Water Supply Coverage and Performance Evaluation of Distribution System Using Hydraulic Simulation Software (The Case of Jijiga Town)
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Date
2020-02
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Addis Ababa University
Abstract
Most Ethiopian cities are characterized by having old water distribution networks upon
which new extensions are linked in order to serve new areas, adding complexity to an
aging network where full rehabilitation may not be practical due to economic constraints.
In this research, the water distribution network of Jijiga City, one of the major Cities in
Somali regional state, was studied for analyzing and optimizing its design and extension
taking into consideration the effect of aging of the network, local conditions such as
intermittent pumping, which is a way of operating the water distribution systems in most
towns of developing world.
The main objective of this study is to improve hydraulics performance of Jijiga city water
supply distribution system and control its operation, Water CAD software was used as
tool to model water distribution system analysis. The modeling effort included only
hydraulic performance modeling. Simulation results for maximum and minimum
pressures were used as base tool to evaluate the hydraulic performance in the distribution
system. The modeling results showed violation of maximum and minimum pressure
requirements. Along with this, the model analysis result shows the different problems of
the system. These are aged pipes, oversized and undersized pipes, low and high pressures
and water demand and supply status. The modeling of the system as continuous supply
system depending on assumptions considering with future water consumption,
availability of water, overcoming the problems of high pressures by using pressure
reducing valves at specific locations, and assuming steady state analysis, shows the
ability of the existing system to serve the Jijiga area and to cope the future extension. The
output values of velocities are parallel reasonably to the assumed limits of velocities (0.1
m/s – 0.3 m/s) to avoid stagnation and quality water problems, also the pressure values
are within the limits of the design pressures in the residential areas. Further evaluation
has been carried out to investigate the total average day demand, peak hour demand
factors and maximum day demand factor and to study the water supply coverage in Jijiga
town. The peak hour demand factor was calculated to be 1.6, and a value of 25 l/c/d was recorded as average daily water consumption. Present nominal water supply coverage is
calculated to be 49.6% and actual water supply coverage of the service is computed to be
43.11%.
Generally, the model analysis result shows the different problems of the system. These
are aged pipes, oversized and undersized pipes, low and high pressures and shortage of
water from the source. The system should be modified using the design criteria of
velocity, pressure and demand required. High pressures in the existing system caused by
customers at too low demand have to be identified and solution is established using
pressure-reducing valves. To retrieve the situation there is a need to intervene.
Modification in operation, design and finding another reliable water source and injecting
to the system will improve the current situation of the Jijiga town water distribution
system.
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Keywords
Water distribution system, modeling, Hydraulic performance, optimum pipe flow velocity, Maximum pressure, Minimum pressure, Pipe age, Jijiga