By the way, did I steer you to the following?

http://www.australianrainbowfish.com/aquaticslife/plants/aponogeton/aponog_t.html

They mention new and established species in Oz and some of the river systems they are in. Perhaps your stream, if connected to one of those drainages, would also allow for I.D.ing your Aponogeton.

I read Kasselmann's essay on Aponogetons while going to sleep last night. (Retention was wayyyyy down.) She mentions four different habitats (temporary pond, permanent pond, temporary stream/ river, permanent stream/river. While some Apon. species are found in a couple of habitats and others just don't pigeon-hole easily, that might help.

Also, she notes in some stream systems, the plants flower and have submerged leaves while the stream water is clear in what may be the dry season. In the rainy season the water goes turbid. The plants may develop all surface leaves. Or they may retreat back into their bulb for a resting period.

If yours are the one which have a resting period, she suggests an interesting strategy to help them go dormant.

They are amazing plants, quite diverse and able to endure some pretty challenging habitats. And Kasselmann & that Austalian Aponogeton paper suggests there are a lot more than most of us would have guessed.

More later, it's a great day here but we have a storm front and miserable weather predicted for later too. First chore - clean up the remains of a venerable metal framed tank which blew off of a stand last night in what must have been quite a wind.