Topic 5: The Water Cycle and Water Insecurity

Lesson 1-

1. The operation of the hydrological cycle at a global scale

Good websites: https://geographyas.info/rivers/drainage-basins-and-the-hydrological-cycle/

https://garsidej.wordpress.com/a-level-new-edexcel-9geo/paper-1/the-water-cycle-and-water-insecurity/

**** These booklets are designed lesson by lesson, any spaces can be used by you to make mini notes alongside diagrams for example. These booklets are to be used together with power points and for information to revise from.

1.The Global Hydrological Cycle at a Global Scale

• Overview

• Water plays a key role in supporting life on earth. The water cycle operates at a variety of spatial scales and also at short- and long-term timescales, from global to local. Physical processes control the circulation of water between the stores on land, in the oceans, in the cryosphere(is the frozen water part of the Earth system- frozen parts of the ocean, such as waters surrounding Antarctica and the Arctic), and the atmosphere. Changes to the most important stores of water are a result of both physical and human processes.

• Water insecurity is becoming a global issue with serious consequences and there is a range of different approaches to managing water supply.

The Hydrological Cycle

• Earth's water is always in movement, and the natural water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Water is always changing states between liquid, vapour, and ice, with these processes happening in the blink of an eye and over millions of years.

• Global water distribution

• For an estimated explanation of where Earth's water exists, look at the chart on the next slide. By now, you know that the water cycle describes the movement of Earth's water, so realize that the chart and table below represent the presence of Earth's water at a single point in time. If you check back in a thousand or million years, no doubt these numbers will be different!

• Notice how of the world's total water supply of about 332.5 million cubic miles of water, over 96 percent is saline. And, of the total freshwater, over 68 percent is locked up in ice and glaciers. Another 30 percent of freshwater is in the ground. Fresh surface-water sources, such as rivers and lakes, only constitute about 22,300 cubic miles (93,100 cubic kilometers), which is about 1/150th of one percent of total water. Yet, rivers and lakes are the sources of most of the water people use everyday.

KEY TERMS TASK

• Water is stored in rivers, streams, lakes and groundwater in liquid form (the visible part of the hydrological cycle)

• Water stored in the soil and vegetation (the invisible part of the hydrological cycle)

• The rate of flow between the stores

• Areas of the Earth where the water is frozen into snow or ice

• Reservoirs where water is held, such as oceans

• The physical mechanisms that drive the fluxes of water between the stores

The Hydrological Cycle on a Global Scale

_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Why is the Hydrological Cycle a closed system and what are the links with solar and gravitational energy? ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

_________________________________________________________________________________________________________________________________________________________________________________________________________

The Hydrological Scale facts______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

STORES (as per the table p3 Hodder)On your sheet, look at 1, 2, 3 and 4. Decide which of the statements in the boxes below correspond to the numbers on the diagram. Write them below:

4

2

3

1

Global Hydrological Cycle

Stores and flows/fluxes

Store Volume (10(3) KM(3)

% of total water Percentage of fresh water

Residence time

1,335,040 96.9 0 3,600 years

26,350 1.9 68.7 15,000 years depending on size

15,300 1.1 30.1 Up to 10,000 years for deep groundwater; 100-200 years for shallow

178 0.01 1.2 2 weeks to 10 years; 50 years for very large scale

122 0.01 0.05 2-50 weeks

13 0.001 0.04 10 days

1. Which is the world’s largest water store and what percentage of the world’s water is contained in it?

2. The atmosphere is the smallest store of water, why might this be?

3. Look at the residence time column. What does that tell you about the different stores of water?

Water Stores

Residence Time (and its link with non-renewable water (p4 Hodder

______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Fossil Water (p 4 hodder) is not considered to be a renewable resource, why is this?_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Annual Fluxes

Use the following data to construct a fourth data column for ‘Accessible Surface Freshwater’ (see page 4 Hodder if you get stuck)Describe the distribution of water in the figure you have just drawn.

Read through the information and highlight the key terms or data.

How accessible is water for human life support? Homework (P4&5 Hodder)__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

____________________________________________________________________________________________________________________________________________________________________________________________________

Global Hydrological Cycle Heads & Tails – Homework

Systems approach Areas of the Earth where water is frozen into snow or ice

Stores These approaches study the hydrological phenomena by looking at the balance of inputs and outputs, and how water is moved by stores and flows

Fluxes Water is stored in rivers, lakes and groundwater in liquid form

Processes The physical mechanisms that drive the fluxes of water between the stores

Cyrosphere Reservoirs where water is held, such as the oceans, lakes etc.

Blue water Water stored in the soil and vegetation

Green water The rate of flow between the stores

Precipitation The diffusion of water from vegetation into the atmosphere, involving a change from a gas to a liquid

Evaporation The change in state of water from a liquid to a gas

Residence time Ancient, deep groundwater from former pluvial (wetter) periods

Fossil Water The slow transfer of percolated water underground through pervious or porous rocks

Transpiration The movement of water in any form from the atmosphere to the ground

Groundwater flow The average times a water molecule will spend in a reservoir or store