Contamination of water resources and sources may arise from microbiological pathogens from human and animal excreta or accidental or deliberate pollution by industries or the agricultural community.
Sources of water that are practicable for public and domestic purposes e.g. rain water, surface water such as lakes, rivers and ponds, groundwater from springs, wells and boreholes should be protected from possible contamination.
Protection and Development of Water Resources
Several issues need to be taken into consideration when planning the protection and development of water sources:
1. Assessing needs
Water source protection should be based on needs identified by the community themselves. The community should identify its own water and sanitation needs through a process of internal discussion and external negotiation.
The internal discussion would involve health experts, community leaders and other members of the community.
The external negotiations may involve local government offices, NGOs and other partners who can assist with the assessment of the communities’ needs with information and technical guidance.
2. Water source identification
All potential water sources should be considered and checked. Issues to consider are the sources of possible contaminants, the amount of water available to users annually and the consistency of the supply.
Other important issues are social acceptance, cost effectiveness and community health. All potential water sources need to be assessed in order to identify the best solution.
3. Water quantity
Whenever a new protected water source is proposed it should have the capability of supplying at least 20 litres of water per person per day to the target population.
The protected water source should provide sufficient quantities of water to meet essential health-related household and personal needs, including drinking, cooking, personal hygiene, clothes washing and cleaning for all community members.
4. Sanitary surveys
A sanitary survey is an evaluation of the physical environment to identify possible health hazards and sources of environmental contamination.
The sanitary survey should include the nature of the water-bearing layer, the hydraulic gradient (i.e. the variations in underground water pressure that affect the natural flow of water), topography, vegetation, potential sources of contamination, and the adequacy of the yield particularly for dry seasons.
5. Health and hygiene education
Before developing any water protection, the health benefits of an improved water supply and sanitation need to be accepted by the local community. Providing hygiene education for the people promotes their behavioural change.
6. Water quality
Water quality is a description of the chemical, physical and biological characteristics of water, usually with respect to its suitability for drinking. Water source development projects should draw water from the best available sources.
Read Also: Concept and Principles of Water Quality
Protection Zones: Construction Requirements and Best Practices
For on-site drinking water system, a minimum distance of 15 meters is to be kept between the water system and potential source of contamination.
Communities must keep clean the protected area surrounding on-site drinking water systems.
All drinking water systems must comply with construction specifications as stipulated by Federal Ministry of Water Resources.
All materials and equipment in contact with drinking water must comply with relevant Industrial Standards (such as casing, drilling additive, hand pumps, fitting, distribution pipe, and reservoir paint). Water containers must be stored away from poisonous materials and contamination sources.
1. Protection of well water
The different types of wells include: dug wells, bored wells (also known as boreholes), and driven and jetted wells.
During heavy rain, dug wells are susceptible to contamination by pathogens which may be deposited on the surface or naturally present in the soil and are washed in to the well, particularly if it is improperly constructed.
Contamination of wells can arise from:
Lack of, or improper, disinfection of a well following repair or construction.
Failure to seal the space between the drill hole and the outside of the casing.
Failure to provide a tight sanitary seal at the place where the pump line(s) passes through the casing.
Wastewater pollution caused by contaminated water percolating through surrounding soil and rocks into the well.
At the time when a new well is constructed or repairs are made to a well, pump or piping, contamination from the work is possible. Therefore, it is important that the well, pump, piping and associated structures should be regularly disinfected using chlorine solution.
Wells can be protected by installing a pump over them, but if a pump is not available then a sanitary bucket and rope system may be used. The surrounding ground of a well should be covered and protected and the immediate area fenced to keep animals away.
Grading off the area surrounding a well can be done to create a slope away from the well, in order to prevent the flow of storm water into the well. Any pipework associated with pumps that enters the well needs to have watertight connections so there can be no contamination from surrounding soil.
Wells should be located on a higher level than possible sources of contaminants such as latrines and cesspits (a pit for collection of waste matter and water especially sewage).
This is because the liquid from the pit may seep into the surrounding ground and into the groundwater. If the latrine is higher up a slope than the well then the contaminated groundwater is likely to flow downwards and into the well.
The natural flow of the groundwater (the hydraulic gradient) should be away from the well and towards the sources of contaminants, and not the other way round. In normal soils, the minimum distance between the well and the source of contaminants should never be less than 15 metres and a distance of 30–50 m is recommended.
However for limestone and some other soil formations this distance need to be greater because groundwater can pass very easily through some rocks and soils.
The inside wall of the well should be made waterproof by constructing a well casing. In small diameter bored wells the casing can be a pipe, but in larger wells the casing needs to be constructed by cementing from the top of the well down to a minimum depth of 3 metres.
The casing of the well should also be extended for a minimum of 60 cm above the surrounding ground level to prevent the entrance of surface runoff.
A concrete cover should be fitted over the casing to prevent dust, insects, small animals and any other contaminants from falling in (Figure 1.1).
2. Spring source protection
Before using a spring a thorough sanitary survey needs to be carried out at the site to assess the quantity and quality of water, and the possible contamination.
If the results of the sanitary survey are satisfactory, the eye of the spring (the point where the water emerges from the ground) should be located by digging out the area around the spring down to the impermeable layer.
Different types of spring protection can be constructed but in general they are as follows:
A concrete waterproof protection box, also known as a spring box, should be constructed over the spring to prevent all actual and potential sources of contamination.
A retention wall in the front part of the protection box should be constructed to keep water flowing to the delivery pipe (Figure 2)
In some situations, if the flow is not constant, a collection box may also be constructed in order to ensure adequate water storage.
The intake and overflow pipes should be screened to prevent the entrance of small animals.
The spring and collection box, if there is one, should have a watertight top, preferably concrete. Water will move by gravity flow or by means of a properly-installed mechanical pump. An inspection hole should be tightly covered and kept locked.
Springs should be protected from flooding and surface water pollution by constructing a deep diversion ditch above and around the spring.
The ditch should be constructed so it collects surface water running towards the spring and carries, or diverts, it away. It needs to be deep enough to carry all surface water away, even in a heavy rainstorm. The surrounding area should be fenced to protect it from animals.
3. Rainwater source protection
Rainwater used for water supply may be contaminated by the air, dust, dirt, paint and other material on the roof the water is collected from or improper methods of storage.
To protect rainwater, precaution must be taken to use a storage tank that is completely covered and well maintained. The roof and gutters should be cleaned regularly, especially before the start of the wet season.
It may be necessary to divert the first rainwater away from the tank so the dust and dirt is washed away. Leaves and other larger debris can be prevented from entering the tank by placing a mesh screen between the guttering and the pipe that leads to the tank; the mesh screen will need to be cleaned regularly.
Surface Water Sources
All surface water sources are subject to continuous or intermittent pollution and must be treated to make them safe to drink.
The extent of the treatment required will depend on the results of a sanitary survey made by an experienced professional, including physical, chemical and microbiological analyses. Surface waters are, by definition, unprotected sources.
In summary, water sources must be protected from contaminants to forestall pollution and water borne diseases. Designated use of a water source will inform the methods required for its protection.
Read Also : Cultural Weed Management System Guide