This value is calculated from two metrics, found on page 118 of the 2015 Annual Report.

This is calculated as:

706,028.3 (Recycled water) / 1,387,120.9 (Water used)

Which gives a value of 50.89%

Page 115 of the report also mentions that "The company has

proprietary facilities for handling and recovering the various

grades of wastewater produced to minimise discharges."

This allows the company to achieve such a high ration of reuse.