Depuis with Passé Composé

Question

If a date or measurement of time is not included in a sentence, can you use passé composé with depuis? Examples:

"On parle de ce qui s'est passé depuis qu'on s'est vues."

" Depuis quelques années, le lac a diminué."

Thank you!

Accepted Answer

Hi Helen,
You can use the passé composé with depuis after certain negative sentences and the following Kwiziq lesson will give you some examples -
https://french.kwiziq.com/revision/grammar/when-to-use-either-le-passe-compose-or-le-present-in-negative-sentences-with-depuis
Your example of the lake is interesting because if you use the passé composé,  it indicates that the level has stabilized.
But if you used the present tense -
Le lac diminue depuis quelques années
you have the impression that this lowering of the lake level is ongoing.
Interesting question, sorry about the delay...

Answer

The first sentence seems ok to me. In the second sentence I would use the present tense, indicating that the lake has started to shrink in the past and is still continuing now: Depuis quelques années, le lac diminue.