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Salinity and Bulk Water Workshop 27 October 2010
Werribee Irrigation District
Today’s workshop
1. Welcome and outline of workshop2. Bulk water discussion
a. Metro water overview – Ian Smith, Melbourne Waterb. Allocation models for river water
3. Soil monitoring resultsa. Update on 2010 soil testing results and analysis – Tony Pitt
Break4. Bulk supply management discussion
a. Managing access to river/recycled/metro water5. Close
Bulk water discussion
Melbourne Water
New River Allocation Model
Some context…
• 13 years of drought• Few years of good river water allocations (except 04/05; 05/06,
10/11)• Allocations less than 15% from 2006/07 until this year.• Historic allocation system:
1. Allocate available water for this year to 100%
2. Put aside 10,000ML for next season
3. Then allocate sales (Low Reliability Water Share)Current allocation system puts away water for next season before we reach 100%
How we propose to allocate available water between 50% – 100% of entitlement
Example 150% of entitlement available this year
Example 150% of entitlement available this yearplus further inflows to allow an extra 30% allocation
Example 150% of entitlement available this yearplus 30% further inflows – split 50:50 this year:next year
Example 1So allocation this year is 65% (50+15) plus 15%* towards next year
Example 265% of entitlement available this year plus greater inflows
Example 265% of entitlement available this yearplus further inflows to allow an extra 20% allocation
Example 265% of entitlement available this yearplus 20% further inflows – split 50:50 this year:next year
Example 2So allocation this year is 75% (65+10) plus 25%* towards next year
How we propose to allocate available water above 100% of entitlement
Example 1So if we have 75% of entitlement available this year (from previous example)
Example 175% of entitlement available this yearplus further inflows to allow an extra 25% allocation
Example 175% of entitlement available this yearplus further inflows to allow an extra 25% allocationyou keep 100% of entitlement
Example 2100% of entitlement available this yearplus 25% further inflows
Example 2 100% of entitlement available this yearplus 25% further inflows – split 50:50
Example 2 New allocation this year 100% plus 37.5%* towards next year and 12.5% Sales
Allocation scenario = 100% HRWS + 12.5% LRWS in 1st year 37.5% in 2nd year
0%
20%
40%
60%
80%
100%
120%
140%
160%
10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110% 120% 125% 130% 140% 150% 48%
Available water
All
oc
ati
on
minimal inflows
HRWS 2011/12
LRWS 2011/12
HRWS 2011/12
LRWS 2010/11
HRWS 2010/11
Benefits of the 2010/11 allocation method
• More conservative; recognises less reliable river flows• Provides more security for following seasons• Manages water to stretch further over dry seasons• Provides a more certain planning horizon for irrigators in dry times
Looking to the future:Continuous Sharing
Continuous sharing …
• Is a method of water accounting• Used in Victoria for large electricity customers in Gippsland• Used in areas of Queensland since 1999
• Growers interest is growing in other parts of Queensland
• Growers have increased production without increasing water use through better water management due to continuous sharing
Continuous sharing provides more individual choice and requires more decision making.However – customers can choose to take standard allocations if they want.
Example of continuous sharing…
Reservoir Inflows less storage losses and environmental flows
Outflows plus delivery losses
Your storage share…
Reservoir
Outflows plus delivery losses
Inflows less storage losses and environmental flows
Your storage share…
Reservoir
Outflows plus delivery losses
Inflows less storage losses and environmental flows
Your storage share…
Reservoir
Outflows plus delivery losses
Inflows less storage losses and environmental flows
Your storage share…
Reservoir
Outflows plus delivery losses
Inflows less storage losses and environmental flows
Your storage share…
Reservoir
Outflows plus delivery losses
Inflows less storage losses and environmental flows
Your storage share…
Reservoir
Outflows plus delivery losses
Inflows less storage losses and environmental flows
Your storage share…
Reservoir
Outflows plus delivery losses
Inflows less storage losses and environmental flows
Your storage share…
Reservoir
Outflows plus delivery losses
Inflows less storage losses and environmental flows
Your limit on seasonal use…
Total Annual Use Limit
Your seasonal cap…
Total Annual Entitlement
Your seasonal cap…
Total Annual Cap
You can trade seasonal cap
Continuous sharing example…Water share account
A
Storage 200ML
-10ML loss
=190ML
-65ML Rel
-10 ML loss
=115ML
-65ML Rel
-5ML loss
=45ML
+50ML trade
=95ML
+25ML inflow
=115ML
Entitlement Cap account
B
Storage 200ML
-10ML loss
=190ML
-0ML Rel
-15ML loss
=175 ML
-0ML Rel
-15 ML loss
=160 ML
-50ML traded
=110 ML
+25 ML Inflow
=140ML
A BEntitlement
100ML
0 ML use
=100 ML
-50 ML use
=50 ML
-50 ML use
=0 ML
+ 25 ML trade
=25 ML
Entitlement
100ML
0 ML use
=100ML
0 ML use
=100 ML
0 Ml use
=100 ML
-25 ML traded
=75 ML
A B
Next season115 ML 140 ML 100 ML 100 ML
What are the benefits of continuous sharing?
• You manage your water share at the storage• No annual allocation made for the district • There is no reset at the end of the season for water shares• The maximum you can store is limited by the size of your storage share• The maximum you can use in a season is capped• The maximum you can use is reset at the end of a season• You can separately trade: water, water share and entitlement caps• The legal water entitlement you currently hold remains the same• The maximum volume in your storage depends on your storage size • You share inflows based on your storage share • You share storage losses based on the volume you store• Your use includes delivery losses• The water you have depends on inflows, losses, use and trades • More flexibility can provide greater certainty and planning horizon
It’s like having your own storage
What next …
• Are you interested?• Customer support – If strong, proceed with initial study• Legislative changes are required – it will take time
• Develop model to suit local conditions • Develop information package for customers • Run information sessions and inform customers on continuous
allocation use
Soil management
Tony Pitt
Six years of soil testing
• In 2005/06, recycled water use was fairly minor – just 47 farms with more than 1 ML/ha.
• For 2006/07, recycled water underpinned crop production for Werribee
• For the following 4 years, recycled water was by far the dominant source of irrigation water for the district.
• The salinity of the recycled water is 1700 to 2300 EC– 1,700 uS/cm to 2,300 uS/cm – units used for irrigation water– 1.7 dS/m to 2.3 dS/m – units used for soil water.
Average Soil Salinity
0
1
2
3
4
5
6
7
8
Baseline 2006 2007 2008 2009 2010
ECe
dS/m
Soil Ece REIP Threshold
Average Soil Chloride
0
100
200
300
400
500
600
700
800
900
Baseline 2006 2007 2008 2009 2010
Conc
entr
ation
mg/
kg
Chloride REIP Threshold
Average Exchangeable Sodium Percentage (ESP)
0
2
4
6
8
10
12
14
16
18
20
Baseline 2006 2007 2008 2009 2010
ESP
%
ESP REIP Threshold Sodic
• Average surface soil salinity is back to baseline values
• District average chloride has fallen by 40 % in 12 months
• Sodium values however are unchanged• Sodicity is apparent when collecting soil samples
• Winter rainfall better but still below average
In 2010
• The Red Brown Earth soils of Werribee South are very forgiving and very responsive to rain
• The late summer and autumn period are the most important times for salinity management
• For every irrigated crop some leaching is required• A negative impact of rainfall on sodic soils is the
dispersion and sealing of the soil surface
Short term
• Natural leaching from rain will remove the surface salinity provided the soils are kept permeable
• Rain or low salinity water doesn’t improve sodicity• Sodicity requires continuous on-farm management• Gypsum dosing of the irrigation water could be better
option than broadcast gypsum
Long term
• Adding calcium– Gypsum broadcast– Gypsum added to water– Other calcium fertilizers
Sodicity management
In summary
• Werribee South soils can handle 2,000 to 2,200 EC water for a season or two with very good farm management
• Evidence from six years of soil testing indicates 1,300 EC –1,800 EC, with minimal leaching should be sustainable provided soil sodicity is kept under control
• Above 1,800 EC leaching has to increase and be planned for each crop
• Lower salinity water may increase the problems of surface sealing and poor aeration
• On-going sodicity management important
Break
Bulk supply management discussion
Planning Scenarios
River flow history
Lerderderg River seasonal inflow 1990/91 to 2009/10(Inflow at Sardine Creek site, Lerderderg ~ 40% of Werribee catchment flows)
-
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
45,000
50,000
55,000
60,000
65,000
70,000
90/9
1
91/9
2
92/9
3
93/9
4
94/9
5
95/9
6
96/9
7
97/9
8
98/9
9
99/0
0
00/0
1
01/0
2
02/0
3
03/0
4
04/0
5
05/0
6
06/0
7
07/0
8
08/0
9
09/1
0
10/1
1
Tota
l Sea
sona
l Flo
w (M
L/ye
ar)
Natural flow Average 20/21 to 89/90 Average 90/91 to 09/10
Average 97/98 to 09/10 Average 05/06 to 09/10 5 year rolling average
Worst caseMediumOptimistic
WIF Climate planning scenarios
Planning scenarios…
Planning scenarios…
Planning scenarios…
How do we use this information to revise the rules
River Water Salinity
Seasonal Allocation
Shandy Target
Less than Shandy Target
Between Shandy Target and 1,800EC
Greater than 1,800EC
Up to 50% 1,800EC Shandy
Target River Water Salinity
Salinity with maximum practical Recycled
Water
50% - 75% 1,600EC Shandy
Target River Water Salinity
Salinity with maximum practical Recycled
Water
75% - 100% 1,400EC Shandy
Target River Water Salinity
Salinity with maximum practical Recycled
Water
Above 100% 1,000EC Shandy
Target River Water Salinity
Salinity with maximum practical Recycled
Water
Possible Salinity Triggers
Adapting to a mixed water approach
Provides more security to customers– critical in low allocation years
Triggers for accessing metro water…
• Metro water is a back-up option only– When river and recycle water salinity too high– Becomes part of the shandy with river and recycled– Increases volume in dry years particularly in peak summer– Increases security of supply
• Considerations when very low river allocation– River water salinity likely to be higher than recycle water– Target salinity level for shandy– How the salinity target may change over the season– The benefit of extra volume in summer
• Planning scenarios
Wet year (100+% allocation) No metro water
Low allocation (50%+) Unlikely to use metro water
Very low allocation (<25%) Consider using metro water
$-
$500
$1,000
$1,500
$2,000
$2,500
$3,000
$3,500
1300 1550 1950 2200
Salinity (ECe)
Costs of Salinity Management Lettuce (per/ha/crop)
Metro WaterYield & Quality LossExtra Ca FertiliserGypsumExtra Water - Leaching
$-
$200
$400
$600
$800
$1,000
$1,200
$1,400
1300 1550 1950 2200
Salinity (ECe)
Cost of Salinity Management Broccoli (per/ha/crop)
Metro WaterExtra Ca FertiliserGypsumExtra Water - Leaching
Salinity targets…
• Summer threshold range from 1,500 – 1,800 EC– Depends on river allocation and salinity of river water
– Volume of metro water to be accessed
– Recycled salinity
– Soil health before summer
• Winter threshold range from 1,800 - 2,000 EC– Recycled water salinity lower in winter and <2,000 EC
– Crops can tolerate higher salinities in winter
• Salinity thresholds will require review by EPA
Shandy scenarios
0
500
1000
1500
2000
2500
500ML 1000ML 1500ML 2000ML
Metro water accessed
Sh
an
dy
EC
Jan Jan-Feb Dec-Feb Dec-March River/Recycle
Adapting to a Mixed Water Approach
Adapting to a mixed water approach
Provides more security to customers– critical in low allocation years
Adapting to a mixed water approach
Provides flexibility to adapt to different seasons
Adapting to a mixed water approach
River water will be the first choice– is unreliable– Salinity too high in low allocation seasons
Adapting to a mixed water approach
Recycled water very reliable– Limits on supply rate– Salinity 1700 – 2200 EC
Adapting to a mixed water approach
Metro water last choice– Very low salinity– Limits on daily volume– Can provide extra water at peak times
Close