North Pine Dam
AN OBSERVATION OF THE CONFLUENCE OF STATISTICAL ABERRATIONS, DAM RATIOS, TIMING AND UNCOMMON RAINFALL EVENTS THAT COMBINED TO HAVE OUR LEADERS DRAW INCORRECT CONCLUSIONS. THEIR INFLUENCE ON ACTIONS TAKEN.

Author : J. V. Hodgkinson F. C. A. Chartered Accountant : Aug 2006 to November 2013    

The principal thrust of this website is
FLOOD PROOFING BRISBANE from damaging floods to the point of extinction. MITIGATING flooding in Ipswich and Gympie. Putting REAL MEANING into "Drought proofing SEQ" and ensuring our water supplies by natural means well into the future

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

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May 2009: No change from first update

Associated evidence. The North Pine Dam.

You will see the evidence that the North Pine Dam mirrors the North Pine Page 1 of 2.jpg (168835 bytes) pattern and volume of rainfall of the BorumbaNorth Pine 2 of 2.jpg (66448 bytes) Dam catchment. In the first instance we will look at the available information from the professionals at SEQWater.


The comparison of rainfall follows :-

NP Rain all stations 6 year lots 65 to 06.jpg (312950 bytes)Boroumba rainfall.jpg (400246 bytes)

A summary of the comparison of three stations in the Borumba catchment now follows :-

Nth Pine V Borumba all 3 stations.jpg (286581 bytes)This shows a high degree of consistency of pattern and volume. The Borumba Dam recording station is the same in the Summer months where all of the majors occur.

 

The SEQWater Dam statistics of the North Pine now follow :-

Dam features from SEQWater Web.jpg (215540 bytes)
Of interest is the catchment area of 348 sq klms and a yield of 54,750ML. You will notice that this yield has remained stable whereas the yield from the Wivenhoe and Somerset has been under consideration for some time.

Catchment variation

The calculation is : 54,750ML X 466 Sq Klms of the Borumba catchment / divided by the catchment of the North Pine at 348 Sq Klms.
Equals 73,314ML.

Flood mitigation

The SEQWater information above shows that there is no flood mitigation in the North Pine Dam with all flood water released in a controlled manner. The photo also shows the flood releases of the 1999 event. A glance at the major rainfall figures above shows a similar pattern to all of the Dams and a substantial volume would have flowed over the Dam. We have sufficient information to examine this aspect.

The Borumba Dam is its own flood mitigation if the Dam wall is raised in accordance with Mr R McMah's contribution. He envisages the Borumba capacity to be in the region of 2,000,000ML capacity.

The Courier Mail article of the 17th February 2007 quoted the Summer Rain Courier Mail 10 02 7.jpg (371046 bytes)Dam manager as saying that it would take 600 to 650 mm of intense rain to fill the Dam. Its capacity is 214,960ML ( see Dam statistics)

 

The attached schedule is a summary of rainfall in that category. Of particular interest is the 1999 rainfall average of 438mm in the North Pine Dam with the photo above clearly showing the flood discharge. The other rainfall events are significantly higher. The higher rainfall can have a much higher impact than a direct correlation.

Catchment efficiency

It is generally recognized that, with its rocky terrain, the Gympie Times P2.jpg (361826 bytes)Borumba Dam catchment is the most efficientGympie times P1.jpg (323632 bytes) of the Dams. In the area of proof, there is a conflict of information. The Regional Manager at the time advised that the "Peak discharge per day" was 154,300ML. The Department of Natural Resources web-site advises that the total discharge for the month of February 1999 was 167,062ML.

The Qld Government advises that the duration of the flood in Flood Mitg 1999.jpg (74680 bytes)the Mary Valley was significantly more than a single day. Examination reveals that the volume of water was most likely to be double the 154,300ML to over 300,000ML.

You will notice that the Dam Manager at the time compared the volume of water in a single day to 1/2 of Sydney Harbour. That converts to 250,000ML a day. However, we should keep in mind that he was making a point.

Using the Dam Manager's advice of the time, the efficiency of the Borumba catchment compared to the rest of the Mary River catchment is above 1.7 times. If the Dept of Natural Resources information is correct, the point is not proven. Refer to my calculations under "Hydrology" button.

Conclusion

With the catchment area of the Borumba being either equal to or more efficient than the North Pine, the Calculation based on the catchment area is stable at 73,314ML. 

The evidence points to a very high volume of inflow not retained by the North Pine because of the lack of flood mitigation or retention availability. This is not so in Mr R. McMah's proposition of the expanded Borumba Dam. This will make a significant addition to the 73,314ML already calculated.