It is recommended the following minimum periods are used:
- 10 years for WSUD treatment performance and small-scale systems.
- 20 years for stormwater harvesting large scale integrated water management plans and strategies (less than 100 hectares) and catchments with an impervious fraction less than 20 percent or where pervious flows are substantial.
Two rainfall regions were identified for the City. Areas with rainfall less than 500 millimetres annually were designated “Little River” and those with rainfall greater than 500 millimetres annually were designated “Geelong North” to coincide with the Bureau of Meteorology (BOM) station names. The rainfall regions are shown in Figure 1.
Figure 1 : Rainfall region boundaries determined for Greater Geelong
Modelling timestep
The modelling timestep should be less than:
- The shortest time of concentration.
- The shortest treatment detention time under design flows.
For the City all models should be run at a 6 minute modelling timestep. The use of larger timesteps reduces model accuracy and can increase the variability of results while allowing it to run faster. There is little justification for using larger timesteps for most practical modelling purposes with modern computers. Where a different timestep is proposed it must be agreed in writing by the City and comply with the above requirements.
Climate templates
The climate templates are available for download on our website.
The filenames are:
- 10year_GeelongNorth_1971-1980_6min_mlb
- 10year_GeelongNorth_1971-1980_6min_sqz
- 20year_GeelongNorth_1971-1990_6min_mlb
- 20year_GeelongNorth_1971-1990_6min_sqz
- 10year_LittleRiver_1992-2001_6min_mlb
- 10year_LittleRiver_1992-2001_6min_sqz
- 20year_LittleRiver_1989-2008_6min_mlb
- 20year_LittleRiver_1989-2008_6min_sqz
The user should select the appropriate template for the project location and type of analysis.
Note that as the templates have been infilled to improve quality they cannot be reproduced by creating a template directly from the raw data.
Where an alternative climate template is proposed to be adopted it must be based on a similarly rigorous approach as that used to determine the above (see Appendix B) and its use is subject to agreement in writing by the City.
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