Model And Design of Water Distribution Network, Mobile Barracks, Ogida, Benin City
Overview
The importance of water to the general health and well-being of humans cannot be overemphasized. Groundwater remains the major source of potable water for household use and sustainable development. Due to negligence and inconsistent infrastructure development, nearly half the nationβs population has little or no access to potable water, with the bulk of the populace being independent providers of personal water supply.
Statement of the Problem
In Ogida Barracks, Benin City, water supply has been a major challenge over the years. Residents and business owners in the community resort to purchasing water from external private sources. And in worse cases, unclean water sources.
This project is an attempt to collect data for the development of an optimal water distribution plan for the housing estate. To promote safe and convenient living conditions. Advanced remote sensing techniques play a major role in the field of Geomatics and are a reliable source of data acquisition and processing.
Aim and Objectives
The aim of this research is to use geoinformatics techniques such as Remote sensing and digital cartography for the geospatial mapping of a water distribution system in Mobile Barracks, Ogida Benin City.
To achieve the above aim, the following objectives will be pursued;
i. To obtain elevation data from online data sources
ii. To develop an elevation model to determine the highest point of the study area.
iii. Calculation of water demand and supply needs
iv. Design of water distribution network using QGIS
Data Acquisition
Reconnaissance Survey
A field reconnaissance survey was first carried out to; understand the above-stated problems, determine the living conditions of residents in the study area, and aid the population estimates and projections used in the project.
An office reconnaissance survey was simultaneously conducted (Using Google Earth Pro) to determine the location of residential and commercial facilities and the ground conditions for sitting the water storage tanks.
Data Collection
After a detailed analysis of the study area, the βDead end water distribution system was chosen to optimize the layout pattern of the housing estate. In this system, main pipes are connected to the storage tanks and further linked with sub-mains and branches, with the latter connected to buildings. Rather than a continuous flow of water, there are dead ends in the network. Cut-off valves are introduced to aid maintenance, to avoid a total disconnection.
Remotely sensed data is regularly collected via satellites and stored using databases of USGS, OpenTopography, etc. For this study, elevation data was downloaded from Open Topography using a custom API key.
Water Demand Calculation and Estimation
Projected Population
To estimate the population of residents in the Ogida Barracks Police housing estate, the following key parameters were considered;
the number of residential buildings (53)
the number of series per building (3)
the number of rooms per series (8), and
an estimate of 4 persons per room.
This provides an estimated population of 5088 people. For the purpose of this project, the natural population growth rate will not apply due to the government's control over structures in the estate. However, the design population will be pegged at 6,000.
Average Daily Demand
The average daily demand is a product of the estimated water demand per person per day and the design population.
Estimated water demand (120)
Design population (6000)
6,000 x 120 = 720,000 L/P/D
Pumping Plan
A pumping plan is developed to offer control over the timing and storage constraints. This aids the design of the storage tanks and the eventual pipe sizing.
Half the maximum daily demand (360,000 L/P/D) will be pumped twice a day for approximately 4 hours (2 hours each). This will allow the storage tanks to be sized for half the daily demand.
Pipe Sizing
To size the final distribution pipes, the following parameters will be considered;
Distance from the final distribution point, d = 1065 meters.
Delivery time for half daily demand, d = 2 hrs.
The estimated available head is 15m
Coefficient of friction (0.04)
πππ‘ππ π π’ππππ¦, T = 720,000 L/P/D = 720 π3
Since half the daily demand is delivered in 2 hrs.,
πππ₯πππ’π ππππ€ = T2 x t x 3600
\= 7202 x 2 x 3600 = 0.05 π3π
βπ = flQ212.1 d2 ;
d2 = flQ2hf 12.1
Where hp = head loss due to friction
f = coefficient of friction
l = length of pipe
Q = discharge through the pipe
d = diameter of the pipe
π2 = 0.04 x 1065 x 0.046 215 x 12.1
diameter, d = 0.022mm
hence, the final distribution pipes should have a minimum diameter of 0.03mm
The capacity of Storage Tanks
The following parameters will be used for sizing the storage tanks;
The volume of a cylinder, V = Β₯βπ2ββ
Where Β₯ = pie[3.142]
r =radius [3m]
h = height [4.2 m]
We have V = 118.8 π3
Three storage tanks were used in the project location. The total reservoir storage capacity is:
Vt = 3 Γ 118.8 = 356.3 π3
The above storage capacity accounts for half the maximum daily demand.
Data Processing
Considering the layout of the housing estate, the Dead-end water distribution system was used for the design of the network. This system requires that the storage tank is situated at the highest possible point in the study area. This helps maintain substantial pressure as water flows down the estate to the furthest point.
A digital elevation model was developed using acquired data from OpenTopography. As shown in the model below, the most convenient and highest points on the map are in the region of the 28β¦E and 21β¦N intersect.
The distribution network was designed using the QGIS software application. The different facilities were added by digitizing a satellite image of the study area.
Using points, lines, and polygons, the following water distribution facilities were shown on the network:
Fire hydrant
Pumping station
Isolated valves
Booster pump
Elevated water tank
Water treatment station
Elbow cap
Tee cap
Cross end
Endcap
Pipes
The above distribution network allows for better overall performance. The design will aid the quantity survey and cost of the project, provide a quick and efficient construction process, and help in infrastructure maintenance.