The idea belonged to Sir William Garstin, an engineer working for the Egyptian government under British oversight. In 1904 he looked at a map of the Nile and saw a problem: the river's southwestern tributaries poured into a vast swamp called the Sudd, and roughly half that water simply evaporated before reaching Egyptian farmers hundreds of kilometers downstream. Cut a canal east of the swamp, he argued, and you could deliver that water to cotton fields in the Nile Delta. Two million extra acres could be brought under cultivation. The calculation made sense on paper. Paper does not account for the people who live on the land you plan to bypass, or for the fact that swamps are not wasted water but living systems. Garstin's proposal sat in drawers for decades while Egypt studied it, restudied it, and waited for the politics to align.

Construction finally began in 1978, with Egyptian money and a French contractor. The plan called for 360 kilometers of canal running from Bor north to the White Nile above Malakal, bypassing the Sudd entirely. Sarah the bucketwheel, assembled on site, chewed northward at a steady pace. But the canal was never just a canal. For the Dinka, Nuer, and Shilluk communities whose dry-season grazing grounds depended on the Sudd's seasonal floods, it was an existential threat designed in Cairo and approved in Khartoum with almost no consultation. Environmental studies were cursory. In 1983, as the Second Sudanese Civil War began, the Sudan People's Liberation Army formed in the south under John Garang, and the canal became one of its most visible grievances. In 1984, at kilometer 240, an SPLA missile struck Sarah, and the diggers stopped. They never started again.

The Sudd is one of Africa's great wetlands, a labyrinth of papyrus channels and floating vegetation islands that shifts with the seasons and covers an area that can swell to the size of England during high floods. Shoebill storks stalk its shallows. Tiang antelope migrate through its fringes. Two million head of cattle move seasonally into and out of its pastures, driven by families who have been making the same journey for generations. The canal, had it been finished, would have starved the Sudd of perhaps fifteen percent of its water. Groundwater levels would have dropped. Rainfall in the surrounding region would likely have fallen too, because swamps do not just lose water to the sky; they feed the sky that feeds them back. What Egypt's engineers had written off as waste was, in fact, the whole ecosystem.

Sudan and Egypt agreed to restart the project in 2008. South Sudan's independence in 2011 effectively ended that conversation. The new country inherited the unfinished trench and the rusting machinery, and while there have been occasional discussions about reviving the project, no agreement exists. From the air the canal still reads clearly: a dark line drawn partway across the plain, stopping abruptly where Sarah stopped, grass slowly closing over its edges. Some see it as a failed dream; others see it as a civil war's most literal monument. For the communities whose lives depended on the Sudd staying a swamp, the half-finished canal is what victory looks like when victory means that the worst thing did not happen.