Agrivoltaics offers synergies for water, food, energy, and environment (WFEE) but typically requires co-location on cropland, creating competition with food production. The potential of using marginally saline lands for photovoltaics to power irrigation on adjacent cropland remains unexplored, and no integrated modeling framework exists to assess such systems at the regional scale. Here we propose a PVM-DIC system that places photovoltaics on marginally saline land to power drip irrigation in adjacent cropland. The SWAT-AG model was enhanced for simulating the hydrological impacts of solar panel placement and mulched drip irrigation. A WFEE nexus evaluation framework was developed based on the enhanced SWAT-AG model and used to quantify the impacts of the PVM-DIC system deployment in China's Hetao Irrigation District. On just 3.1% of the area, the system increases soil moisture by 7.3-13.3% and reduces salinity by 2.7-12.8% under panels; in drip-irrigated fields, yields rise by 2.5% (corn) and 1.7% (sunflower) despite a 2.3-17.0% salinity increase. Regionally, the system reduces evapotranspiration by 2.0%, saves 153 m3 ha-1 of irrigation water in drip-irrigated areas, generates 734 MWh ha-1 yr-1 of electricity from solar area, and avoids emissions of 207 t CO2 ha-1 yr-1 across the total system area. The net incremental benefit is 39.3 USD hae yr-1 ine system area, with environmental services contributing more than a quarter. The PVM-DIC system demonstrates a scalable pathway for sustainable intensification in arid regions by resolving the land competition inherent in conventional agrivoltaics.