Alice Springs recreational dam hydrology report project 6
Jackson, D.; Paige, D.
E-Publications; E-Books; PublicationNT; Report no. 12/1979
1979-10-01
Date:1979-10
English
Northern Territory Government
Darwin
Report no. 12/1979
application/pdf
Attribution International 4.0 (CC BY 4.0)
Northern Territory Government
https://creativecommons.org/licenses/by/4.0/
https://hdl.handle.net/10070/228346
https://hdl.handle.net/10070/674275
Technical Report WRD79012 Viewed at 00:02:46 on 18/02/2010 Page 68 of 153. I I I I I I I I I I I I I I I I I I I I 42 Estimates of the time required to fill the reservoir with silt are 120 years I 40 years and 400 years for average, dry and wet conditions respectively. Those estimates of useable reservoir volume and time to fill with silt are lower limits. Brune's analysis uses mean annual sediment loads . .t'"or the Todd Catchment median values are up to 50% lower than mean values and are a better estimate of the most frequently occuring annual load in the arid environment. Furthermore a deterltion time of 0.42 years (ISO d~ys) is unrealistic in relation to typical lengths of hydrographs (one to three days) and tile short length of the dam at top water level (1600m) For a typical 1 in 10 year hydrograph in which mean daily flow is of the order of 100 m 3 /s; detention time 5.1 Mm 3 100 x 3600 x 24 K 0.59 days 0.002 year. Trap efficiency from Brune's curve approaches 5% for a 0.002 year detention time instead of the 95\ obtained for a 0.42 year detention time. Table 5 shows reworked estimates of useable reservoir capacity for a 0.002 year detention time and the media~ annual sediment load. Table 5 PERCENTAGE OF ORIGINAL CAPACITY REMAINING AFTER DIFFERENT PERIODS OF OPERATION ASSUMING 5% TRAP EFFICIENCY. Time 25 Years 50 Years 100 Years Suspended Sediment Relationship .~ Average Conditiuns 99 98 97 Dry (1965) Conditions 98 97 94 Wet (1979) Conditions [ Negligihle1 Reductlon i j