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7 p.m. on PBS Rivers of Life

Journey from source to mouth along Africa’s wildest river and travel through awe-inspiring landscapes to discover the spectacular wildlife and fascinating people that thrive along one of Earth’s greatest rivers in the Season 2 premiere episode “Zambezi.” Featuring breathtaking photography, the second round of this landmark series also explores Europe’s Danube River, which travels through more countries than any other river; and North America’s great frozen river, the Yukon.

8 p.m. on PBS NOVA

Leading scientists and engineers are racing against the clock and battling the forces of nature to try and save Venice, Italy, from rising sea levels and sinking land for future generations. In the new episode “Saving Venice,” discover the innovative projects and feats of engineering currently underway, including a hi-tech flood barrier, eco-projects to conserve the lagoon and new efforts to investigate erosion beneath the city. This is Venice as never seen before at a critical moment in its rich history.

9 p.m. on SYFY Resident Alien

Meeting another out-of-towner while traveling is usually a cause for celebration. But small-town Colorado is a different place altogether. In the Season 2 finale episode “I Believe In Aliens,” Harry (Alan Tudyk) comes face to face with his greatest enemy and makes a choice that may affect Earth forever. Alice Wetterlund, Judah Prehn, Corey Reynolds, Levi Fiehler and Elizabeth Bowen also star.