Author : J. V. Hodgkinson F. C. A. Chartered
Accountant : Aug 2006 to April 2013
The principal thrust of this
This is my review based on official
statistics and documents. It is done in conjunction with Ron McMah, grazier
of Imbil and Trevor Herse, retired of the Gold Coast
The Traveston dam is designed to permit the overflow of large scale meteorological events. Refer to Hydrology Mary Valley
Currently the Mary River has ceased flowing above the dam site (CM October 2009). The Mary River mirrors the Stanley River which is our main water supply. It has the backup storage of the Wivenhoe dam and even that dam is proving inadequate to control major events.
It is my view and others that the 85% requirement of all water that flows in the Mary River must reach the River mouth is made up almost entirely of flood water. We now know for certain that flood water is damaging to the eventual point where it enters the sea.
Here again, the use of the "mean annual flow" includes all of this flood water. It is not difficult to envisage a distortion to percentages when most of the water is flood water and especially the very high rainfall events inclusion.
The following give one an appreciation of how our main water supplies fall and why they are our main water supply.
Pattern of Rainfall
The Mary Valley is the site of the proposed Traveston Dam. Its catchment is adjacent to the Somerset Dam catchment. Its rainfall operates in the same way as the Somerset. A comparison of the rainfall of the two catchments is attached.
There are no inflow figures as there is no Dam. However the Bureau of Meteorology do have the River heights at Gympie located below the Dam. They effectively replace inflow assessments. In addition their web-site records the major floods and it is also attached. These majors date back to 1893 and are mirrored by the "uncommon events" of the Somerset with the exception of 1968.
Photos : Bureau flood heights at Gympie and Maryborough together with major flood heights at various location on the Mary River