Salinity and Bulk Water Workshop 27 October 2010 Werribee Irrigation District

Today’s workshop 1. Welcome and outline of workshop 2. Bulk water discussion a. Metro water overview – Ian Smith, Melbourne Water b. Allocation models for river water 3. Soil monitoring results a. Update on 2010 soil testing results and analysis – Tony Pitt Break 4. Bulk supply management discussion a. Managing access to river/recycled/metro water 5. Close

Introduction – Where we are today Five years of recycled water supply experience Extensive soil health data On-going access to metro water now an option Recycled contracts renewal required 1 July 2011

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 1 50% of entitlement available this year

Example 1 50% of entitlement available this year plus further inflows to allow an extra 30% allocation

Example 1 50% of entitlement available this year plus 30% further inflows – split 50:50 this year:next year

Example 1 So allocation this year is 65% (50+15) plus 15%* towards next year

Example 2 65% of entitlement available this year plus greater inflows

Example 2 65% of entitlement available this year plus further inflows to allow an extra 20% allocation

Example 2 65% of entitlement available this year plus 20% further inflows – split 50:50 this year:next year

Example 2 So allocation this year is 75% (65+10) plus 25%* towards next year

How we propose to allocate available water above 100% of entitlement

Example 1 So if we have 75% of entitlement available this year (from previous example)

Example 1 75% of entitlement available this year plus further inflows to allow an extra 25% allocation

Example 1 75% of entitlement available this year plus further inflows to allow an extra 25% allocation you keep 100% of entitlement

Example 2 100% of entitlement available this year plus 25% further inflows

Example 2 100% of entitlement available this year plus 25% further inflows – split 50:50

Example 2 New allocation this year 100% plus 37.5%* towards next year and 12.5% Sales

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 B Entitlement 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 season 115 ML140 ML100 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 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

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

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, ,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

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