Utilizing both ministerial records at the national level and local archival documents from Lankao County, Henan Province, this article examines how small-scale water projects turned into environmental disasters during the Great Leap Forward (1958-62). Previous scholarship has often regarded the Great Leap water policy, namely, the Three Priorities (water storage, small scale, and mass based), as a testimony to the irrationality of Maoist mass mobilization. This article, by contrast, interprets the Maoist technological complex as a troubled marriage between two variants of developmentalism: the high-modernist pursuit of productivism and scientific rationality (water storage) and the Maoist faith in decentralized mass initiatives (small-scale, situated, local projects). The article argues that Maoist water politics were undone by their internal contradictions, because high-modernist centralism undermined populist, revolutionary mass activism-a conflict that extended beyond hydrological engineering and weakened Mao's revolution as a whole.