The principal concentration of Ritharngu-speaking people was in the general area of the upper Koolatong River (Heath 1980:3). An inland group east and south of the Arafura Swamp and east of the true Goyder River, extending to about the Mitchell Ranges and Koolatong River headwaters; southern boundary near the headwaters of the eastern tributaries of the Goyder River (Tindale 1974).
Ngukurr Language Centre has run intermittent Ritharr?u (and Wägilak) language programs at the Ngukurr Community Education Centre (2005 - 2007; 2019).
Ngukurr Language Centre https://ngukurrlc.org.au/
Speaker numbers were measured differently across the censuses and various other sources listed in AUSTLANG. You are encouraged to refer to the sources.
Speaker numbers for ‘NILS 2004’ and ‘2005 estimate’ come from 'Table F.3: Numbers of speakers of Australian Indigenous languages (various surveys)' in 'Appendix F NILS endangerment and absolute number results' in McConvell, Marmion and McNicol 2005, pages 198-230 (PDF, 2.5MB).
Heath, Jeffrey. 1980. Basic materials in Ritharngu : grammar, texts and dictionary: Pacific Linguistics B62. Canberra: Pacific Linguistics.