The water cycle – timeline
In the future, water may be our most valuable commodity. Understanding the water cycle – the continuous movement of water through the Earth's upper crust, surface and atmosphere – is crucial.
The water cycle involves events that happened millions of years to milliseconds ago. Find out more about these unpredictable forces in this timeline.
20,000,000 BC – Polar ice sheets growing
It is estimated that the ice sheets at the poles start growing, trapping the Earth’s atmospheric gases in the ice at that point in time.
18,000 BC – Kapua peat bog begins accumulating
The Kapua peat bog in the Waikato begins accumulating and will be about 14 metres thick with plant material in 2009.
140 years – Groundwater intake of Lake Rotorua
Water that is infiltrating the ground around Lake Rotorua will take approximately 140 years before it enters Lake Rotorua through the Hamurana Stream at about 3 m3/s.
100 years – Lake water storage
Water can be stored in lakes from a matter of a day or two to maybe 100 years in the deepest lakes.
100 years – 100-year flood event
The term ‘100-year flood’ is used in an attempt to simplify the definition of a flood that, statistically, has a 1% chance of occurring in any given year. It doesn’t mean that there can’t be two 100-year flood events in 1 year.
Whanganui floods in 2015
In June 2015, the Whanganui River overflowed, flooding many farms and businesses in the area. The aim of the Resilience to Nature’s Challenges National Science Challenge was to enhance resilience to natural disasters such as this.
75 years – Rivers in the sea
Ocean currents are like huge rivers that move large amounts of water around the Earth. The Earth’s circumference is 24,000 kilometres, so if you were travelling on a boat at 1 km an hour it would take you 75 years to go around the Earth at that speed.
10 days – Water in the atmosphere
If all the water that is stored in the atmosphere rained out and fell to the surface, we would have about 27 millimetres of water on the surface and it would rain for approximately 9–10 days.
Days–seconds – Weather scales
Weather scales range from the synoptic scale (hundreds to a few thousand kilometres in distance over a few days), to the mesoscale (individual storms), the microscale (hydrological processes over only a few hours) and the misoscale (wind gusts that change minute by minute or even quicker).
Age of water
In this video, 4 New Zealand scientists – Dave Campbell, Louis Schipper, David Hamilton and Keith Hunter – talk about what it means if we say that the water cycle is dynamic and changing, highlighting variables like time and space.
The scientists point out that changes can sometimes take very long periods of time.
Keith explains that sometimes water will be stored for long periods, such as in a lake or in the groundwater. When water is stored like this, we call it a reservoir. The largest reservoir is the Earth’s oceans, which cover two-thirds of the Earth’s surface. How long water stays in a reservoir depends on factors like the size of the reservoir and movement within it, and in and out of the reservoir. How long water stays in a reservoir is called residence time.
Louis explains that sometimes not only does the water move, but it can carry nutrients with it too. Water moving through the soil will take soil particles and any chemicals with it, and these can then enter the groundwater.
Related content
Discover more about the water cycle, this article includes the interactive Dynamic and complex: the global water cycle. It describes the exchange of water in every form between the Earth’s systems and is part of what makes the Earth so unique.
Activity ideas
These activities can help students model aspects of the water cycle.
Follow the water droplet takes a literary approach to the water cycle.
Building a water cycle models evaporation and precipitation.
Constructing an aquifer model explores the link between precipitation, surface and ground water.
What is the Earth system? is a teacher resource that explains the concept of systems.
Tie it all together with a unit plan featuring resources in Water on the go or use the interactive Learning about the water cycle.
