David Stephenson

• BSc(Eng) MSc(Eng) PhD DSc(Eng)
• University of Botswana

AMAZON BOOKS 2024 183pp Pipelines are a major component in any water supply project. Appurtenant infrastructure cannot be separated and pumping, storage and water distribution need to be coordinated. The author's book Pipeline Design for Water Engineers went through 3 editions and a new version is required in view of the changes in technology and n...

Will water be a limiting factor to world growth? Or should we control population growth and actions to ensure sustainability? The environment is deteriorating and our wastes including carbon emissions are causing climate change which will affect the environment, especially water, and our very existence. Our lifestyle needs to change to ensure water...

Rivers, Dams, Water resources, Uses, Hydro power, Pollution, Floods, Rights

In finite difference solutions of the kinematic equations for overland flow, uncontrolled numerical diffusion can be introduced into a system by the finite difference scheme. A formulation for overland flow based on the Muskingum-Cunge routing procedure [4] incorporating a four-point numerical scheme is described and the results of numerical experi...

Pipelines are prone to leaks, bursts, damage and poor jointing. The longer the pipeline, the greater the risk of downtime to make repairs. The engineer frequently does not relate the standards to the risk. The greater the geometry of the pipeline the bigger the risk. A systems analysis is required to select the correct reliability factors. Pipeline...

It is recognised that environmental and riparian water requirements should be accommodated in designing dams. World Bank and other lenders suggest the volume of release for downstream uses should be as high as 5% of the inflow. It is shown, however, that in the case of arid catchments, the release could affect the reliable yield of the dam by up to...

Diamond mines in Botswana are constrained by the availability of water for conducting the mining and extraction processes. The use of water on diamond mines is reviewed and the destination of the water identified. Large proportions of the water are lost by evaporation from slimes dams and some water is retained in the mud in the dams. Alternatives...

The modelling system could be a tool for predicting the flow regime in water management operations. The modified RAFLS model has exhibited a profound accuracy in the simulations of the Itezhi-tezhi/Kafue River system. The simulated flows and reservoir levels portrayed the dynamics in terms of time and magnitude. The use of the RAFLS model for water...

Hydrological data (e.g. rainfall, river flow data) are used in water resource planning and management. Sometimes hydrological time series have gaps or are incomplete, or are not of good quality or are not of sufficient length. This problem seems to be more prevalent in developing countries than in developed countries. In this paper, feed-forward ar...

This study estimates Rand Water's water demand in South Africa for 2000 to 2020. It indicates lower growth in water consumption in the foreseeable future than in the past century. The reduced growth is due to: Economic slowdown (international and South African); Lower standard of living/residences for the “white” population; Corresponding decrease...

It is known that plastics, in particular PVC and mPVC, experiencechanges in properties over time. The tensile rupture strength andelastic modulus are known to decrease with time. The design stresses anddeflections of PVC pipe therefore need to account for the long-termproperties. Laboratory tests indicate that strength does decrease over time ifa l...

Owing to development pressure for land bordering the Vaal river, in South Africa. Rand Water are revising their development policy. Restrictions were in place to avoid flooding and obstructing the flood flow of the river. Relaxation of the regulations will permit controlled development along the river. A flood hazard-risk index was developed to ind...

Air vessels offer an effective means of reducing water hammer overpressures and negative pressures due to pump trip in pipelines. The process of sizing air vessels is simplified with the nomographs presented. Both air volume and total vessel size are calculated. The size can be minimized by correct selection of outlet and inlet connector diameter,...

Electrification can reduce the dependence on combustible fuels and therefore also reduce the concomitant health risks. Hydro power is one possible method of generating electric power close to the potential consumers, thereby cutting out expensive reticulation costs in widely spread rural areas. For sustainable electricity generation there must be s...

Demand management is an alternative to increased water supply to meet growing demand. Control of water usage can be effected by the supplier or the consumer. The supplier can use physical methods to limit supply or economic, and the consumer can adjust his way of living either voluntarily or under pressure by the supplier. The classical supply-and-...

The Min-Der Reservoir in Taiwan is undersized for meeting the full demand from it, so it is necessary to manage the water in the reservoir to meet demands in the best possible way. The monthly inflow series was extended using a rainfall-runoff deterministic model. Probabilities of end storages, given different initial and operating conditions, were...

In many developed countries, we have been accustomed to receiving all the water we require. Historically the cost may have been relatively low due largely to bulk supplies. the quality has been good and the reliability acceptable. As the cost of tapping additional sources increases (Stephenson, 1995) due to greater distances and pumping lifts and i...

The availability of potable water and its scarcity is the cause of many international incidents and outcries. the fact that water is indispensable makes it a critical issue from the start. It’s variable distribution in time and space and quality, makes it more and more expensive to exploit. It’s location in water courses make it easier to control a...

A way of reducing the risk of running out of water could be to conjunctively use different sources. Different sources of water could be reservoirs on different rivers, or in different hydrological regions. Different types of sources may be used, e.g. groundwater, reclaimed waste water or saline water, rainfall stimulation or snowmelt Langenbaugh (1...

The average cost of water is influenced considerably by the decisions of the water supply authority with regard to source, quality, level of supply and extent of supply. Costs can be minimized by good management of planning and operations. It is now realized that all decisions cannot be made in isolation and interaction with the consumers and publi...

Improved international communication means that the developed world can no longer avoid the spill-over of the problems of the developing countries. for example, the breakdown in the economy of the Eastern European countries is having a marked effect on the economy of Western Europe. South American financial defaults and more recently economic turmo...

This chapter addresses the water supply issue from the consumers’ point of view, whereas the previous chapter was written for the engineer, economist or planner concerned with establishing water supply. It also assists in establishing a pricing policy. Demand management refers to the control of use of water, but equally well requires consumer inter...

In a typical water supply system, water is abstracted from a source, purified and pumped to a storage reservoir. From there it is gravitated to consumers connected to the reticulation system.

Preface. 1. Water Sources. 2. Water Requirements. 3. System Design. 4. Supply Management and Water Cost. 5. Demand Management, Price and Reliability. 6. Drought Management of Reservoirs. 7. Conjunctive Use of Alternative Sources. 8. Loss Control and Rehabilitation. 9. Asset Management and Computer Technology. 10. Water Quality and Treatment. 11. Wa...

The proportion of hydroelectric power generation in South Africa is small relative to many other developed and developing countries. This may be because South Africa has an abundance of fossil fuels, especially coal, supplied at a relatively low cost. On the other hand, river flows in South Africa are highly variable and therefore difficult to cont...

Many water hammer studies concentrate on the main pipeline and pump stopping. Important details can be overlooked. The rigidity of pipe walls, coatings, and surrounding fill on water hammer in pipes is evaluated. It is shown that backfill increases rigidity and celerity marginally, but pipe material is a major factor in water hammer pressures. The...

Rand Water controls the catchment of the Vaal River Barrage in South Africa and wanted to reassess its policy regarding development on the banks of the Barrage. A flood risk analysis was performed. This accounted for catchment urbanization up to the year 2020, and the routing effect of the Vaal Dam upstream of the Barrage. Water levels were then ca...

Instead of planning water resource projects to yield a constant maximum rate, it is advocated that reservoirs be operated on a variable draft basis. That is, when water levels drop to predefined levels the supply rate is decreased accordingly. This will increase the yield of the reservoirs and reduce the necessity to build additional dams. The leve...

The Transkei area in Southern Africa is highly dependent on hydroelectricity generated from a number of interconnected hydroelectric stations on various rivers in the area. In order to optimize the generation in a system subject to severe engineering limitations, advance estimates of river flows and power demands are required. These are obtained fr...

Developing countries are rarely self-sufficient, yet large scale public works are generally regarded as the best way of developing infrastructure and employment. Water is often the most accessible resource for exploitation in such countries, with irrigation providing food and hydro electric power energy. A basic lack of hydrometeorological data mea...

Different methods of considering the shear stresses between a main channel and its flood plains are discussed. The methods considered include the simplistic method of considering the entire hydraulic cross section as one, dividing the cross section into independent sections, assuming limited shear stresses between main channel and the flood plain,...

Use of a microcomputer catchment modelling program designed for stormwater management studies is described. The program is a kinematic type model, ie hydrodynamics are based on uniform flow conditions and continuity in conduits. The advantages of modular over finite elements and finite difference models are discussed. The modules in the program inc...

Stormwater models, which are used extensively for stormwater drainage design and management, require calibration. The parameters usually estimated by calibration include infiltration and roughness. Parameters that can be determined by measurement include catchment area, slope, and length of flow path. The dependency of parameter values on the level...

A review of stormwater model arrangements is made. Computer programs able to assemble loosely-connected elements are simplest to use and understand. Arrangement of elements and assembly in parallel or series enables all possible types of models to be accommodated. Hydraulic elements are used for surface runoff visualization and groundwater aquifers...

Two catchments in Johannesburg, one a densely built-up city catchment and the other a suburban catchment were monitored under a storm-water research programme. Continuous flow and conductivity measurements were taken, and spot sampling for selected ions made during storms. Pollution loading is highest from the city catchment and in both cases storm...

A series of synthetic five-year return period storms having rectangular, triangular and bimodal (triangular) temporal profiles was compiled from depthduration-frequency (D-D-F) relationships based on (a) standard sorted clock time depths and (b) complete storms only. These were used as inputs to a catchment runoff model to simulate the peaks and vo...

A methodical method of integrating water resources planning at national, regional and project levels is described. The planning approach is based on the principle of decomposition of linear programs. The method is applied at the project and basin levels to a developing African country. Models at these levels use optimization techniques to size proj...

Whereas it is recognized that desalination is not economically justifiable in many water supply situations, this paper describes how by careful re-planning of the water distribution system in a gold mine, the installation of a desalination plant underground can be shown to be economic despite cheaper fresh water being available on the surface. The...

A need is expressed for dimensionless unit hydrographs which account for catchment shape and topography, as well as for rainfall intensity. Such hydrographs were previously derived by the authors for a variety of catchment shapes and configurations using kinematic theory. Dimensionless equations are derived for planes, converging surfaces and V-sha...

The use of numerical modelling for prediction of water levels and flows is introduced. Models are classified and simplifications appropriate to various configurations are suggested to minimise programming effort and computational capacity and time. The use of animated colour graphics is advocated for depiction of results, and for setting up the num...

A 5,000 km² catchment in Transkei, Southern Africa is monitored with 10 rain gages which transmit data to a microcomputer model. The numerical model is based on the kinematic equations with both an overland flow/stream flow component and a subsurface component of flow for 14 sub-catchments. Both flood flows and base flows from the catchment are pr...

Incluye bibliografía e índice

The Nuclear Development Corporation of South Africa (Pty) Ltd. (NUCOR) is constructing a low-level radioactive waste disposal site near Springbok in Namaqualand, an arid region to the west of South Africa. A groundwater model was developed which required site-specific data and this work describes procedures developed to assess the dispersivity of t...

Hydrologists frequently employ simplifying assumptions when using so-called design storms for estimating runoff. In particular, uniform rainfall rates are often assumed as well as a uniform spatial distribution and a stationary storm. In this paper attention is brought to the variability of real rainfall rate in time and space, and to the movement...

The 20 km long raw water canal between Vaal Dam and Zuikerbosch discharges into a large terminal reservoir which acts as a forebay for the Rand Water Board treatment plant and high-lift pumping station. A spillway was required for the reservoir to avoid overtopping of the embankments following a trip-out of the pumping station to the power failure....

Since there is a general shortage of water on the South African goldfields, the re-use and recycling of water in mines is necessary. Water quality deteriorates with recycling and the reasons and extent of deterioration were researched. A large proportion of the inorganic salts appearing in solution in the water appear to originate from the ore. Hig...

Gold mines in South Africa use large volumes of water for cooling and other purposes underground. The mines are often at great depths, for example 3600 metres below surface level. Water piped down the shaft can therefore be at high pressures unless a system of pressure reducing dams or valves is installed. Modern practice is to utilize the high wat...

Surface water resources are exhibiting deterioration in quality as greater use is made of them and more effluent is discharged into them. As water resources become scarcer the planner will have to consider the options before him in selecting new sources. These will include fresh water from further afield, purification of waste waters or optimum uti...

Groundwater flow near the Koeberg Nuclear Power Station was investigated by Stephenson in order to evaluate the extent of seawater intrusion around the foundations. In particular he studied the movement of the interface between fresh groundwater and seawater. For the purpose of such study it has been found necessary to determine the dispersion coef...

This books aims to rationalize and systematize storm water drainage design methods. Storm hydrology and runoff and computation methods using a time/area basis or kinematic routing are covered. Sections on computer modelling methods, risk analysis, optimization, storm water quality and flood management are also included, and there are hydraulic desi...

Advances in the design of water pipelines and benefits of pipeline transport are presented and some of the limits in knowledge and manufacture are discussed. Friction formulae used in hydraulic engineering practice are compared, in particular, with the Darcy-Weisbach formula.

The kinematic approximation to the equations of flow that facilitates analysis of overland flow is presented. When used in conjunction with a head loss equation such as that of Manning and Strickl the equations can be solved for specific cases. The equations are solved together with an empirical equation for the rainfall intensity-duration relation...

Criteria for stability of stones in flowing water are established. Friction loss of water flowing over rockfill is evaluated. The velocity reduction in rockfill is shown to be of use in reducing erosion of underlying soil and for minimizing the effect of wave action. Head loss due to cascading down stepped gabion slopes can also be employed for ero...

A direct method of calibrating the Muskingum routing equation is explained. Linear programming techniques are used to minimize the absolute value of the error. The error is defined as the difference between an observed and a routed outflow hydrograph. An alternative but more complicated objective function would be to minimize the sum of the squares...

The science of thin-wall flexible pipeline design has advanced rapidly in recent years. The advantages of flexibility in shedding load and developing lateral soil resistance are now realized. When it comes to the design of sewers, drain pipes and other non-pressure pipes, thin-wall pipes compete favourably with rigid pipes. Advances in plastics tec...

The water resources of South Africa are limited and it may soon become necessary to recycle reclaimed waste water for the Witwatersrand area. Optimum planning of the location of waste water treatment works, sewers and quality of effluent is desired. A plan may be prepared with the assistance of computer models. The system may be described in terms...

2. ed.

The specific requirements for a hydrological network in a developing country are discussed. These include low cost, reliability, wide distribution and training. Different standards for developing countries may be accepted owing to the limitations of finance, spares, skilled staff, poor access, and extreme climates. The establishment of a network in...

A hydro-electric station in Transkei, Southern Africa generates 42MW with very little river storage. Rain data are collected from 11 gauges distributed in the 5000 km catchment and telemetered to a central processor. The data are logged on floppy discs and transferred to a dedicated micro computer for computing streamflows. A kinematic catchment mo...

The Transkei area in Southern Africa is highly dependent on hydroelectric ity generated from a number of intercon­ nected hydroelectric stations on various rivers in the area. In order to optimize the generation in a system subject to severe engineering limitations, advance estimates of river flows and power demands are required. These are obtained...

A brief description is presented of the standard methods of flood estimation including the rational method, the unit hydrograph method and the kinematic method. The S-curve/critical direction method is then described with the aid of worked examples and comparison is made with other networks. (T.R.A.)

Typescript (Photocopy) Thesis (M.Sc.)--University of the Witwatersrand, 1968.

The book is aimed at the water engineer who has to design water reticulation pipe networks, trunk mains, pumping lines and storage reservoirs. The practicing engineer often tends to neglect the theoretical side, but when the occasion arises a rapid simple answer is required to problems of head loss, discharge capacity and pressures. The various com...

Optimization of water distribution plans is facilitated by transportation programming. Application of the technique to minimizing total cost of water conveyance is illustrated with an example. Extension of the method, using the principle of decomposition of linear programmes, permits selection of optimum areas for development. Results of a large sc...