In arid regions, the water savings delivered by improvements in irrigation technology are often offset by concurrent expansion of irrigated area, resulting in a water rebound effect. Quantitatively disentangling the respective impacts of technological improvements and area expansion on water-balance components has been hampered by the limited availability of irrigation data. Focusing on the Ebinur Lake Basin irrigation district in China, we integrated multisource remote-sensing and statistical datasets and used a two-stage optimized SM2RAIN algorithm to reconstruct dynamic irrigation schedules for 2002-2023, which were then coupled with the SWAT+ gwflow model. Through multivariable calibration against lake inflow, groundwater levels, and terrestrial water storage anomalies (TWSA), the model robustly reproduced seasonal cycles and long-term trends of key hydrological components. We then used multi-scenario experiments to quantify the individual effects of technological efficiency gains and irrigated-area expansion on the water balance. Results showed a gradual transition from furrow irrigation toward drip irrigation across the basin, accompanied by a decline in mean annual irrigation depth at the field scale. Nevertheless, despite these technological improvements, total basin water use increased by 43%-driven by a 116% expansion of irrigated area-and was accompanied by reduced lake inflow and persistent TWSA deficits. Scenario attribution showed that technological progress reduced annual water use by about 8%, increased lake inflow by about 7%, and slowed the TWSA decline rate by 10%. By contrast, concurrent irrigated-area expansion fully offset these benefits, increasing annual water use by about 13%, reducing lake inflow by about 10%, and accelerating the TWSA decline rate by 14%. The hydrological attribution framework driven by irrigation schedules provides a practical tool to evaluate the net effects of agricultural water-saving policies and offers actionable insights for sustainable water resources management in arid regions.