Before….usIn its natural state, during severe droughts, theMurray River became a chain of waterholes. Theriver was too unreliable to enable intensesettlement. Bend it to our will!The Hume Dam completed in 1936 now ensuresa continuous flow of water. The massiveconstruction of regulation structures and waterstorages of the last 100 years has made itpossible to develop the MDB irrigation industry.
• The Hume Dame is the main operating storage of the Murray System. It takes a month for water released from the Hume Dam to reach South Australia.• Water is diverted from the Murray River all year round but demand is lower in winter. During winter and spring, as much water is stored as possible. Low inflows during summer mean more water is released, mostly for irrigation but also helps navigation and recreation on the river.• 90% of all diversions are for IRRIGATION.
Barrages, Weirs and Locks• To prevent saltwater entering the system in the lower lakes during times of low flow, 5 barrages were constructed from Lake Alexandrina to the Murray mouth.• There are 14 weirs and locks originally constructed for cargo boats to navigate the river and to divert irrigation water by gravity. They are still important for recreational boating although no longer used for cargo ships.
Snowy Mountains Scheme• 5% of the flows in the Murray come from the snowy river to boost irrigation supplies.• An agreement ensures that water is diverted to the Murray at a guaranteed minimum of 1000GL especially in dry periods.
Impacts of regulation• Of the water that would have originally reached the sea from the Murray-Darling Basin, over two-thirds is now diverted from its rivers each year. On some occasions flows have been so low that water has ceased to flow to the sea, though it is usually in drought conditions.
From this… To this…
Full river in summer
Interpreting Graphs Add another acronym to your toolbelt!• Trend – what is the general trend? i.e. growth, decline, stationary• Example – give specific points/periods from the graph to back your statement!• Exception – are there any points/periods on the graph that do not fit the general trend?• Quantify – USE NUMBERS AND NAMES.