Spatiotemporal variability in the water conservation amount in Gansu Qilian Mountain National Nature Reserve

Based on calculations of water balance and water conservation depth, this study analyzed the spatiotemporal variation of water conservation depth and its main driving forces in Gansu Qilian Mountain National Nature Reserve during 2000 − 2018. The results showed that the annual average water conservation depth was 34.23 mm, with the total water conservation amount reaching 8.56 × 10⁸ m³·a⁻¹. The water conservation depth of woodlands, grasslands, and wetlands was significantly higher than that of cultivated and unused land (P < 0.05). The water conservation depth was higher in the middle and eastern parts but lower in the northwestern part. Areas with higher values of water conservation depth showed greater inter-annual variability. The overall trend in water conservation depth was not significant for the entire study period. Areas with significant increases in water conservation depth grouped at middle-high altitudes, whereas areas with significant decreases in water conservation depth were distributed mainly at low altitudes (P < 0.05). The spatiotemporal variation of water conservation depth was driven by changes in precipitation and land cover types, followed by leaf area index and temperature. A significant positive correlation between water conservation depth and precipitation was observed (P < 0.05), together with a negative correlation of water conservation depth with leaf area index and temperature. The middle and eastern Gansu Qilian Mountain National Nature Reserve is the priority area for water conservation, and the protection of woodlands, grasslands, and wetlands should be strengthened. Under the background of a warm-humid climate, water conservation depth is projected to remain stable in the future.