Dry weather | The Water Services Authority

This guidance is intended for small community supplies. However, much of the information is relevant to larger urban supplies and people who provide water for their own domestic use. Planning for floods and other natural hazards is essential.

Know the risks

Reduced availability of source water is the most significant risk to a drinking water supply during a prolonged dry spell.

Supplies that use rainwater collected from a roof are particularly vulnerable. Rainwater stored in tanks can be depleted very quickly if there’s insufficient replenishing rain and water use doesn’t reduce. Bear in mind that water use tends to increase during dry weather.
Surface water sources (particularly streams and rivers) are also vulnerable. Dry weather might reduce stream or river flows to the extent that you can’t meet normal demand for water from your community
A long dry spell might cause the water in a stream, river or lake to drop below the level of your supply intake, cutting off the supply altogether.
While less vulnerable, groundwater sources (bores and springs) can also be impacted. Prolonged dry weather will cause groundwater levels to drop and, depending on the depth to groundwater and the depth of your bore, it might mean you can no longer draw water.
Local authorities might impose restrictions on the amount of water that can be drawn from surface and groundwater sources during dry weather to make sure there’s enough to go round. This might affect the ability of your supply to meet usual demand.
If you’re in a rural area, dry weather is likely to increase demand for irrigation water, placing additional strain on local water sources.
Dry weather simultaneously increases the risk of wildfires and reduces the availability of water for firefighting. Wildfires can cause significant and long-lasting problems for drinking water supplies.

The quality of your source water might also decrease during dry weather.

Reduced flows in streams and rivers will mean that any contaminants (particularly chemical contaminants) and debris are less diluted and slower to move away from the area of your water intake.
A drop in water pressure in your supply can act like a vacuum, sucking things into the pipes (this process is called backflow or infiltration) and increasing the risk of contaminants entering the water.
In some coastal areas, declining groundwater levels can allow saltwater to enter, which can affect the quality of drinking water supplies.
Warm weather increases the risk of algal blooms, including cyanobacteria, in surface water sources. Cyanobacteria can release toxins that are harmful to human and animal health.
The risk of contamination can sharply increase when significant rain follows a prolonged dry spell.

How you can prepare for dry weather

Understand the risk in your area

Learn how often and severely droughts or dry spells have affected your area in the past, particularly during El Niño and La Niña climate cycles. Your regional council, Earth Sciences New Zealand, the Ministry for Cities, Environment, Regions and Transport and the Ministry for Primary Industries (see links below) are good sources of information that can guide your preparations.

The frequency and severity of past dry spells can inform:

the design of your water supply (e.g. the level of your surface water intake, the depth of your groundwater bore, the number and size of your storage tanks) so disruptions from dry weather are minimised
the extent of water restrictions and conservation measures typically applied in your community when dry weather continues
the nature, extent and duration of any alternative drinking water supply that might be needed if your usual supply is disrupted.

It can be helpful to seek advice from a water supply professional on designing your supply infrastructure for typical local conditions.

Plan for the worst case

At worst, dry weather might cut off your water source completely. Your planning should address how you and your community can top up storage tanks or access an alternative drinking water supply if a severe dry spell takes hold. Possible alternative sources are:

water from a registered water carrier ('water tanker')
a back-up source (e.g. a groundwater bore if your primary source is a stream)
bottled water.

Find out about the registered water carriers serving your area and add their details to your drinking water safety plan (DWSP) if you’re following the Drinking Water Quality Assurance Rules or your emergency risk management plan if you’re following an Acceptable Solution. Remember to submit your updated DWSP to us via Hinekōrakooutbound whenever you make changes.

Encourage any large consumers connected to your supply to prepare for possible dry weather and consider how they can reduce their use of drinking water if necessary.

Work together with key decision makers

Get to know the people who make decisions affecting your supply.

For example, it’s a good idea for small community suppliers to know who to contact in their local council for advice or help when dry weather or other natural hazard events impact their supply. A good relationship with your council encourages clear and open communication about emerging risks and the steps that might be taken to address them (e.g. restrictions on surface water takes).

Get to know your local registered water carriers to understand how their services work and how quickly they can supply you if dry weather takes hold.

We also encourage you to talk to the people using your supply about the potential impacts of dry weather and share ways they can conserve water (see below). Have a clear plan in place for communicating any water restrictions to your community.

Working together will ensure everyone has sufficient water that’s safe to drink, even when the weather is challenging.

If dry weather is impacting your water supply

Let people know early

If dry weather conditions in your area are impacting your ability to provide safe and sufficient drinking water, we encourage:

smaller suppliers to inform the right person in their local council as early as possible
council suppliers/water organisations to notify us as early as possible.

Early notification will ensure steps can be taken to keep your community supplied with safe drinking water even if the dry spell continues.

We also encourage you to engage as early as possible with:

the people connected to your supply, so they can begin conserving water (see below for advice you can pass on)
Fire and Emergency New Zealand
anyone else you provide water to (e.g. a water carrier).

Consider increasing the frequency of monitoring and testing

As dry weather takes hold, the quality of your source water and the risk of contaminants entering your supply can change (see Know the risks above).

During a prolonged dry spell, it’s a good idea to ask an accredited laboratory to test samples of your source water and treated water for microbiological (germs) and chemical contaminants more often than usual (i.e. more frequently than required under the Drinking Water Quality Assurance Rules or Acceptable Solution you’re following).

If your water comes from a surface source (river, stream or lake), check more frequently for cyanobacteria, which can thrive during warm weather.

If you supply drinking water domestically for 25 or fewer people and therefore don’t need to follow the Drinking Water Quality Assurance Rules or an Acceptable Solution, you might still choose to have your water tested to ensure the health of your household is protected. Check these guidelines for domestic self-supplies or shared domestic supplies to learn how to keep your water safe at any time, not just during a natural hazard event.

Act fast if contamination is found in treated water

If a laboratory test indicates your treated water is contaminated with E. coli or total coliforms, act fast to protect the health of your community. E. coli or total coliforms indicate that there could be other germs in the water that can make anyone who drinks it very sick.

Take all practicable steps to tell the people who use your water that it's not safe to drink. Issue a consumer advisory (e.g. Boil Water notice) without delay.
Notify us.
Find and fix the cause of the contamination as quickly as possible.

Tips for water conservation

Conserving water is critical during long spells of dry weather. There are simple things you and your community can do every day – no matter what the weather – to help ensure water is available whenever it’s needed.

Here are a few top water-saving tips to pass onto the people who use your supply.

Be aware how much water you use

When standing at the sink to wash hands, wash and prepare food or clean the dishes, it’s easy to lose track of time. Being aware of how much water you’re using makes you less likely to waste it.

Create a community of leak detectives

Encourage the people connected to your supply to report any leaks they spot while they’re out and about, so you can arrange for repairs.

Conserve water in the bathroom

Over 50 percent of the water used at home is in the bathroom so it’s a great place to look for savings.

Fit low-flow taps and shower heads – they’re an easy way to save lots of litres.
Fix the drips. A dripping tap or toilet can waste a lot of water in a day. Check your toilet by placing a few drops of food dye into the cistern and seeing if it makes its way into the bowl without flushing. Until it’s fixed, you could collect the water from a dripping tap and use it on your garden or houseplants.
Stick to four-minute showers. That’s about as long as a song, so it’s also a great excuse to sing in the shower. Turning off the water while you soap up or wash your hair will save those litres too. If water is very scarce, adults don’t need to shower every day.
Turn off the tap when you brush your teeth or shave. A running tap can use up to 10 litres of water a minute.
If your hands have no visible dirt you could use an alcohol-based hand sanitizer to wash them instead of water.
Catch the ‘warm-up water’ from a tap or shower in a bucket (that’s the water that flows when you’re waiting for the tap to run hot). You can use it on your garden or houseplants, or to flush the toilet, wash floors or clean clothes by hand.
Use the half flush on the toilet.

Conserve water in the kitchen

Modern dishwashers are effective without a pre-rinse. Scrape food waste into the compost or a bin to save water. Wash only full loads of dishes using the eco setting if you have one.
Fill the sink rather than running the tap when washing dishes by hand.
Store a pitcher of drinking water in the fridge rather than waiting for the tap to run cold each time.
Use a bowl of water when washing vegetables rather than running the tap. You can use the leftover water on your houseplants or the garden.

Conserve water in the laundry

Use your washing machine only when you have a full load of laundry.
Wash clothes only if they really need it!
Consumer research shows that front loading washing machines use considerably less water than top loaders.

Conserve water in the garden

In summer, around 18 percent of household water use happens outside. There are lots of ways you can save water in and around your garden.

Sweep your paths rather than hosing them down.
Mulch your garden by putting pea straw, dry leaves, grass cuttings or wood chips around your plants. This is like putting a blanket around your plants that helps reduce evaporation from the soil by up to 70%.
Add a nozzle to your hose before you wash your car or tend to your garden. This can help you use less water.
Water using a watering can rather than a hose or sprinkler. This uses less water and it’s easier to get the water right where it’s needed most.
Water plants in the early morning or evening. This reduces the amount of water taken away from the plants by evaporation.
Collect rainwater to use to water your garden. But make sure you don’t drink untreated rainwater! Untreated water can contain germs that could make you sick.

More information

Earth Sciences New Zealand maintains online tools that track developing drought conditions over different timeframes.

Online tool	What it's for
Drought Forecasting Dashboardoutbound	Shows areas where dryness or drought are predicted over the next 35 days
New Zealand Drought Monitoroutbound	Tracks drought conditions across New Zealand
Seasonal Climate Outlookoutbound	Provides air temperature, rainfall, soil moisture and river flow predictions for the coming season

You can also learn more about drought and El Niño and La Niñaoutbound more generally on Earth Sciences New Zealand’s website.

The Ministry for the Environment has produced information on expected changes to the frequency and severity of droughts and floodsoutbound as a result of climate change.

For rural communities, the Ministry for Primary Industries has produced guidance on preparing for El Niño and dealing with drought conditions.outbound

Health NZ has produced guidance on saving water and keeping healthyoutbound during a natural disaster.