It is hell’s own job to find much information about some of these Australian species. Of Rhadnosticta simplex Theisinger/Hawking is cursory, to say the least, and there is little help online. The former says simply, “inhabits streams and rivers” (at least that precludes lakes) and the latter adds, of the Australian distribution, “fairly common and localized”. Very helpful.
In Queensland, 2019, we bumped into this species twice and I just about managed to snag a picture of each specimen. The pictures are of differing aspects so they at least complement each other. The first, from an evening visit to Yabba Creek, looks quite freshly emerged but the second picture from Emerald shows something of the derivation of the common name, Powdered Wiretail.