Pietz is among the world's preeminent scholars researching China's environmental transformations. His award-winning research has focused on the management of water in China, with an emphasis on two issues: how China has managed water to advance its state- and nation-building efforts, and the domestic and international environmental consequences of those efforts.

His research has been supported by several of the most prestigious foundations in the United States, including the Carnegie Foundation for the Advancement of Teaching, the John Simon Guggenheim Memorial Foundation, the Fulbright Program and the Andrew W. Mellon Foundation, along with the National Endowment for the Humanities, the National Science Foundation and the Institute for Advanced Study in Princeton, New Jersey. In spring 2020, Pietz became UArizona's first Andrew Carnegie Fellow, selected because of his capacity to "address important and enduring issues confronting our society." Pietz received the recognition at the same time he was awarded a Guggenheim Fellowship – giving him the two top awards for scholars in the arts, humanities or social sciences.

Pietz is author of "The Yellow River," which examines more than 2,000 years of Chinese history and has been called transformational in the field. It received the 2016 Cecil B. Curry Book Award from the Association of Global South Studies.