Lake Albert Study Notes - Riverina Environmental Education Centre

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Feb 22, 2014 (3 years and 8 months ago)

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Lake Albert





DEC NSW


December 2013

Riverina Environmental Education Centre

Riverina Environmental Education Centre


Table of Contents

1. Lake Albert: introduction

2. Background: catchments

3. Background: soil erosion

4. Background: land use

5. Background: water as a solvent

6. Topographic map

7. Satellite image


8. Sub
-
catchments

9. Salinity

10. Water cycle

11. Groundwater

12. Piezometer

13. Soils

14. Soil erosion

15. Management: erosion

16. Deposition: delta

17. Water quality
: nutrients

18. Water quality
: coliforms

19. Artificial wetlands

20. Change
: air photos













Research Resources

Report

by Wagga Wagga City Council on the Lake,
importance and problems.

(Word)

CSIRO report on erosion and sedimentation in Lake
Albert
(pdf)

Monthly rainfall data

1898
-

2007
(Excel)

History of Lake Albert
(pdf)

Catchment Detox, an excellent interactive catchment
game
www.catchmentdetox.net.au

Class water pollution activity

(pdf)


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1. Issue: Lake Albert

"Lake Albert has a high recreational value providing for a wide variety of nature based
activities including fishing, swimming, boating, water skiing, bird watching and scenic
viewing. Its location makes it a valuable recrea
tional asset for the people of Wagga Wagga."

Lake Albert Monitoring Report, Wagga Wagga City Council, 2000



Background knowledge

To understand the environmental issues in Lake Albert there are four important
understandings:



catchments



erosion



land use



water as a solvent



















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2.
Background knowledge: catchments

1. A catchment is an area of land which catches water. The water flows to the lowest point in
the catchment.


Many small catchments combine to make up larger
catchments. The satellite image below
shows part of the Murray
-
Darling Basin (catchment). It is made up of the smaller catchments
of the Murrumbidgee, Lachlan, Murray, Darling and other rivers.




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3.
Background knowledge: soil erosion


As water moves
over a catchment,

it flows downhill because of
gravity.

Kinetic energy is the energy from
the movement of an object,
1/2
mv
2
, where
m
is mass and
v
is
velocity.

The faster the water is flowing (v)
and the greater the volume (m),
the more energy it has and

the
more work it can do such as erode
soil.

When water removes soil and
transports it, it is called soil
erosion.

When the water slows down as it
enters a still lake, it loses energy
and cannot do as much work. The
water can't keep transporting the
eroded soil and it is deposited as sediment in the lake.
















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4.
Background knowledge: land use

Land use is t
he way we use the land. It includes farms, urban areas and natural bushland.
Land use causes many of the land degradation problems in a catchment.

Look at some of the land uses surrounding Lake Albert. How could each impact on the lake?






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Images below
show farming in the upper catchment, rehabilitation of an erosion gully, a
rubbish tip near the lake and a new housing sub
-
division.






Tasks

The way we use the land is called land

________________________________________



Draw a sketch map of the a
e
r
i
al

photo showing the various land uses and indicate how each
could impact on the lake.

Name the seven or more land uses which could be a source of nutrient (fertiliser) pollution to
the lake.

List the ways the rubbish tip

could impact on the catchment.


Explain how new housing sub
-
divisions could impact on the lake.




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5.
Background knowledge: water as a solvent



Water is a very powerful
solvent. Substances such
as salt dissolve very easily
in water.

As water moves
over and
through a catchment it
dissolves many substances
it comes into contact with
such as salt, fertiliser and
other pollutants and
transports them lower
down the catchment.

If the water enters a lake,
the pollutants can collect
in the lake and become
c
oncentrated as lake water
evaporates.


When they dissolve, salts break down into their ions which are
located between the water molecules. Table salt or sodium chloride,
which is the main salt in the catchment, forms individual sodium and
chloride ions w
hen it dissolves.

If some of the water evaporates and the sodium and chloride become
more concentrated, they can come out of solution and salt crystals
will form on the soil surface
.








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6.

Lake Albert topographic map


Map© Land and Property
Information Panorama Ave. Bathurst 2795 www.lic.gov.au



The Lake Albert catchment in Wagga Wagga, New South Wales is approximately 7 700
hectares in size.

Water drains from the hills in the south, (upper catchment) to the lake, (lower catchment).





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7.
Lake Albert: satellite image


Satellite image copyright © ACRES Commonwealth of Australia 1992



A
false colour satellite image of the Lake Albert catchment. The different wavelengths of
radiation detected by the satellite have been assigned colours to sh
ow land use more clearly.








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8. Sub
-
catchments

The lake has three main sub
-
catchments providing water to the lake. Scientists researching
environmental problems in the lake investigated each sub
-
catchment to see if they are all at
fault or if a particular sub
-
catchment is worse than the others. Land us
e managers can then
target particular catchments.


The CSIRO
conducted
a survey of sediment entering the lake. There were fears the lake was
filling with soil eroded from the catchment. (
Click for full report
)

Below are their findings.


Over 6,000 cubic metres of sediment was entering the lake each year from Stringybark and
Crooked Creeks and the lake would be full of sediment in 600
years. Originally the lake was
a swamp until the creeks were diverted into it to turn it into a lake. Crooked Creek was
diverted into the lake in 1902 and Stringybark Creek in 1977.


Quiz

Name the sub
-
catchment with the worst soil erosion
?

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Explain why Stri
ngybark Creek contributes far more sediment to the lake each year than
Crooked Creek but only 15% o
f the sediment has come from it?


9. Salinity

The map shows areas of high risk of salinisation in pink. When the water table is within two
metres of the sur
face it is within the root zone of many plants. At this depth the soil also acts
like a sponge, drawing the sal
ine

water up as groundwater evaporates from the surface, this is
called capillary rise.


The blue salinity meters in the diagram measure salini
ty in EC's (electrical conductivity
units). The digital display is not wide enough to show the full number so there is a small 100
in the top left corner indicating all readings need to be multiplied by 100 e.g. a reading of 5
would be 500 uS. The Pacific
Ocean is approximately 58 000 EC.









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10. Salinity: water cycle

The top of the groundwater, the water table, is in dynamic equilibrium. It rises or falls as it
adjusts to changes in either the inputs from rainwater or outputs from evaporation,
transpiration or drainage. If there are a number of wet years, inputs increa
se and the water
table rises, in dry years it falls.


Trees transpire water from their leaves and act like pumps, taking water out of the ground. If
trees are cleared from the catchment, less water is taken out of the groundwater and the water
table adjusts by rising.

Cloud droplets like to form around a nuc
leus, usually a dust particle if the air came from
central Australia or a salt crystal if the air mass came from over an ocean. In our area, about
12 kilograms of salt per hectare, rains out each year and becomes part of the soil.

If the water table rises
, some of the salt in the soil dissolves and moves with the groundwater
down the catchment.

Tasks

As the water table rises and falls as inputs and outputs of
water vary it is said to be in?

What type of particle will cloud droplets form around if the air
has come from over the
ocean?





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11. Salinity: groundwater

Groundwater moves down the catchment but the soils around the lake have low permeability
forcing the groundwater to the surface. Where this occurs it is called a groundwater discharge
area.


There are a number of factors contributing to dryland salinity around the lake:



the upper catchment is a groundwater recharge area, the weathered rock is permeable
and allows rainwater to infiltrate to become part of the groundwater



the soils around the
lake have very low permeability so groundwater passes through it
very slowly, forcing it to back up and come to the surface



watering of gardens in the urban area around the lake



most native vegetation has been cleared from the catchment

Quiz

What is the
t
erm
for the top of the groundwater?


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12. Salinity: piezometer

Piezometers are bores which allow access to
the groundwater for sampling. The bore is
lined with plastic pipe which is protected at
the surface by a steel pipe.

The diagrams show changes to the

depth of
the water table and salinity of the
groundwater at piezometer 2d located near
the south east corner of Lake Albert.

The height of the water table and groundwater
salinity concentration change over
time
as
inputs and outputs of groundwater vary.















A bore used t
o gain access to the watertable

is
called a ______________________________














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13. Soils

The photo shows a typical soil profile in the upper catchment. There are three main layers or
horizons: A1 and A2 (top soil) and B (subsoil).



Two important soil characteristics are slaking and structure:



Slaking
is the stability of soil aggregates
(natural chunks of soil) in water. An
aggregate of soil about the size of a pea is placed in water for several minutes. If the
aggregate falls apart it is slaking

(unstable)
, if it stays together, it is stable.

The A1 and A2 horizons are stable while the
B horizon

is unstable
.
T
he B horizon is
an erosion hazard and is a problem to manage.



Structure
is the arrangement of soil particles and the air spaces between them.
Particles are held together in chunks called aggregates which are separated by cracks
thr
ough which air and water pass.

Good structure has cracks and aggregates which allow the infiltration of water and air to
circulate and at the same time hold the soil in natural chunks which resist erosion. Soil
Conservationists refer to the soil in the up
per catchment as "spew" soil because during
winter, when it is wet, it is like porridge but during summer it dries out to be like concrete.



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14. Soil erosion: gullies

Soil erosion is severe in the upper catchment which occupies 25% of the catchment area
.
There are three main causes:



steep slopes which gives the creek water a faster velocity (increased energy)



the soils have a very poor structure, the particles are not held together well



landuse which is not suited to the slope or soil

type
. Parts
of the

catchment
should not
have been cleared of vegetation.






















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15. Soil erosion: management in the steeper catchment

The photo shows a gully in the upper catchment that has been partly rehabilitated (it
originally continued past the people).


Make a line drawing of the photo and indicate three things which have been done to fix the
gully.

Land capability mapping is
the classifying of land for its suitability for various uses. Major
factors are the slope of the land and soil characteristics.

Land Capability Classification

Class

Land Limitations

Management

i.

slope 0
-
1
0
, prime agricultural land,
fertile

many

uses, no special soil conservation
practices or structures.

ii.

slope 1
-
3
0
, gently sloping, similar to i.
but minor limitations.

Strip cropping, conservation tillage, crop
rotation.

iii.

slope 4
-
7
0
, soil erosion problems can
be severe and limit crop yi
elds

As for ii. but also structural works including
graded banks, waterways and diversion
banks.

iv.

slope 7
-
10
0
, not suitable for cropping
on a regular basis, soil erosion,
shallow, rocky soil, occasional
cultivation for pasture renewal.

Better grazing
land, practices such as pasture
improvement, stock control, fertiliser,
minimal cultivation to establish pasture

v.

slope 10
-
14
0
, soil erosion problems
severe, shallow, rocky soil.

As for iv. and

structural works including
diversion banks, contour ripping.

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vi.

slope 14
-
18
0
, no cultivation, less
productive grazing land, shallow,
infertile soil

Less productive grazing land. No cultivation,
aerial sowing of permanent pasture, limit
stocking rate, pr
event fire and vermin.

vii.

18
-
27
0
, steep slopes, rocky outcrops

Protect land with trees, important habitat for
biodiversity

viii.

Unsuitable for cropping or grazing,
cliff, lake, swamp

Land incapable of sustaining agriculture or
pasture, protect as wat
er supply and wildlife
refuge.


Different slopes in the Lake Albert catchment



























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16. Soil erosion: deposition

Some soil eroded in the upper catchment is transported to the lake in creeks.

S
ediment
ha
s
be
en

deposited in the lake at a rate of over 6,000 cubic metres each year. The catchment of
Stringybark C
reek

supplies 230 tonnes of sediment per square kilometre of catchment area
each year. Cox's C
ree
k catchment yields 25 tonnes per square kilometre each yea
r.


Deltas

Where Stringybark and Cox's Creeks enter the lake the sediment is deposited form
ing

deltas.
The lake is rapidly filling with sediment. Investigations show the lake has a life of 600 years
before it is full.


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Flowing water has energy (kinetic energy =
1/2
mv
2

where m = mass and v = velocity). A
definition of energy is the capacity to do work which in this case is to erode and transport
soil. If the water has a lot of energy it can erode and transport a lot of so
il. When the water
loses energy such as when its velocity slows or stops as it enters the lake it cannot do as much
wo
rk and deposits some or all of the

sediment

form
ing

the deltas.


Tasks

Name for a depositional landform where a river or creek enters a
s
till water body such as a
lake?




















































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17. W
ater quality
: nutrients

The Lake sometimes experiences summer/autumn blue
-
green algal blooms from excessive
nutrient levels. Phosphorus and nitrogen are key nutrients for the development of algae.



Graphs courtesy Wagga Wagga City Council



Australian Water Quality Guidelines for Fresh and Marine Waters suggest that a range of
0.005 to 0.05 mg/L of phosphorus and 0.1 to 0.5 mg/L of nitrogen are sufficient to support an
algal bloom in fresh waters.

The photo below shows a type of blue
-
green a
lgae called Anabaena magnified 400 times
(Photo: 'What scum is that?', Simon Mitrovic )
. Individual cells have joined to form chains.
Blue
-
green algae cells are tiny and exist in low numbers in most bodies of water. The highest
concentration deemed safe to

drink in untreated water is 2,000 cells per millilitre (mL) of
water (5mL = one teaspoon). For non
-
drinking purposes it is recommended to have less than
15,000 cells/mL.

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If each red dot represents 10 algal cells, the number
of red dots is the number
of cells recommended as
safe to drink in each millilitre (ml) of water. A
teaspoon has 5 ml.















































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18. Water quality: coliforms

Faecal coliform levels indicate the presence of domestic sewage or animal waste and
are
monitored so early warning
s

can be given to lake users. For the purpose of water quality,
recreational uses are divided into two categories:



primary contact such as swimming; and



secondary contact such as fishing.

The Australian Water Quality Guidel
ines for Fresh and Marine Waters states

faecal coliforms for primary users should not exceed 150 cfu/100mL. For secondary users the
limit is 1000 cfu/100mL. Tests are reported as cfu/100mL (colony forming units per 100
mL).


The graph shows the results for Lake Albert between the years 1994 and 2000.

Graph courtesy Wagga Wagga City Council



Tasks

What i
ndicates the presence of
domestic sewage or animal waste?


Which type of contact would water skiing?









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19. Artificial
wetlands

To improve water quality in the lake, an artificial wetland was constructed where Stringybark
Creek enters the Lake.

The wetland was designed to trap sediment and keep inflow water until there had been time
for macrophytes

(large water plants) and the biofilm (slime) on the plants to use the nutrients.


Phosphorus in the water has a positive charge and is attracted to clay particles which have a
negative charge. The brown colour of the Lake is due to the large amount of s
uspended clay
particles in the water. When the clay settles out of suspension to become part of the sediment
on the bottom, it takes much of the phosphorus with it and it no longer contributes to the
blue
-
green algae problem unless the sediment is stirred
up by wave action.

The wetland is a form of "ecological engineering". It is low cost, has low maintenance,
provides a water bird habitat and improves lake water quality.

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The table below is a "rule of thumb" for nutrient removal in wetlands.

Length of Detention

Expected Percentage

of Nutrient Removal

Sedimentation of particles:

* half day detention

* three day detention


< 25%

25
-
50%

Sedimentation and biological removal, three to five days detention

50
-
70%

Optimum nutrient removal greater than six days

> 70%

The Lake also performs an important function in trapping sediment and nutrients before they
can enter the Murrumbidgee River.
So the Lake itself has the benefits of a wetland for the
Murrumbidgee River.

Tasks

Name for large water plants?




Describe the benefits of the artificial wetland.



Explain how the wetland works.



Explain why the wetland is a form of ecological engineering.



The energy barrier is a chunk of concrete. Explain its purpose and how it works.

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20. Lake Albert: change

Land use in the lower part of the catchment changed greatly between 1971 and 2004. Try to
identify three things which have changed and three which ha
ve stayed the same. What
impacts might the expanding urban area have on the Lake during housing construction and
once the gardens are established?



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Air photos © Land and Property Information Panorama Ave. Bathurst 2795 www.lic.gov.au




Tasks

Draw a

sketch map of the 1971 photo showing the Lake and surrounding land use.

Draw over the 1971 map in a different colour
only
showing the features which changed up to
1988.

Modify the 1988 sketch map with the new features shown on the 2004 photo. Use the land

use photo on
page 6

to help you.