To support carbon neutrality and accelerate its energy transition, China has prioritized the development of largescale photovoltaic (PV) bases in the arid and semi-arid regions of Northwest China. However, environmental challenges such as frequent sandstorms and limited precipitation necessitate comprehensive assessments of solar potential and operational resource demands. In particular, estimating water requirements for PV panel cleaning is critical for sustainable deployment. This study introduces an integrated spatial modeling framework to quantify the technical potential of solar PV power and estimate associated water consumption. The results indicate that the annual electricity potential across six northwestern provinces reaches 105.2 PWh, which is 10.7 times China's projected electricity demand in 2024. This corresponds to a carbon mitigation potential of 80.9 Gt, equivalent to 6.4 times the country's total emissions in the same year. Under optimal deployment scenarios, 6.1 TW of PV capacity could meet national electricity demand in 2030 while occupying only 36,052 km2, representing 0.4 % of China's total land area. However, the rapid PV expansion would significantly increase water use for panel cleaning. By 2030, water demand is expected to rise 4.2-fold compared to current levels, reaching 129.49 million m3, roughly equal to the annual domestic water use consumption of 2.84 million people. Annual water costs under high-tariff scenarios could exceed 1.15 billion CNY, with total cleaning expenses (including labor and logistics) reaching 1.67-2.36 billion CNY. These findings highlight the need for strategically balancing energy infrastructure expansion with water resource management, supporting sustainable low-carbon development and ecological resilience.