Landlocked and surrounded by South Africa on all sides, the mountain kingdom of Lesotho became the world’s first water-exporting country when it signed a 1986 treaty with its powerful neighbor. An elaborate network of dams and tunnels now carries water to Johannesburg, the subcontinent’s water-stressed economic epicenter. Hopes that receipts from water sales could improve Lesotho’s fortunes, however, have clashed with fears that soil erosion from overgrazing livestock could fill its reservoirs with sediment. In this wide-ranging and deeply researched book, Colin Hoag shows how producing water commodities incites a fluvial imagination. Engineering water security for urban South Africa draws attention ever further into Lesotho’s rural upstream catchments: from reservoirs to the soils and vegetation above them, and even to the social lives of herders at remote livestock posts. As we enter our planet’s water-export era, Lesotho exposes the possibilities and perils ahead.