using gis to determine the coverage of a...
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USING GIS TO DETERMINE THE
COVERAGE OF A WATER SUPPLY
SYSTEM
CASE STUDY: UMOJA INNERCORE
GIBENDI K. WAMBUAF19/2484/2009
SUPERVISOR: Mr. B.M. OKUMU
OUTLINE
Background of the Study
Problem Statement
Objectives
Methodology
Results
Analysis of Results
Conclusions and Recommendations
BACKGROUND OF THE STUDY
Water and sanitation services are considered as essential
basic human needs.
Furthermore access to these services plays a vital role in the
overall socio-economic development of any community or
country.
However water services in Kenya has often been
characterized with low levels of access with recent statistics
showing the coverage to be at only 42-59% (World Bank).
Acceptable coverage is defined as at least 80% of the
population having access to water services, whereas good
coverage is defined as at least 90% having access.
PROBLEM STATEMENT Statistics on coverage and access of Water Supply Systems
(WSS) are usually obtained from sample-based surveys often
with different sampling sizes, methods and procedures, hence
giving quite variable results.
This makes it difficult to assess trends over time as well as
provide reliable information on the progress of the nation as a
whole.
However through the use of various GIS analysis functions
such as overlay and query analysis, highly reliable and timely
information on the coverage and access of such systems, can
be obtained at both the national, regional and sub-regional
levels.
OBJECTIVES
The main objective of this study is to demonstrate how GIS can be used to show the extent of coverage of a WSS visually on digital maps, as well as how such coverage can be determined statistically in the GIS environment.
The specific objectives are:
To produce a digital map showing the water supply infrastructure
To build a geometric network of the water distribution system
To determine the percentage of residential parcels with service meter connections
METHODOLOGYAREA OF STUDY
The area lies in the UTM zone 37S between the extents;Eastings: 264713.55 - 265968.49 m and Northings: 9857825.61 - 9859003.28 m.
It has an area of 1.07 km2 and a population density of 32472.64 per km2.
It is located in Umoja Sub-location, Embakasi West Constituency, Nairobi County, Kenya.
Data Sources
Data Source Remarks
Satellite Imagery Google Earth Pro DigitalGlobe QuickBird (2013),
2.5m Spatial Resolution
Shapefiles
Nairobi Land Use Spatial Information
Design Lab
UTM Arc 1960
Created from JICA/GOK map,
Printed by SoK (2005)
Nairobi Roads Spatial Information
Design Lab
UTM Arc 1960
Created from JICA/GOK map,
Printed by SoK (2005)
Land Parcels Survey
Department,
NCWSC
UTM Arc 1960
Water Pipes Survey
Department,
NCWSC
UTM Arc 1960
Water Meters Survey
Department,
NCWSC
UTM Arc 1960
Hardware
PC (Intel Core 2 Duo CPU @2.33 GHz, 3.00 GB RAM & 80
GB HDD)
Memory Stick (2GB) – for data backup
Software
ESRI’s ArcGIS Desktop, version 10.1
Overview of the Methodology
Data identification and Collection
Data Preparation
Geodatabase Creation
Results and Analysis
Conclusions and Recommendations
Data Identification and Collection
Based on the title and the specific objectives of the study.
Efforts to acquire valid data items: internet searches & visit to the relevant facilities
Data Preparation
Clipping of data to within the extents of the area of study
Georeferencing of the image – UTM Arc 1960
Overlay operations
Identification of missing parcels depictions and digitization of representative “sketches” for the purposes of point-in-polygon search and query analysis
Identification of
• “idle” parcels – no visible land use activity or meter connection
• “Representative” parcels – where a building occupied more than one parcel
Connecting service meters with their respective service lines
SKETCHES IDLE & REPRESENTATIVE
Geodatabase Creation
File Geodatabase was created to manage water network
items. A feature dataset for the network was hence created
and related data classes (Meters & Pipes) imported to this
database. This allowed for:
◦ Topology Creation – To maintain data integrity by checking the
connectivity of features and identifying and correcting connectivity
errors.
◦ Geometric Network Building - set of connected edges (pipes) and
junctions (meters & orphan junctions) along with connectivity rules
that are used to represent and model the behavior of the network.
RESULTS
Maps
Database Query Results
◦ Service Specifications
Service Registered Accounts
Water and Sewerage 2126
Water 36
Sewerage 20
N/A 48
Total 2230
◦ Establishments served
Establishments Accounts
Institutional Schools 10
Hospitals 9
Clinics 1
Churches 7
County Offices 7
Total 34
Commercial Factories 2
Shops 4
Hardware 2
Bars 4
Carwash Points 1
Laundry 1
Total 14
Residential Single dwellings 72
Multiple dwellings 2060
Total 2132
N/A 50
Total 2230
WATER & SEWERAGE SCHOOLS
PARCELS WITH METER CONNECTIONS
Retrieved by:
◦ Point in Polygon Search to Identify Parcel & Meter Coincidence
◦ Attribute Query to determine type of connected service
The results obtained:
◦ 830 out of a total of 1,533 parcels had meter connections
◦ 801 out of a total of 1,533 parcels had access to water services
◦ 797 out of a total of 1,533 parcels had access to sewerage services
◦ 794 out of a total of 1,533 parcels had access to both water and
sewerage services
ANALYSIS OF RESULTS
Majority of the services beneficiaries, approximately 95.3% of the total
recipients, received both water and sewerage services concurrently.
Approximately 1.6% received water services only whereas 0.9% received
sewerage services only.
Main recipients of water utility services are the residential establishments.
They account for 95.6% of the total number of customers. Institutional
and Commercial establishments accounted for only 1.5% and 0.6%, of the
total number of registered customers.
The maps provide a general overview of the coverage of the WSS which as
shown is quite extensive. This is despite evidently some parcels having no
connections to the system.
The effective coverage of the WSS is approximately 54% and 52% of the
considered parcels have access to either water, sewerage, or both water
and sewerage services.
CONCLUSIONS AND
RECCOMENDATIONS
CONCLUSIONS
The stated objectives were attained as reflected by the results.
Utility water and sewerage services in this region are offered mostly
concurrently and are largely utilized for domestic purposes. However
despite an extensive water supply network, the effective coverage of the
system is still quite low, with just over half of the considered parcels having
access to water services.
GIS therefore as has been demonstrated is a valuable resource in
providing reliable and timely information, as well as in analyzing various
aspects of water utility service systems; such as coverage, service
specifications and location of service assets.
RECOMMENDATIONS
Similar approach to identify specific areas without utility
water services and implement initiatives to facilitate access to
water services in these areas.
More embracement in the use of GIS in water and other
utility service sectors, to improve information management
and consequently service provision.
