Flatsedges

I have spent hours trying to identify these flatsedges. The only thing I can say with certainty is that they belong to the genus Cyperus. But when trying to identify the species, things get complicated.

At first, I thought the plants with brownish inflorescences were Cyperus erythrorizos. Even the plant at the bottom right of the third picture could be one of those.

But when I searched again, it turned out that the first two look more like Cyperus ligularis and that the most conspicuous specimen in the third photo might be Cyperus strigosus or Cyperus odoratus.

These plants were growing in the margins of a coal pit lake (Anzoátegui state, eastern Venezuela.)

Does anyone know if I'm on the right track with the identification attempts?

Useful references:

Cyperus erythrorizos (Wikipedia)
Cyperus ligularis (Wikipedia, Spanish)
Cyperus strigosus (Wikipedia)
Cyperus odoratus (theferns.info)

I took these photos with my Kodak EasyShare V1003 and edited them with Snapseed.