Decoupling Energy Expansion from Water Constraints: Spatiotemporal Evolution and Mechanisms of the Energy–Water Nexus in Northwest China

It is very important to interpret the synergistic relationship between energy and water in the northwest inland river basin, which can solve the problem of “energy expansion and water use constraints. This study examines the energy–water nexus in Northwest China’s inland river basins using panel data from 22 prefectures from 2007 to 2023. Results show persistent asymmetric development: the energy subsystem index rose by 214.29 percent while the water subsystem index grew by only 42.31 percent, and coupling coordination improved from 0.31 to 0.49. Water use efficiency mediates 58.32 percent of energy production’s total effect on coupling coordination. When water use efficiency equals 0.0052, below this value, energy expansion yields no synergy, while above it, the effect becomes positive at 0.572. The green transition positively moderates this relationship with an interaction coefficient of 0.168. Traditional energy intensity hinders coupling at negative 0.152, whereas clean energy intensity promotes it at 0.408. Spatial spillovers are significant with an indirect effect of energy production intensity of 0.097. These quantifiable findings support threshold-based, spatially differentiated water–energy governance in arid regions.