Water-yield Supply–demand Relationships in Northwest China Three Water Lines Region: an InVEST–glacier Assessment

Water scarcity poses a major challenge to sustainable development in arid regions, particularly where agricultural irrigation dominates water consumption. In glacier-influenced regions, conventional water yield assessments may underestimate water availability by neglecting glacier meltwater contributions. This study developed an InVEST–Glacier framework to quantify water yield service supply and demand in Northwest China Three Water Lines region (TWL region) and identify their dominant driving factors. The results showed that low water-yield areas (0–25 mm) accounted for 60.06%–70.19% of the region, while high water-yield areas were concentrated in mountainous regions. Glacier meltwater contributed more than 70% of water yield in most inland basins of the Tarim Basin and exceeded 90% in some years, but contributed less than 10% in the Yellow River and Datong River. Water demand was highly concentrated in irrigated plains and urbanized areas. The supply–demand relationship exhibited a pattern of “widespread surplus with localized stress”, with areas of ESDR < 0.2 increasing from 67.59% to 79.50%, while areas with ESDR > 0.8 accounted for 14.68%–23.90%. Natural factors dominated the spatial differentiation of ESDR, with elevation, precipitation, and NDVI showing the highest integrated driving scores.These findings highlight the stage-dependent buffering role of glacier meltwater and the need for differentiated water-resource management in glacier-dependent and water-stressed regions.