Evolution and Action Mechanisms of Dual Trade-Offs Under Water-Saving Improvement in Arid Irrigated Zones: Evidence from Ningxia

While continuously promoting agricultural water-saving and efficiency improvement, Ningxia is confronted with problems such as deepening groundwater tables and growing ecological vulnerability. Exploring the trade-off relationships and their evolutionary characteristics between socioeconomic development and water resource carrying capacity, as well as between water use efficiency improvement and groundwater-ecosystem maintenance, is of great significance for coordinated water resource governance in arid irrigation districts. Based on time-series data covering 2000–2024, this paper establishes a DPSIR evaluation model and constructs a progressive quantitative analytical framework coupling the entropy-weight-Tapio decoupling, rate-scissors difference and PLS-SEM models. During the study period, the growth rate of the response (R) dimension (13.76%) was far higher than that of the state (S) dimension (3.23%) from 2011 to 2020, confirming the objective existence of dual trade-offs. The two categories of trade-offs underwent a three-stage evolution of “latent-intensified-remediation”, showing the counter-intuitive feature of “effective total-volume control alongside continuous groundwater table deepening”. Hidden transmission barriers were identified for 2008–2016 (θ1, θ2 dropped to 0.46–1.32°): the transfer of water-saving dividends to industry caused groundwater extraction to rise rather than fall to a certain extent. PLS-SEM analysis reveals that structural lock-in acts as the core inhibiting factor for ecological protection. The total effect of socioeconomic development on ecology reaches 0.921, whereas structural lock-in produces a chained negative mediating effect of −0.192 by suppressing water use efficiency. Improvement in water use efficiency presents dual characteristics of overall ecological gain and localized groundwater-recharge loss. It can be concluded that engineering-only water-saving measures cannot balance water-intake reduction and recharge deficits. It is necessary to simultaneously advance low-water-consumption cropping-pattern restructuring, rigid enforcement of the 2.5 m ecological groundwater table threshold, and the substitution mechanism for saved-water volume between industry and agriculture, so as to build a coordinated “water-saving-recharge-ecology” regulation system.