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Alice Springs recreational dam hydrology report project 6



Alice Springs recreational dam hydrology report project 6


Jackson, D.; Paige, D.


E-Publications; E-Books; PublicationNT; Report no. 12/1979







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Northern Territory Government

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Report no. 12/1979

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Attribution International 4.0 (CC BY 4.0)

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Northern Territory Government



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Technical Report WRD79012 Viewed at 00:02:46 on 18/02/2010 Page 100 of 153. I I I I '. I I I I I I I I 1 I I I I 12 3 ANALYSIS OF DATA 3.1 General This section discusses the analysis of the hydrographic data to determine flood frequency, unitgraphs and maximum probable floods, and also the generation of stream flow sequences. 3.2 Flood Frequency At G.S. 006046 peak annual gauge heights are known for years 1960/61 to 1977/78 except for 1975/76. The peak water year floods and gauge heights are included in Table 6. The peak flood in 1975/76 was in early February, but there are no records from 6/2/76 to 16/2/76. Three approaches were used to analyse records from G.S. 006046. These were: Case (a, Ignore the 1975/76 water year and analyse 17 years of records . Case (b) Case (cl Assume the peak discharge at G~S. 006046 in 1975/76 is of the same o~der of magnitude ~s that at G.S. 006009 in the same year. Estimate a peak discharge for 1975/76 by using a rainfall - peak discharge correlation. This correlation used maximum daily rainfall from both Alice Springs Post Office, and Bond Springs. Ranked peak discharges at Wigley Gorge and ranked maximum daily rainfalls were plotted at points of equal probability. Close examination indicated that storms in the Todd River catchment are often isolated thunderstorms. This is thought to indicate that a rainfall event of a particular return period need not necessarily be associated with a stream flow of the same return period. Correlation between ranked rainfall and runoff at G.S. 006046 resulted in a correlation of 0.92 for Alice Springs rainfall data and 0.8S for Bond Springs rainfall data. Using rainfall data from 1975/76 the peak discharge at G.S. 006046 in that year was estimated to be 650 m3/s. This is considered to be excessively high especially when compared with the peak discharge at G.S. 006009 and G.S. 006126 (see Table 6). Correlation with the actual storm also overestimated the peak discharge.