Some over stuff whhich are cool to read about:
Redirecting Siberian rivers into Central Asia https://en.wikipedia.org/wiki/Northern_river_reversal
Redirecting Congo basin rivers to replenish Lake Chad https://en.wikipedia.org/wiki/Lake_Chad_replenishment_projec...
Filling in a depression in Egyptian Sahara desert and fllooding it with Mediterrraanean water to generate huuuuuuuuuuuuge hydro https://en.wikipedia.org/wiki/Qattara_Depression_Project
(Similar ideas proposed for Lake Eyre, the lakes in Tunisia, and the Afar Depression in Djibouti, too).