Research Articles (Civil Engineering)

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Accounting for moment-rotation behaviour of connections in portal frames
(South African Institution of Civil Engineering, 2014-04) Albertyn, Heindrich L.; Haas, T. N.; Dunaiski, Peter E.
Portal frames are steel structures used to construct industrial buildings. Conventional analysis techniques used by practising engineering professionals assume that the eave, ridge and base connections are either infinitely rigid or perfectly pinned. This approach leads to less accurate analysis of the displacement behaviour of portal frames when subjected to external loading. Portal frames must therefore be analysed with rotational springs at all connections to yield accurate displacement behaviour. This investigation focused on determining the accuracy and economic feasibility of modelling portal frame connections with rotational springs. The rotational spring stiffnesses of all connections were required before the portal frame could be analysed in a second-order two-dimensional non-linear analysis. The rotational spring stiffnesses unique to each connection were determined from the moment-rotation behaviour obtained from a series of finite element analysis simulations of each connection. Thereafter these stiffnesses were used to determine the vertical and horizontal displacements of the portal frame. These displacements were compared with experimental test results. The reasons for the discrepancies between the numerical and experimental results were investigated through a sensitivity analysis. The findings suggest that it is not computationally feasible to analyse portal frames with rotational springs, even though the model’s predicted results are more accurate than those of conventional analysis using rigid and pin connections.
Alternative wall‑to‑slab connection systems in reinforced concrete structures
(South African Institution of Civil Engineering, 2017-09) Gerber, Johann; Van Zijl, Gideon Pieter Adriaan Greeff
ENGLISH ABSTRACT: In many reinforced concrete structures the walls precede the construction of the connecting floors. A system is, therefore, required to connect the floors to the already cast walls. There are many different floor-to-wall connection systems available in South Africa, but their behaviour and capacity are not always fully understood, especially when the moment capacity of the joint is to be utilised. This study focuses on four systems: continuous starter-bars, pre-bent site-installed starter-bars, preassembled starter-bars and cast-in anchors with mechanical couplers. The design procedure for the continuous starter-bar system is well understood and documented in design codes, but not enough information is available on the design procedure for the other systems. Certain practical aspects of the installation process are also not fully understood. Cold-bending and straightening of the starterbars are inevitable in both bend-out systems. Previous research shows that this cold-working of the reinforcement can reduce the yield stress and E-modulus of the steel. In order to investigate these findings, a series of tensile tests are conducted. The results indicate that a significant reduction can be expected in both the yield stress and modulus of elasticity of the steel. Low-cycle fatigue tests further suggest that cold-bent steel also has a reduced ductility. The tensile tests are followed by the construction and testing of the systems in full-scale wall-to-slab connections. The effect of the coldbending on the starter-bars is clearly visible, as both the responses of the bend-out systems are less satisfying than the results from the continuous starter-bar system. The experimental phase is followed by numerical analysis of the connection systems. The finite element analyses show that the structural performance is significantly more sensitive to a reduction in the yield stress of the starter-bars, than to the use of a lower concrete grade. It is concluded that all the alternative connection systems can be implemented successfully in a moment-fixed wall-to-slab connection, but that the site-installed bendout system is the preferred method. However, in order to ensure that the system performs on the same level as conventional systems, it is recommended that the design should be conducted with a set of modified steel properties to allow for the negative effect of the cold-working on the starter-bars.
Analysis of water use by gated communities in South Africa
(South African Water Research Commission, 2018) Du Plessis, Jacques J. L.; Jacobs, Heinz E.
ENGLISH ABSTRACT: Gated communities (hereafter GCs) are popular in many countries, including South Africa, because added security and lifestyle improvements are offered relative to homes built on freestanding properties. One of the key factors for the popularity of GCs is the availability of amenities to support the demands of the residents, such as gymnasia, walkways, golf courses, play parks and polo fields. Further benefits include the improved management of infrastructure such as telecommunication services, roads, water, sewer, electrical and stormwater assets. GCs are often governed by trustees or homeowners’ associations, responsible for the operation and the maintenance functions of the infrastructure, as well as implementing and adhering to legislation that pertains to the GC. As part of this study, the monthly water-use records of 2 888 GCs in 3 different South African cities were analysed. Water use was evaluated for each GC as a whole, and also per household in each case. The average number of homes per GC was 33 households/GC, with the smallest GC in the study sample containing 3 houses and the largest 524 houses. One of the study sites was in the winter rainfall region, while 2 sites were in the summer rainfall region. The average annual water use of individual households in each GC was plotted against current guidelines and was found to be relatively low. The average annual daily demands of all properties in the winter rainfall region was 0.63 kL/d, compared to 0.66 kL/d and 0.49 kL/d for the two study sites in the summer rainfall region. The results highlighted peculiarities in the water use of GCs that have not been reported on before, in particular the relatively low water use and the differences between GC homes’ water use in the various rainfall regions.
Applying geographic information systems to delineate residential suburbs and summarise data based on individual parcel attributes
(AOSIS Publishing, 2013) Sinske, Stefan A.; Jacobs, Heinz E.
Background: Information aggregation to suburb level is of interest to engineers and urban planners. Readily available suburb boundaries do not always correspond to the suburb names recorded for individual properties in different data bases and unwanted errors are inherent. This mismatch of suburb names at different spatial scales poses a particular problem to analysts. As part of a parallel research project into the development of a robust guideline for suburb-based water demand analyses it was necessary to evaluate a large number of suburbs in terms of various attributes, one of which was the total suburb area. Objectives: Suburb boundaries were needed to assess the total suburb area. The objective of this research was to develop a novel geographic information system (GIS) application to delineate suburbs with boundaries corresponding to information contained in another data base comprising individual property records. The suburb boundaries derived in this manner may not relate to municipal boundaries, or sociopolitical boundaries, nor do they have to. The fundamentally correct suburb boundary would be the one encompassing what is perceived to be the suburb based on the suburb name in a particular data base that also contains other interesting attributes, such as water use, of individual properties. Method: The ArcGIS environment was used to delineate suburbs by means of triangulated irregular network (TIN) modelling. Boundaries for suburbs with predominantly residential land use were created that included all residential properties according to the suburb name field as recorded in the treasury system. Other vacant areas were also included so as to obtain the total suburb area. The methodology was developed to assist research in the field of potable water services, but the method presented could be applied to other services that require management of information at suburb level. Results: This article illustrates how a tedious task of suburb delineation could be automated in the GIS environment. The tool prevents subjective results that would be prone to error. The automated procedure described could effectively delineate a large number of predominantly residential suburbs in a relatively short time span and produce repeatable results. A reasonable outline could only be obtained if a sufficient number of parcels in the area contained the same suburb name. Functionality was added to the tool so that a limit could be set for this purpose. The default was that if more than 20% of the records were erroneous it was considered impractical to delineate a suburb. The derived suburb boundaries correspond to useful information in other data bases and would thus enable more effective management of the information. Conclusion: A novel procedure to delineate suburb boundaries in the GIS environment was illustrated in this article. Information at two different spatial scales, namely, individual consumers and suburbs, could be married for the purpose of further research into suburban attributes. The tool was applied as part of a parallel research project to delineate 468 suburbs in this manner, results of which were submitted for publication elsewhere.
Artificial aeration of stepped spillways by crest piers and flares for the mitigation of cavitation damage
(South African Institution of Civil Engineering, 2019) Koen, J.; Bosman, D. E.; Basson, G. R.
ENGLISH ABSTRACT: Stepped spillways are one of the oldest spillway designs dating back to 500 B.C. With technical advances in Roller Compacted Concrete (RCC) construction, the stepped spillway has become increasingly popular over recent decades. However, the use of this spillway is limited to a maximum safe unit discharge of 25 m2/s due to the risk of cavitation. In order to increase the discharge capacity on stepped spillways, various crest pier designs were introduced for flow aeration, thereby reducing the risk of cavitation damage. These pier designs were investigated on two physical models, constructed on a scale of 1:15 and 1:50, both with a standard ogee crest profile which transit to a stepped spillway chute. Air concentration was recorded along the pseudo-bottom, while pressures were measured at the step riser. The results of the 1:15 scale model indicated that the implementation of a short bullnose pier increased the safe unit discharge capacity to 30 rm/s. The innovative Flaring Gate Pier design, which was adapted on existing spillways in China, with reported design prototype unit discharges exceeding 200 m2/s, was investigated on the 1:50 scale model. Based on the experimental results of the current study, the safe unit discharge capacity (i.e. a discharge satisfying the relevant criteria defined for this study) was increased to 50 m2/s with an X-shape Flare Gate Pier (FGP) on the spillway crest.
Assessment of the behaviour factor for the seismic design of reinforced concrete structural walls according to SANS 10160 : part 4
(South African Institution of Civil Engineering, 2012-04) Le Roux, Rudolf; Wium, Jan
Reinforced concrete structures, designed according to proper capacity design guidelines, can deform inelastically without loss of strength. Therefore, such structures need not be designed for full elastic seismic demand, but could be designed for a reduced demand. In codified design procedures this reduced demand is obtained by dividing the full elastic seismic demand by a code-defined behaviour factor. There is, however, no consensus in the international community regarding the appropriate value to be assigned to the behaviour factor. The purpose of this study is to assess the value of the behaviour factor currently prescribed by SANS 10160-4 (2011) for the design of reinforced concrete structural walls. This is done by comparing displacement demand to displacement capacity for a series of structural walls. The first step in seismic force-based design is the estimation of the fundamental period of the structure. The influence of this first crucial step is investigated in this study by considering two period calculation methods. It was found that, regardless of the period calculation method, the current behaviour factor value prescribed in SANS 10160-4 (2011) is adequate to ensure that inter-storey drift of structural walls would not exceed code-defined drift limits.
Associations between stormwater retention pond parameters and pollutant (suspended solids and metals) removal efficiencies
(South African Water Research Commission, 2018) Brink, I. C.; Kamish, W.
ENGLISH ABSTRACT: Presented in this paper are the results of correlational analyses and logistic regression between metal substances (Cd, Cu, Pb, Zn), as well as suspended solids removal, and physical pond parameters of 19 stormwater retention pond case studies obtained from the International Stormwater BMP database. Included are cross-correlations between metals and solids in pond influent, effluent and removals. The findings provide insights fundamental to further development of improved models and design guidelines for stormwater ponds. Indications were that (i) pond efficiencies differed between high and low influent concentrations and masses, (ii) concentration was an invalid indicator of correlations between substances in pond influent and effluent as well as the fractions of substances removed within ponds, (iii) total cadmium, copper, lead, zinc and total suspended solids (TSS) were associated in surface runoff and similarly removed within ponds, (iv) statistically significant correlations were often only found in data groups either above or below a specific statistic (quartile value, median) for specific pond parameters, indicating that removals may have been differently influenced by pond parameters over different data ranges, and (v) the volume within the permanent pool was of greater importance to pond efficiencies than the volume captured during storm events.
Baseline adjustment methodology in a shared water savings contract during severe water restrictions - a case study in the Western Cape, South Africa
(2020-01) Jacobs, H. E.; Du Plessis, J. L.; Nel, Nicole; Gugushe, S.; Levin, S.
A novel method for baseline adjustment in a shared water savings contract under serious drought conditions was presented in a companion paper. The newly developed baseline adjustment method was subsequently applied to a case study, as discussed in this manuscript. The case study involved application of the method to 24 relatively complex sites, spread over the Western Cape Province in South Africa. The sites included, for example, military bases, naval dockyards, an airforce base, prison facilities, large multi-storey blocks of flats and administrative office buildings. Baseline adjustment became essential mid-contract during the serious water restrictions in Cape Town at the time. The restrictions were linked to the 'Day Zero' scenario in 2018 when water supply would potentially run out, and resulted in water savings at baseline sites that were ascribed to external factors. The study incorporated a comprehensive review of the approved baseline reports with site visits to 12 of the properties. The baseline adjustment method provided a robust means to obtain adjustments for sites with relatively limited data. The minimum data requirement was a record of monthly water consumption per site. The adjustments varied between 0% and 64% of the original baseline value for the different sites in the study sample. The relatively higher adjustments were linked to sites where outdoor irrigation and pool water use was prevalent during the baseline-setting period, but was banned during the drought. Zero adjustments were found for sites with exceptionally high leakage flows that had subsequently been repaired; leaks dwarfed actual use in these cases. The results for all 24 sites were accepted by the contracting parties as being reasonable and fair.
Baseline adjustment methodology in a shared water savings contract under serious drought conditions
(Water Research Commission, 2020-01) Jacobs, H. E.; Du Plessis, J. L.; Nel, Nicole; Gugushe, S.; Levin, S.
ENGLISH ABSTRACT: Baselines are often employed in shared water saving contracts for estimating water savings after some type of intervention by the water service company. An adjustment to the baseline may become necessary under certain conditions. Earlier work has described a number of relatively complex methods for baseline determination and adjustment, but application in regions faced with relatively limited data becomes problematic. If the adjustment were determined before finalising the contractual matters, it would be possible to gather the required data in order to determine the adjustment. However, in cases where no adjustment was fixed prior to the contract, a method is required to determine an adjustment mid-contract based on whatever data are available at the time. This paper presents a methodology for baseline adjustment in an existing shared water savings contract and explains how adjustment could be determined mid-contract, under conditions of limited data. The adjustment compensates for expected reduced water consumption due to external influences induced by serious water restrictions, typically introduced during periods of drought. The fundamental principle underpinning the baseline adjustment methodology presented in this paper involved segregating real water losses from the actual consumption of end-users, preferably by analysing the minimum night flow. In the absence of recorded night flows, an alternative procedure involving the minimum monthly consumption pre- and post-baseline was employed. The baseline adjustment method was subsequently applied in a South African case study, reported on separately. This technique is helpful because adjustments could be determined without adding unnecessary complexity or cost, and provides a means to resolve disputes in cases where unexpected savings occur mid-contract.
Capacity self-assessment as a catalyst for improved municipal service delivery
(South African Institution of Civil Engineering, 2015-03) Van Baalen, S. M.; Schutte, C. S. L.; Von Leipzig, K.
ENGLISH ABSTRACT: This research paper illustrates that accurate and truthful capacity assessments are a fundamental phase of any capacity building process, and that capacity assessments play a fundamental role in reaching the necessary performance efficiency. Service delivery performance enhancements by municipalities are becoming increasingly necessary. At the same time, however, the majority of municipalities in South Africa find themselves under-capacitated. Some municipalities are aware of the lack of capacity within their organisation, but are unable to identify, define and quantify these shortcomings. Many other municipalities are not aware of their capacity shortfalls. In both cases, this is often caused by the lack of necessary systems and procedures to assess the different dimensions of organisational capacity. In this regard, this research paper introduces a proposed Subjective Municipal Capacity Self-Assessment Model (SMCSAM) as an alternative solution to the current practices of the Municipal Demarcation Board. It is intended that this model be used internally by municipalities to sustain internal capacity building and performance enhancement initiatives.
A case for the adoption of decentralised reinforcement learning for the control of traffic flow on South African highways
(South African Institution of Civil Engineering, 2019) Schmidt-Dumont, T.; Van Vuuren, J. H.
ENGLISH ABSTRACT: As an alternative to capacity expansion, various dynamic highway traffic control measures have been introduced. Ramp metering and variable speed limits are often considered to be effective dynamic highway control measures. Typically, these control measures have been employed in conjunction with either optimal control methods or online feedback control. One shortcoming of feedback control is that it provides no guarantee of optimality with respect to the chosen metering rate or speed limit. Optimal control approaches, on the other hand, are limited in respect of their applicability to large traffic networks due to their significant computational expense. Reinforcement learning is an alternative solution approach, in which an agent learns a near-optimal control strategy in an online manner, with a smaller computational overhead than those of optimal control approaches. In this paper an empirical case is made for the adoption of a decentralised reinforcement learning approach towards solving the control problems posed by both ramp metering and variable speed limits simultaneously, and in an online manner. The effectiveness of this approach is evaluated in the context of a microscopic traffic simulation model of a section of the N1 national highway outbound from Cape Town in South Africa's Western Cape Province.
Catchment parameter analysis in flood hydrology using GIS applications
(South African Institution of Civil Engineering, 2012-10) Gericke, O. J.; Du Plessis, J. A.
ENGLISH ABSTRACT: The use of Geographical Information Systems (GIS) has permeated almost every field in the engineering, natural and social sciences, offering accurate, efficient, reproducible methods for collecting, viewing and analysing spatial data. GIS do not inherently have all the hydrological simulation capabilities that complex hydrological models do, but are used to determine many of the catchment parameters that hydrological models or design flood estimation methods require. The purpose of this study was to perform catchment parameter analysis using GIS applications available in the ArcGISTM environment. The paper will focus on the deployment of special GIS spatial modelling tools versus conventional manual methods used in conjunction with standard GIS tools to estimate typical catchment parameters, e.g. area, average catchment and watercourse slopes, main watercourse lengths and the catchment centroid. The manual catchment parameter estimation methods with GIS-based input parameters demonstrated an acceptable degree of association with the special GIS spatial modelling tools, but proved to be sensitive to biased user-input at different scale resolutions. GIS applications in an ArcGISTM environment for the purpose of catchment parameter analyses are recommended to be used as the standard procedure in any proposed hydrological assessment.
A chronological review of South African guidelines for residential average annual water demand with property size as independent variable
(AOSIS OpenJournals, 2008-12) Jacobs, Heinz E.
ENGLISH ABSTRACT: Guidelines for residential average annual water demand (AADD) based on property size were introduced to the South African Civil Engineering fraternity in about 1960, with the most recent publication of such guidelines in 2008. The AADD forms the basis of calculations performed during the design and analysis of water systems. Over the years technology has improved, scientific progress was made and demand has changed, resulting in improved and updated guidelines for AADD. Changes in the guidelines over the years could be considered to be a result of improvement – larger and more accurate data sets are nowadays analysed statistically by improved computer technology. Also, the changes are considered to be the result of scientific advances in the fields of metering, modelling and analysis of water demand. Finally, actual changes in demand occur with time. This research provides the first documented review of the chronological development of AADD guidelines in South Africa. It is noted that only two guidelines were used for relatively long periods of time. In both cases the guidelines would not compare favourably to others from a pure research perspective, but their successful application is the result of a co-ordinated educational and marketing effort. The value of a sustained guideline structure (AADD versus stand size in this case) is also underlined.
’n Chronologiese oorsig van Suid-Afrikaanse riglyne vir residensiële gemiddelde jaarlikse waterverbruik met erfgrootte as onafhanklike veranderlike
(AOSIS OpenJournal, 2008) Jacobs, Heinz E.
ENGLISH ABSTRACT: Guidelines for residential average annual water demand (AADD) based on property size were introduced to the South African Civil Engineering fraternity in about 1960, with the most recent publication of such guidelines in 2008. The AADD forms the basis of calculations performed during the design and analysis of water systems. Over the years technology has improved, scientific progress was made and demand has changed, resulting in improved and updated guidelines for AADD. Changes in the guidelines over the years could be considered to be a result of improvement– larger and more accurate data sets are nowadays analysed statistically by improved computer technology. Also, the changes are considered to be the result of scientific advances in the fields of metering, modelling and analysis of water demand. Finally, actual changes in demand occur with time. This research provides the first documented review of the chronological development of AADD guidelines in South Africa. It is noted that only two guidelines were used for relatively long periods of time. In both cases the guidelines would not compare favourably to others from a pure research perspective, but their successful application is the result of a co-ordinated educational and marketing effort. The value of a sustained guideline structure (AADD versus stand size in this case) is also underlined.
The collapsible nature of residual granite soils of the Cape Granite Suite
(South African Institution of Civil Engineering, 2019) Fouche, N.; Asante, S. Y.
INTRODUCTION: Where residual granite soils of the Cape Granite Suite, located in the Western Province of South Africa are identified on-site during a geotechnical investigation, the potential risk of collapse settlement should not be overlooked and will, in all instances, require investigative measures to determine the likelihood and extent of sudden and excessive settlement. The majority of research pertaining to collapsible soils has focused on the problematic basement complex granites situated in the northern part of the country, with much less attention paid to the weathered Cape granites. However, the research carried out on these, often troublesome, Cape granite soils at Stellenbosch University has allowed the researchers to gain valuable insight into their collapse behaviour.
A comparison of technical and practical aspects of Eurocode 3-1-1 and SANS 10162-1 hot-rolled steelwork design codes
(South African Institution of Civil Engineering, 2016) Walls, R. S.; Viljoen, C.
In South Africa engineers are starting to use the Eurocode guidelines for steelwork design, and it is important to understand the implications and differences in results that are obtained when applying the different codes. This paper presents a comparison between the Eurocode 1993-1-1:2005 and SANS 10162-1:2005 hot-rolled steelwork design codes. Numerical comparisons of predicted member design strengths for the important modes of failure and the complexity of calculations are presented, along with considerations regarding the parameters used in design. The following are explicitly shown for both codes: (a) differences in the classification of commonly used H, I, PFC and equal L sections, (b) differences in tension resistance calculations, (c) comparisons of all axial buckling curves, (d) calculations for a selection of members in flexural buckling which have different classifications, and (e) a summary of the shear resistances of commonly used H and I sections. It is shown that, on average, Eurocode 3 predicts higher member design strengths than the SANS 10162 code for most failure modes, primarily because of material partial safety factors closer to unity, less conservative buckling curves and the consideration of plastic resistance of sections. These EC3 design capacities can be higher by up to 11% for tension, 35% in compression, 31% in bending and 51% in shear, although there are cases where strengths of up to 33% lower were calculated, such as for an IPEAA-200 in shear. Results are influenced by design geometric tolerances, which are based on section classifications. The Eurocode's equations and design methodologies are more complex and computationally demanding. Since South Africa has started moving in the direction of adapting or adopting Eurocodes with the SANS 10160 Loading Code (from EN 1) and SANS 10100 Structural Concrete Code (from EN 2), it should be considered whether or not the steelwork code should be adopted or adapted in a similar fashion in the future.
Conceptual framework for sewer pump problems allowing for fuzzy logic application
(Water Research Commission, 2015-04) Bester, A. J.; Jacobs, H. E.; Tulleken, J.; Civil Engineering
Sewer pump station problems in separate sewer systems (separate from stormwater drainage systems) were investigated in order to derive a conceptual framework for decision making. Notwithstanding the fundamental service that efficient sewage pumping provides to a community, it was apparent that limited research has been published on the topic. Research was undertaken to identify, investigate and classify problems at existing operational sewage pump stations by means of site visits, interviews, and an extensive knowledge review. A conceptual framework for sewer pump problems was subsequently derived. The application of the framework is illustrated by means of a fuzzy logic approach to one of the problem classes identified. This study sets the scene for further research into fuzzy-based efficiency indices pertaining to different sewer system components and the ultimate application in sewer system decision support tools.
A conceptual index for benchmarking intermittent water supply in a water distribution system zone
(Water Research Commission, 2020-01) Loubser, Carlo; Basson, Suzanne Esther; Jacobs, Heinz Erasmus
Various challenges, such as limited freshwater resources, climate change impacts, rapid population growth, urbanisation and underinvestment in water supply infrastructure, have led to intermittent water supply (IWS) in potable water distribution systems. Earlier research has confirmed that IWS negatively impacts the consumers, the infrastructure and the water supply authorities. Water supply authorities need tools to help understand IWS and the associated implications. A new indexing framework involving the causes and impacts associated with IWS is presented in this paper. In addition, a novel approach allows for quantification of the severity of IWS based on knowledge of a few readily available inputs. The severity quantification is based on two ratios: the intermittency ratio is a temporal measurement, accounting for supply duration; the connection ratio describes spatial aspects, using the number of service connections affected. The indexing framework and quantification tool could lead to improved understanding of IWS and could assist water supply authorities faced with IWS to make informed decisions. Improved planning of remedial actions to mitigate or avoid risks associated with IWS is aided. The tools presented in this paper could be used as basis for future development of a key performance indicator.
A conceptual theoretical framework to integrally assess the possible impacts of climate change on domestic irrigation water use
(South African Water Research Commission, 2015-10) Jacobs, Heinz Erasmus; Houssa, Fadoua; Fuamba, Musandji; Makwiza, Chikondi
Southern Africa is likely to experience higher evapotranspiration and altered rainfall characteristics due to global warming and climate change. Climate-driven water use may potentially stress water supply facilities due to increased demand and reduced surface water yield. This paper presents a conceptual theoretical framework for assessing impacts of climate change on domestic irrigation water use. The prediction of climatic conditions that may potentially influence future water use is reviewed together with regional capacity for downscaling global climate projections. The impact assessment of water use is based on the modification and adaptation of an existing end-use model for water demand to include parameters for climate change. The Penman-Monteith equation and the soil water balance equation are incorporated for the estimation of daily water needs of vegetated areas in residential properties. The paper also discusses data requirements and a calibration procedure to improve model fit to the observed domestic irrigation water use. The proposed approach could form a basis for constructing a detailed model for planning various adaption measures relating to climate-driven domestic irrigation water use.
Consideration for design of river abstraction works in South Africa
(Water Research Commission, 2006) Basson G. R.
ENGLISH ABSTRACT: The South African climate oscillates between drought and flood. This leads to extremes in river flow and sediment transport. While storms last for minutes to days, the hydrological critical low flows can last for years during droughts. The strong variation in river flow associated with even higher variability in sediment loads make the design of river pumpstations and diversions highly complex in South Africa, especially if the water supply should have a low risk of failure.

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