988 research outputs found
Validation and downscaling of Advanced Scatterometer (ASCAT) soil moisture using ground measurements in the Western Cape, South Africa
No full textSatellite-based remote sensing of soil water content (SWC) is a promising technology for hydrological applications to overcome large spatiotemporal variabilities of SWC. This study investigated the performance of the Advanced Scatterometer (ASCAT) soil moisture product on METOP satellite (~12.5 km and downscaled to ~1 km resolution), against ground measurements of SWC taken with a Hydrosense II probe along transects of 360?820 m on agricultural and natural land at locations in the Western Cape. The ASCAT products estimated fairly accurately seasonal trends of SWC; performance was better on lower slopes (R 2 = 0.66) and uniform vegetation. ASCAT 12.5 km performed better in estimating SWC than the downscaled product (average concordance coefficient = 0.60 and 0.39, and R 2 = 0.84 and 0.74, respectively). ASCAT 12.5 km was more responsive to rainfall events, whilst the downscaled product was more sensitive to vegetation characteristics (normalised difference vegetation index and land surface temperature). In situations with ground measurement networks and data availability constraints, remote sensing could be a feasible alternative to monitor SWC for hydrological applications at the meso-scale (regional scale).Fil: Moller, Jason. University of the Western Cape; SudáfricaFil: Jovanovic, Nebo. CSIR Natural Resources and the Environment; Sudáfrica. University of the Western Cape; SudáfricaFil: García, César Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Católica de Córdoba; ArgentinaFil: Bugan, Richard D. H.. CSIR Natural Resources and the Environment; SudáfricaFil: Mazvimavi, Dominic. University of the Western Cape; Sudáfric
From Foucauldian Biopower to Energopower and Infopower:An Interview with Dominic Boyer and Colin Koopman
No full textKirsten Hasberg talks to Dominic Boyer, anthropologist and author of Energopolitics: Wind and Power in the Anthroprocene, and to Colin Koopman, philosopher and author of How We Became our Data: A Genealogy of the Informational Person. Their books published in mid-2019 put forward novel conceptualizations of Foucauldian biopower, which they term infopower and energopower, respectively. Criss-crossing between philosophical conceptualizations and concrete problems like the struggles of renewable energy communities (Boyer) and the influence of economic thinking on datafication (Koopman), the conversations show how Foucauldian concepts are relevant to today's power struggles inherent to the energy transition and the digital transformation.Kirsten Hasberg talks to Dominic Boyer, anthropologist and author of Energopolitics: Wind and Power in the Anthroprocene, and to Colin Koopman, philosopher and author of How We Became our Data: A Genealogy of the Informational Person. Their books published in mid-2019 put forward novel conceptualizations of Foucauldian biopower, which they term infopower and energopower, respectively. Criss-crossing between philosophical conceptualizations and concrete problems like the struggles of renewable energy communities (Boyer) and the influence of economic thinking on datafication (Koopman), the conversations show how Foucauldian concepts are relevant to today's power struggles inherent to the energy transition and the digital transformation
A comparative analysis of long-term variations of temperature and rainfall in rural and urban areas, and their effects on the estimation of design storms in Kenya
No full textPhilosophiae Doctor - PhD (Earth Science)My Thesis aimed at expanding the current knowledge on how variations of temperature
characteristics including the possible existence of urban heat islands (UHI) over urban areas
of Kenya could be influencing rainfall characteristics, and to examine if the stationary
extreme value distributionis still suitable for modeling urban storm designs in view of the
global climate change. My hypothesis was that the floodingoccurring frequently in major
urban areas of Kenya are due to increased rainfall caused by global climate change, and the
urban heat island (UHI) effect. To put this perception into perspective, temperature and
rainfall characteristics and their inter-relationships, of four of the major urban areas in Kenya
namely, Nairobi, Mombasa, Kisumu, and Nakuru, were investigated. I obtained data from
meteorological stations in and around each urban area, which had at least thirty (30) years of
continuous monthly (or daily) temperatures and rainfall values, from the Kenya
Meteorological Department. I checked the datasets for quality and missing values and
adjusted where necessary before commencing with analysis. I sourced other supporting
global dataset from various websites' data banks.I used various methods of data analysis
which included; i) exploratory data analysis techniques such as the continuous wavelet
transform (CWT), geographical information system (GIS) maps, and visual time series plots.
In particular and unique in my Thesis was the use of the CWT method as a diagnostic tool to
examine non-stationaritiesand variability of temperature and rainfall time series
An assessment of the river flow contributions of tributaries and the effects of floodplain wetlands on spatio-temporal variations of river flows in the Nuwejaars river catchment, Cape Agulhas
No full text>Magister Scientiae - MScImproved knowledge is required on the quantity and source of water resources, particularly evident during periods of drought currently being faced in South Africa. There is inadequate knowledge with regards to the flood attenuating properties of wetlands, particularly evident in the ungauged catchments of Southern Africa. This study aims to improve the knowledge on the contribution of flow from tributaries with headwaters in mountainous regions to low lying areas and the effects of wetlands on river flow patterns. Several river flow monitoring sites were established along the major upper tributaries of the Nuwejaars River at which daily water levels were recorded and bi-weekly discharge measurements were conducted. Weather data was collected using four automatic weather stations and three automatic rain gauges’ setup throughout the catchment. Rainfall data coupled with rating curves and daily discharges were used to assess the flow responses of these tributaries to rainfall events. Additionally, stable isotope analysis and basic water quality analysis was used to determine the major sources of flow within the major tributaries. The rainfall and river flow data collected, coupled with the characterization of the wetland was used to determine the flood attenuation capabilities of the wetland. Lastly, a conceptual model based on a basic water balance was developed to further explain the role of the wetland and its effects on river flows. The results showed a 27-hour lag time in peak flows from the upper tributaries at the inflows of the wetland to the outflow. Two of the upper tributaries had flow throughout the year and were fed by springs in the upper mountainous regions of the catchment and all tributaries were largely reliant on rainfall for peak flows. The temporary storage of flows within the wetland occurred as a result of the Nuwejaars River bursting its banks, filling of pools, or ponds and the Voëlvlei Lake. It was concluded that the wetland increased the travel time and decreased the magnitude of flows of the Nuwejaars River. However, due to the fact that wetlands are interlinked on a catchment scale and have a collective effect on flood attenuation this study may be improved by looking at the wetlands within the catchment holistically
Flood alleviation and restoration on the Lourens river, Somerset west, South Africa
No full text>Magister Scientiae - MScSomerset West and Strand in the Western Cape, South Africa, were developed on the Lourens
River floodplain. This hardened the catchment and reduced the capacity of the river to transport
and store floodwaters. The result was recurrent flooding of residential and industrial areas and
a fear that this could lead to loss of human life. In response to these concerns, the City of Cape
Town implemented flood alleviation measures with a ‘soft’ engineering approach that
incorporated geomorphological and ecological principles into their design. This was one of the
first engineer/ecologist collaborations in South Africa, which attempted to make better
decisions for the river ecosystem within the constraints imposed on it by urban development;
and in so doing to create a self-sustaining river that requires little ongoing manipulation. The
aim of this dissertation was to assess the extent to which ecological considerations were
incorporated into the flood alleviation works on the Lourens River and whether this improved
physical habitat and the diversity of riverine biota. Physical habitat was mapped from 1:50 000
topographic maps and aerial imagery in a GIS, and cross-sectional profiles, diversity of
hydraulic biotopes and subtsrate composition were surveyed in the field
Spatial and temporal variations of inundation and their influence on ecosystem services from a shallow coastal lake. A case study of Soetendalsvlei in the Nuwejaars catchment, South Africa
No full textPhilosophiae Doctor - PhDEnhancing our understanding of wetland properties and the ecosystem services provided by wetlands within a dynamic landscape, is fundamental to ensuring appropriate management strategies for enhanced biodiversity and ecosystem benefits. With increased anthropogenic activities and the impacts of climatic variability, a better understanding of the factors influencing the water balance dynamics of wetlands can provide insight into how wetlands respond to change. The main aim of the research was to improve the understanding of the spatial and temporal availability of water and storage of a depression wetland in a semi-arid climate, and to relate these to ecosystem functions. As ecosystems are intricately connected to society, a secondary aim of the research was to gain insight to how wetland ecosystems, within a changing climate and landscape, provide benefits to society, and add value to human-wellbeing. Soetendalsvlei, a shallow freshwater depression, and one of the few coastal freshwater lakes of South Africa, was the focus of the research
An assessment of the influence of water allocation on sustainable water resources management: A case study of the Nyando river basin, Kenya
No full textPhilosophiae Doctor - PhDWater problems prevalent in the Nyando River Basin are due to an ineffective water allocation
system and lack of adequate conditions for implementation of sustainable integrated water
resources management (IWRM) strategies. The basin is bedevilled by poor water resources
management, inequitable allocation of water among consumers, physical infrastructural
deficiencies, inefficient water utilisation, illegal water abstractions, natural resource
mismanagement, conflicting and weak institutional roles and lack of stakeholder involvement in
water resource management. The results of the study reveal sufficient per capita annual water
availability with the potential to realise both Sustainable Development Goals (SDGs) and the
Kenyan Vision 2030. However, analyses from flow duration curves (FDCs) and the water
evaluation and planning (WEAP) model show that monthly water demands including environmental
flow requirements (EFRs) are met only between 43% and 94% of the time. While the Water Act
(2002) upholds the principles of IWRM on equitable and sustainable water resources allocation, in
practice the current water allocation system falls short of implementing these strategies due to lack
of a water allocation plan (WAP), inadequate water demand management (WDM), low
infrastructural development and lack of community participation in WRM. For example, the total
revenue generated in water supply schemes is only about 25 to 30% of their operational costs,
which means that in the absence of subsidies the schemes cannot operate. The goal of this study
was to examine the influence of the current water allocation system on water resources management
in the Nyando River Basin by comparing the various sectoral water demands in the basin with the
available water resources in order to improve understanding of how water allocation systems work
in practice. The analyses further revealed that irrigation uses up to 72% of the available water,
which is mainly drawn from the regular low flow contrary to the permit order. For example, the
Ahero National Irrigation Scheme is permitted to draw 47 m3/day of water from regular flow and
13,500 m3/day from flood flow, but draws the whole amount from the regular flow; hence irrigation
is the main cause of water deficits in the basin. Projections show that the irrigation sector will
experience 300% increase in an unmet demand of 92.4 Mm3 by 2030 up from the current annual
deficit of 2.9 Mm3. In light of the above challenges, both improvement of WDM and infrastructural
provision have complementary roles in contributing to sustainable water availability,
socioeconomic growth and poverty eradication in the basin and help achieve SDGs at the local
scale. The results of the study will facilitate an understanding of the influence of water allocation
systems on regional hydrology and form the basis of improving water allocation systems, and
inform policy formulations to ensure sustained water availability and environmental sustainability
in river basins. In that regard, this study contributes to the on-going global debate on Sustainable
Development Goals by exploring ways of realising and improving IWRM strategies and the
National targets
Investigating the effects of nutrients and chlorophyll concentrations on the water quality of the Nuwejaars River, Cape Agulhas, Western Cape
No full text>Magister Scientiae - MScThe Nuwejaars River flows into the largest natural freshwater lake in South Africa, Soetendalsvlei, which relies on and interacts with the Nuwejaars River. Therefore, the water quality of the Nuwejaars River plays a role in the health of the surrounding ecosystem.
Over a period of three years, concentrations of nutrient constituents, physicochemical parameters, chlorophyll and phycocyanin, were measured in an attempt to investigate the water quality of the river. This study aimed to identify the patterns of nutrients, chlorophyll and phycocyanin down the length of the Nuwejaars River by assessing the physico-chemical parameters, nutrients and chlorophyll concentrations in the surface water to determine the temporal and spatial variations of these parameters, and to examine the relationships between the concentrations of selected nutrients, chlorophyll a and phycocyanin in the river water
An assessment of the contribution of surface and subsurface flows to river flows of the Sandspruit in the Berg River Catchment, South Africa.
No full textMagister Scientiae - MSc (Environ & Water Science)Studies have shown that the primary origin of salinity in river flows of the Sandspruit in the Berg
Catchment located in the Western Cape Province of South Africa was mainly a result of atmospheric
deposition of salts. The salts are transported to rivers through surface runoff and subsurface flow (i.e.
through flow and groundwater flow). The purpose of this study was to determine the contributions of
subsurface and surface flows to the total flows in the Sandspruit, Berg Catchment. Three rain events
were studied. Water samples for two rain events were analysed for environmental tracers ?18O, Silica
or Silicon dioxide (SiO2), Calcium (Ca2+) and Magnesium (Mg2+). Tracers used for two component
hydrograph separation were ?18O and SiO2. The tracers, Ca2+ and Mg2+, revealed inconsistent
contributions of both subsurface flow and surface flow. Two component hydrograph separations
indicated is that groundwater is the dominant contributor to flow, while surface runoff mainly
contributes during the onset of the storm event. Groundwater response to precipitation input indicated
that boreholes near the river have a quicker response than boreholes further away from the river.
Boreholes nearer to the river also indicate higher water levels in response to precipitation, in comparison
to boreholes further from the river
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