scholarly journals An assessment of sub-standard water pressure in South African potable distribution systems

2017 ◽  
Vol 7 (4) ◽  
pp. 557-567 ◽  
Author(s):  
Louis Strijdom ◽  
Vanessa Speight ◽  
Heinz Erasmus Jacobs
Keyword(s):  
South African ◽  
Distribution Systems ◽  
High Pressures ◽  
Water Pressure ◽  
Residual Pressure ◽  
Residual Water ◽  
Flow Conditions ◽  
Minimum Requirement ◽  
Hydraulic Models ◽  
Standard Pressure

Abstract Sub-standard residual water pressures in urban water distribution systems (WDS) are a prevalent phenomenon in developing countries – South Africa being no exception. The phenomenon of sub-standard pressure is poorly understood, with intermittent supply ultimately resulting when there is no residual pressure left in the system. This research addressed the prevalence and extent of sub-standard pressures by using hydraulic models of potable WDS for 71 South African towns, located in 17 different South African municipalities geographically spread over the country. The hydraulic models included 539,388 modelled nodes, which were analysed to determine the number of nodes with sub-standard pressure heads during peak hour flow conditions. The results show that the residual pressure head was <24 m at 16.5% of the model nodes under peak hour flow conditions, with 6.7% of the nodes having pressure heads <12 m. In contrast, the results also report relatively high pressures in certain parts of the systems, far in excess of the minimum requirement, underlining the need for better pressure management at both high and low ranges. It was also noted that the South African design criterion is relatively stringent compared with some other countries and could potentially be relaxed in future.

scholarly journals Coexistence of free-living amoebae and bacteria in selected South African hospital water distribution systems

2016 ◽  
Vol 116 (1) ◽  
pp. 155-165 ◽  
Author(s):  
P. Muchesa ◽  
M. Leifels ◽  
L. Jurzik ◽  
K. B. Hoorzook ◽  
T. G. Barnard ◽  
...  
Keyword(s):  
South African ◽  
Distribution Systems ◽  
Water Distribution ◽  
Water Distribution Systems ◽  
Free Living

Dehydration and decomposition of pyrophyllite at high pressures: electrical conductivity and X-ray diffraction studies to 5 GPa

1997 ◽  
Vol 34 (6) ◽  
pp. 875-882 ◽  
Author(s):  
Tara L. Hicks ◽  
Richard A. Secco
Keyword(s):  
Electrical Conductivity ◽  
South African ◽  
Pressure Dependence ◽  
High Pressures ◽  
Ionic Conduction ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Dependence Of Conductivity

The dehydration and decomposition of South African pyrophyllite were studied in the pressure range 2.5–5.0 GPa and in the temperature (T) range 295–1473 K using both in situ electrical conductivity measurements and X-ray diffraction studies on the recovered samples. Activation energies for conduction (Qc) vary in the range 0.02–0.07 eV for T ≤ 500 K where the dominant conduction mode is electronic, and Qc is in the range 1.10–1.28 eV for T ≥ 500 K where ionic conduction dominates. Abrupt changes in the isobaric temperature dependence of conductivity mark the onset of dehydration and subsequent decomposition into kyanite plus quartz–coesite. At 2.5 GPa, South African pyrophyllite forms the dehydroxylate phase at 760 K with a pressure dependence of ~30 K/GPa and complete decomposition follows at 1080 K with a pressure dependence of ~41 K/GPa. The resulting pressure–temperature phase diagram is in very good agreement with many previous studies at 1 atm (101.325 kPa).

scholarly journals Boulder Pickup by Tsunami Surge

2019 ◽  
Vol 13 (05n06) ◽  
pp. 1941006
Author(s):  
Samuel Harry ◽  
Margaret Exton ◽  
Harry Yeh
Keyword(s):  
Pore Water Pressure ◽  
Initial Conditions ◽  
Scale Effects ◽  
Traditional Approach ◽  
Water Pressure ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Flow Conditions ◽  
The Difference ◽  
The Impact

Study of boulder transport by tsunamis is challenging because boulder size, shape, and composition vary greatly; furthermore, flow conditions, topography, and initial conditions are generally unknown. To investigate the mechanism of boulder pickup, experiments of tsunami-like flow past spherical boulders partially buried in a sediment bed are conducted. The experiments are performed in a large centrifuge facility to reduce scale effects and the corresponding dynamic similitude is discussed. The traditional approach to determine boulder pickup is adapted for the case of a half-buried spherical boulder. The adapted model predicts that the boulders are transported, but does not accurately predict the timing of pick up. To investigate the difference in pickup timing, two physical phenomena are discussed: pore-water-pressure dissipation in the soil, and the impact of the free-surface flow on hydrodynamic forces. For a spherical shaped boulder, vertical forces (i.e. buoyant and lift forces) are critical for the initiation of boulder pickup. It was found that spherical boulders that are three-quarter buried in the soil are not transported, even when exposed to flow conditions that would otherwise predict transport.

scholarly journals Stability Evaluation of Overtopped Concrete Hydraulic Structures Using Computational Fluid Dynamics

2020 ◽  
Author(s):  
Mario Freitas ◽  
Etienne Favre ◽  
Pierre Léger ◽  
Lineu José Pedroso
Keyword(s):  
Water Pressure ◽  
Back Analysis ◽  
Hydrodynamic Pressure ◽  
Flow Conditions ◽  
Gravity Dams ◽  
Pressure Fields ◽  
Dam Stability ◽  
The Stability ◽  
Resultant Forces ◽  
Safety Guidelines

A particularly challenging aspect in gravity dam stability assessment is the estimation of the induced hydrodynamic water pressure when water with significant velocity is overtopping gravity dams and flowing in or over spillway components. The water flow conditions, including the related pressure fields and resultant forces, are difficult to quantify accurately. Herein, existing dam safety guidelines to estimate the weight of the overflowing water nappe on gravity dams with rectangular crests are first reviewed. Then, a CFD methodology is developed to improve the simplified estimation of hydrodynamic pressure fields acting on the rectangular crests of submerged gravity dams. The CFD pressures are used as input data to classical structural stability analyses based on the gravity method to more adequately quantify the dam stability during overtopping. A back analysis is also performed on the stability of an existing gated spillway that was overtopped during the 1996 Saguenay flood in Québec.

The Design of a Self-Monitoring Thermoplastic Composite Pipe for High Pressure Gas/Liquid Transport

2010 ◽  
Author(s):  
Melvin F. Kanninen ◽  
Randall B. Stonesifer ◽  
Kyle Bethel
Keyword(s):  
High Pressure ◽  
Distribution Systems ◽  
High Pressures ◽  
Gas Permeation ◽  
Thermoplastic Composite ◽  
Advanced Technology ◽  
Fiber Optic Sensor ◽  
Flow Area ◽  
Liquid Distribution ◽  
Nonlinear Stress

Pipes made of high density polyethylene (HDPE) and other thermoplastic materials do not corrode. However, this considerable advantage, because HDPE is limited to a line pressure of 125 psig, cannot be utilized for the replacement or rehabilitation of trunk lines in gas/liquid distribution systems and transmission lines where pressures range from 150 psig up to 1500 psig or more, without some form of reinforcement. This paper describes an advanced technology for accomplishing this by use of a composite of thermoplastic materials. This technology can be used for high pressure applications in either a stand-alone mode, or as a pipe within a pipe, by its insertion into an existing damaged/degraded high-pressure steel pipeline. In either mode, arbitrarily high pressures can be achieved, health can be monitored with a built-in fiber optic sensor system, and wall loss due to corrosion precluded. The focus of the paper is on addressing some of the ancillary issues that arise in the utilization of the technology that are not usually of concern in steel pipelines: nonlinear stress analysis of heterogeneous materials, time/temperature dependent mechanical properties, greenhouse gas permeation, and the diminution of flow area associated with internal reinforcement.

scholarly journals A Pressure Monitoring System for Water Distribution Networks Based on Arduino Microcontroller

Water ◽  
2021 ◽  
Vol 13 (17) ◽  
pp. 2321
Author(s):  
Federica Bruno ◽  
Mauro De Marchis ◽  
Barbara Milici ◽  
Domenico Saccone ◽  
Fabrizio Traina
Keyword(s):  
Monitoring System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Water Pressure ◽  
Distribution Networks ◽  
Water Utilities ◽  
Water Distribution Networks ◽  
Prototype System ◽  
Pressure Monitoring ◽  
Arduino Microcontroller

Efficient management of water distribution networks (WDNs) is currently a focal point, especially in countries where water scarcity conditions are more and more amplified by frequent drought periods. In these cases, in fact, pressure becomes the fundamental variable in managing the WDNs. Similarly, WDNs are often obsolete and affected by several points of water losses. Leakages are mainly affected by pressure; in fact, water utilities usually apply the technique of pressure management to reduce physical losses. It is clear how pressure plays a fundamental role in the management of WDNs and in water safety. Even though the technologies are quite mature, these systems are often expensive, especially if a capillarity monitoring system is required; thus, water managers apply the measurement of the flow rate and pressure at very few points. Today, the implementation of the Internet of things (IoT) can be considered a key strategy for monitoring water distribution systems. Once the sensors are installed, in fact, it is relatively easy to build a communication system able to collect and send data from the network. In the proposed study, a smart pressure monitoring system was developed using low-cost hardware and open-source software. The prototype system is composed of an Arduino microcontroller, a printed circuit board, and eight pressure transducers. The efficiency of the proposed tool was compared with a SCADA monitoring system. To investigate on the efficiency of the proposed measurement system, an experimental campaign was carried out at the Environmental Hydraulic Laboratory of the University of Enna (Italy), and hydrostatic as well as hydrodynamic tests were performed. The results showed the ability of the proposed pressure monitor tool to have control of the water pressure in a WDN with a simple, scalable, and economic system. The proposed system can be easily implemented in a real WDN by water utilities, thus improving the knowledge of pressure and increasing the efficiency level of the WDN management.

scholarly journals A regional flow type classification for South African perennial rivers

Water SA ◽  
2020 ◽  
Vol 46 (3 July) ◽  
Author(s):  
NA Rivers-Moore ◽  
RE Schulze ◽  
NS Davis
Keyword(s):  
South African ◽  
Flow Volume ◽  
Flow Conditions ◽  
Flow Classification ◽  
Regional Flow ◽  
Reference Flow ◽  
Rainfall Seasonality ◽  
Type Classification ◽  
Frequency Magnitude ◽  
Daily Flows

Flow classification provides a statistically robust method of defining an expected range of variability for flow metrics describing frequency, magnitude, duration and timing of events.  Here, we characterised reference mean daily flows for 1950–1999 for all 5 838 quinary catchments of South Africa based on 150 metrics.  Using a two-tiered approach, where sub-catchments were classified into similar flow types using principal components and cluster analyses, we defined 6 to 12 flow types for each of 8 hydrological regions reflecting rainfall seasonality.  Redundancy between variables was 87% on average, so that site variability could be accounted for using 8–28 metrics.  In general, flow volume metrics accounted for Axis 1 variability, while coefficients of dispersion had 1.8 times less leverage in Axis 2.  With the incorporation into a spatial product and an associated database, this study provides a basis for defining statistically robust reference flow conditions for multiple flow metrics, against which current observed flows at specific sites may be compared.

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