71 people, whose contracts are not being renewed by the council, will lose their jobs between now and the end of the year.
49 others are to be let go between January and March next year.
IMPACT representative Richie Carruthers said the situation of the remaining 118 contract workers is under discussion.
Donegal County Council is making no comment on the situation until after a council meeting next Monday when the matter will be discussed.
Donegal, like all other local authorities, has to make a saving of 3% on its payroll costs.
Fine Gael TD for Donegal South West Dinny McGinley described the situation as a 'virtual tsunami' for the county.
He said he had been in touch with colleagues in other counties and it appeared nothing as shocking was happening in other local authorities.
