l Overall, the water resource available for vegetation restoration was 28±114 (mean ± SD) mm in the drylands (Fig2 a), approximately one-tenth of the national average in China. Water deficit areas accounted for 43.26% of the total drylands and had been recorded mainly in the western drylands, especially in the hyperarid areas (median value was -38.04mm). Water-surplus areas accounted for 56.74%, concentrated in the east and south (median value was 69.62mm).