TECHNICAL PAPER # 28
 
                         UNDERSTANDING WATER SUPPLY:
                            GENERAL CONSIDERATIONS
 
 
                                      By
                                 Joe Remmers
 
                              Technical Reviewers
                              Dr. F. O. Blackwell
                            Morton S. Hilbert, P.E.
 
                                 Published By
 
 
                                     VITA
                       1600 Wilson Boulevard, Suite 500
                        Arlington, Virginia 22209 USA
                      Tel: 703/276-1800 . Fax:703/243-1865
                          Internet: pr-info@vita.org
 
 
              Understanding Water Supply: General Considerations
                              ISBN: 0-86619-231-X
                  [C]1985, Volunteers in Technical Assistance
 
 
                                    PREFACE
 
 
This paper is one of a series published by Volunteers in Technical
Assistance to provide an introduction to specific state-of-the-art
technologies of interest to people in developing countries.
The papers are intended to be used as guidelines to help
people choose technologies that are suitable to their situations.
They are not intended to provide construction or implementation
details. People are urged to contact VITA or a similar organization
for further information and technical assistance if they
find that a particular technology seems to meet their needs.
 
The papers in the series were written, reviewed, and illustrated
almost entirely by VITA Volunteer technical experts on a purely
voluntary basis. Some 500 volunteers were involved in the production
of the first 100 titles issued, contributing approximately
5,000 hours of their time. VITA staff included Maria Giannuzzi
as editor, Julie Berman handling typesetting and layout, and
Margaret Crouch as project manager.
 
The author of this paper, VITA Volunteer Joe Remmers, is a civil
engineer who designs and constructs water and wastewater facilities
for Black & Veatch Construction Engineers. He has prepared
plans and specifications for various construction projects in
Saudi Arabia. The reviewers are also VITA volunteers. Dr. F.O.
Blackwell is an associate professor in environmental health with
the East Carolina University School of Allied Health. He has
worked as a health and sanitation adviser with the United States
Agency for International Development in Pakistan, and has taught
at the American University of Beirut, Lebanon School of Public
Health. Morton S. Hilbert, P.E., is chairman and professor in the
department of environmental and industrial health at the University
of Michigan School of Public Health. He is a registered
professional engineer and has worked in the field of environmental
health in 20 countries in Africa, South America, Central
America, and Asia.
 
VITA is a private, nonprofit organization that supports people
working on technical problems in developing countries. VITA offers
information and assistance aimed at helping individuals and
groups to select and implement technologies appropriate to their
situations. VITA maintains an international Inquiry Service, a
specialized documentation center, and a computerized roster of
volunteer technical consultants; manages long-term field projects;
and publishes a variety of technical manuals and papers.
 
 
              UNDERSTANDING WATER SUPPLY--GENERAL CONSIDERATIONS
 
                       by VITA Volunteer Joe Remmers
 
 
I. INTRODUCTION
 
Water supply systems have been a vital part of human life since
before recorded history. Early "systems" consisted of no more
than simply drawing water out of a river or lake with a jar or
bowl. Later, aqueducts were built to move water to more desirable
locations. Such was the case in ancient Egyptian societies. The
Romans were known to have developed aqueducts for conveying water
for use within their cities. Cast iron piping was reportedly used
in Europe in the seventeenth century. Hand pumps appeared for the
first time toward the latter half of the eighteenth century.
Water system technology changed drastically during the Industrial
Revolution when engine- and motor-driven pumps were developed.
Chlorine was discovered to be an effective germ-killing agent and
modern pipe manufacturing techniques were invented. Today, water
systems around the world provide safe drinking water for millions
of people.
 
In those parts of the world not served by water systems, however,
inadequate water supplies continue to be a major problem. The
World Health Organization has estimated that approximately 1,100
million people do not have access to safe and adequate water supplies.
In response to this urgent need for improved water supply
and sanitation, the United Nations declared the 1980s to be the
International Drinking Water and Sanitation Decade. The goal is
to provide safe water in sufficient quantity for all the world's
people by 1990.
 
Improved water systems can help to provide adequate supplies of
safe drinking water in these regions. "Safe" water is water that
does not contain disease-producing organisms e.g., cholera,
typhoid fever, dysentery, worms) and does not contain harmful
chemicals (e.g., arsenic, lead). The reasons for developing a
water supply system are simple: to transport water from its
source; to treat it so that it is safe to drink; to distribute it
to wherever it is needed; and to store it whenever necessary for
future use.
 
A properly designed and constructed water system, which is operated
and maintained correctly, will provide a safe and adequate
water supply for the people of the district the system supports.
In addition to furnishing safe drinking water for a community, a
water supply system can provide irrigation water and water for
industrial purposes. A safe, adequate, and economical source of
water for agricultural and industrial uses could stimulate the
economic growth and overall well-being of a particular region.
 
The purpose of this paper is to provide basic information and
data for those individuals responsible for developing a safe,
economical, and practical water system for their communities. It
examines the various factors that must be considered before
development of a water system is started. More detailed information
can be found in the other papers within VITA's "Understanding
Water Supply" series. These other papers cover the following
topics:
 
                       Water Supply--sources
                       Water Supply--treatment
                       Water Supply--storage
                       Water Supply--distribution
 
This paper is not intended to serve as a design manual; for particular
design problems, the services of specially trained persons
should be sought.
 
 
II. COSTS AND BENEFITS OF WATER SYSTEMS
 
The construction and operation of a water supply system can be
costly, so the benefits of constructing such a system must be
properly assessed. Usually, the benefits far outweigh the costs.
Having a readily available source of water provides economic
benefits because people who formerly needed to carry water for
long periods every day will be free to attend to other matters
such as farming, trade, or business. The most important benefit
of a safe and adequate water supply is the prevention of waterborne
diseases that are present where water is not good.
 
The most expensive items in a water supply system would be heavy
equipment such as pumps, motors, and treatment equipment. Next
would be buildings and tanks. Depending on the size of the system
and type of piping material used, the least expensive component
would be the distribution piping.
 
The cost of labor must also be considered. Community members may
wish to do the job themselves to avoid having to hire outside
help. But this approach may have a hidden cost if it distracts
people from their primary job, farming for example, and causes
productivity to go down. But community projects are working well
in many areas, and the inherent pride of ownership may offset
other costs.
 
 
III. SYSTEM DESCRIPTION
 
CHARACTERISTICS
 
Water systems consist of the following basic components:  (1) a
water source, such as a lake, stream, spring, river, or underground
aquifer; (2) a method of transportation from the source to
the user, such as a canal system or pump/pipe system; (3) a
method of treatment, such as sedimentation, filtration, or disinfection;
and (4) a method of storage, such as a closed tank,
standpipe, or a protected reservoir. A system does not necessarily
need all of the above components. Required components would
depend on the particular needs of the community served.
 
 
RESOURCES
 
The resources required for the development of a water system
depend on the complexity of the system. In general, a system
should be kept as simple as possible to minimize the strain on
available resources. The resources required to develop a water
supply system are discussed below.
 
Materials
 
Materials that are needed for building a water system may include
concrete for storage tanks and treatment facilities; steel, cast
iron, copper, and plastic (among other materials) for piping; and
other construction materials, such as wood, brick, mortar and
clay, to build units to house treatment and pumping facilities.
Hypochlorite or chlorine gas will be needed for disinfection of a
newly-constructed system. In the event of the threat of disease,
a continuing supply of these chemicals should be available to
disinfect the daily water supply.
 
Labor
 
A substantial amount of hand labor is required to construct a
water system. The number of laborers depends on the availability
of equipment--the more heavy machinery available the less need
for manual laborers. Labor would be needed to construct dams or
canals, to dig trenches about .3 to 1 meter deep, to carry and
lay pipe, and to construct treatment facilities, pump houses, and
tanks. Most of the required labor could be unskilled, but some
semi-skilled or skilled workers would also be needed. Pipe laying
techniques can be learned rather quickly, but construction of
buildings and tanks is more complex and must be learned over a
period of time. If an area contains very few skilled individuals,
a training program may have to be established before undertaking
construction projects.
 
Equipment
 
Equipment as simple as a shovel or as complicated as power-operated
heavy machinery (such as a backhoe) can be used. A
community should use what is available and affordable to them.
For instance, when only shovels are available, the project would
be labor-intensive, and probably less costly. It would also
probably take longer. If backhoes, bulldozers, or trenchers are
available and affordable, the project would be equipment-intensive.
It would probably also be more costly, but would likely be
finished more quickly than a labor-intensive system.
 
To construct treatment works, pump houses, and tanks, concrete
mixers, wheelbarrows, scaffolds, and assorted hand tools would be
helpful. Tanks and facilities constructed of steel would require
more complex equipment such as welding kits, cranes, and precision
measuring instruments.
 
Components of the system include equipment such as pumps, engines,
motors, valves, gauges, screens, filters, flocculators,
sludge collectors, and chlorinators. Again, not all this equipment
would necessarily appear in one system--the amount depends
on the system's level of complexity.
 
Energy
 
Energy is needed to run any water system. Energy is required to
pump water up from aquifers, to move it from the treatment plant
to storage tanks at higher elevations, and to send it through the
distribution system. This energy can come from gravity--water
flowing downhill--or it can come from human resources--applying
mechanical motion to a hand pump. Energy can also be derived from
the wind, the sun, fossil fuels, or from the water itself, as
with a hydraulic ram or water wheel. If electric generating
plants are in the area, this source of energy should be investigated.
Energy is costly, so the most economical and reliable
source should be considered.
 
Design
 
Before any effort is made to develop a water system, the services
of competent design professionals should be sought. These professionals
are typically civil or mechanical engineers, or other
water resource specialists. Contractors who are in the water line
construction business, as well as plumbers and pipefitters, could
also be of assistance. Design professionals can help with sizing
a water system, determining water pressures, determining the
right treatment methods to use, designing structures, and estimating
construction and operating costs.
 
Testing
 
To ensure that a water supply is safe for drinking, some method
of periodic testing should be provided for. If the water supply
is suspected as the source of a disease outbreak, additional
bacteriological testing is required. Laboratories that can check
water for both bacteriological and chemical safety are generally
operated by government health agencies. Field kits and equipment
for bacteriological testing are also available and local persons
can be trained to use them. In the event a laboratory is not
available, these kits should be used for testing water supplies.
 
Special Circumstances
 
The community owning a water supply system must have contingency
plans in case certain events occur. Such an event might be the
outbreak of a waterborne disease. Or, the water source could dry
up, as in the event of a drought. Contingency plans should include
alternate sources of water or an emergency tank or reservoir.
 
MAINTENANCE REQUIREMENTS
 
Water pipes or mains, when properly installed, do not often
require maintenance. Occasionally, a line may break, requiring a
crew to go out and repair it. Valves require some maintenance.
They should be operated periodically to avoid the build-up of
mineral deposits.
 
The greatest maintenance requirements are found at the pumping
and/or treatment works. Any time there are moving parts, mechanical
breakdowns will occur and experienced mechanics will be
needed to fix them. Filters at the treatment works will need
periodic cleaning, as will any settling basins. Routine checks
and inspections as well as data collection and recording (pumping
records, electricity used, chemicals used, etc.) must be carried
out.
 
Laboratory tests for bacteria (coliform) must be done at regular
intervals (daily, weekly, or monthly, depending on the number of
Persons served). Chemical testing needs to be done only yearly
unless problems are suspected.
 
Maintenance is an ongoing expense. It must be considered in the
early cost/benefit analysis and provided for as resources are
allocated. Some communities cover maintenance costs through a
system of user fees.
 
IV. DESIGNING THE SYSTEM RIGHT FOR YOU
 
DESIGN CONSIDERATIONS
 
The first consideration in designing a water supply system is to
determine the total quantity of water the system would be required
to deliver. Water quantities are usually based on the
number of persons a community's system is required to serve. A
commonly accepted water demand factor used in practice today is
550 liters per person per day, a figure that allows for some
commercial and laundry use. In areas where survival is threatened
by water shortages, a smaller amount per person should be considered
so that water can be provided to more people. Under extreme
conditions, the minimum allotment should be 90 liters per person
per day.
 
The figure per person should then be multiplied by the total
population of the community to arrive at the average daily demand
(ADD). The peak flow, defined as the consumption during the time
of heaviest use, should be used to determine the volume of storage
required and the pipe sizes needed in the system. The peak
flow can be estimated by multiplying the ADD by 2.5.
 
The second consideration in designing a water system is to determine
the pressure requirements at various points in the system.
The pressure requirements affect energy costs, and, therefore, a
good portion of operating costs. Calculating the pressures in the
system also gives an indication of the type and size of pumps
that may be required. A piped system should, ideally, be under
positive pressure at all times to minimize any infiltration of
contaminated water, and thus prevent disease.
 
 
SCALE
 
Water systems can be constructed to serve large regions such as
entire countries or cities; they can serve small communities; or
they can serve only a single family residence. In some cases, a
centralized system having only a few sources of supply and distributing
water areawide may be preferable to many small systems
serving individual communities or residences. Because its main
waterworks can be monitored more easily, the centralized system
has lower operating costs and better control over the safety of
the water. In other cases, smaller systems may be a better
choice. The choice of either a centralized plant or smaller
systems should be determined by the users' needs and resources.
If energy supplies are limited and hand pumps are the only pumps
available, a system using hand pumps should be considered rather
than one requiring motor- or engine-driven pumps. The availability
of trained, qualified persons to operate and maintain the
system properly must also be assessed.
 
Water systems should be constructed as simply as possible. Gravity
storage tanks supplied by a single-speed pump are favored over
variable-speed pumps feeding a water network. Treatment units,
such as settling basins, can be cleaned manually rather than with
automatic scrapers and sludge pumping systems. Provision for
disinfecting the water should be made when there is the possibility
of contamination. Water taps can be centrally located, or the
water can be piped to each individual home. Transport distances
must be considered carefully because of costs and other technical
questions.
 
A major factor in determining the size of a water system is the
consumers' ability to pay for the water service. If sufficient
revenues can be generated, the water district can become self-supporting.
This should be the ideal goal.
 
USE OF LOCAL RESOURCES
 
A list should be compiled to see what manufacturers and suppliers
are available in a given area as a source for pipes, supplies,
pumps, valves, and replacement parts. Also, an investigation
should be made to see what raw materials might be available. Such
an investigation should include searches for the right clays to
make brick, minerals for cement, and sand and rock for concrete.
Available manpower should be assessed to see who would be qualified
to work on a water project. An inventory of equipment such
as backhoes, cranes, trenchers, and bulldozers should also be
made to determine availability.
 
PUBLIC EDUCATION
 
An aggressive public education campaign may be necessary to
ensure the acceptance and proper use of a water supply system by
consumers. If people have never had safe water, they may not at
first appreciate its value and use it in a manner that will
preserve the system and conserve the water.
 
Long-term use and maintenance of the system will require the
support of the users. If the users of the system are involved in
its planning, construction, operation, and maintenance, the acceptance
and use of the supply will be much greater than in
situations where the system is installed without local participation.
The involvement of local residents in the development of
four new community water supply systems in Honduras is described
in the October 1982 and January 1985 issues of VITA News (see
Bibliography). The success of these water systems is due in large
part to the efforts of community members.
 
POSSIBLE PROBLEMS TO CONSIDER
 
The more complex a system is, the more likely it will have water
line breaks or maintenance problems. The design phase of a water
system should contemplate the simplest system possible that meets
the needs of the community. Acquiring the necessary raw materials
might also be a major problem. If materials are not readily
available and must be brought in from long distances, the development
costs will be increased. Sources of safe drinking water
are not always obvious to the community. Locating sources, such
as underground aquifers, can be time consuming and costly. In
many parts of the world, a water supply system is totally foreign
to the residents. Personnel would have to be trained in constructing,
operating, maintaining, and administering the system.
As stated earlier, the public may also need to be made aware of
the importance of safe water and of their role in using and
preserving the system.
 
The potential problems outlined above and any others must be
carefully studied and resolved before development of a water
supply system is started to ensure the success of the system.
 
                     BIBLIOGRAPHY/SUGGESTED READING LIST
 
American Water Works Association. Recommended Practice for Distribution
     Systems Records. New York, New York: AWWA, 1940.
 
Borjesson, E., and Bobeda, C. "New Concept in Water Service for
     Developing Countries." Journal of the American Water Works
     Association. Vol. 56, No. 7, July 1964.
 
Cairncross, S., and Feachem, R. Small Water Supplies. London,
     England: Ross Institute, 1978.
 
Clark, Viessman, and Hammer. Water Supply and Pollution Control.
     2nd edition. Scranton, Pennsylvania: International Textbook
     Company, 1971.
 
Dallaire, G. "United Nations Launches International Water Decade;
     U.S. Role Uncertain." Civil Engineering Magazine. Vol. 51,
     No. 3, March 1981: 59-62.
 
McJunkin, F. and Pineo, C. U.S. Agency for International Development.
     Water Supply and Sanitation in Developing Countries.
     Washington, D.C.: USAID, 1976.
 
Schiller, E.J., and Droste, R.L., eds. Water Supply and Sanitation
     in Developing Countries. Ann Arbor, Michigan: Ann Arbor
     Science Publishers, 1982.
 
Spangler, C. United Nations and World Bank. Low-cost Water Distribution:
     A Field Manual. Washington, D.C.: World Bank,
     December 1980.
 
Swiss Center for Appropriate Technology (SKAT). Manual for Rural
     Water Supply. Zurich, Switzerland: SKAT, 1980.
 
University of Akron, College of Engineering. Engineering Management
     of Water Supply Systems. Washington, D.C.: United
     States Agency for International Development, 1965.
 
U.S. Department of Health, Education, and Welfare. U.S. Public
     Health Service. Individual Water Supply Systems. Washington,
     D.C.: HEW, 1950.
 
U.S. Environmental Protection Agency. Manual of Individual Water
     Supply Systems. Washington, D.C.: EPA, 1975.
 
U.S. Peace Corps. Water Purification, Distribution, and Sewage
     Disposal for Peace Corps Volunteers. Washington, D.C.: Peace
     Corps, 1969.
 
Volunteers in Technical Assistance. "Wind Power for Roatan Island:
     Pumping Water in Honduras." VITA News, October 1982:
     3-7.
 
Volunteers in Technical Assistance. "Four Island communities
     Inaugurate Water Systems." VITA News, January 1985: 8-9.
 
Wagner, E.G., and Lanoix, J.N. Water Supply for Rural Areas and
     Small Communities. Geneva, Switzerland: World Health Organization.
     1959.
 
                            SOURCES OF INFORMATION
 
American Society of Civil Engineers (ASCE)
345 East 47th Street
New York, New York 10017 USA
 
American Water Works Association (AWWA)
6666 West Quincy Avenue
Denver, Colorado 80235 USA
 
Environmental Sanitation Information Center
Asian Institute of Technology.
P.O. Box 2754
Bangkok 10501
Thailand
 
International Reference Centre for
  Community Water Supply and Sanitation (IRC)
P.O. Box 5500
2280 HM Rijswijk
The Netherlands
 
Pan American Health Organization
525 23rd Street, N.W.
Washington, D.C. 20037 USA
 
TOOL
Entrepotdok 681/69a
1018 AD Amsterdam
The Netherlands
 
Water and Sanitation for Health Project (WASH)
1611 N. Kent Street, Room 1002
Arlington, Virginia 22209 USA
 
World Bank
1818 H Street, N.W.
Washington, D.C. 20433 USA
 
World Health Organization
20 Avenue Appia
1211 Geneva 27
Switzerland
 
World Water (monthly magazine)
201 Cotton Exchange
Old Hall Street
Liverpool 3
England
 
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