Which criteria should I consider to select a water source during an emergency?
This is a question that I've been asked in the field so I wanted to share it with everyone on KnowledgePoint
Before selecting any water sources, consider the following points:
- Acceptable yield?
o Demand vs yield
o Seasonal yield
o Future yield
Ease / ability to obtain an acceptable quality
Proximity to population
Time of set up vs urgency
o Resource / logistical
- Impacts of development on:
o Existing users
o Operation and maintenance
o Who pays?
- Ease of O&M:
o Resource / logistical
o Availability of trained staff
- Security, socio-political & cultural constraints:
o Cultural & socio-political issues
o Needs of host vs refugee population
o User preferences
- Management & legal constraints?
o Land ownership
Technical options for water sources
For smaller population:
Groundwater and springs are best because:
No or little treatment needed (low turbidity = only chlorination)
No pumping needed
For larger populations in emergencies:
Disinfection is vital and quantity needs to be reliable.
Often surface water is a better early source until a more sustainable solution is exploited. For all sources seasonality is important.
Sometimes there is no choice
Quick and easily recharged source
Borehole water unacceptable to users (e.g. too saline)
Be careful with:
If a body of open water is the only source of water it is likely to be used for many purposes by the community
Improvement of source & treatment therefore necessary
Sanitary surveys for risk assessment
Some basic things can be done prior to treatment to improve the source:
o Fence off the catchment, or at least prevent certain activities
o Keep people & animals out: bank-mounted devices
o Water is cleaner away from edges: floating intakes
Often shallow sources are available but have not been considered as options
Borehole drillers tend to disregard significant shallow aquifers:
o Access is cheaper & quicker than deeper water = good for emergency
o Bacteriological & chemical water quality can be very good = less treatment
o Can be good source for tinkering
o Quantities vary - seasonal
During your survey, find out where local people get their water from – these are often shallow sources
See if these sources can be upgraded or maximised
Open water can be treated at source by:
o Package treatment kits
o Your own treatment kit made up of bits & pieces
Open water can be treated at collection by:
o Household water treatment
Technical options for transporting water
Provides immediate supply
Water source can be borehole with gantry or treated surface water
Tankers can vary in size (5,000 litres up to 20,000 litres)
Need supervision that number of trips on paper is what actually happened – also that each tanker is full and empties completely
Chlorination – for clear water, where would it take place? Chlorination impossible into metallic tankers…
Problems with water trucking:
High cost – tends therefore to be short-term option allowing you to find other alternatives
Availability/ reliability of tankers
Quality of source
Pumps and pipelines:
Water is sometimes transported from the source to site in other ways
One of ...
Good list, but really only a rough outline :) In addition for surface water the quality can also vary considerably with the season, and for example we had huge issues with the treatment this year in northern Uganda, due to a huge spike in turbidity after the unset of the rainy season.
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