This plant is similar to Fimbristylis dichotoma, but different enough to raise doubts about that species as a correct ID. David Albrecht at the CSIRO wants to get a correct ID and will follow it up. Michael Bedingfield has supplied him with 2 sets of specimens. In his latest communication (20 Sept 2018) David said: "I think Fimbristylis aff. dichotoma is the best name to use for it at this stage. I’ll try to get out to the site this season and collect a small amount of live material. If I can get it going and keep water up to it over summer we might be able to get some fully developed mature fruits, which with help with the identification."