The problems encountered in the design and operation of water supply systems in
developing countries are described. In these countries the availability of water is either
inadequate or restricted due to difficulties such as power cuts. Field information and
data was collected from Madras, India to illustrate the problem and provide a case
study area.
The conventional approaches to network analysis are described and discussed with
respect to their suitability for simulating conditions of water shortage. The
modifications required to model such conditions are identified and incorporated into a
modified network analysis simulation tool.
The use of optimisation techniques to identify the least cost design of distribution
systems was investigated and a methodology based upon sequential quadratic
programming was found to be the most appropriate.
The use of flow reduction valves was explored as a means of achieving the most
equitable distribution of water where the overall supply is limited. A mixed integer
nonlinear optimisation model was formulated to establish the optimal locations and
settings of the flow reduction valves. A new solution method was developed which
involves the solution of nonlinear and mixed integer linear programming subproblems.
The optimisation methods developed were applied to several networks including a
network used for benchmark testing least cost design optimisation algorithms. The
proposed techniques proved to be an advance of previous methods and were found to
be vely effective in accommodating the particular problems posed by intermittent
systems.
The principal problem of intermittent systems, namely contamination, is reviewed
briefly and factors affecting the levels of contamination in a network identified. Based
upon the results of limited data collected in Karachi, Pakistan, measures are proposed
to reduce contamination, taking into account the conclusions of the modified network
modelling.
It is concluded that the conventional approaches to network analysis are inappropriate
for the majority of water supplies in developing countries which operate on an
intermittent basis. An alternative approach to design has been developed which
employs a modified network analysis procedure and utilises formal optimisation
techniques to ensure the maximum uniformity in supply.