2.1.4.2 Statistical analysis and interpolation

Table 7 shows the maximum and the 10th, 25th, 50th (median), 75th and 90th percentile daily flows for the 37 streamflow gauging stations for data available from 1983 to 2012. Half of the catchments have their 10th percentile flow (a flow that is exceeded 90% of time) less than 1 ML/day. Similarly, 19% of the catchments have their 25th percentile flow less than 1 ML/day. About 8% of catchments also have a median flow of zero or close to it (≤1 ML/day) implying flow in the stream occurs for less than half the time in these catchments. The majority of smaller catchments (<1000 km²) have their 10th and 25th percentile flows as zero except for the Peel River downstream of Chaffey Dam (407 km²).

Table 7 Maximum, median, 10th, 25th, 75th and 90th percentile flows for the Namoi subregion using data from 1983 to 2012

Data: NSW Office of Water (Dataset 1, Dataset 2, Dataset 3)

This table follows BA convention of assigning percentile values which is different to the NSW Policy Advice Note No. 6 at: http://www.water.nsw.gov.au/__data/assets/pdf_file/0010/548848/plans_notes_policy06.pdf