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The 650-mile-long Vistula River, the longest in Poland, gathers in the country’s southern highlands. It courses northward through both Krakow and Warsaw before ending where this photo was taken, about 15 miles east of Gdansk, carrying the winter floes seen here into the Baltic Sea. 

The nation’s iron-blue artery is one segment of the E40 waterway, a system of naturally occurring rivers augmented by manmade canals that linked markets from the Black Sea to the Baltic for nearly 200 years. After World War II, however, the waterway, which also cuts through Belarus and Ukraine, was abandoned as a commercial conduit. Now the three countries hope to restore it.

The economic upsides are obvious for all three countries but especially for landlocked Belarus, which would gain access to two of Europe’s busiest ports. There’s an environmental plus, too: By cruising on currents, barges release just one-third the CO₂ that freight trucks do, and are four times more fuel-efficient.

Still, there are plenty of unknowns. The dams and locks that would have to be built could severely damage two flood-prone areas along the Polish portion of the E40, and even more contaminants could enter the already heavily polluted Vistula. A feasibility study launched in 2013 wraps up in November; its results will reveal how soon the estimated 4 million tons in annual cargo shipments will replace the calm flow of these lily pads of ice.

Editor's note: Pilot and photographer Kacper Kowalski’s newest book, Side Effects (2014), offers a bird’s-eye view of human activity etched on Poland’s land and seascapes. Side Effects—which includes the image above—took second place in the 2015 World Press Photo Contest in the "Long-Term Projects" category, which recognizes outstanding work in photojournalism around the world. An exhibition featuring the collection opens April 22 at The Curator Gallery in New York City. See more of Kowalski's work here.