[1] It is a chief source of fresh water for the city of Dakar, hundreds of kilometers to the south-west, through underground pipes.

[citation needed] Water flows out to the Senegal River north through the Taouey [fr], which has been straightened and canalized as it passes through Richard-Toll.

The north shore and surrounding area have been converted to a large sugar-growing region irrigated with water from the lake.

Lac de Guiers is designated an Important Bird Area by BirdLife International; the key species are lesser flamingo (Phoeniconaias minor), glossy ibis (Plegadis falcinellus), Eurasian spoonbill (Platalea leucorodia), African spoonbill (Platalea alba), white-winged tern (Chlidonias leucopterus) and river prinia (Prinia fluviatilis).

Notably, the settlement of N'Der, the third and final capital of the former Kingdom of Waalo, was located on the west shores of the Lake.