You will be given a definition of a task first, then some input of the task.
In this task, we ask you to elaborate the sentence without changing its general meaning. You can do so by explaining further the input sentence, using more precise wording, adding qualifiers and auxiliary information etc.

The differences between perennial , intermittent , and ephemeral streams are not exact and can change if different measures are used by different groups .
Output:
The boundaries between perennial , intermittent , and ephemeral channels are not defined , and subject to a variety of identification methods adopted by local governments , academics , and others with a need to classify stream-flow permanence .