Evaluation of the Spatio-temporal Matching between the Forest and Grassland Vegetation Pattern and Blue-green Water Resources in the Inner Mongolia Plateau

The Inner Mongolia Plateau is a significant implementation area of the Three-North Shelter Forest Program in China and a critical zone for climate, hydrology, and ecology. The current pattern of artificial forest and grassland vegetation construction based on precipitation has overlooked the soil water and groundwater carrying capacity. Balancing the effective and sustainable supply capacity of water resources and maintaining the ecological stability of vegetation is a challenge in the governance of desertified and degraded land. This study developed an integrated framework to analyze the spatiotemporal matching degree between vegetation patterns and blue and green water resources, and to evaluate the relationship between vegetation coverage changes and water sources, water balance, and hydrological thresholds. The results show that the green water resource carrying capacity in the Three-North Shelter Forest Program implementation area of the Inner Mongolia Plateau has been underestimated. In contrast, the blue water resource carrying capacity has been overestimated. The water resource demand for forest and grassland vegetation construction is approximately 470 ± 5 million cubic meters, while the available blue water resource is only 178 ± 7 million cubic meters. The areas with increased vegetation coverage are mainly concentrated in basins where blue water resources are declining, and the areas with decreasing groundwater levels are increasing. Increasing vegetation coverage by consuming groundwater for irrigation is not a sustainable path. Under the same precipitation conditions, the spatio-temporal matching degree between vegetation patterns and blue and green water varies significantly. In areas where precipitation is converted into green water resources, vegetation coverage is relatively low, with NDVI values ranging from 0.23 to 0.41; however, the stability of the vegetation ecosystem is relatively strong. In areas where precipitation is converted into blue water resources, the vegetation coverage and its interannual variation trend tend to be stable only when the groundwater depth is between 3 and 12 meters. The research results can provide a scientific basis for ecological restoration and sustainable utilization of water resources in the critical zone of climate-hydrology-ecology.