The proliferation of water distribution system (WDS) optimisation algorithms has been extensive over the past four decades. The utilisation of these algorithms in practice has been less popular, as most models have been relegated to the confines of academia. The unsustainability of small water reticulation networks (WRNs) in many South African low-income communities continues to be a reality. This is particularly significant in light of the free basic water policy, which places the responsibility of basic potable water provision into the hands of local councils faced with the constraints of inadequate systems, sub-optimal systems, tight budgets and inadequate skills. To facilitate the provision of basic water to many poor communities, effective and efficient planning, design and operation tools are required. Presented herein is a generic and robust WRN design optimisation algorithm within a decision support system (DSS) software called Wadessy (an acronym for water decision support system). Wadessy comprises a suite of computer programs useful for facilitating the optimal design, planning and daily operation of small WDSs. The design algorithm employed is based on the concept proposed by Featherstone and El-Jumaily (1983).
<br>The validity of Wadessy is proved by comparison with a well-known example from Alperovits and Shamir's (1977) linear programming gradient (LPG) model and a practical case study in Selebi-Phikwe, Botswana. Wadessy achieved a 1, 91 % cost saving in comparison to that obtained by Alperovits and Shamir (1977) and a 32, 52 % cost saving (about 1 497 190 Pula) for the Selebi-Phikwe WRN based on October 2001 pipe costs.
The presentation of data comprises<ul>
<li>selected wave theory, sufficient for wave revetment and wave baffle boards design purposes
<li>rock rip-rap wave revetments, which includes the original derivation of a new modified Hudson formula (the design of the underlayers is included)
<li>concrete-filled Hyson Cell wave revetments, which include the original derivation of a simple, safe method of design of such revetments
<li>cement stabilised soil wave revetments, which provide the ingredients of a specification for such revetments</ul>
The conclusions given in this paper contradict to some extend the findings obtained from extensive local and international reasearch using South African fly ashes and are also not supported by the practical experience gained is the last 20 years using these fly ashes in southern Africa as well as the Middle East (exports) as extender and constituent in cement.
<br>Worldwide in-house research currently undertaken by the writer's organisation, which ranks as world No 1 cement manufacturer, supports this statement.