The lake flows into the sea near Goolwa at the Murray Mouth, but when the river flow is low the entrance is often blocked by a sand-bar. Originally subjected to tidal and storm inflows of seawater the lake is now maintained as fresh water by a series of barrages across the islands near the Murray Mouth. This has produced an annual requirement for more than 1 million mega-litres of fresh water to replace losses from evaporation that once came from sea water.
Traditionally the irrigation water for all the vineyards managed by FABAL was taken from Lake Alexandrina. Lake Alexandrina is primarily fed by the River Murray at its north eastern end but is also fed by the Bremer, Angas, and Finniss Rivers, all from the eastern side of the southern Mount Lofty Ranges. The lake is shallow and subject to relatively high evaporative rates.
DROUGHT IMPACTS MURRAY FLOW
(1 in 1000 year drought)
The Murray-Darling basin system has the capacity to store significant water reserves in major dams, but with the unprecedented low rainfall and resultant low inflows to the system from essentially 2002 – 2011 (the lowest on record), those reserves were largely depleted.
As a result of the drought the flow into Lake Alexandrina has been negligible and the level of the Lake fell steadily since during this period. In 2008, water levels in Lake Alexandrina and the connected Lake Albert became so low that large quantities of acid sulphate soils threatened to form. The soils on the lake beds are naturally rich in iron sulphides. When exposed to the air, such as may occur in a time of severe drought, the sulphides oxidize, producing sulphuric acid. The barrages now prevent seawater inflows that have prevented these phenomena in every drought since the last ice age.
As the level of Lake Alexandrina fell, the salinity of the remaining water increased and by spring 2007 was high enough to cause long term impacts when used for irrigation. By that stage, FABAL had already initiated a range of measures to not only secure its water supply but also the quality of its irrigation water.
IRRIGATION WATER MANAGEMENT
The wine grape projects in Langhorne Creek managed by FABAL each hold a water licence entitlement to a water allocation drawn from the River Murray. The ownership of the licence is either through a trust or through the land owning company. The water under these licences is drawn from the River Murray and piped to the property under licence.
Underground Water Licenses
A number of the vineyard projects in Langhorne Creek also own underground water licences which allow the drawing of the underground aquifer water for irrigation. Unfortunately this water is usually too saline for use untreated with wine grapes.
DESALINATION: REVERSE OSMOSIS
In late 2007, FABAL established a reverse osmosis (RO) plant on the Kayinga Vineyard in Langhorne Creek to secure reliability of quality water supply to the vineyard. RO is the preferred method to reduce water salinity and entails filtering out salts, under high pressure, through membranes. The RO plant allows the vineyard to desalinate underground water from the aquifer.
The underground water, due to its high salinity, is not suitable untreated for long term use for irrigation, but after desalination provides a high quality resource that provides an alternative water supply. After desalination, the water can be stored underground as part of the ASR (Aquifer Storage and Recovery) project, to be withdrawn and applied as irrigation.
WATER STORAGE: DAMS
Marandoo Estate Limited has built two large storage dams to provide additional storage of irrigation water.
A 200ML earth lined dam was constructed in 2007 at the Old Marandoo property and also supplies water to the adjoining property owned by National Vineyard Fund of Australia Limited.
At its Belvidere vineyard, a lined 100ML dam was also constructed in 2007 to store water for the MEL vineyard and the adjoining vineyard of National Vineyard Fund of Australia (No.4) Limited (NVFA-4L). Each vineyard has an equal right to water within the dam.
WATER STORAGE: ASR (Aquifer Storage and Recovery)
FABAL also commenced aquifer storage and recovery (ASR) in 2007 at the Marandoo Estate vineyard and the Kayinga Vineyard.
This process involves the storage of water (either drawn from the River Murray / Lake Alexandrina or from the desalination plant) in the underground aquifer for a period of up to 5 years. This effectively allows water to be stored in an underground ‘dam’ and then re-pumped at a later date for irrigation of the vineyard.
In April 2008, Marathon Water was created as a joint venture between FABAL and a near-neighbour at Belvidere, CMV Farms, to construct a 42 km pipeline to draw River Murray water above Wellington on the River Murray and pump it to the vineyards in Langhorne Creek.
This has secured not only access to River Murray water at a time when access to pumping sites in the Lake has been difficult, but also at a salinity that is more suitable for application to the grapevines without causing them significant stress.
Following the development of the Marathon Water pipeline and direct and indirect investment in the new Creeks Pipeline Company (a government backed community pipeline for Langhorne Creek built in late 2009), the irrigation water for the vineyards at Langhorne Creek can be sourced and transported via these pipelines from the River Murray, effectively bypassing Lake Alexandrina in the event of a recurring drought.
Despite the extreme hardships of the ‘Millennial’ Drought, the silver lining for the Langhorne Creek region and the FABAL managed sites is the fact that they are now some of the most secure sites in the country. The infrastructure development has created a level of adaptability and robustness that is unrivalled in most other regions.