Guidance on Drinking Water Safety Planning

This guide will assist drinking water suppliers to carry out drinking water safety planning as required by the Water Services Act 2021 (the Act). It covers the importance of risk management in the supply of safe drinking water and provides examples of risk management approaches that can be used as part of the drinking water safety planning process.

This guide describes good risk management practice for drinking water safety planning. We recognise that some suppliers, particularly those who operate very small drinking water supplies, won’t have previous experience of drinking water safety planning, so will need time to fully implement this guidance. Taumata Arowai will provide templates to support people who operate very small (serving less than 50 people) and small (serving 50 – 500 people) drinking water supplies to complete plans in a way that is proportionate to the scale, complexity and risks associated with their supply.

A supplier doesn’t have to complete a drinking water safety plan if:

  • They have implemented an Acceptable Solution that specifies that a drinking water safety plan isn’t required.

If you're a drinking water supplier who wasn’t registered with the Ministry of Health before 15 November 2021, you won’t need to prepare a drinking water safety plan until after your supply is registered. You have up to November 2025 to register your supply, and up to November 2028 to prepare and provide a drinking water safety plan or comply with an Acceptable Solution.

Overview

Drinking water safety planning is a risk management process that aims to ensure a safe supply of drinking water to consumers. It focuses on identifying, assessing, and managing the risks across the whole drinking water supply system - from where the water is sourced to the point of supply to consumers.

‘Safe’ in relation to drinking water is defined in the Act. It’s drinking water that is unlikely to cause serious risk of death, injury, or illness immediately or over time. This is whether or not the serious risk is caused by consumption or use of the drinking water, or other causes together with consumption and use of the drinking water. Drinking water is not unsafe merely because a person objects to it, or it doesn’t comply with aesthetic values.

By using a broad risk management approach in water safety planning (one that suits the size, complexity, and risk associated with each water supply), you can also drive improvements to your infrastructure as well as in your organisations and people. We encourage you to focus on the process of continuously managing risks to your supply and how effectively you’re doing so – not solely on the completion of a drinking water safety plan.

The outcome of an effective planning process (as documented in your drinking water safety plan) is a resilient approach to supplying a sufficient quantity of safe drinking water to consumers. If an issue affects the sufficiency or safety of the drinking water you supply, your planning should enable you to quickly respond to prevent or minimise the potential of people being harmed.

What is required?

Drinking water safety plan

There are specific requirements that a drinking water supplier must include in their drinking water safety plan as outlined in the Act. This includes:

  • Identifying any hazards that relate to the drinking water supply
  • Assessing any risks associated with those hazards
  • Identifying how those risks will be managed, controlled, or eliminated to ensure that drinking water is safe and complies with legislative requirements
  • Identifying how the drinking water safety plan will be reviewed on an ongoing basis, and how it will be amended (if necessary) to ensure that drinking water remains safe and complies with legislative requirements
  • Identifying how the drinking water supply will be monitored to ensure that drinking water is safe and complies with legislative requirements, including;
    • procedures to verify that the drinking water safety plan is working effectively
    • a multi-barrier approach to drinking water safety that will be implemented as part of the plan
    • a source water risk management plan if required
  • Where a drinking water supply includes reticulation, the requirement for the use of residual disinfection in the supply unless an exemption is obtained
  • Identifying how a supplier will meet the supplier’s duty to ensure that a sufficient quantity of drinking water is provided to each point of supply
  • Identifying how a supplier will respond to events and emergencies.

Source water risk management plan

The Act also details specific requirements to manage the risks to your source water in the form of a source water risk management plan. This includes:

  • Identifying any hazards that relate to the source water, including emerging or potential hazards
  • Assessing any risks that are associated with those hazards
  • Identifying how those risks will be managed, controlled, monitored, or eliminated as part of a drinking water safety plan
  • Having regard to any values identified by local authorities under the National Policy Statement for Freshwater Management that relate to a freshwater body that you use as a source of your drinking water supply.

Separate guidance sets out the specific requirements for source water risk management planning in more detail.

Principles of drinking water safety

As part of the drinking water safety planning process, you should be mindful of the principles of drinking water safety (as identified and endorsed by the 2017 Havelock North Drinking Water Inquiry):

Water safety principles

Overview

Principle 1: A high standard of care should be embraced

As unsafe drinking water can cause illness or death, all those involved in supplying drinking water must embrace a high standard of care.

Principle 2: Protection of source water is of paramount importance

The risks to sources of drinking water must be well understood and managed since the protection of source drinking water provides the first barrier against drinking water contamination and illness.

Principle 3: Maintain multiple barriers to contamination

Drinking water systems must have robust, multiple barriers against contamination. No single barrier is effective against all sources of contamination and barriers can fail at any time.

Principle 4: Change precedes contamination

As contamination is almost always preceded by change of some kind, water suppliers must monitor and respond to any changes as part of their due diligence.

Principle 5: Suppliers must own the safety of drinking water

Drinking water suppliers must manage the risks to their water supply operation to ensure they supply safe drinking water to their consumers.

Principle 6: Apply a preventative risk management approach

Drinking water suppliers should conduct a systematic assessment of risks throughout their drinking water supply. This will provide the best protection against waterborne illness.

Te Mana o te Wai

You must also integrate the principles of Te Mana o te Wai into your water supply operation. Te Mana o te Wai is a holistic concept that recognises the importance of water (wai) and how by protecting the health of water, you also protect the health and wellbeing of people and the wider environment. This whole system approach, embodied in Te Mana o te Wai, from maunga (mountain) to moana (sea) or ki uta ki tai, is unique to Aotearoa New Zealand. Te Mana o te Wai is defined in the National Policy Statement for Freshwater Management 2020.

Leadership demonstrating a duty of care

Commitment from the leaders of a drinking water supply (for example, the owner of the supply, a Chief Executive, a Board member, or an elected official) to provide safe drinking water is fundamental to increasing the focus on risk management throughout an organisation. Leaders need to understand their water supply system and the risks associated with the supply. This does not mean each leader has to have deep technical understanding of all aspects of the drinking water supply system, but they must have sufficient knowledge to ensure that risks are being managed effectively and they are delivering on their duty of care.

Leaders of a drinking water supply must ensure that:

  • there are sufficient resources and processes for the supply to be established and maintained in a way that ensures a sustained supply of a sufficient quantity of safe drinking water
  • people with the right skills and experience are available to operate the supply and there is a commitment to ongoing capability building and succession planning
  • they understand that the risk controls are effective and appropriate for the level of risk
  • they have sufficient information available to them, so they are assured that the controls are implemented and are working as intended.

Other ways in which leaders should embed a culture of risk awareness and management throughout their organisation include:

  • Ensuring all organisational planning documents support their commitment – for example in an Asset Management Plan and Long-term Plan.
  • Actively involving all people across the water supply operation in risk management planning. The people who operate the system may be best placed to identify the risks and to suggest workable solutions.

For smaller drinking water suppliers, the responsibilities are the same as for larger suppliers. The difference is that they will likely sit with a small team of people and those people will require a deeper and broader understanding of their drinking water supply system. Scale, complexity and risk will also likely differ between small and large drinking water supplies, which affects what leaders, employees and agents must reasonably do to satisfy their ongoing due diligence obligations.

Risk management and its importance

Drinking water is essential for life, however it has the potential to carry contaminants (hazards) which can affect the health of consumers. Water may be unsafe, or not comply with the Standards, due to contaminants in the source water, or it can become unsafe at a later stage in the water treatment or distribution processes. This may be due to problems arising within the supply or external events such as extreme weather events, natural disasters, chemical incidents, or infrastructure failures which result in a hazard being present in drinking water (hazardous events).

Water suppliers in Aotearoa are required to ensure a sufficient supply of safe drinking water that complies with the Drinking-Water Standards for New Zealand and the Drinking Water Quality Assurance Rules. While following the relevant rules is an important step towards achieving safe water, there may be risks that arise from your water supply arrangements that cannot be managed appropriately by only following compliance rules. This is one of the reasons why a broader risk-based approach to drinking water safety planning is necessary.

Effective risk management is about identifying all potential hazards and hazardous events that could affect your drinking water supply, assessing the likelihood and consequences of these, and implementing suitable controls to reduce the risk of the unwanted event occurring.

Failure to supply safe water will have consequences for your consumers and communities more widely. These may include acute or chronic illness or death, lost productivity, impact on health services inconvenience, additional expense, and damage to local and international reputation. While a drinking water supplier may choose how they manage the risks to their supply, Taumata Arowai will act if we become aware that a drinking water safety plan is inadequate or has not been followed by a supplier.

The distinction between hazard and risk is important

Water suppliers need to focus on preventive measures selected primarily on the level of risk, rather than only the existence of a hazard.

  • A hazard is something that can cause harm - for example, the bacteria Campylobacter.
  • Risk is the likelihood that the hazards will cause harm combined with the severity of the consequences if the hazard does occur - for example, probability that Campylobacter will cause illness and the potential severity and extent of that illness.
  • A control is a measure or step which is designed to reduce the likelihood or severity of harm.
  • An uncontrolled risk is the likelihood that harm will occur combined with the severity of the harm (consequences) without any controls - for example, how likely is it that source water would contain Campylobacter and what would be the consequences if this was supplied untreated to consumers.
  • Residual risk is the risk remaining after controls are applied. for example, the possibility of campylobacter entering a water reticulation system after the water has been treated.

Approaches to risk management

There are many different risk management approaches and tools you can use for drinking water safety planning. Some of the common approaches and tools are summarised below:

  • The Plan-Do-Check-Act Cycle: Used to identify what you will do to operate your drinking water supply safely. This includes identifying the hazards and risks to your water supply and the measures you will use to prevent them occurring (Plan); implementing the measures to control the hazards/risks (Do); monitoring and measuring your processes and reporting your results (Check); then reviewing based on your learnings or to improve your processes (Act).
  • ISO 31000 Risk Management: An international standard that provides guidelines for managing risks.
  • The bow tie method: A visual representation of risk, mapped out as a bow tie shape with the top hazardous event in the centre, controls to manage the likelihood of the event occurring on the left-hand side and the controls on the right-hand side to reduce the consequences of the event and to aid in the recovery.
  • World Health Organisation Water Safety Plan Guide: A step-by-step guide to risk management for drinking water suppliers, using the likelihood/consequence risk assessment approach.

You can choose the risk management approach that works best for you based on the scale, complexity, and risks of your supply.

Risk management planning process

Drinking water safety planning is the process to ensure your water supply operation has appropriate and effective controls in place to prevent any hazard being present at a level that could make drinking water unsafe. A structured approach is important to ensure that significant problems are not overlooked and that areas of greatest risk are identified and prioritised.

Scalability of your risk management approach

The risk management approach you choose will depend on the size and complexity of your drinking water supply operation. If you operate a very small water supply (for example, serving a few households only), then a template will be available to record your drinking water safety plan. Monitoring results and observations could be recorded in a diary or a notebook. In contrast, larger water suppliers will use more sophisticated risk management tools as part of their drinking water safety planning and record keeping.

Most risk management approaches follow a similar cycle that includes planning, implementing and then reviewing and making improvements if required.

Plan-Do-Check-Act Cycle process

This section uses the Plan-Do-Check-Act Cycle to outline important points to consider in drinking water safety planning.

PLAN

Governance and leadership

Think about how your water supply operation is governed and who the key decision makers are. Examples of good governance and leadership practice include:

  • Having a drinking water safety policy in place that has been endorsed by leaders and is reflected in their attitudes and decisions.
  • Involving everybody in the drinking water safety planning so that all people involved in the water supply operation have a good understanding of risk and their due diligence obligations under the Water Services Act 2021.
  • Understanding that drinking water safety planning is broader than just complying with rules and is an on-going process of risk management.
  • Working with your community, mana whenua and other water suppliers to share ideas, get feedback and improve your practice.

Management and planning

Think about how your water supply operation is managed and how you will plan for future improvements in your people, processes, and your equipment. Below are some questions for reflection:

  • Do you have enough people in your water supply operation for it to run effectively?
  • Do your people have the right skills and experience to operate and maintain your drinking water supply?
  • Are key responsibilities and knowledge shared across the water supply operation or sitting with one person or group of people?
  • How do you train and support your people?
  • How will you cover key people when they are unavailable or leave the drinking water supply operation?
  • How have you involved mana whenua in your risk management planning activities and used mātauranga Māori (Māori knowledge) to inform the risk management practice of your drinking water supply operation?
  • Have you sought feedback from your consumers to inform and improve your risk management practice?
  • What will you do in an emergency?

Understand your drinking water supply system

You should have a thorough understanding of your drinking water supply from source to the point of supply to the consumer. It’s important you involve the people who operate the drinking water supply in this process. Collectively they should have a good understanding of how the supply is operated in practice. They’ll also likely understand many of the risks to supplying a sufficient quantity of safe drinking water, in the context of your particular supply or supplies.  

To understand your supply and ensure you have considered all the potential associated risks, you should map your water supply system as a flow chart showing the different parts of the water supply and how they work together. The flowchart should tell the story of your water supply on one page. Example flowcharts can be found at Appendix 2 but generally your flowchart should include:

  • All elements of the water supply – including water sources, treatment plants, reservoirs, pump stations, and booster chlorination facilities (where they exist)
  • The connections between each of the elements that make up your supply
  • Monitoring points - for example for turbidity, pH and Free Available Chlorine (FAC)
  • Barriers to contamination
  • Key processes associated with the supply - for example for clarification, treatment, sedimentation, filtration, chlorination, ultraviolet light (UV) disinfection
  • Any recycling of water.

Identify the hazards and how they can create a risk to your supply

At every stage of your water supply operation, identify the hazards that may cause failure to your ability to provide safe water, or a sufficient quantity of water, to your consumers. Think about the hazards that impact your source water, treatment, or distribution processes, as well as those that pose risk through your people, processes, and equipment.

Then for every hazard you identify, assess the likelihood of it becoming a source of harm and the severity of its consequences (risk).

Appendix 3 outlines some biological and chemical hazards that may affect your water supply operation.

The following table outlines some points to consider in identifying hazards:

People

Think about how your water supply operation is managed and the people involved in the day-to-day operation of your supply.

Consider whether you have enough people for your water supply operation to run effectively and whether they have the right skills and experience.

Think about what you’ll do if key operational people are unavailable and who you’ll call on in the event of an emergency.

Source water (Source)

Routinely test your water at source to ensure your treatment processes are adequate, in accordance with the Act and the Drinking Water Quality Assurance Rules.

Assess recent and historical water quality data from the monitoring of source waters.

Think about the events that could happen that affect the quality of your source water - for example: increased rainfall (increases the turbidity of surface water), discharge from an industrial plant upstream or farm run-off (introduces contaminants), seasonal droughts (affect the quantity of source water and concentration of contaminants, trigger toxic algae blooms).

Obtain information from local authorities and others about their knowledge of hazards in the water source and how land use in the catchment may affect your source water.

Note: If there’s more than one source for your drinking water supply, you must understand the potential hazards associated with all of them. Refer to the Source Water Risk Management Planning guidance.

Treatment processes (Treatment)

Test your treated water in accordance with the Drinking Water Quality Assurance Rules (when applicable).

Assess recent and historical water quality data from the operation of your treatment processes.

Think about what could go wrong with the treatment of your drinking water.

Consider how you maintain your treatment system (for example the replacement of your filters or the cleaning of your UV lights and bulbs) and how often you carry out maintenance on your equipment.

Assess whether your equipment is in good condition and whether new technology could provide a better solution or improved reliability in your treatment processes.

Consider what other services your treatment processes depend on. For example, what happens if there’s a power cut?

Distribution processes (Distribution)

Test the drinking water supplied to consumers according to the Drinking Water Quality Assurance Rules.

Assess recent and historic data about the quality of the drinking water supplied to consumers.

Routinely test your water at distribution to ensure that the water complies with standards and is safe for consumers.

Consider what events could cause damage to your distribution network and how you’ll supply an alternative source of drinking water to your consumers in an emergency.

Think about the number of consumers you’re supplying and whether you’ll be able to satisfy the demands of an increased population (for example, from increased housing development or holiday population surges).

Managing the risks by setting controls

Identify the actions, activities, or processes (controls) you will put in place across your water supply operation to manage the likelihood of the hazard or hazardous event occurring and how the control will reduce its impact if it does occur.

The level of protection used to control the hazard should be proportional to the associated risk. High risk events will require multiple barriers/controls in place (from source, during treatment and during distribution to the consumer) to prevent hazards from reaching consumers. There are four types of barriers to contamination:

  1. Preventing hazards entering the source water (Source water barrier)
  2. Removing particles and hazardous chemicals from the water (Treatment barrier)
  3. Killing or inactivating pathogens in the water (Treatment barrier)
  4. Maintaining the quality of the water in the distribution system (Distribution barrier).

Other hazards may have a lower risk threshold and may include controls such as: routine monitoring of your water and your processes; calibration and inspections of your equipment; and routine training to ensure your people have the know-how to use equipment and carry out their roles effectively.

Respond when your water becomes unsafe

Plan how you will respond if, despite your controls, a hazardous event occurs, and you’re unable to provide safe drinking water, or a sufficient quantity of water, to your consumers.

Examples of situations that will result in failure of your controls and require an immediate response include:

  • accidents that increase levels of contaminants to unacceptable levels (for example, chemical spills in catchments or the incorrect dosing of chemicals)
  • natural disasters (for example, fire, earthquakes, lightning damage to equipment)
  • extreme weather events (for example, flash flooding or a drought)
  • equipment breakdown and mechanical failure
  • human action (for example, operator error or sabotage)
  • prolonged power outages.

You need to document an incident and emergency response plan to manage each hazardous event you’ve identified as part of your drinking water safety planning. Your plan should include:

  • your planning to ensure the efficient operation of each plan – for example:
    • step by step detail of your response
    • consultation with the people, community and agencies who are likely to be involved in the response
    • the staff training you have undertaken by running emergency drills
    • pre-prepared communication with key messages such as boil water or don’t drink notices
  • your response actions – for example increased monitoring
  • the responsibilities of internal and external parties
  • the plan for emergency water sources outlining the availability of alternative sources and information on its quality, including how it will be treated
  • communication strategies and plans, including notification procedures for internal staff, consumers, regulatory bodies, and the media. It’s important that you know what events or occurrences must be reported to Taumata Arowai and who will be responsible for making each notification.
  • how you’ll evaluate your response, including a staff debriefing to learn from the experience
  • a reporting plan outlining what needs to be reported, to who and when, including situation reports and debriefs.

DO

Implement the measures to control the hazards

Implement your drinking water safety plan and make sure you’re following it as recorded.

It’s important care is taken at this stage to implement the plan as intended. If the plan is amended because of operational constraints, it’s important time is taken to consider the impact of the changes on the overall plan.

You need to record any changes implemented in the amended plan.

CHECK

Monitor your processes

Check your drinking water safety plan to verify whether you have maintained the appropriate capability of people in your water supply operation to operate plant equipment and that planned maintenance is being undertaken.

Check your supply is being operated as you intended and that your controls across your water supply operation are working effectively. All your controls should be functioning properly, with critical limits and corrective actions to shut down the drinking water supply if the system fails. The critical control limits are monitoring thresholds which if breached indicate that drinking water is likely to be unsafe. The limits need to be monitored frequently so that action can be taken before consumers are harmed. As part of this monitoring, you may find you require additional controls to manage your risk.

Make sure you’re following the Drinking Water Quality Assurance Rules which set out what water quality monitoring you must do and how you should verify that your processes are effective. These rules set the minimum requirements for sampling and verification of controls. Your drinking water safety plan may impose more stringent requirements, or address risks that aren’t specifically controlled through the rules, if you think that is necessary as part of the response to the hazards and risks you've identified.

Analyse water quality results for trends over time and following specific extreme events. Data showing exceedances, major variations, abnormal results, or absences of results is valuable and helps you to recognise potential problems or hazards, as well as any gradual changes or cumulative effects.

Report your results

Record your findings about the activities and performance of your drinking water supply operation. You should keep a record of the following:

  • The water quality monitoring you have undertaken
  • Routine checks and audits of your overall system performance
  • The corrective actions that you have taken, if you may have provided unsafe water or water that does not comply with standards
  • The training your people have undertaken and the upskilling that is required
  • Your maintenance schedule of your infrastructure
  • Any other changes or amendments that you have made to your risk management plan.

ACT

Review your processes

Review your water supply operation regularly to determine the effectiveness of your risk management planning. Think about all aspects of your operation – your people, your processes, and your infrastructure.

Some of the things to consider in your review include:

  • How can you use the information from your operations, monitoring and external sources to improve your processes?
  • Has there been a change in the water supply system or in the context in which the water supply is operated (for example, in the size of the population that the water supply supports)?
  • What sort of risks have you seen?
  • Have there been any incidents or near misses?
  • Has there been any complaints from consumers?
  • What did you do about them and what were the outcomes?
  • Did you manage the risks well?
  • What could have been improved?
  • How are you preparing for future risks?
  • What happened that you cannot explain?
  • What happens more/less often that you expected?
  • What episodic events happened and what were the consequences?
  • How can you further develop the capability of your people?

When reviewing your drinking water safety plan, it will be useful to consider whether you have applied the six principles of drinking water safety.

Principle 1: A high standard of care should be embraced

Are the risk controls that you have set adequate to ensure a reliable, sustained, and sufficient quantity of drinking water? Are there more effective controls that you could implement, that are proportionate to the scale, complexity and risk of your supply? 

Principle 2: Protection of source water is of paramount importance

Have you adequately identified the existence or potential for hazards in your source water? What steps are you taking to ensure that your supply operation isn’t negatively impacting on the source from which you are taking water (for example, by preventing backflow)?

Principle 3: Maintain multiple barriers to contamination

Have you considered all four levels of barrier?

  1. Preventing hazards entering the source water (Source water barrier)
  2. Removing particles and hazardous chemicals from the water (Treatment barrier)
  3. Killing or inactivating pathogens in the water (Treatment barrier)
  4. Maintaining the quality of the water in the distribution system (Distribution barrier).

Principle 4: Change precedes contamination

Does your plan ensure that a review is undertaken if there is an identifiable change to your drinking water supply or its operation?

Principle 5: Suppliers must own the safety of drinking water

As a supplier, have you overseen this risk management process to ensure that it’s fit for purpose and controls risks to the quantity and the safety of the supply in a way that’s proportionate to the scale, complexity and risks associated with the supply?

If you have a large and complex supply and rely on workers and contractors to undertake and implement risk management for your drinking water supply or supplies, how are you assured that risks are being appropriately controlled?

Principle 6: Apply a preventative risk management approach

Do you have a robust ongoing approach to identifying risks to your drinking water supply and ensuring that the risk controls are focused towards preventing harm to people?

It’s also essential to review how you have responded to, and given effect to, Te Mana o te Wai through your drinking water safety plan. The principles above are all conducive to Te Mana o te Wai, but it also introduces consideration of the steps you can take to restore and preserve the balance between water, the wider environment, and the community through a number of freshwater management principles and a hierarchy of obligations between the health and wellbeing of water bodies and freshwater ecosystems, the health needs of people, and other interests.

Ongoing drinking water safety planning

It’s important drinking water safety planning is treated as an ongoing risk management process. You should avoid focusing only on creating a documented plan to provide to Taumata Arowai. The plan is important to provide a reference for your people on how risks should be controlled and set out clear responsibilities for implementation. However, it’s most important that you maintain a process of ongoing monitoring and review to ensure your supply is being operated as you intended and the controls that are in place continue to be effective.

It's good practice to set timeframes for the routine review of your plans, but there are many and varied circumstances that may trigger a review outside of the routine review cycle. Examples of events that may trigger a review include (but aren’t limited to):

  • water quality testing persistently showing exceedances of a MAV despite treatment being in place to control the contaminant
  • an operator identifying a risk or concern that was not previously considered
  • the occurrence of an emergency event that wasn’t previously contemplated or planned for
  • a treatment system outage not being quickly identified despite surveillance controls being in place
  • a change to treatment processes, plant, or equipment
  • a change to key operating personnel.

A review of the plan might reveal a need for only minor adjustments or may result in more substantive or material changes. In effect, your plan becomes a living document. This position is reinforced by the Act requiring an owner of a drinking water supply to provide Taumata Arowai with an updated version of a plan if there are material changes or the plan has been replaced. This is a change from the requirement in previous legislation to update a plan every five years.

When engaging with a drinking water supplier, Taumata Arowai will refer to the drinking water safety plan to help understand how risks associated with a supply are being controlled and how effective the implementation of the controls has been. We’ll also expect to see evidence of ongoing monitoring and review.

APPENDIX 1: Key terms explained

Term

Definition

Drinking water

Water that is used for human consumption; oral hygiene; preparation of food, drink, or other products for human consumption; washing of food utensils (excludes bottled water and water regulated under certain other statutes, including the Food Act 2014).

Source water

The water body from which water is abstracted for use in a drinking water supply (e.g., river, stream, lake or aquifer) and rainwater.

Hazard

An object, substance (including biological, chemical, physical or radiological agents) or a set of circumstances that has the potential to make a drinking water supply unsafe or insufficient to meet the drinking water needs of consumers.

Hazardous event

An incident or situation that can lead to the presence of a hazard in the drinking water supply or prevent sufficient supply of drinking water.

The point at which control of the hazard is lost.

Risk

The likelihood that the hazards will cause harm combined with the severity of the consequences if the hazard does occur.

Controls

A measure or step which is designed to reduce the likelihood or severity of harm.

Also known as “preventative measures”, “mitigation measures” and “barriers to contamination”.

Critical control limits

A monitoring threshold which if breached indicate that drinking water is likely to be unsafe.

Corrective actions

Remedial action taken to correct a problem (for example, the breach of a critical limit) and measures taken to prevent recurrence.

 

 

APPENDIX 2: Examples of a water supply flowchart

A flowchart mapping your water supply system tells the story of your water supply on one page. Here are some examples of flowcharts for supplies of different sizes:

APPENDIX 3: Example of some potential hazards and sources of hazards to a water supply.

Components of the drinking water supply system

Hazard

Potential sources of hazard/hazardous event

SOURCE

Lake, river (surface water)

Bacteria

Animal or human waste entering the source water from farm run-off, wastewater treatment plant discharges, or septic tanks.

Protozoa

Viruses

Chemicals

Chemicals used on farms within the catchment, discharges from industry within the catchment, run-off from roads, vehicles entering water (road accidents), chemicals from natural sources (e.g. deposition of volcanic ash).

Cyanotoxins

Benthic or planktonic cyanobacteria producing toxins (seasonal).

Bore, spring (ground water)

Bacteria

Animal or human waste entering the aquifer from farm run-off, wastewater treatment plant discharges, or septic tanks.

Protozoa

Animal or human waste entering the aquifer from farm run-off, wastewater treatment plant discharges, or septic tanks (typically only in very shallow aquifers, or through defective bore heads).

Viruses

Animal or human waste entering the source water from farm run-off, wastewater treatment plant discharges, or septic tanks.

Chemicals

Chemicals used on farms within the catchment, discharges from industry within the catchment, run-off from roads, vehicles entering water (road accidents), naturally occurring chemicals from soil and rock.

Radiological determinands

Chemical isotopes from soil and rock that are radioactive (alpha and beta emitters including radon) (typically naturally occurring).

Roof

Bacteria

Animal or bird waste entering rainwater system.

Protozoa

Viruses

Typically, only an issue when people have direct access to the roof.

Chemicals

Chemical found in roofing materials, discharge from nearby chimneys.

TREATMENT

Treatment

Chemicals

Failure of the water treatment equipment, impurities in treatment chemicals or unloading of the wrong chemical.

Chemicals added for the purposes of water treatment (e.g. aluminium from aluminium-based disinfection by products)

DISTRIBUTION

Storage (tanks/reservoirs)

Bacteria

Animals or birds able to enter the reservoir, or from human access to reservoirs (e.g. swimmers, divers).

Protozoa

Animals or birds able to enter the reservoir.

Viruses

Human access to reservoirs (e.g. swimmers, divers).

Chemicals

Materials used in the construction of reservoirs, deliberate tampering.

Reticulation systems

Bacteria

Biofilms building up inside the water pipes and entering the supply system when repairs are undertaken or via backflow.

Viruses

Viruses entering system through leaks when repairs are undertaken or via backflow.

Chemicals

Chemicals entering system through leaks, when repairs are undertaken or via backflow. Leaching from pipe materials, joints and fixtures (e.g. lead).