Mid to Lower Light River
Salinity
Management Plan
Report to N&Y NRM Board
Chris Henschke
Andrew Harding
Stuart Wright
December 2008
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Executive Summary
There is a relatively low risk of any future increases in the area of salt-affected land for
the Mid and Lower Light River sub-catchments.
However, there is a significant risk of an increasingly adverse impact on water quality
from saline groundwater baseflow into rivers and streams.
While baseflow maintains permanent pools, concentration by evaporation combined
with a lack of flushing flows has resulted in increasing steam salinity, which impacts on
biodiversity values and the use of springs and soaks for stock water supplies.
The focus for management of land salinity in the Mid to Lower Light River will be
towards protection and utilisation of salt-affected land with saltland agronomy or fodder
shrub options. This applies specifically in the floodplain areas of Stockwell Creek and
areas adjacent to the Lower Light estuarine zone.
As the Light River estuary is of considerable environmental value, management of
water quality and water flow issues within the catchment is important. Dispersed areas
of saline seepage along stretches of the Mid to Lower Light River and its tributaries
may be revegetated with salt-tolerant / riparian species.
Continued monitoring of surface water and groundwater salinity is required, along with
the impact of salinity on valuable NRM assets within the Mid and Lower Light River
sub-catchments.
Contents
1
INTRODUCTION
1
2
CATCHMENT DESCRIPTION
2
2.1 climate and native vegetation
2
2.2 topography and drainage
3
2.3 land use
5
2.4 geology
5
2.5 land systems
6
2.6 surface water hydrology
6
2.7 groundwater hydrology
8
3
SALINITY ISSUES
11
3.1 land salinity
11
3.2 water salinity
13
4
MANAGEMENT OF SALINITY ISSUES
16
5
RECOMMENDATIONS
21
6
REFERENCES
22
7
GLOSSARY
23
APPENDIX 1:
LAND SYSTEMS
25
APPENDIX 2:
LIGHT RIVER SALINITY DATA FROM WATERWATCH
27
APPENDIX 3:
GROUNDWATER DATA FROM OBSWELL
28
APPENDIX 4:
SPECIES FOR REVEGETATION
31
List of Figures
Figure 1:
Light River catchment
1
Figure 2:
Surface hydrology
4
Figure 3:
Land systems
7
Figure 4:
Groundwater and surface water monitoring sites
10
Figure 5:
Salinity induced by watertables
12
Figure 6:
Salinity risk
17
List of Tables
Table 1:
Average annual rainfall and evaporation data
2
Table 2:
Areas of salt affected land
11
Table 3:
Water grab-samples from the Light River and tributaries
15
List of Photos
Photo 1:
View of Mingays Waterhole stream gauging station
9
Photo 2:
Mingays Waterhole stream gauging weir
9
Photo 3:
Excavated drain on the Stockwell Creek floodplain
14
Photo 4:
Saline baseflow in northern tributary of St Kitts Creek
14
Photo 5:
Chenopod shrubland on the Light River floodplain
19
Photo 6:
Bean crop affected by dryland salinity on the Light River floodplain
19
List of Abbreviations
DWLBC
Department of Water, Land and Biodiversity Conservation (Government of
South Australia)
GDE
Groundwater Dependent Ecosystem
GFS
Groundwater Flow System
N&Y
Northern and Yorke
NRM
Natural Resources Management
EC
Electrical Conductivity
PIRSA
Primary Industries and Resources South Australia (Government of South
Australia)
Acknowledgments
Craig Liddicoat (Rural Solutions SA) provided the hydrogeology map for Figure 4 and
the borehole data in Appendix 3.
Cover Photo
Weir on the Light River at Hamley Bridge
Mid to Lower Light River salinity management plan
1
INTRODUCTION
This report has been prepared at the request of the Northern and Yorke
Natural Resources Management Board (N&Y NRM Board), and resourced
under the Strategic Reserve funding.
The salinity management plan covers two (Mid Light and Lower Light) of the
four sub-catchments of the Light River (Figure 1). Plans have previously been
prepared for the other two sub-catchments:
Upper Light River salinity management plan (Harding et al., 2003)
Gilbert River salinity management plan (Harding et al., 2005).
Other reports include:
Salinity benchmarking and monitoring strategy, covering both the
Broughton and Light River catchments (Liddicoat and Dooley, 2004)
River management plan for the Light catchment (VanLaarhoven et al.,
2002).
Previous findings have been reviewed and integrated into this report,
supplementing new analysis, interpretation, mapping and field inspection of
salinity within the Mid to Lower Light River.
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Mid to Lower Light River salinity management plan
The location of the southern boundary of the N&Y NRM Board is currently
under review, and parts of the Light River catchment may transfer to the
neighbouring Adelaide and Mt Lofty Ranges NRM region.
2
CATCHMENT DESCRIPTION
The Mid Light River and Lower Light River sub-catchments have an area of
59,780 ha and 14,920 ha respectively. This gives a combined total area of
74,700 ha (Figure 2).
Towns and localities include St Kitts, Stockwell, Neukirch, Kapunda, Hamley
Bridge, Redbanks and Lower Light. Mallala is located just outside of the
boundary for the Lower Light River sub-catchment.
The climate, topography and geology have been described in Harding et al.,
(2003 and 2005) and are similar for the Mid Light sub-catchment. Further
details specific to the Mid and Lower Light River sub-catchments are
described below.
2.1 CLIMATE AND NATIVE VEGETATION
Rainfall in the hilly areas of the Mid Light sub-catchment ranges from 450500mm, decreasing to 350-450 mm on the plains of the Lower Light subcatchment. In wetter winters, seasonal flooding and waterlogging affects
poorly drained low-lying areas. Wet seasons can also result in recharge to
groundwater causing watertables to rise and expansion of dryland salinity.
Average annual rainfall and evaporation data from various localities across
the region are presented in Table 1.
Table 1:
Average annual rainfall and evaporation data1
Locality
St Kitts
Stockwell
Kapunda
Hamley Bridge
Mallala2
Lower Light
1
Rainfall (mm)
Evaporation (mm)
477
496
493
429
402
374
2037
2050
2019
2024
-
Various sources including BoM website
Note that Mallala is located just outside the official DWLBC catchment boundary for
the Lower Light River sub-catchment
2
2
Mid to Lower Light River salinity management plan
Native vegetation in the Mid Light sub-catchment comprised an open
woodland of eucalypts and understorey species. Clearing commenced in the
mid to late 1800s.
Historically, river red gum forests (Eucalyptus camaldulensis) extended along
the Light River from the estuary through to its junction with St Kitts creek
(Brown and Kraehenbuehl, 2000). Much of the red gum forest has since been
cleared, particularly in the Kapunda area. Red gum remnants still occur along
St Kitts Creek and on the Stockwell Creek floodplain.
Other vegetation associations include open woodland of SA blue gum (E
leucoxylon), peppermint box (E odorata) and southern cypress pine (Callitris
gracilis).
Sedgeland communities and reed beds can be found along the length of the
river system. Low shrubby vegetation such as Lignum (Muehlenbeckia
florulenta) occurs on floodplain areas often in association with red gums.
Mangrove (Avicennia marina) forests are located at the Light River estuary
(VanLaarhoven et al., 2002). Samphire marshes occur on the tidal flats.
2.2 TOPOGRAPHY AND DRAINAGE
The Mid Light and Lower Light sub-catchments form the southern part of the
Light River drainage basin.
The Mid Light sub-catchment occurs in hilly country of the northern Mt Lofty
Ranges. A number of major tributaries to the Light River include St Kitts
Creek, Stockwell Creek, Allen Creek, Ross Creek, Hawker Creek and Fannel
Creek.
The official DWLBC catchment boundaries are used to define the Mid and
Lower Light catchments (Figure 2). While the Bagot Well sub-catchment is
now officially included in the Mid Light sub-catchment it was previously
described in the Upper Light River plan (Harding et al., 2003).
After St Kitts Creek joins the Light River, the river then meanders westwards
in a deeply confined channel between Kapunda and Hamley Bridge.
The Lower Light sub-catchment commences from the junction of the Gilbert
River at Hamley Bridge.
The river then enters the coastal plain of the Northern Adelaide Plains and the
catchment boundary generally follows the riparian zone of the river. It flows in
a single deep channel towards the town of Lower Light.
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Mid to Lower Light River salinity management plan
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Mid to Lower Light River salinity management plan
A feature known as The Rockies occurs 8 km downstream of Hamley Bridge
and is characterised by permanent pools along with abundant reeds and
riparian vegetation (VanLaarhoven et al., 2002).
The locality of Redbanks occurs at the downstream end of the permanent
pools section of the river. The river then changes from a gaining stream
(inflow of groundwater to streamflow) to a losing stream (where streamflow
contributes to groundwater).
The Light River estuary extends from the mouth of the river at Gulf St Vincent
to 4 km inland. It is characterised by a shallow main channel surrounded by
mangrove forest and samphire flats. There are numerous smaller tidal
channels across the delta / estuary.
2.3 LAND USE
The predominant land use is dryland agriculture which includes cropping and
grazing. Since the 1980s, many farmers have increased their cropping areas
and cropping intensity. Pulse crops and canola are now included in the
cropping rotation.
Vineyards occur between Stockwell and Kapunda and in the St Kitts area.
These are generally irrigated and groundwater is being increasingly
supplemented by imported water from outside the region (i.e. from the River
Murray). This may lead to a rise in local watertables and associated salinity
issues (Evans et al., 2003).
2.4 GEOLOGY
The geology of the Mid Light sub-catchment is characterised by hard
basement rocks of the Adelaide Geosyncline.
Rocks resistant to weathering such as sandstone and quartzite outcrop along
the higher ridges and hills and produce ridges that help to define the
catchment boundaries. The softer shales and siltstones have been
weathered back to clays with much of this material eroded away forming
valleys and plains.
A Tertiary sedimentary basin (Barossa Basin) is an in-filled basin of fluviolacustrine sand, silt, clay and lignite. The flat plains of this basin support an
expanding viticulture industry in the Stockwell and Neukirch areas.
The coastal plain of the Lower Light sub-catchment is underlain by the St
Vincent sedimentary basin. This basin contains a deep sequence of Tertiary
marine sediments (sand, clay, sandstone and limestone).
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Mid to Lower Light River salinity management plan
2.5 LAND SYSTEMS
A land system is an area of land with a common set of features that
distinguish it from surrounding land. The features can include geology,
topography, soils and vegetation.
There are 26 land systems in the Mid and Lower Light River sub-catchments
as shown in Figure 3.
Fourteen of the land systems are listed below from east to west across the
two sub-catchments. More details are provided in Appendix 1. Land systems
occupying small to insignificant areas have not been listed.
Land Systems of the Mid Light sub-catchment (from east to west)
TAB = Tableland – high plateau with arable loamy soils
STK = St Kitts – steep hills separated by eroded watercourses
TRI = The Triangle – steep rocky hills, mostly non-arable
KNG = Koonunga – steep hills and undulating rises
BAV = Barossa Valley – flat valley formed on outwash fan
HMP = Hampden – ridges, rocky rises, outwash fans and valley flats
BAW = Bagot Well – undulating rises and low hills
KPD = Kapunda – steep rocky ridges, rolling hills and outwash fans
LIN = Linwood – undulating land surface with deep fertile soils
PNR = Pine Ridge – sandy rises and low hills with low productivity
Land Systems of the Lower Light sub-catchment (from east to west)
PIP = Pinkerton Plains – gently undulating plains with loamy calcareous soils
MLL = Mallalla – alluvial plains of deep silty loams
LOL = Lower Light – low lying floodplain of the Light River
PRH = Parham – coastal and near coastal flats with salt pans
2.6 SURFACE WATER HYDROLOGY
The Light River is an ephemeral stream that occasionally flows to the coast.
Episodic high rainfall events produce large flows, although flooding is rare.
The main tributaries of the Mid Light River sub-catchment include St Kitts
Creek, Stockwell Creek, Allen Creek, Ross Creek, Hawker Creek and Fannel
Creek.
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Mid to Lower Light River salinity management plan
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Mid to Lower Light River salinity management plan
Significant areas of permanent groundwater baseflow occur along the Light
River from the junction with St Kitts Creek and extending downstream to
Kapunda (VanLaarhoven et al., 2002). This may be caused by the presence
of rock bars in the riverbed forcing groundwater to discharge (Photos 1 and
2).
The river is deeply incised to bedrock in many areas with permanent pools
being found along the river and its tributaries. Permanent pools are also
found in the lower reaches of the major tributaries forming groundwater
dependent ecosystems (GDE) that support macroinvertebrates and other
wildlife.
There are only two stream gauging stations on the Light River (Figure 4). The
original Kapunda station operated from 1973-1989 and the current Mingays
waterhole station commenced operation in 1985 (Photos 1 and 2).
Streamflow data is summarised in VanLaarhoven et al., (2002), Murdoch
(2003), Harding et al., (2003) and Liddicoat and Dooley (2004).
Monitoring of surface water salinity is limited in scope. Available Waterwatch
monitoring data is given in Appendix 2.
2.7 GROUNDWATER HYDROLOGY
There are three groundwater flow system (GFS) types in the Mid and Lower
Light River sub-catchments as shown in Figure 4:
Local and intermediate flow systems in fractured rock on steep hills
Local and intermediate flow systems in fractured rock and sedimentary
infill on broad valleys
Regional flow systems in sand / clay aquifers
The first system occupies only a very small area in the SE corner of the
catchment.
Local-scaled flow systems within fractured rock aquifers occur across most of
the Mid Light sub-catchment. In a local GFS, recharge occurs within a
relatively short distance of the discharge area. Groundwater flows from
elevated areas in the landscape towards valley floors and drainage lines
where discharge (and dryland salinity) then occurs. The Light River is
predominantly a gaining stream in the Mid Light sub-catchment as evidenced
by numerous pools and springs.
In the Lower Light sub-catchment a regional-scale GFS occurs in sedimentary
basin aquifers of the St Vincent Basin. The river becomes a losing stream on
the plains. This provides recharge to the regional groundwater system.
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Mid to Lower Light River salinity management plan
Photo 1:
View of Mingays Waterhole stream gauging station on the
Light River near Kapunda
Photo 2:
Mingays Waterhole stream gauging weir, September 2003
9
Mid to Lower Light River salinity management plan
10
Mid to Lower Light River salinity management plan
There are eleven groundwater monitoring sites recorded in the Obswell
database. These are focussed mainly in vineyards around Neukirch and
Stockwell. Another monitoring well is located near the town of Lower Light
(Figure 4).
Groundwater data including hydrographs from Obswell sites is summarised in
Appendix 3. Various aquifers are monitored including the deep basement
rock and Tertiary aquifers. Three observation wells in the Neurkirch area
monitor the shallow Quaternary aquifer.
Groundwater levels in the deep aquifers showed a falling trend during the
1980s and early 1990s in response to groundwater pumping. Since then, the
trend has been relatively stable or rising slightly, due primarily to less reliance
on pumping for irrigation water supply. The Quaternary aquifer shows
seasonal responses, reaching their highest levels during the wet spring of
2005, but falling in recent drier years.
3
SALINITY ISSUES
Figure 5 illustrates the distribution of land salinity, across the Mid and Lower
Light sub-catchments. Water salinity issues are of more concern than the risk
of increasing areas of saltland.
3.1 LAND SALINITY
Estimates of land affected by dryland salinity are taken from the DWLBC Land
Resource Information database (DWLBC, 2007).
Table 2:
Areas of salt affected land
Sub-catchment
Secondary Salinity
(ha)
Primary Salinity
(ha)
Mid Light
12
0
Lower Light
0
3026
Most of the land mapped as being moderately salt affected occurs on the
Stockwell Creek floodplain near Neukirch. It is expressed as sea barley grass
areas which have remained relatively stable over the past couple of decades.
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Mid to Lower Light River salinity management plan
12
Mid to Lower Light River salinity management plan
Stockwell Creek flows across the flat red gum plains of the northern Barossa
Valley, ending up as a broad shallow sedgeland (VanLaarhoven et al., 2002).
The stream becomes a small shallow watercourse with an extensive flood-out
area. The watercourse has been modified by removal of red gums, and
straightened into an artificial channel (Photo 3).
A relatively shallow watertable (2-3 m) occurs under the Belvidere plains
(Stockwell Creek floodplain) in the vicinity of Neukirch. The salinity of the
watertable is over 15,000 μS/cm (10,000 mg/L) in this area. Groundwater
flows from a subdued east-west groundwater divide in a northerly direction
towards the St Kitts Creek (Cobb, 1984).
Importation of water from outside the catchment for irrigation purposes may
lead to rising watertables and potential salinisation problems in this area
(VanLaarhoven et al., 2002).
The Stockwell Creek floodplain is poorly drained and low-lying areas are
generally waterlogged following heavy rainfall. Cobb (1984) indicated that the
plain was at risk of salinity if the watertable came to within 2 metres of the
surface.
Only isolated areas of saline seepage occur along the other major tributaries
of the Light River (Photo 4). A field inspection was carried out in September
2008 confirming that dryland secondary salinity is confined to small areas
along various watercourses in the St Kitts, Neukirch and Kapunda areas.
High to very high salinity occurs in the Light River estuary near the coast.
This is largely primary (natural) salinity with some adjacent areas of
secondary (man-induced) salinity.
3.2 WATER SALINITY
Besides results from the Mingays Waterhole gauging station and short term
Waterwatch activites, there is very little data available for surface water and
groundwater salinity for the Light River catchment (VanLaarhoven et al., 2002,
Liddicoat and Dooley, 2004).
The stream gauging weir situated at Mingays Waterhole near Kapunda
(Photos 1 and 2) only samples the eastern part of the catchment.
Measurements indicate that the Light River has a highly variable salinity
range. The median EC of winter baseflow was estimated (Murdoch, 2003) at
7000 μS/cm (4000 mg/L) and summer baseflow at 10,000 μS/cm (5700
mg/L).
The mean flow weighted stream EC is 2700 μS/cm (1500 mg/L). The amount
of salt exported is 57 tonnes/day which gives an annual saltload of around
20,000 tonnes.
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Mid to Lower Light River salinity management plan
Photo 3:
Excavated drain on the Stockwell Creek floodplain
Photo 4:
Saline baseflow in northern tributary of St Kitts Creek
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Mid to Lower Light River salinity management plan
High stream salinity is caused by the input of naturally saline groundwater as
baseflow. In dry periods, permanent pools increase in salinity due to
concentration by evaporation. Periodic surface flows are therefore important
to flush pools and prevent the build up of salts.
VanLaarhoven et al., (2002) surveyed macro-invertebrates along the Light
River and its tributaries and found lower levels to that recorded in other
catchments in the N&Y region. It was suggested that low flows and high
salinity levels may be responsible. They conclude that high salinity levels
may be a natural feature of the Light River catchment and that the catchment
may never have contained a diverse macro-invertebrate population.
Grab samples were taken during a field inspection of the Light River and its
tributaries in September 2008 and the results are shown in Table 3.
Table 3:
Water grab-samples taken from the Light River and its tributaries,
September 2008
Sample Site
EC
(μS/cm)
TDS
(mg/L)
Remarks
St Kitts Creek
10,400
5,940
Waterhole with permanent baseflow
St Kitts Creek
Tributary- Watunga
7,860
4,440
Saline seepage in creek
Stockwell Creek Neukirch
10,010
5,710
Baseflow with salt scalds and salt
tolerant grasses along drain
10,690(1)
6,114(1)
Ross Creek Kapunda
13,970
8,080
baseflow
Hawker Creek Kapunda
20,150
11,930
rock pools
Light River Linwood
13,040
7,530
waterhole
Light River – Hamley
Bridge
15,320
8,910
flowing weir
St Kitts Creek Koonunga
(1)
Sampled in September 2003
15
Creek was dry on this trip, but was
previously sampled in September 2003
Mid to Lower Light River salinity management plan
Figure 6 is a map of salinity risk sourced from the DWLBC Land Resource
Information database (2007). It indicates a worst possible case scenario if
watertables were to rise significantly following a wetter climatic cycle, with
increased severity of saline seepage apparent along several drainage lines.
Under the current scenario of climate change, the trend to a drying climate
and falling watertables suggests that saline areas are unlikely to expand.
Episodic flood events may see a temporary increase in seepage from rising
watertables.
Surface water and stream salinity could increase in the future due to less
regular flushing of the river system. Lower flow rates and higher evaporation
rates will see a concentration of water salinity. Continued monitoring of
stream and surface water salinity is therefore of importance for assessing risk
to biodiversity and stock water supplies.
4
MANAGEMENT OF SALINITY ISSUES
Options for dryland salinity management fall into three main categories:
recharge reduction
engineering options
living with salt.
Salinity management strategies will be most successful if they include a
combination of options from each of these three categories.
The area of primary (natural) salinity exceeds the area of secondary (maninduced) salinity within the two sub-catchments. Photos 5 and 6 illustrate the
more extensive areas of primary and secondary salinity found on the Light
River floodplain. Such areas are the focus for management of land salinity in
the Mid to Lower Light River, along with the floodplain areas of the Stockwell
Creek.
As the Light River estuary is of considerable environmental value,
management of water quality and water flow issues within the catchment is
also important. Dispersed areas of saline seepage along stretches of the Mid
to Lower Light River may be revegetated with salt-tolerant / riparian species
(refer to Appendix 4).
Recharge reduction
Recharge reduction refers to the increased use of rainfall across a catchment
to reduce the amount of excess water entering the watertable. Revegetation
with trees, shrubs and grasses in selected areas will reduce recharge and
minimise the effects of salinity.
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Mid to Lower Light River salinity management plan
17
Mid to Lower Light River salinity management plan
There will be local opportunities for recharge reduction as an appropriate
response to salinity risk, especially in the eastern section of the Mid Light subcatchment and where additional NRM benefits (decreased waterlogging,
flooding and erosion along with enhanced biodiversity) can also accrue.
Protection and re-invigoration of remnant native vegetation not only enhances
biodiversity value but also contributes to increased water use and recharge
reduction. Existing remnant stands may be buffered and connected through
revegetation with appropriate tree, shrub and grass species (Appendix 4).
Recharge reduction, when applied on a significant scale, may impact on
runoff and lessen available surface flow to streams and dams. Similarly,
placement of revegetation and other recharge reduction activities needs to
consider the proximity of groundwater dependent ecosystems, and the
importance of baseflow to maintaining those systems (Vanlaarhoven et al.,
2002). However, it is unlikely that small area of riparian zone revegetation will
impact significantly on existing waterholes.
Excess application of irrigation water can increase recharge to the watertable
and contribute to salinity problems both locally and downstream. In vineyard
areas, minimal drainage past the root zone of vines should be maintained.
Engineering options
Engineering options aim to accelerate the removal of excess water from the
landscape. Managing surface water flows helps reduce the incidence of
flooding and waterlogging, which tends to exacerbate soil salinity.
Shallow surface drains including contour banks are designed to intercept
surface flows and remove excess surface and shallow sub-surface water from
accumulating, thereby reducing waterlogging and recharge potential.
Enhanced surface drainage has been undertaken on the Stockwell Creek
floodplain (near Neukirch) to confine floodwaters to a central watercourse.
With any types of drainage, suitable disposal sites are an important
consideration. Landholders may be liable for any off-site effects, which may
result from engineering works.
Living with salt
Saltland can be managed productively while ensuring the maintenance of a
protective vegetative cover by using salt tolerant trees, shrubs and grasses.
Species suitable for revegetation work in saline discharge areas include salt
tolerant eucalypts, melaleucas, casuarinas, saltbush, puccinellia and tall
wheat grass.
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Mid to Lower Light River salinity management plan
Photo 5:
Chenopod shrubland on the Light River floodplain
Photo 6:
Bean crop affected by dryland salinity on the Light River
floodplain
19
Mid to Lower Light River salinity management plan
Salt tolerant grasses and fodder shrubs increase grazing production on saline
land. This can provide stock with fodder during the autumn when other feed
sources are low.
Revegetating saline areas improves aesthetics and controls degradation.
Benefits include protecting the soil from erosion, reducing evaporation,
lowering the watertable locally and improving the visual appearance. The risk
of flooding is also significantly reduced since bare saline areas are source
areas for run-off.
Salt tolerant grasses include puccinellia which is suitable in areas where there
is patchy sea barley grass and will also establish well in some bare saline
areas. Tall wheat grass has been assessed as having a moderate risk of
being an environmental weed in the N&Y region. Its establishment should be
subject to a more detailed local assessment, along with the formulation and
implementation of a management plan which confidently nullifies its escape
potential.
Saltbushes and salt tolerant trees can be planted around the perimeter of the
salt areas. If trees and shrubs are planted with salt tolerant grasses, grazing
will be limited until the trees are established.
Revegetation with saltbush will mainly be targeted to the Light River floodplain
in the Lower Light sub-catchment where extensive areas of dryland salinity
occur on the broad plains and is affecting annual cropping (Photo 6).
Riparian zones
Protecting, maintaining and enhancing riparian vegetation is an important
consideration (VanLaarhoven et al., 2002). Vegetation along watercourses
including buffer strips of grasses and low shrubs are effective in trapping
sediments and nutrients as well as pollutants before they contaminate
streams. This will help to improve water quality as well as reducing
evaporation and potential salinity problems.
Riparian areas are best fenced off from stock access, but may be grazed as
long as grazing is controlled to maintain a protective surface cover to prevent
erosion. Local species should be used to revegetate these areas (refer to
Appendix 4) and weeds need to be controlled to reduce competition and allow
natural regeneration to take place.
Various on-ground works projects to date have included fencing off native
vegetation, fencing off watercourses, relocating watering points, removal of
woody weeds along watercourses and water erosion control. These all have
indirect benefits for salinity control.
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Mid to Lower Light River salinity management plan
The River Light estuary
Of the 16 estuaries identified within the N&Y NRM region, the Light River
estuary has particular significance for environmental protection (N&Y NRM
Board, 2008). Estuaries are usually at the outflow end of a river system and
are essential for the health and well-being of the marine environment and are
heavily dependent on the catchment-coast-ocean connection.
Naturally saline ecosystems such as the Light River floodplain and estuary
can have considerable environmental value for plant and animal biodiversity.
There is potential to enhance the environmental value of these areas. This
will help to manage salinity and improve landscape aesthetics. These areas
can also be used for educational purposes and eco-tourism.
5
RECOMMENDATIONS
The following general recommendations are suggested for the Mid and Lower
Light River sub-catchments.
Management of land salinity should be focussed on the higher salinity
risk floodplain areas of the Stockwell Creek floodplain and the Light
River floodplain downstream of Lower Light. Dispersed areas of saline
seepage along stretches of the Light River and its tributaries require
revegetation with salt-tolerant / riparian species.
Water-affecting activities such as:
- new dam construction
- importation of water
- groundwater pumping
- irrigation
- broadscale establishment of perennials
needs to be assessed in terms of water salinity and environmental
flows, and subsequent potential impacts on valuable groundwater
dependent ecosystems and estuarine habitats.
Broader agency networks are required for the monitoring of surface
and groundwater salinity, and its impact on NRM assets. In addition,
community programs such as Waterwatch should be mobilised for
regular planned auditing and benchmarking of salinity levels and
environmental flows across the Mid and Lower Light River subcatchments.
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Mid to Lower Light River salinity management plan
6
REFERENCES
Brown W and Kraehenbuehl D (2000) Riparian rehabilitation and revegetation
in the Light catchment. Unpublished report to the Dept of Environment,
Heritage and Aboriginal Affairs. PIRSA, Adelaide.
Cobb MA (1984) Groundwater resources of the Barossa Valley – a summary
report. Dept of Mines and Energy SA, Geological Survey Report Book No.
84/22.
DWLBC (2007) Regional Land Resource Information for Southern South
Australia. Soil & Land Program, Dept of Water, Land and Biodiversity
Conservation, South Australia [DVD ROM].
Evans T, Liddicoat C, Henschke C and Dooley T (2003) North and South Para
catchments salinity management plan. Rural Solutions SA, report prepared
for the Adelaide and Mt Lofty Ranges INRM Committee, March 2003.
Harding A, Henschke CJ, Ciganovic P and Dooley T (2003) Upper Light River
salinity management plan. Rural Solutions SA, report prepared for the
Northern and Yorke INRM Committee, November 2003.
Harding A, Henschke CJ, Ciganovic P and Dooley T (2005) Gilbert River
salinity management plan. Rural Solutions SA, report prepared for the
Northern and Yorke INRM Committee, August 2005.
Liddicoat C and Dooley T (2004) Broughton and Light River catchments
salinity benchmarking and monitoring strategy. Rural Solutions SA report
prepared for the Northern and Yorke INRM Committee, April 2004.
Murdoch B (2003) Light River environmental water requirements: hydrology.
Dept of Water, Land and Biodiversity Conservation. DWLBC report 2003/22.
N&Y NRM Board (2008) Northern and Yorke regional NRM plan, Volume A:
State of the regional report, 2008. Draft Plan Produced by the Northern and
Yorke NRM Board.
VanLaarhoven J, Scholz G, Phipps L and Favier D (2002) A river
management plan for the Light catchment, South Australia. Dept. of Water,
Land and Biodiversity Conservation. Report, DWLBC 2004/17.
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Mid to Lower Light River salinity management plan
7
GLOSSARY
Aquifer — An underground layer of rock or sediment that stores and transmits water.
Baseflow – The water in a stream that results from groundwater discharge to the
stream. This discharge often maintains flows during seasonal dry periods and has
important ecological functions.
Biodiversity – The variety of life forms, the different plants, animals and microorganisms, the genes they contain and the ecosystems they form.
Catchment — An area of land that drains water to a common outlet.
Discharge – Outflow of groundwater as seepage or as evaporation from shallow
watertables. This often produces the symptoms of dryland salinity (i.e. bare ground,
salt crusts or waterlogging).
Dryland salinity — The process whereby stored salts are brought close to the
surface by a rising watertable. The accumulation of salt degrades the upper soil
profile, with impacts on agriculture, infrastructure and the environment.
EC — Electrical conductivity; 1 EC unit = 1 micro-Siemen per centimetre (µS/cm)
measured at 25°C; commonly used as a measure of water salinity.
Ecosystem – A biological system involving the interaction between living organisms
and their immediate physical, chemical and biological environment.
Ephemeral – Temporary or intermittent, for example a creek that dries up during
summer and flows in winter.
Estuary – The end of a river, where it’s current meets, and is affected by the ocean’s
tides.
Floodplain – Land adjacent to streams that is regularly flooded; often includes
seasonal and perennial wetlands.
Gauging station – Location at which stream flow is quantitatively determined using
gauges, current meters, weirs or other measuring instruments.
Geosyncline – A large scale linear trough that subsided over a long period of time,
allowing the accumulation of a thick succession of sedimentary rocks. The rocks of
many geosynclines have been folded into mountain belts.
Groundwater – Underground water contained in a saturated zone of soil or
geological strata.
Land system – An area of land, distinct from the surrounding terrain, within which
there are particular land characteristics or components that occur repeatedly in
sequence.
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Mid to Lower Light River salinity management plan
Macroinverterbrates – Animals without backbones that are typically of a size that is
visible to the naked eye. Aquatic macroinverterbrates are an important part of aquatic
ecosystems.
Observation well — Is a bore, narrow well or piezometer that measures
groundwater levels.
Obswell — The South Australian observation well network.
Quartzite - Fine-grained quartz rock formed by metamorphic (heat and pressure)
processes.
Quaternary – An arid cold geological period when wind blown and episodic flood
deposits were formed (salt lakes, lunettes, sand dunes and gravelly outwash
deposits).
Recharge – Unused rainwater which moves down through the soil (below root
zones) to the watertable and causing watertables to rise.
Recharge area — The area of land from which water from the surface (rainfall,
streamflow, irrigation, etc.) infiltrates into an aquifer.
Reeds – Classified as any one of the following four types of plant Typha, Phragmites,
Juncus ignens and Eragrostis australasica.
Riparian – The area immediately next to and influenced by a watercourse.
Sedges – Aquatic and semi-aquatic plants of the family Cyperacae. They are mostly
perennial grasses or rush-like herbs. Common types include club-rush, bog-rush and
sword-sedge.
Sediment – Material deposited as a result of transportation by wind, water or
gravitational processes or a combination of these.
TDS — Total dissolved solids, measured in milligrams per litre (mg/L); a measure of
water salinity (also expressed as parts per million, ppm).
Tertiary – A warm wet geological period when sea levels were higher and marine
sediments (fossiliferous limestones) were deposited. Large flowing rivers resulted in
alluvial floodplain deposits of sands and clays.
Waterlogging – Where the surface soil is saturated with water from rising
groundwater or surface run-off collecting in low areas.
Watertable – Is the surface in an unconfined aquifer where the pore water is at
atmospheric pressure. It is the height to which the water level will rise in a well drilled
in an unconfined aquifer.
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Mid to Lower Light River salinity management plan
APPENDIX 1:
LAND SYSTEMS
A more detailed description of the major land systems occurring in the Mid
and Lower Light sub-catchments is provided.
Land Systems of the Mid Light River catchment
Bagot Well (BAW)
Undulating rises and low hills are the main feature of this land system. Soils
are red loams with clayey sub-soils and clay loam gradational soils. There is
a moderate erosion potential.
Barossa Valley (BAV)
The land system is dominated by a gently inclined outwash fan. The northern
part of this system is very flat and poorly drained. Waterlogging and sporadic
salinity occur in lower lying areas.
Hampden (HMP)
The land is mainly undulating with some ridges and rocky rises. Outwash
fans, creek valleys and flats are also a feature. Well structured loamy soils
overlie clay, carbonate material or basement rock. While there is no evidence
of surface salinity, soil acidity is becoming an increasing problem.
Koonunga (KNG)
This land system consists of several sub-catchments of the lower St Kitts
Creek watershed. It comprises undulating rises with some steeper slopes.
Although moderately deep and fertile, these soils need careful management.
Many soils have dispersive subsoils which restrict drainage. This is common
on the lower slopes and flats, and can be associated with sporadic saline
seepage.
Kapunda (KPD)
This is an area of undulating to rolling rises and low hills. An extensive
quartzite ridge occurs on the western side with scattered steep rocky ridges
elsewhere. There are outwash fans and drainage depressions. Only minor
areas are affected by saline seepage on the lower slopes.
Linwood (LIN)
Consists of dissected slopes and outwash fans of the Light River in the Bethel
to Linwood area. It is an undulating land surface with deep fertile and well
drained soils. The river has cut a gorge up to 50m deep in places.
Pine Ridge (PNR)
This system comprises sandy rises and low hills between Hamley Bridge and
Fords. The soils are sands over clay with low fertility along with waterlogging,
water repellence and subject to wind and water erosion.
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Mid to Lower Light River salinity management plan
St Kitts (STK)
There are steep hills separated by eroded watercourses in this system. Soils
are mainly sandy loam on clay. Where the clay subsoil is dispersive it can
result in perched watertable development and subsurface waterlogging. Most
soils are poorly structured and highly erodible.
Tableland (TAB)
Comprises a high plateau with arable loamy soils. There are some
moderately steep slopes and eroded watercourses that are non-arable.
The Triangle (TRI)
This land system consists of steep rocky hills which are mostly non-arable.
Soils are shallow loams over bedrock and are subject to severe erosion.
Land Systems of the Lower Light River catchment
Lower Light (LOL)
This land system is a flat alluvial plain in the Lower Light area. It is a low-lying
(below 10m AHD) floodplain of the Light River and is influenced by saline
watertables. While it has deep fertile soils, productivity is restricted by soil
salinity, sodicity and possible boron toxicity induced by saline watertables.
Highly saline flats occur at the western margin of this land system.
Mallalla (MLL)
This system is formed on flat alluvial plains of the Light River. The soils are
deep silty loams. The river has incised a well defined narrow channel into the
alluvium and low levees border the river in the lower reaches.
Parham (PRH)
This is a coastal environment with a complex of samphire and saltbush flats
and bare salt pans. Some low linear sand dunes and low coastal sand hills
occur. The soils range from shallow and stony to saline or sandy and are very
infertile. Where mangrove swamps occur, the soils are at risk of becoming
acid sulphate.
Pinkerton Plains (PIP)
This is a very gently undulating plain with loamy calcareous soils. The bulk of
the area comprises flats with vague watercourses and low stony rises.
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Mid to Lower Light River salinity management plan
APPENDIX 2: LIGHT RIVER SALINITY DATA FROM
WATERWATCH
Light River salinity data is available for the only two sites monitored by
Waterwatch in the Mid and Lower Light sub-catchments. Site LIG400 is
located at Hamley Bridge and site LIG550 is located SW of Hamley Bridge at
Rockies Reserve. The readings are in EC units of micro Siemens per cm
(μS/cm).
Date
LIG400
LIG550
March 2004
May 2004
May 2004
June 2004
July 2004
September 2004
November 2004
10500
11700
12000
13500
14100
11300
11700
7700
4500
9700
10300
10600
8800
7700
March 2005
May 2005
June 2005
August 2005
September 2005
October 2005
15650
16520
13330
9500
8300
7760
19420
8500
9300
8300
March 2006
May 2006
June 2006
August 2006
September 2006
October 2006
10300
12590
12840
12300
13100
13440
14000
11500
13100
13000
April 2007
May 2007
June 2007
August 2007
September 2007
November 2007
-
19600
18800
12800
10800
13600
-
March 2008
-
19500
13110
11980
Average
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Mid to Lower Light River salinity management plan
APPENDIX 3:
GROUNDWATER DATA FROM OBSWELL
Data from Obswell operational wells
Obs No.
Depth of
well (m)
Aquifer
Depth to
water (m)
EC
(μS/cm)
TDS
(mg/L)
PTG073
91.44
Tertiary
2.50
13047
8135
MOR054
38.40
Tertiary
9.70
430
237
MOR055
15.54
Tertiary
8.10
3350
1861
MOR133
76.00
Basement
25.98
2830
1569
MOR198
62.00
Basement
11.22
4430
2471
BLV005
41.00
Tertiary
6.07
13560
7843
BLV006
72.00
Basement
21.95
5780
3240
BLV007
114.00
Basement
51.30
5470
3063
BLV008
12.00
Quaternary
5.91
18050
10613
BLV009
8.00
Quaternary
5.94
5550
3109
BLV010
10.00
Quaternary
3.51
18570
10939
PTG = Hundred of Port Gawler
MOR = Hundred of Moorooroo
BLV = Hundred of Belvidere
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Mid to Lower Light River salinity management plan
Hydrograph (BLV007) from Basement Rock aquifer – 1979 to 2008
Hydrograph (BLV010) from Quaternary aquifer – 2002 to 2008
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Mid to Lower Light River salinity management plan
Locations of Obs wells in the Stockwell and Neukirch areas
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Mid to Lower Light River salinity management plan
APPENDIX 4:
SPECIES FOR REVEGETATION
A tree, shrub and grass species list provides guidelines for the most suitable
species for revegetation purposes in the Mid and Lower Light River subcatchments (S Gillett, Revegetation Consultant, Rural Solutions SA, pers
comm.). This includes species for both saline and non-saline areas.
(1) Species suitable for saline areas
Scientific Name
Eucalyptus largiflorens
Rhagodia candolleana
Rhagodia parabolica
Common Name
river box
sea-berry saltbush
mealy saltbush
Salinity
Level
tolerated
Moderate
Moderate
Moderate
Atriplex cinerea
Atriplex amincola
Atriplex nummularia
coast saltbush
river saltbush
old-man saltbush
Mod - High
High
High
Atriplex semibaccata
Casuarina obesa
Enchylaena tomentosa
Puccinellia ciliata
Eucalyptus kondininensis
berry saltbush
swamp oak
ruby saltbush
puccinellia
Kondinin blackbutt
High
High
High
High
High
Eucalyptus occidentalis
Eucalyptus platypus
Nitraria billardierei
flat topped yate
platypus gum
nitre-bush
High
High
High
short-leaf honey-myrtle Very High
Melaleuca brevifolia
Melaleuca halmaturorum ssp.
swamp paper-bark
halmaturorum
Very High
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Other Comments
Tolerant of waterlogging
Tolerant of grazing
Quick growing but short
lived. Useful for
establishing cover
quickly
Grow from seed that
comes from salt tolerant
strains of this tree
Not very long lived
Tolerant of waterlogging.
Plant near the waterline
in creeks
The most salt tolerant
species available
Mid to Lower Light River salinity management plan
(2) Species suitable for non-saline areas
Scientific Name
Common Name
Acacia acinacea
Acacia paradoxa
Acacia pycnantha
Acacia retinodes var. retinodes (hill form)
Allocasuarina verticillata
Aristida behriana
wreath wattle
kangaroo thorn
golden wattle
Wirilda
drooping sheoak
brush wire-grass
Atriplex semibaccata
Danthonia caespitose
berry saltbush
common wallaby-grass
Danthonia geniculata
Dodonaea viscosa ssp. Spatulata
Enchylaena tomentose
Enneapogon nigricans
Eucalyptus leucoxylon ssp. Pruinose
Eucalyptus odorata
Melaleuca brevifolia
Rhagodia candolleana
Rhagodia parabolica
Stipa blackii
Stipa elegantissima
Stipa nitida
Themeda triandra
Vittadinia blackii
kneed wallaby-grass
sticky hop-bush
ruby saltbush
black-head grass
inland South Australian blue
gum
peppermint box
short-leaf honey myrtle
sea-berry saltbush
mealy saltbush
crested spear-grass
feather spear-grass
Balcarra spear-grass
kangaroo grass
narrow-leaf New Holland daisy
Allocasuarina muelleriana
Bursaria spinosa
Callitris gracilis
common oak-bush
sweet bursaria
southern cypress pine
Clematis microphylla
Correa glabra
Dianella revoluta var. revoluta
Einadia nutans
Elymus scabrus var. scabrus
Eucalyptus goniocalyx
Eucalyptus microcarpa
Lomandra multiflora ssp. dura
Vittadinia gracilis
Xanthorrhoea quadrangulata
Arthropodium strictum
Convolvulus erubescens
Goodenia pinnatifida
Lomandra densiflora
Lomandra effusa
Prostanthera behriana
old man's beard
rock correa
black-anther flax-lily
climbing saltbush
native wheat-grass
long-leaf box
grey box
hard mat-rush
woolly New Holland daisy
rock grass-tree
common vanilla-lily
Australian bindweed
cut-leaf goodenia
soft tussock mat-rush
scented mat-rush
downy mintbush
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