jewitt is an academic researcher from University of KwaZulu-Natal. The author has contributed to research in topics: Water resources & Surface runoff. The author has an hindex of 32, co-authored 101 publications receiving 3112 citations. Previous affiliations of Graham Jewitt include Institut de recherche pour le développement & UNESCO-IHE Institute for Water Education.

Impacts of climate change on water resources in southern Africa: A review

Abstract: The Intergovernmental Panel on Climate Change concluded that there is consensus that the increase of atmospheric greenhouse gases will result in climate change which will cause the sea level to rise, increased frequency of extreme climatic events including intense storms, heavy rainfall events and droughts. This will increase the frequency of climate-related hazards, causing loss of life, social disruption and economic hardships. There is less consensus on the magnitude of change of climatic variables, but several studies have shown that climate change will impact on the availability and demand for water resources. In southern Africa, climate change is likely to affect nearly every aspect of human well-being, from agricultural productivity and energy use to flood control, municipal and industrial water supply to wildlife management, since the region is characterised by highly spatial and temporally variable rainfall and, in some cases, scarce water resources. Vulnerability is exacerbated by the region’s low adaptive capacity, widespread poverty and low technology uptake. This paper reviews the potential impacts of climate change on water resources in southern Africa. The outcomes of this review include highlighting studies on detected climate changes particularly focusing on temperature and rainfall. Additionally, the impacts of climate change are highlighted, and respective studies on hydrological responses to climate change are examined. The review also discusses the challenges in climate change impact analysis, which inevitably represents existing research and knowledge gaps. Finally the paper concludes by outlining possible research areas in the realm of climate change impacts on water resources, particularly knowledge gaps in uncertainty analysis for both climate change and hydrological modelling.

A GIS-based approach for identifying potential runoff harvesting sites in the Thukela River basin, South Africa

Abstract: Water scarce countries such as South Africa are subject to various hydrological constraints which can often be attributed to poor rainfall partitioning, particularly within resource poor farming communities that are reliant on rainfed agriculture. Recent initiatives to address this have shifted focus to explore more efficient alternatives to water supply and the recognition of numerous opportunities to implement runoff harvesting as a means to supplement water availability. However, increasing the implementation of runoff harvesting, without encountering unintended impacts on downstream hydrological and ecological systems, requires better understanding of the hydrologic and environmental impacts at catchment scale. In this paper the representation of spatial variations in landscape characteristics such as soil, land use, rainfall and slope information is shown to be an important step in identifying potential runoff harvesting sites, after which modelling the hydrological response in catchments where extensive runoff harvesting is being considered can be performed and likely impacts assessed. Geographic information systems (GIS) was utilised as an integrating tool to store, analyse and manage spatial information and when linked to hydrological response models, provided a rational means to facilitate decision making by providing catchment level identification, planning and assessment of runoff harvesting sites as illustrated by a case study at the Potshini catchment, a small sub-catchment in the Thukela River basin, South Africa. Through the linked GIS, potential runoff harvesting sites are identified relative to areas that concentrate runoff and where the stored water will be appropriately distributed. Based on GIS analysis it was found that 17% percent of the Potshini catchment area has a high potential for generating surface runoff, whereas an analysis of all factors which influence the location of such systems, shows that 18% is highly suitable for runoff harvesting. Details of the spatially explicit method that was adopted in this paper are provided and output from the integrated GIS modelling system is presented using suitability maps. It is concluded that providing an accurate spatial representation of the runoff generation potential within a catchment is an important step in developing a strategic runoff harvesting plan for any catchment.

The Development of the Water-Energy-Food Nexus as a Framework for Achieving Resource Security: A Review

Abstract: This paper presents a study of the evolution of the water-energy-food (WEF) nexus since its rise to prominence in policy and development discourses in 2011. The paper presents various interpretations of the concept as well as the novelty the WEF nexus. The challenge of integrating and optimising the components of this multi-centric nexus is examined, with four case studies being presented. Various criticisms levelled at the WEF nexus, such as the neglect of livelihoods and the environment in assessments, are noted, together with governance considerations associated with this framework. Finally, the potential of the WEF nexus to contribute to the achievement of the Sustainable Development Goals is reviewed.

Mapping ecosystem services across scales and continents – A review

Abstract: Tremendous progress in ecosystem service mapping across the world has moved the concept of ecosystem services forward towards an increasingly useful tool for policy and decision making There is a pressing need to analyse the various spatial approaches used for the mapping studies We reviewed ecosystem services mapping literature in respect to spatial scale, world distribution, and types of ecosystem services considered We found that most world regions were represented among ecosystem service mapping studies and that they included a diverse set of ecosystem services, relatively well distributed across different ecosystem service categories A majority of the studies were presented at intermediary scales (municipal and provincial level), and 66% of the studies used a fine resolution of 1 ha or less The intermediary scale of presentation is important for land use policy and management The fact that studies are conducted at a fine resolution is important for informing land management practices that mostly takes place at the scale of fields to villages Ecosystem service mapping could be substantially advanced by more systematic development of cross-case comparisons and methods

A watershed approach to upgrade rainfed agriculture in water scarce regions through Water System Innovations: an integrated research initiative on water for food and rural livelihoods in balance with ecosystem functions

Abstract: The challenge of producing food for a rapidly increasing population in semi-arid agro-ecosystems in Southern Africa is daunting. More food necessarily means more consumptive use of so-called green water flow (vapour flow sustaining crop growth). Every increase in food production upstream in a watershed will impact on water user and using systems downstream. Intensifying agriculture has in the past often been carried out with negative side effects in terms of land and water degradation. Water legislation is increasingly incorporating the requirement to safeguard a water reserve to sustain instream ecology. To address the challenges of increasing food production, improving rural livelihoods, while safeguarding critical ecological functions, a research programme has recently been launched on “Smallholder System Innovations in Integrated Watershed Management” (SSI). The programme takes an integrated approach to agricultural water management, analysing the interactions between the adoption and participatory adaptation of water system innovations (such as water harvesting, drip irrigation, conservation farming, etc.), increased water use in agriculture and water flows to sustain ecological functions that deliver critical ecosystem services to humans. The research is carried out in the Pangani Basin in Tanzania and the Thukela Basin in South Africa. A nested scale approach is adopted, which will enable the analysis of scale interactions between water management at the farm level, and cascading hydrological impacts at watershed and basin scale. This paper describes the integrated research approach of the SSI programme, and indicates areas of potential to upgrade rainfed agriculture in water scarcity-prone agro-ecosystems while securing water for downstream use.

반도체 공정 overview

Abstract: With digital equipment becoming increasingly networked, either on wired or wireless networks, for personal and professional use alike, distributed software systems have become a crucial element in information and communications technologies. The study of these systems forms the core of the ARLES' work, which is specifically concerned with defining new system software architectures, based on the use of emerging networking technologies. In this context, we concentrate on the study of distributed systems which bring to life the vision of ubiquitous computing systems, also known as ambient intelligence.

SWAT: Model Use, Calibration, and Validation

Abstract: SWAT (Soil and Water Assessment Tool) is a comprehensive, semi-distributed river basin model that requires a large number of input parameters, which complicates model parameterization and calibration. Several calibration techniques have been developed for SWAT, including manual calibration procedures and automated procedures using the shuffled complex evolution method and other common methods. In addition, SWAT-CUP was recently developed and provides a decision-making framework that incorporates a semi-automated approach (SUFI2) using both manual and automated calibration and incorporating sensitivity and uncertainty analysis. In SWAT-CUP, users can manually adjust parameters and ranges iteratively between autocalibration runs. Parameter sensitivity analysis helps focus the calibration and uncertainty analysis and is used to provide statistics for goodness-of-fit. The user interaction or manual component of the SWAT-CUP calibration forces the user to obtain a better understanding of the overall hydrologic processes (e.g., baseflow ratios, ET, sediment sources and sinks, crop yields, and nutrient balances) and of parameter sensitivity. It is important for future calibration developments to spatially account for hydrologic processes; improve model run time efficiency; include the impact of uncertainty in the conceptual model, model parameters, and measured variables used in calibration; and assist users in checking for model errors. When calibrating a physically based model like SWAT, it is important to remember that all model input parameters must be kept within a realistic uncertainty range and that no automatic procedure can substitute for actual physical knowledge of the watershed.