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