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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 101 of 153. I I I I I I I I I I I I I I I I I I 13 A log-Pearson Type III distribution was fitted to the data for cases (a), (b) and (0). Low flows were treated in accordance with the recommendation in IIAustralian Rainfall and Runoff" section 9.2.9. The distribution from case (p) was selected as being a suitable representation of the flood frequency although the difference between (a) and (b) is small and both distributions well within the confidence limits of each other. The adopted flood frequency curve for G.S. 006046 is shown in Figure 4. At G.S. 006009, maximum gauge heights for all the water years 1952/53 to 1977/78 are known and it has been possible to reliably estimate the peak annual discharges a (see Table 6). A log-Pearson Type III distribution was fitted to the data using the technique outlined in "Australian Rainfall and Runoff" section 9.2.9 (see Figure 5). At G.S. 006126 only the water years 1965/66, 1974/75 and 1975/76 have complete records though the maximum gauge heights are known for all years since 1960/61 except 1976/77 (see Table 6). The very small peak discharge for 1976(77 was estimated from G.S. 006046 and G.S. 006009. Again a log-Pearson Type III distribution was fitted to the data (Figure 6) using the same techniques as above. The small number of records and the large number of low discharges result in the confidence limits for the G.S. 006126 annual flood frequency distribution being very large, especially when compared with the confidence limits obtained for G.S. 006046 and G.S. 006009. A comparison of confidence limits for the 100 year return period flood is shown in Table 5. Table 5 CONFIDENCE LIMITS FOR 100 YEAR RETURN PERIOD FLOOD G ... S .. 006046 G S . 006009 G.S. 006126 5\ Limit (m 3/s) 2300 1800 3800 Value (m 3/s) 1040 890 1120 95'5 Limit(m 3/s) 720 620 660 Table 5 also demonstrates that even at a fairly high return period the adopted peak discharge at G.S. 006009 is smaller than that at G.S. 006046 and G.S. 006126.