Water Cycle | How the Hydrologic Cycle Works

Summary

The video explores Earth's ancient and continuous water cycle, highlighting how water moves through various stages: precipitation, collection, runoff, interception, infiltration, percolation, discharge, transpiration, evaporation, and condensation. Experts discuss the importance of this cycle for life on Earth, the various forms water takes, and its constant movement through different environments, from oceans and rivers to underground aquifers. The water cycle's complexity and significance are emphasized, showcasing its role in sustaining life and influencing natural processes.

Takeaways

• 🌍 All of Earth's water is part of a continuous cycle, with no new water being created or lost.
• 💧 Freshwater is millions of years old, continuously recycled through the environment.
• 🌱 The presence of a perfect water cycle is fundamental to the existence of life on Earth.
• 🔬 The water cycle is a complex process studied by various scientific disciplines, including earth scientists, hydrologists, geologists, and biogeochemists.
• 🌧️ Precipitation is the initial phase of the water cycle, where water falls to Earth in various forms such as rain, snow, hail, and even fog or mist.
• 🌊 A significant portion of Earth's water is found in oceans, ice sheets, glaciers, and other large water bodies.
• 🌿 Vegetation plays a role in the water cycle by intercepting precipitation and contributing to transpiration.
• 🏞️ Water not absorbed by the soil can run off, especially on impermeable surfaces or when the soil is saturated.
• 🌱 Water that infiltrates the soil can percolate down to bedrock and even reach deep underground aquifers.
• 🌡️ Evaporation is the process by which water turns from liquid to gas, influenced by the sun's heat.
• 🌬️ Transpiration is the release of water vapor from plants, an important part of the water cycle.
• 🌧️ The cycle is completed as water vapor in the atmosphere condenses into clouds, leading to further precipitation.

Q & A

What is the significance of Earth's water being millions of years old?

Earth's water being millions of years old signifies that the water we have today is the same water that has been cycling through the environment for millions of years. This ancient water is part of a continuous cycle of precipitation, collection, evaporation, and condensation.

What role does the water cycle play in sustaining life on Earth?

The water cycle is essential for sustaining life on Earth because it ensures the continuous movement and availability of water in various forms, which is crucial for all living organisms.

What are the two key components of the water cycle?

The two key components of the water cycle are 'flows' and 'stores.' Flows refer to the movement of water between different stages, while stores refer to places where water is held, such as oceans, glaciers, and underground aquifers.

How does water move from the atmosphere to the Earth's surface?

Water moves from the atmosphere to the Earth's surface through precipitation, which can occur in various forms including rain, snow, hail, and mist.

What happens to precipitation that falls directly into the ocean?

Precipitation that falls directly into the ocean becomes part of the surface ocean water, where it can be mixed by wave and wind action into ocean currents.

How does vegetation intercept precipitation?

Vegetation intercepts precipitation when raindrops are caught by leaves, branches, and other parts of plants before reaching the ground, similar to how a football pass is intercepted by a player.

What is the process of percolation in the water cycle?

Percolation is the process by which water infiltrates the soil surface and moves downwards through the soil and rock particles, eventually reaching underground aquifers.

What is evapotranspiration?

Evapotranspiration is the combined process of evaporation from soil and water surfaces and transpiration from plants, where water is drawn up through plant roots and released into the atmosphere from the leaves.

How do water molecules transition from a liquid to a gas in the water cycle?

Water molecules transition from a liquid to a gas through evaporation, which occurs when the heat of the sun causes water to vaporize and rise into the atmosphere.

What triggers precipitation in the water cycle?

Precipitation is triggered when water droplets in clouds collide, merge, and grow bigger and heavier until they become too heavy to remain suspended in the air, causing them to fall as rain, snow, sleet, or hail.

Outlines

00:00

🌊 The Eternal Water Cycle

This paragraph introduces the concept of Earth's water cycle, emphasizing its perpetual nature with water being recycled through various forms and stages. It explains that all water on Earth today is as old as the planet itself, highlighting the continuous loop of precipitation, collection in various bodies of water, and eventual return to the atmosphere through evaporation. The paragraph also underscores the importance of the water cycle to life on Earth and its complexity, which is studied by various scientific disciplines. It introduces the basic components of the water cycle, including precipitation, the role of clouds and atmospheric humidity, and the vast storage of water in oceans, glaciers, and underground aquifers.

05:01

💧 The Dynamics of Water Movement

This paragraph delves into the mechanisms of water movement within the water cycle. It describes precipitation as the starting point, detailing the different forms it can take such as rain, snow, hail, and even fog and mist. The paragraph explains how water from precipitation either becomes part of the ocean currents or makes its way into rivers and streams through runoff and infiltration. It also discusses the role of vegetation in intercepting precipitation and the process of water percolating through the soil into underground aquifers. The paragraph further explains the process of evaporation, including the transformation of water into vapor due to heat, and the subsequent condensation into clouds, which completes the cycle by leading to more precipitation. The summary concludes with a list of key terms that encapsulate the various stages of the water cycle.

Keywords

💡Water Cycle

The Water Cycle is the continuous movement of water on, above, and below the surface of the Earth. It is a fundamental concept in the video, illustrating the journey water takes from the atmosphere to the Earth's surface and back again. This cycle includes processes such as evaporation, condensation, precipitation, and the storage of water in various forms. The video emphasizes its simplicity and complexity, highlighting how it supports life on Earth and is a subject of ongoing study by scientists.

💡Precipitation

Precipitation is defined as water falling from the atmosphere to the Earth's surface, occurring in various forms such as rain, snow, hail, and sleet. In the context of the video, precipitation is a key part of the Water Cycle, where water returns to the Earth, feeding into rivers, oceans, and other bodies of water, and contributing to the continuous circulation of water.

💡Evaporation

Evaporation is the process by which water changes from a liquid to a gas or vapor, primarily driven by the heat of the sun. The video script uses the example of water disappearing from a bowl left outside on a sunny day to illustrate this concept. Evaporation is crucial for the Water Cycle as it returns water to the atmosphere, where it can later condense to form clouds.

💡Transpiration

Transpiration refers to the process by which plants release water vapor into the atmosphere through their leaves. The video explains that plants pull water up from the ground through their roots and release it back into the air, contributing to the overall Water Cycle. This process is part of the larger concept of evapotranspiration, which includes evaporation from soil and water surfaces.

💡Infiltration

Infiltration is the process where water seeps into the soil after precipitation, as opposed to running off the surface. The video describes how water can percolate through the soil if the ground is not saturated, eventually reaching deeper layers and even underground aquifers. This process is essential for replenishing groundwater and maintaining the Water Cycle.

💡Runoff

Runoff is the movement of water over the Earth's surface, typically occurring when the ground is impermeable or saturated, preventing further infiltration. The video mentions that runoff can occur over hardscapes like asphalt or concrete, or when the soil is too wet to absorb more water, leading to water flowing into rivers, lakes, or other bodies of water.

💡Interception

Interception in the context of the Water Cycle refers to the process where vegetation, such as plants and trees, captures precipitation before it reaches the ground. The video likens this to a football player intercepting a pass, illustrating how leaves can collect raindrops, thereby reducing the amount of water that directly hits the ground.

💡Percolation

Percolation is the movement of water through the soil, from the surface down to the underlying rock and possibly into deeper aquifers. The video uses the analogy of water percolating through coffee grounds to describe this process, emphasizing the role of gravity in drawing water downward through the soil layers.

💡Condensation

Condensation is the process where water vapor in the atmosphere cools and changes back into liquid form, resulting in the formation of clouds. The video script explains that as evaporated water molecules rise and cool, they combine with particles in the air to form visible clouds, which are a critical part of the Water Cycle as they lead to precipitation.

💡Aquifers

Aquifers are underground layers of water-bearing permeable rock or unconsolidated materials from which groundwater can be extracted. The video mentions the Ogallala-High Plains Aquifer as an example, highlighting how these natural storage systems hold significant amounts of water that is part of the Water Cycle, even though the water in aquifers can take a very long time to replenish.

💡Hydrologists

Hydrologists are scientists who study the distribution, movement, and quality of water throughout the Earth's hydrosphere. The video script points out that even though the Water Cycle is simple enough for children to understand, it is complex enough that hydrologists, along with other earth scientists, continue to study its various parts and processes.

Highlights

All the water on Earth today is the same water that has ever been on the planet, emphasizing the continuous nature of the water cycle.

Freshwater is millions of years old, highlighting the age and recycling of water through the water cycle.

The water cycle is fundamental to life on Earth, as explained by Anna Michalak.

The simplicity and complexity of the water cycle are both acknowledged, with advanced scientists still studying its processes.

Martha Conklin expresses the fascination with the water cycle and its ubiquitous yet poorly understood nature.

The water cycle is summarized as a series of flows and stores, indicating the movement and storage of water in various forms.

Tom Harmon discusses the presence of water in the atmosphere, even on dry days, through relative humidity.

Thompson explains the vast amount of water in oceans, ice sheets, glaciers, and other storages, emphasizing the scale of Earth's water.

Water is described as always in flux and moving, with various forms of movement named in the water cycle.

Precipitation is defined as the process of water falling onto the Earth's surface in various forms such as rain, snow, and hail.

Conklin describes the path of snowmelt into streams and rivers, illustrating a key component of the water cycle.

Harmon uses the analogy of football to explain how vegetation intercepts precipitation before it reaches the ground.

Thompson details how precipitation infiltrates the soil and percolates into the ground, contributing to groundwater.

Conklin mentions the long time it takes for some water to move through fractured rock, highlighting the slow process of water movement.

The process of water returning to the atmosphere through evaporation is explained, including from wet surfaces and through respiration.

Michalak describes the concept of evapotranspiration, where plants release water back into the atmosphere.

Thompson concludes with a summary of the water cycle's key processes, including precipitation, collection, runoff, and more.

Transcripts

♫MUSIC♫

ANNE THOMPSON: All the water on Earth today, every drop, is all

the water there has ever been on the planet. Freshwater is

actually millions of years old. The same water, flowing in a

continuous loop- falling as rain and snow from clouds to the

Earth's surface, running in rivers, pooling in ponds,

flowing from faucets, irrigating crops, traveling through plants,

generating power, eventually evaporating into the air and

condensing into clouds again.

ANNA MICHALAK: Why is there life on Earth? The reason

there is life on Earth is because Earth has this

perfect water cycle.

THOMPSON: The Water Cycle, so simple even small children

understand the basics, yet so complex, the most advanced earth

scientists, hydrologists, geologists, and biogeochemists

are studying every part and process.

MARTHA CONKLIN: The Water Cycle is fascinating. It's something

that's around us all the time, and yet we don't

really understand it.

THOMPSON: How to summarize what is known about the Water Cycle?

With two words- flows and stores. The Water Cycle is a

series of flows of water between various water stores or

storages. Clouds in the atmosphere...

TOM HARMON: There's always a little bit of water in the

atmosphere. We talk about relative humidity- it's a humid

day, it's a dry day- either way, there's water, sometimes a

little, sometimes a lot.

THOMPSON: There's a lot of water in the oceans – 70% of all

the water on Earth, in the ice sheets and glaciers - two-thirds

of all the fresh water on Earth, in the snow packs atop mountains

like the Sierra Nevada, in the Great Lakes, in rivers and

streams, in reservoirs and watersheds, in wetlands, in the

soil, in and on plants and trees rooted in the soil, and beneath

the soil, in water tables and underground aquifers like the

Ogallala-High Plains, which runs underneath parts of eight

states, from South Dakota to Texas. All this storage is

temporary. Water, in all its forms, is always in flux and

always moving. And there's a name for every kind of movement

in the Water Cycle starting with precipitation.

MICHALAK: Precipitation is the process of water falling onto

the surface of the Earth. You can have precipitation in many

forms- rain, snow, hail.

THOMPSON: Rain is falling water in liquid form. Snow,

ice, hail and sleet are falling water in solid, or frozen form.

Fog and mist? Falling water in gas or vapor form. Precipitation

that falls directly into the oceans becomes part of surface

ocean and can be churned by wave and wind action into ocean

currents. Rain and snow that falls directly on rivers and

streams becomes one part of stream flow. Rain that falls

onto land takes a different path to the river as does the

snow and ice that falls and collects on mountaintops

when temperatures warm.

CONKLIN: When snow melts, some of it runs through the snowpack

and goes into small streams, tributaries that feed

into large rivers.

THOMPSON: What about the precipitation that falls on and

over land? Some is intercepted by vegetation -

plants and trees.

HARMON: Like you might imagine, someone in a game of football

intercepting a pass, these are raindrops trying to come to the

ground, and leaves on the tree intercept them before they

hit the ground.

THOMPSON: And the precipitation that does hit the ground? It can

run off if the ground is hardscaped - covered with

asphalt or concrete- or if the soil is too wet, or saturated to

absorb more water, like an over soaked sponge. Otherwise,

precipitation infiltrates the soil surface, percolates

into the ground.

HARMON: Think of it as the water percolating through your

coffee grounds in the morning. Gravity continues to pull it

downwards so it will move through.

THOMPSON: Through the topsoil, into spaces between soil and

rock particles, down to bedrock, and further, into fractures,

into deep underground aquifers. Even groundwater here

is moving sideways, or laterally, discharging toward a

river, lake or the sea, generally the deeper the flow,

the slower the flow.

CONKLIN: Some of that fractured water might take a very long

time, thousands to millions of years, to get out.

THOMPSON: And how does water get back out into

the atmosphere? It evaporates, is turned from a liquid

into a gas or vapor, by the heat of the sun.

MICHALAK: If you put a bit of water into a bowl and you set it

outside on a sunny day, it's going to disappear. It's still

water, it's just in the form of a gas rather than in the form

of a liquid.

THOMPSON: Water evaporates from every wet surface – even from

wet air. Some rain and snow evaporates into the air while

falling. Water evaporates through our respiration and

perspiration and from plants, through transpiration. Trans

means through or across. Plant roots draw up groundwater.

MICHALAK: And plants pull that water up through their stems

into their leaves and then release it back out

through evapotranspiration.

THOMSPON: Evaporanspiration, a spelling bee worthy term for

evaporation from soil and water surfaces, plus transpiration

from plants. Evaporated water molecules are tiny enough to

flow into the air. Mix with smoke and dirt particles in the

atmosphere. Cool, condense, into visible masses of water vapor –

clouds. Winds move clouds into colder air, water droplets

collide and merge, grow bigger and heavier, until they

are so heavy, they fall again as rain or snow, sleet or hail.

Precipitation. Collection. Runoff. Interception.

Infiltration. Percolation. Discharge. Transpiration.

Evaporation. Condensation. The Water Cycle.

♫MUSIC♫