PART 3-LESSON 1Salinity of soils and water

INTRODUCTION

Salinity is the word used to describe the salt content of soil or water. When this salt content is excessive it degrades water quality and land productivity.

Soluble salts are often found in water and soil but usually not in sufficient concentrations to affect plant and animal survival.

INTRODUCTION

Salinity is a growing concern around the world. Much of the worlds farm land is becoming to salty for crops to tolerate.

INTRODUCTION

Soil salinity is associated with increased salinity in rivers. Today scientists understand what causes these problems but is it to late to fix the damage already caused?

WASHING SALT FROM THE SOIL

Australia naturally has salinity problems. Visit the site below to learn more about this topic.

http://www.napswq.gov.au/publications/brochures/salinity.html

WASHING SALT FROM THE SOIL

Great inland seas and inward drainage of great river basins have produced areas of naturally saline soil in Australia. Lake Eyre and the south western wheat belt of Western Australia are examples of such places.

WASHING SALT FROM THE SOIL

The salinity problem has steadily increased because of agricultural practices inappropriate for the Australian environment.

Farmers within the Murray-Darling Basin are culprits to this problem. For example:

THE MURRAY-DARLING BASIN

Irrigation Salinity Diverting water for irrigation causes areas of the

river to be lower than normal and increases the water table under the areas of irrigation. The salinity rises in these areas and if water from these areas makes its way back to the river via run-off increases the salinity of the river system.

THE MURRAY-DARLING BASIN

Irrigation Salinity Damming areas of the river can encourage

salinity because these damns are not flushed out allowing salt to accumulate in these areas.

THE MURRAY-DARLING BASIN

Dryland Salinity: Huge amounts of land has been cleared for

farming and grazing. Replacement crops with shallow root systems allows water to penetrate down to the water table causing it to rise. This rising water table brings dissolved salts with it.

REFLECTION

Dryland Salinity Caused by the removal of native plants by

overgrazing or clearing land for non native plants

When large areas are cleared or replaced with plants with shallow root systems water can penetrate through the soil carrying dissolved salts and minerals which would have otherwise been absorbed by plants into the water table. As a result, more water reaches the water table which causes it to rise and carry dissolved salts with it.

REFLECTION

Irrigation Salinity: This is caused by over irrigation. The additional

irrigation water causes the underground water-table to rise, bringing salt to the surface. When the irrigated area dries and the underground water-table recedes, salt is left on the surface soil. Each time the area is irrigated this salinity process is repeated.

HOMEWORK

Read pages 119-120 HSC Spotlight Text

Update Electronic Vocabulary

Complete DOT Point 3.1 pg 61

PART 3-LESSON 2Salinity of soils and water

COMBATING SALINITY

Salinity has become such a concern communities and governments have come together to combat the problem. Salinity contributes to agricultural losses and environmental damage so this should be a concern for us all.

COMBATING SALINITY

Different forms of salinity need different management strategies.

Any strategy should involve managing the movement of ground water through the subsurface

COMBATING SALINITY

Local farmers can use prevention strategies that focus on reducing the amount of water reaching the water table. For example:

Ensure vegetation covers the entire catchment Constant monitoring of the water table depth Budgeting only appropriate amounts of water to be

used for irrigation Use drip irrigation systems to control the amount of

water being used Using deep rooted crops Decrease fallow time (the time between harvesting

one crop and planting another)

COMBATING SALINITY

State Governments and Councils can also help combat salinity by implementing strategies on a larger scale. For example: Designing and building drainage systems to

divert water before it reaches the water table. Surface drainage management (collecting and

controlling water entering and leaving an area to minimise infiltration)

Draw up water from the water table through bores to keep it at a level below root systems. The saline water drawn up can be collected in evaporative basins or disposed of appropriately.

COMBATING SALINITY

The only way to effectively combat this problem is to all work together. We all need to learn from our mistakes and take the appropriate steps to fix the problems.

ACTIVITY

Discuss Activities 3.5 and 3.6 (HSC Spotlight Text page 121-123) together

HOMEWORK

Read Pages 120-122 HSC Spotlight Text

Update Electronic Vocabulary

Complete DOT Point 3.2

PART 3-LESSON 3Salinity of soils and water

CASE STUDY

In this lesson we are going to process a case study to reduce dryland salinity on a Temora Farm. Follow the steps below to access the study:

1. Go to Earth Wiki2. Click on ‘Useful Links’3. Click ‘

http://www.hsc.csu.edu.au/earth_environmental/’4. Under the ‘CORE’ heading click on ‘Caring for our

country’5. Under the ‘Students’ heading, click on ‘identify data

sources and gather, process and present information as a case study of a successful rehabilitation program of a salt-affected area, including’

6. Click on ‘A case study to reduce dryland salinity on a Temora farm’

CASE STUDY

Read and discuss the Case Study

If time, complete DOT Point 3.3 together (Otherwise its homework)

HOMEWORK

Complete ‘To Think About’ pg 124-126 HSC Spotlight Text

Complete DOT Point 3.3 pg 62