T OPIC 5-L ESSON 1 Maintenance of environmental flows and natural processes in water

TOPIC 5-LESSON 1Maintenance of environmental flows and natural processes in water

INTRODUCTION

How important is the management of water? Who controls the water in our river? Should this be controlled? In this topic we will discuss why water management is important feature of society.

INTRODUCTION

Farmers need water, especially farmers in dry countries like Australia. However, there needs to be a plan in place so as to ensure those farmers are using it efficiently.

INTRODUCTION

The misuse of water in agriculture can cause huge problems, many of which we have already discussed. Water is important to us all and must be managed appropriately.

EFFICIENT USE OF WATER FOR IRRIGATION

Irrigation is the artificial supply of water to plants and soil. It is one of the most important uses of water. About 60% of the worlds fresh water is used for irrigating.

Without irrigation, large scale farming would not be possible and there would almost certainly be a shortage of food.


Irrigation makes farming possible in dry places like Menindee and much of the Australian continent.

Unfortunately irrigation is not always efficient. For example, a lot of irrigation methods lose large amounts of water through evaporation.

What are some irrigation methods farmers use?


Below are the two most common methods of irrigation used in Australia. What are the positives and negatives of each? Overhead irrigation Drip Irrigation


Overhead Irrigation Positives

A wide are can be covered Control of the depth of water seeping into the ground Small effect on overland water flow

Negatives Run-off or tail water (this excess water can carry

nutrients and pesticides away from the farming area) Large evaporation rates Land clearing


Drip Irrigation Positives

Good control of water No run-off or tail water (better conservation of soil

which reduces the chances of nutrients and pesticides being carried away into other areas)

Little or no percolation to the water table (reduces the likelihood of irrigation salinity occurring)

No loss due to evaporation Delivery of water straight to roots

Negatives More expensive to install (will save costs on water over

the long run)


What’s your opinion about farming irrigation methods?

Using the most efficient irrigation methods can make a big difference to farmers but also to the whole community.


The government monitors water usage by issuing licenses to consumers for specific amounts of water per year.

What impact do you think this has on the community? Other farmers?


Should diverting water into water courses be taken into consideration in the allocation to farmers? What about people who pump water from bores? Should they also be issued with a license?

Why or why not?


Licensing enables governments and Landcare groups to monitor and control the volume of water flowing into and out of the environment.

This allows for the prediction of ground water movement and depths and also help prevent salinity problems.


Does this effect your community in any way? How? Do you think it’s important? Why/why not?

HOMEWORK Read pages 137-138 HSC Spotlight Text

Update electronic vocabulary


THE EFFECTS OF DAMS

Dams are important and essential to our society because they provide fresh water reservoirs for us to use. Can you think of an example of such a dam?

THE EFFECTS OF DAMS

Did you think of the Murray-Darling Basin as a dam? Well it is. The Murray-Darling Basin stores water for irrigation as well as domestic use.

THE EFFECTS OF DAMS

Such dams are essential for us, but what are the effects on the environment? This has become a major issue and will continue to be so for a long time.

THE EFFECTS OF DAMS

Dams are a barricade which restricts the natural movement of organisms up and down the river. They regulate and control river levels which stop natural flooding processes. This has been addressed by introducing “environmental flows” (artificial inputs of water) into rivers and other areas that miss out on natural flows because of upstream damming.

THE EFFECTS OF DAMS

Environmental flows are designed to: Mimic natural flow variations of the river Maintain natural water levels in pools, creeks

and rivers during periods where the river is not flowing

Maintain river height within natural limits to ensure growth and reproduction of natural flora and fauna

Ultimately environmental flows replace or stimulate chemical, geological and ecological processes essential to a healthy river system.

THE EFFECTS OF DAMS

Many people believe these environmental flows are a waste of water?

What do you think?

HOMEWORK

Read pages 138-139 HSC Spotlight Text


Complete DOT Point 5.1.2 pg 71


STORMWATER TREATMENT

Effective stormwater treatment is another essential part of maintaining the health of our waterways.

What is stormwater?


Stormwater is rainwater and anything it carries which runs into our waterways untreated.

What are some of the things which might be carried in stormwater? Why would it be important to manage this?


Stormwater is managed and treated by local councils to reduce the likelihood of pollutants entering our local waterways.

How do you think they might do this?


Floating barrier booms trap large solid components floating on the surface of water which are then disposed of appropriately. These are positioned at the mouth of creeks to prevent rubbish from entering the waterways.

What might these fail to do?


Gross pollution traps also capture surface rubbish however they are placed at the point of entry of stormwater into the creek. This prevents the rubbish from even entering the creek capturing objects which may have become submerged which the floating barrier would have missed.


Both methods depend on regular maintenance and cleaning of the devices.

Are there any pollution traps in your area? Why/why not?


The best way to ensure pollution free storm water is to prevent pollution in the first place. There are three categories of pollutants:

Litter (cigarette butts, plastics, paper, bottles and cans

Chemicals (detergents, solvents, oil, pesticides and fertilisers

Natural (leaves, grass clippings, animal faeces)

How do you think councils prevent these things from entering our waterways?


The effects of such items entering our waterways are: Excess sediments and soil can lesson the amount

of light that penetrates through water reducing photosynthesis.

Sediments can also clog fish gills Organic matter removes oxygen from the water Litter such as cigarette butts can add toxins to

waterways Bacteria associated with pollutants affects

humans and often leads to the closure of beaches and other waterways for recreational use

HOMEWORK

Read pages 139 HSC Spotlight Text


Complete DOT Point 5.1


SEWAGE TREATMENT

Another type of waste water that needs to be treated is sewage. Human wastes, paper and vegetable matter which is 99.9% liquid, .01% solid.

SEWAGE TREATMENT

Where does home sewage come from?

Toilets 40%

Bathing 30%

Laundry 15%

Kitchen 10%

Miscellaneous 5%

SEWAGE TREATMENT

It is essential that sewage be treated because it harbours very dangerous bacteria that can impact on the health of living organisms including humans.

SEWAGE TREATMENT

The treatment of sewage in NSW has three stages:

Primary Secondary Tertiary

What do you think happens in each stage?

SEWAGE TREATMENT

Primary Stage:

Removal of large particles and objects by screens

Removal of suspended matter via the process of sedimentation (solids are allowed to settle to the bottom)

This part of the treatment process removes

about 30% of the total pollutants and about 30% of the organic matter that consumes oxygen as it decays

SEWAGE TREATMENT

Secondary Stage

Bacteria consumes more of the total pollutants and organic matter

As a result a sludge settles to the bottom The liquid upper layer is then disinfected in

ponds by chlorination or ultraviolet radiation The sludge can be used on agricultural land,

disposed of in landfills or incinerated

SEWAGE TREATMENT

Tertiary Stage

The liquid is filtered again usually through sand filters to remove any remaining solids

Further disinfection Nutrients such as phosphorous and nitrogen are

removed The effluent is then discharged at deep ocean

outfalls kilometres off the coast

Why do you think nutrients are removed?

SEWAGE TREATMENT

That’s great if you live along the coast, but what do places that are not near the coast do?

There are three main types of land based methods which can be used.

SEWAGE TREATMENT

Land based method 1: Lagoons Bacteria in a series of interconnecting lagoons

breaks down sewage. Unfortunately this produces gases with a strong

odour. It is possible to collect the gases and burn them to generate electricity

The sludge produced needs to be removed every few years and disposed of.

SEWAGE TREATMENT

Land based method 2: Land filtration This involves flooding a gently sloping paddock from

the elevated end with raw sewage about 10cm thick. The sewage is broken down and purified as it filters

through the soil The liquid component is captured at the bottom of

the hill above the water table Any nutrients in the sewage is utilised by the grass

and bacteria in the soil. The paddock is let to dry for a week and then used

for grazing This process can be repeated but is only suitable

for warm areas low in rainfall and high in evoporation

SEWAGE TREATMENT

Land based method 3: Artificial wetlands Sewage is passed through the roots of a bed of

aquatic grasses and plants The plants enable oxygen to move into the

sewage from the roots The plants also take up any nutrients through the

roots This method requires a large amount of land and

the sludge remains in the system

Which system do we use in Menindee?

SEWAGE TREATMENT

We use what is called a septic tank system.

Sewage travels to a leaching field after it goes through the septic tank.

SEWAGE TREATMENT

Once in the leeching field sandy sediments are necessary in order to oxidize the sewage water, and filter out the bacteria from it.

Ammonium that travels through the unsaturated zone is oxidized and converted to nitrate by the time it reaches the water table.

Areas with high populations that rely on septic tank systems have to be concerned about the possibility of the groundwater achieving high nitrate concentrations.

ACTIVITY

Discuss Activity 3.10 pg 141 HSC Spotlight Text

HOMEWORK

Read pages 139-141 HSC Spotlight Text


Complete ‘To Think About’ pg 142-144 HSC Spotlight Text

Complete DOT Points 5.2

Documents

T OPIC 5-L ESSON 1 Maintenance of environmental flows and natural processes in water