This study assessed the performance of the drinking water distribution system of the
Tavua/Vatukoula network, Fiji. An important aim and a requisite of the work was the
collection and assessment of pertinent data, to enable the development of a detailed
hydraulic system model for analyses and simulations.
This study utilized EPANET v2, a popular and freely available software package developed
by US Environment Protection Agency. The major features and most important
characteristics of EPANET presented and discussed in detail in this report.
The technical focus of this study was mainly on available water pressures in various
hydraulic loading scenarios. Pressure conditions were determined for average daily demand,
maximum hourly demand, minimum demand, and peak hourly at maximum water plant
delivery, as well involved extended (24 h) simulation runs. These examinations revealed
various bottlenecks and shortcomings in the network, and provided insight into the
underlying causes to suggest effective remediation approaches.
System simulations show that currently the Tavua/Vatukoula system is capable of providing
satisfactory supply to the gross majority of customers, and only several distinct locations
experience pressure deficiencies. System capacity also would allow the connection and
supply of the proposed new sugar mill south of Tavua town (up to 4.63 L/s continuous
demand) with not significant impact on existing customers. However, service would be
severely limited for increased demand, and widespread pressure problems would arise at
maximum water plant deliveries, indicating that network augmentation will be necessary in
the coming years.
There was no sufficient data to allow for any disinfectant residual modelling. Nevertheless,
water age simulations were carried out over extended (168 hours) periods, which identified
various mains and branch pipelines prone to water stagnation. Analysis of operational issues,
such as access for maintenance, placement of pressure regulating (PRV) valves, and the
promptness with which repairs can be made, among other multidisciplinary concerns, were
outside the scope of this study.
While various shortcomings and problems of the water network system were identified in
this study, the current hydraulic model has limitations and will benefit from future
improvements. The design and planning of remediation and augmentation works will require
more and better quality data for model calibration.