AN OBSERVATION OF THE CONFLUENCE OF STATISTICAL ABERRATIONS, DAM RATIOS, TIMING AND UNCOMMON RAINFALL EVENTS THAT COMBINED TO PRESENT OUR DAMS AS VICTIMS OF A SEVERE DROUGHT. THIS IS NOT THE CASE. THEIR INFLUENCE ON CONCLUSIONS REACHED AND ACTIONS TAKEN.

Author : J. V. Hodgkinson F. C. A. Chartered Accountant : August 2006 to December 2009

The Underlying cause of our depleted dams had the appearance of "drought". However most people would not class 80 percent of rainfall compared with the Bureau of Meteorology long term average 1961 to 1990 as a "drought". This is the case in the catchments. Even less people would class it as a "drought" when closer examination of the rainfall shows that the inflow producing four Summer months had been quite normal with 99.7% in the Wivenhoe and 91.3% in the Somerset catchments. The 20% deficiency was in the low inflow producing eight non-summer months.

This incorrect conclusion of "drought" has clouded the real underlying cause of our depleted dams. It is the random nature of large scale rain depressions and they are our main water supply. They occur on average every 4 years and have the capacity to fill our dams in a few days. The last gap was six years 2001 to 2007 and caused a major and expensive panic. Further evidence is available in the tab DEPLETED DAMS or Click here

Dealing with those large scale events that extend beyond the 4 year average requires a very different approach than dealing with a "drought". The current water resource strategy has ignored the short history of the Wivenhoe dam.

May 2009 : No change since August 2007. 

The basis of this web site is Bureau of Meteorology rainfall Stations in the catchments and the Web-site of SEQWater, the Dam managers. Their Annual Reports reveal that they are a truly professional body. Their public announcements have been helpful and they are to be commended.

This is an example of the data provided by the Bureau. It is obtained through identification of the Rainfall Station numbers and then by request to the data section. A small fee is required. You will observe that the information is in EXCEL spread sheet format which gives easy access to assessing the required information.

The Bureau of Meteorology measures rainfall against the 30 year average (or mean)  1961 to 1990. To maintain statistical purity, I have used all the rainfall stations that have been in continuous operation from 1961 to 2006. The remaining stations were mostly closed prior to 2006 but have been inspected for possible aberrations.

These charts were initially used to confirm the rainfall maps. The Qld. Govt. Climate Change Centre for  excellence has since confirmed the overall percentage as 76.2%. The relationship of the Somerset and Wivenhoe dams is one of the central ingredients of this examination. The Somerset is on the Stanley river and the Wivenhoe on the Brisbane River at the junction of the Brisbane and Stanley Rivers. It backs up to the foot of the Somerset.

They have separate catchments but as we will see the Somerset is the dominant partner.

The North Pine Dam is completely separate to the other dams. (SEQWater verbal advice). It experiences similar rainfall patterns. A reading of the "water grid" indicates that the proposed Traveston dam will feed into the North Pine dam.