Water Supply Systems

Question 1

Factors that influence water use are:

Answer 1

• accessibility of the water source
• quality of the water
• local customs
• socioeconomic status
• whether or not people pay for the water

Question 2

Further consideration for water demand

Answer 2

Obtain local information
Other factors:
- irrigation of gardens
- industries and commercial enterprises
- changes in population and development
- water lost, wasted or unaccounted for water (UFW) can be as high as 50%

Question 3

A good standard of hygiene can be achieved by supplying :

Answer 3

40 L/p/d

15-20 l/p/d minimum supply needed

Question 4

Relationship between level of service and usage patterns (leading to health outcomes)

Answer 4

A communal water point - 5 to 25 l/p/d depending on distance from the house, consumption and hygiene may not be met, potentially high health concern

Single water point in house or yard - comfortable 20 l/p/d - consumption assured, most hygiene ok - low health concern

Multiple taps will allow >40 L/p/d, very low health concern

Question 5

Water storage

Answer 5

Objective: water as close to the home as possible
Reason: ensure adequate consumption and hygiene, improve availability and quality

Question 6

Goals for drinking water quality:

Answer 6

• free from pathogenic organisms
• free of compounds that have any adverse effect on health
• fairly clear (low turbidity, little colour)
• no taste or smell
• not cause corrosion, encrustation nor staining

Question 7

Water Safety Plans (WSPs) are

Answer 7

a comprehensive risk assessment and risk management approach that encompasses all steps in water supply from catchment to consumer. This allows for a progressive approach to improving water quality rather than applying the blanket application of water quality standards

Question 8

Options for improving the quality of water at source:

Answer 8

• filtration

- chlorination

Question 9

Options for improving the quality of water at household level

Answer 9

• chlorination
• thermal or solar disinfection
• filtration
• combination of flocculation and disinfection

Question 10

What are the 3 types of water sources used in rural areas?

Answer 10

• rainwater
• groundwater
• surface water

Question 11

Considerations for surface water:

Answer 11

• easiest water source to access
• easily polluted
• affected by seasonal variations in turbidity and flow
• often only cost-effective if the intake structures are sized to produce large volumes of bulk water supplies to be shared

Question 12

Groundwater may be obtained from:

Answer 12

• springs
• hand dug wells
• boreholes

Question 13

Considerations for protected springs:

Answer 13

• need to be properly designed, built and maintained to protect the water from contamination
• simple protection measures include fencing off the spring, building a headwall and a drainage system to protect the spring from erosion and steps or a ramp so that users can access the source easily

Question 14

Considerations for protected hand dug wells:

Answer 14

Pollution problems can be eliminated by some simple improvement:

• deepening to reach groundwater
• lining the well (except the bottom) to stop it from collapsing
• providing a parapet wall around the well head and a cover
• laying a hard-standing around the well-head which drains the wastewater away from where people stand
• installing a lifting mechanism that prevents the vessel and rope form being contaminated

Question 15

Considerations for boreholes

Answer 15

• the hole must be sealed and lined and a plinth with adequate drainage should be provided at the well-head
• only work where a suitable aquifer is found

Question 16

Advantages of boreholes compared to hand-dug wells:

Answer 16

• greater depths
• mechanised drilling rigs can deal with any type of rock stratum
• quicker to dig
• small diameter hole when sealed properly completely prevents pollution
• fitted with either a narrow bucket or handpump which prevents contamination by users

Question 17

Disadvantages of boreholes compare to hand-dug wells:

Answer 17

• material cost is higher
• materially may not be available locally
• maintenance of a handpump or narrow bucket pump is more complicated than a bucket and windlass system and replacement parts may again be expensive and difficult to source

Question 18

Concluding comments on rainwater catchment

Answer 18

Low to medium capital cost with storage tanks needed

Low running cost

• depends on climate
• poor water quality

Question 19

Concluding comments on surface water

Answer 19

High capital cost. Design and construction of intake

High running cost due to treatment and pumping needed

• filtration essential
• maintenance required for filtration and pumping

Question 20

Concluding comments on spring protection

Answer 20

Low to medium capital cost if piped to the community

Low running cost

• requires a reliable spring flow throughout the year

Question 21

Concluding comments on hand dug wells

Answer 21

Low capital cost

Low running cost

Abstraction can be by bucket and windlass or by handpump

Question 22

Concluding comments on boreholes

Answer 22

Medium capital costs since well drilling equipment and lining needed

Medium running costs since requires mechanical pumping

• Suits deep underground aquifer
• Needs maintenance of mechanical pump

Question 23

Levels of urban water supply service:

Answer 23

0. Hand-carried non-piped supplies
1. Hand-carried piped supplies
2. Yard-tap piped supplies
3. Multiple-tap in-house piped supplies

Aim for Level 2

Question 24

What is condominial water supply?

Answer 24

Each community forms a cooperative or "condominium" and choses the level of water service that they are willing and able to pay. 
Supply water (and sanitation) to groups of households instead of individual households to reduce costs.

In any one urban situation there would be a mix of:

• standpipe cooperatives
• yard-tap cooperatives
• multiple tap in house cooperatives