The United Nations Convention on the Law of the Non-Navigational Uses of International Watercourses, 1997, finally entered into force in August 2014 after nearly 17 years. To explain this delay scholars point to, among other reasons, misconceptions of the substantive rules of equitable and reasonable use and the duty not to cause significant harm, particularly between upstream and downstream states. Reciprocity plays an important role within international law especially in treaties, where it informs the distribution of rights and duties, advantages and disadvantages, establishing balance and fairness in the legal regime. Together, this ensures that states cannot interpret treaty provisions in their favour. Using the Convention on the Law of the Non-Navigational Uses of International Watercourses as an authoritative text, this article aims to analyse the substantive rules of international law concerning transboundary water resources including equitable and reasonable use and the duty not to cause significant harm through the lens of reciprocity and the interests of China. In doing so, it aims to provide a more nuanced understanding of the rules and to establish that these principles do not favour upstream or downstream states, but instead promote balance among riparians.