An Analysis of Agricultural Water Eco-efficiency in Chongqing: Measurement, Decoupling Relationships and Driving Forces Based on a Three-dimensional Ecological Footprint Model

The effective supply of agricultural water resources is critical for promoting sustainable agricultural development. This study constructs an agricultural water eco-efficiency evaluation system by incorporating the three-dimensional ecological footprint of agricultural water use as an undesirable output indicator. Utilizing panel data from 37 districts/counties in Chongqing (2015-2021), we implemented an integrated analytical framework combining: static assessment via the super-efficiency SBM model; dynamic evolution analysis through ML productivity index; decoupling relationship examination using the Tapio model; and driving factor decomposition via Kaya identity and LMDI method. Key findings reveal: (1) The three-dimensional ecological footprint of agricultural water exhibited an upward trend, peaking in the Main Urban New Area while remaining lowest in the Central Urban Area. (2) Static eco-efficiency demonstrated gradual improvement yet remained suboptimal, with significant regional disparities and weakened spatial agglomeration, demonstrating that there's much room for improvement. (3) Dynamic eco-efficiency followed a U-shaped trajectory, outperforming static measurements, driven primarily by technological progress. Efficiency growth rates varied substantially across regions: the Central Uban Area experienced the fastest growth, while the Main Urban New Area presented the slowest growth. (4) Four decoupling states were identified between eco-efficiency and economic growth: strong decoupling, weak decoupling, and expansion negative decoupling, indicating that the decoupling relationship was not ideal. (5) Economic development exerted positive impacts while labor input and technology adoption showed inhibitory effects on eco-efficiency. Thus, to enhance agricultural water utilization efficiency, it is suggested that such measures should be taken, including optimizing soil-crop systems through structural adjustments, promoting water-saving irrigation technologies and improving water infrastructure.