UNIVERSITY OF NAIROBI
DESIGN OF A WATER SUPPLY SYSTEM IN ONGATA RONGAI
By Joan Karimi Mwiti, F16/36367/2010
A project submitted as a partial fulfillment for the requirement for the award of the degree of
BACHELOR OF SCIENCE IN CIVIL ENGINEERING
2015
Abstract
The purpose of this project was to design a water supply system for Ongata Rongai. Ongata Rongai is one of the fastest growing towns in Nairobi’s Metropolitan area.The water supply system in the area therefore needs to be upgraded to meet the ever increasing demand from both the domestic and industrial use.
The report therefore outlines the steps taken to collect the data needed for the design which includes use of questionnaires, interviews and literature documents. It goes a step ahead to show how the data collected was analyzed to get the demand of the area. The data collected also gave an overview of water shortage in the area and the different ways in which water is utilized. The main trunk line from the Kiserian dam, which is the source, was then designed together with a distribution network for only a portion of the area. This was because the discharge from the source was not adequate to meet the demand of the area. The profiles of the designed pipelines were then plotted.
Dedication
I would like to dedicate this project to my parents especially my mum who tirelessly worked to ensure I did my best in everything particularly in my education. As Abigail Adams once said, “Learning is not attained by chance; it must be sought for with ardor and intelligence.”
Acknowledgements
I would like to express my very great appreciation to everyone who helped me out in my project. Without you all I would not have made it this far.
Special thanks should be given to my supervisor Dr. Z. N Oonge for his tireless efforts in teaching and guiding me throughout this period.
My deep gratitude goes out to all the staff at the county government for devoting their time to make sure I got the data I required. Their efforts are much appreciated.
Finally, I wish to thank my family and friends for their support and encouragement throughout this period.May the Almighty bless you all abundantly.
Table of contents
Abstract
Dedication
Acknowledgements
List of figures
List of tables
Chapter One
1.0 Introduction
1.1 General
1.2 Problem Statement
1.3 The objective and scope of study
Chapter Two
2.0 LITERATURE REVIEW
2.1 Water Occurrence and Hydrology
2.2 Description of area
2.3 Water sources
2.4 Water Demand
2.5 Population projections
2.6 Water distribution
Chapter Three
3.0 METHODOLOGY
3.1 Introduction
3.2 Data collection methods
3.3 Problems in collection of data
3.4 Data analysis
Chapter Four
4.0 RESULTS AND DISCUSSION
4.1 Questionnaire analysis
4.2 Population data
4.3 Water Demand
4.4 Pipe Network Design
Chapter Five
5.0 CONCLUSION AND RECOMMENDATION
5.1 Considerations in design
5.2 Community involvement
5.3 Recommendations
6.0 REFERENCES
APPENDICES
Appendix 1: HGL calculations
Appendix 2: Moody chart
Appendix 3: Standard pipes
Appendix 4: Questionnaire sample
List of figures
Figure 2.1 The hydrological cycle...... 4
Figure 2.2Branched and looped distribution system...... 16
Figure 2.3Fully interconnected pipes...... 17
Figure 2.4 Overcrossing single pipes...... 17Figure 2.5 House connection...... 18
Figure 2.6Yard connection...... 19
Figure 2.7 Public Standpipes...... 20
Figure 2.8 Variation of domestic water demand during the day...... 22
Figure 2.9 Design capacities for water supply system components...... 23
Figure 4.1 Gender distribution...... 35
Figure 4.2 Type of family...... 35
Figure 4.3 Household size...... 36
Figure 4.4 Monthly income...... 36
Figure 4.5 Sources of water available in the area...... 37
Figure 4.6 Utilized sources...... 38
Figure 4.7 Time taken to fetch water...... 38
Figure 4.8 Frequency of buying water...... 39
Figure 4.9 Shortages...... 39
Figure 4.10 Price of water per jerrican...... 40
Figure 4.11 Frequency of water supply...... 41 Figure 4.12 Sufficiency of supply...... 41
Figure 4.13 River Mbagathi...... 42
Figure 4.14 Adequacy of main source...... 43
Figure 4.15 Availability of water throughout the year...... 43
Figure 4.16Taste...... 44
Figure4.17 Turbidity ...... 44
Figure 4.18 Paying for water...... 45
Figure 4.19 Monthly water payments...... 45
Figure 4.20 Willingness to spend more on better quality...... 46
Figure4.21 Water utilization...... 46
Figure 4.22 Rainwater Harvesting...... 47
Figure 4.23 Drinking water...... 47
List of tables
Table 4.1 Human population data...... 49
Table 4.2 Population projection for the area...... 50
Table 4.3 ECD schools population data...... 50
Table 4.4 Public primary schools population data...... 50
Table 4.5Private primary schools population data...... 51
Table 4.6 Secondary schools population data...... 51
Table 4.7 Schools population projection for the area...... 52
Table 4.8 Health centres data...... 52
Table 4.9 Livestock population data...... 53
Table 4.10 Livestock conversion data...... 54
Table 4.11 Service type...... 55
Table 4.12 Human population data according to service type...... 55
Table 4.13 Water consumption rates...... 55
Table 4.14 Water demand used in l/p/day...... 57
Table 4.15 Water demand in m3/day human population...... 57
Table 4.16 Water demand in m3/day institution population...... 58
Table 4.17 Water demand in m3/day health centres...... 58
Table 4.18 Water demand in m3/day livestock population...... 59
Table 4.19 Summary of water demand in m3 / day...... 59
Table 4.20 Pipeline details...... 63
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Chapter One
1.0 Introduction
1.1 General
Water sustains life. It essential to man, animals and plants and without water life on earth would not exist. One of the most basic human commodities is access to clean water. A country or community without access to clean and safe water, good sanitation and hygiene facilities is one without a future. This will be mainly due to the fact that the people will not be able to prevent water-borne diseases which are one of the leading causes of death of children under five years. In addition to that, they will not be able to practice farming for their consumption as well as have water for their animals.
One of the MillenniumDevelopment Goals is to ensure that by 2015, the proportion of people in the world without access to sustainable safe drinking water and basic sanitation is halved. In order to do this, it is necessary to provide access to safe drinking water. This can only be done through design and construction of various water supply/distribution systems in the urban and rural areas. If this is not possible in the rural areas, provision of water pans may be necessary.
Water supply and sanitation in Kenya is characterised by low levels of access, in particular in urban slums and in rural areas, as well as poor service quality in the form of intermittent water supply. Only 9 out of 55 water service providers in Kenya provide continuous water supply.
According to the Joint Monitoring Programme’s 2012 report, access to safe water supplies throughout Kenya is 59% and access to improved sanitation is 32%. There is still an unmet need in rural and urban areas for both water and sanitation. In urban areas access to improved water has steadily declined over time. This is because of the rapid urban population growth. In addition to that, the high percentage of inactive connections means that the actual coverage is less than stated. Kenya faces challenges in water provision with erratic weather patterns in the past few years causing droughts and water shortages.
Kenya also has a limited renewable water supply and is classified as a water scarce country. Urban migration contributes to challenges in sanitation, as people crowd into cities and urban growth is unregulated.
The Ministry of Water and Irrigation remains the coordinator, policy formulator and quality controller for the water sector. Under the Water Act 2002, an institutional setup was created as follows: Water Service Providers (WSPs) are linked to 8 regional Water Services Boards (WSBs) in charge of asset management through Service Provision Agreements (SPAs). The Act also created a national regulatory board, Water Services Regulatory Board (WSRB) that carries out performance benchmarking and is in charge of approving SPAs and tariff adjustments.
Ongata Rongai is under the Tanathi Water Services Board. Oloolaiser Water and Sewerage Company is the Water Service Provider located in the town and it is responsible for supplying water from the recently completed Kiserian dam among other sources that they utilise.
1.2 Problem Statement
Ongata Rongai is one of the fastest growing towns in Nairobi’s Metropolitan area. It was originally occupied by the Maasai. Since it was a rural area in the 1980’s and early 1990’s, it was not planned. The transport, water supply and sewerage aspects of the town were not considered at that time. However over the past fifteen years, Ongata Rongai has grown immensely in population. This has brought up the need for better infrastructure and social amenities like schools, hospitals and market centres to cater for the large population.
This alone is not adequate the water supply in the area needs to be upgraded to meet the ever increasing demand from both the domestic and industrial use. The area is currently supplied with water from boreholes from small-scale WSPs. This presents another challenge because the underground water in the area is hard and most of the water is not adequately treated to the required WHO drinking water standards. The water from the boreholes from recent studies is found to contain high amounts of iron which is in excess of the recommended Drinking Water Quality Standards for Kenya. This poses as a health risk to the users. There was therefore need to source out another water source that would be reliable and provide safe water for consumption.
This need lead to the construction of the Kiserian dam. The project included the construction of a dam on the Kiserian River, raw water mains, treatment works and storage tanks. The dam was designed to meet the current water demand for the surrounding towns which are Ngong, Kiserian, Kajiado and Ongata Rongai.
The water from the dam is treated to the required standards before it is supplied. This solves the problem of inadequate water quality standards. It is also necessary to provide a means of distribution of the water from the dam hence the need for design of a water supply system.
1.3 The objective and scope of study
Main Objective
The objective of this project is to design a water distribution system that will supply safe drinking water that will meet the demand of people in the area.
Specific Objectives
To achieve this objective, the following studies will be done:
Find out the water utilization in the area.
Find gaps in demand and recommend other alternative sources of water to fill the gaps.
Find out the current supply from the dam.
Chapter Two
2.0 LITERATURE REVIEW
2.1 Water Occurrence and Hydrology
The first step in designing a water supply system is to select a suitable source or a combination of sources of water. The source must be capable of supplying enough water for the community. If not perhaps another source or several sources will be required.
The water on earth whether as water vapour in the atmosphere, as surface water in rivers, streams, lakes, seas and oceans or as ground water in sub surface ground strata is for the most part not at rest but in a state of continuous recycling movement. This is called the hydrological cycle. (E. H. Hofkes et al 1981)
Figure 2.1 The hydrological cycle (Ingles II, 2013)
By far the greatest part of the water on earth is found in the oceans and seas. However this water is saline. The amount of fresh water is less than 3%, about two thirds of which is locked up in ice caps and glaciers. The fresh water contained in the underground and in all lakes, rivers, streams, brooks, pools and swamps amount to less than 1% of the world’s water stock.
Information regarding the amount of rainfall, the flow of rivers and streams, the quantity and depth of groundwater and evaporation is needed by the engineer. This information is rarely available so that it will be necessary to take field measurements or extrapolate data from such records as available. (E. H. Hofkes et al 1981)
2.2 Description of area
2.2.1 Location
Ongata Rongai is situated 17km south of central business district of Nairobi city, the capital city of Kenya. It is one of the locations in Ngong Division, Kajiado District. Its coordinates are approximately 20 45’’ 00’ S and 370 23’’ 00’ E.
The physical boundaries of the town are Kandisi River to the South and Mbagathi River to the North. The town can be accessed through the Nairobi-Magadi road. It covers an area of about 16.5 Km2. The town’s administrative boundaries have changed over years and it covers a much larger area with its ever increasing population. This could be attributed to its proximity to Nairobi and its cost of living compared to the capital city.
2.2.2 Climate
The largest part of Kajiado is semi-arid. The mean annual rainfall ranges from 300 to 800 mm. Rainfall is bimodal, with "short rains" from October to December and "long rains" from March to May. The distribution of rainfall between the two seasons changes gradually from east to west across Kajiado District. In eastern Kajiado more rain falls during the "short rains" than during the "long rains". In western Kajiado the majority of rain falls during the "long rains.Heavy rains occur around Ngong Hills, Chyulu Hills, Nguruman escarpment and the foothills of Mt. Kilimanjaro. This is because the rainfall in the district is strongly influenced by altitude.
The temperatures in the district also vary according to altitude. Mean maximum of 34ºC around L. Magadi and a mean minimum of 10ºC on the foothills of Kilimanjaro have been recorded. Moisture deficit is also observed in the greater part of the year. This gives the district a dry season of between 7-9 months.
As for the region around Ongata Rongai, the climate is warm and temperate. There is significant rainfall throughout the year in Ongata Rongai. The average annual temperature in Ongata Rongai is 18.3 °C. About 844 mm of precipitation falls annually.
2.2.3 Topography and Geology
The main physical features in the district are plains, and occasional hills and valleys. Several valleys dissect the plains and its physiography is influenced by geology. The land rises from 500m asl around L. Magadi to 2500m asl in the Ngong hills area. Ongata Rongai lies at approximately 1731m asl. The area slopes as you move towards Ongata Rongai town from Kiserian and Ngong.
The ground surface represents eroded remnants of a former volcanic or string of volcanoes that previously measured over eleven kilometres in diameter. The area is covered mainly by black cotton soils which is essentially not suitable for farming.(Kajiado District Environment Action Plan 2009-2013)
2.2.4 Socio-economic Infrastructure
2.2.4.1 Administration
Ongata Rongai is one of the locations in Ngong Division. It covers Ongata Rongai and Ole Kasasi sub-locations. It is under Kajiado north constituency and Kajiado County. It has one of the highest population growth rates with its population increasing after every census since 2009.
2.2.4.2 Education
Ongata Rongai has many schools distributed within the area most of them being primary schools. Most of them are private. The area basically has a shortage of public schools. There are two main universities which are within the area namely, Africa Nazarene University and Adventist University of Africa. Catholic University of East Africa is also located a few kilometers from the town itself. There are also quite a number of ECD schools and high schools in the area. (Kajiado District Environment Action Plan 2009-2013)
2.2.4.3 Health Facilities
Ongata Rongai has a number of health facilities most of them being clinics. They are both private and public namely, Garlands, Aga Khan, Kenyatta national hospital. These are some of the hospitals that have opened clinics in the town itself.
2.2.4.4Transport
In Kajiado district, the major roads tend to follow the north-south direction connecting to the Nairobi-Mombasa road. With Nairobi outside Kajiado as the focal point, three major road networks emerge: to Magadi; to Namanga through Athi River and Kajiado to Loitokitok through Sultan Hamud and Emali on Mombasa road.
The only tarmac roads in the whole district are the Nairobi to Namanga (153kms), Nairobi Magadi roads, which passes through Ongata Rongai/Kiserian or Ngong/Kiserian (102kms) and the Kiserian Isinya road. The road which leads to the dam itself is an all-weather road. Most of the access roads are not tarmacked and some become impassable during the rainy season.
There is a railway line passing through the area but it used to transport Soda ash from Magadi. People in the town also use motorbikes and bicycles to move around and also transport their goods. This is in addition to the donkeys and the carts which are also used. (Kajiado District Environment Action Plan 2009-2013)
2.2.4.5 Commerce and Industry
The area is growing at a very high rate. This has created business opportunities in the area. The town currently has three large supermarkets. These are all accompanied by hotels, bars, shops and many more. The town also has water vendors who use donkeys as their mode of transport.