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GAWB Drought History

GAWB completed the raising of Awoonga Dam to 40m AHD in June 2002.  The Boyne Resource Operations Plan (ROP) and the Resource Operations Licence  (ROL) issued to GAWB restrict the amount GAWB can take from Awoonga Dam to 78,000 MLpa, the assessed Historic No Failure Yield (HNFY) of the 40m Dam. The current HNFY of Lake Awoonga is determined by the long-term drought that ended in 2003.

There are further provisions which restrict the amount which GAWB may take from Awoonga Dam  to 70,000Ml in the period until the 40m spillway is first overtopped.  GAWB will not enter into contractual obligations to sell more water in a year than permitted by the Boyne ROP. 

 The term “drought” can be defined as meaning a period of time where, having regard to predicted inflows, there is insufficient water stored within Lake Awoonga to provide Contracted Supply (which includes meeting customer reservations) some time within the next 60 months as predicted using GAWB’s drought model.

 There are two types of droughts (as the term is informally understood, not as drought is referred to in GAWB’s Drought Management Plan) on the rainfall record.

•  “Short-term” droughts where there was a severe rainfall deficit over periods of up to 12 months and typically with several months with zero rainfall and zero or very low flows in the Boyne River.  The worst short-term droughts with annual rainfall less than one half of the annual mean rainfall were in 1941 and 1969.

• “Long-term” droughts with a series of very weak wet seasons and subsequently low annual flows in the Boyne River, sometimes (but not always) coinciding with short-term droughts. The long-term droughts on record occurred during 1964–67, 1969–70, 1984–85, 1993–95, and 1997–2003.

The decades of the 1950s and 1970s had relatively high rainfall.

GAWB has carefully reviewed experiences from the imposition of water restrictions in 2002 and consulted with customers in setting its approach to managing the impact of drought on the volume of water available for supply.  

As required by the Department of Natural Resources and Water, GAWB’s Drought Management Plan has been registered.