Green development threshold effect and its spatial heterogeneity from the perspective of water resources utilization: A case study of three urban agglomerations in the Yangtze River Economic Belt
Clarifying the spatial differentiation characteristics and response mechanism of green development is a key link in achieving the coordinated development of three major urban agglomerations in the Yangtze River Economic Belt (YREB). This study proposed a cloud model-based green development evaluation framework and a water resources ecological footprint model to explore the spatial-temporal characteristics of green development and water resources utilization pattern in the three urban agglomerations from 2000 to 2025. On this basis, the threshold effect of industrial agglomeration on regional green development and its spatial heterogeneity were investigated from the perspective of water resources utilization, and differentiated development strategies were further proposed. The results showed that the green development level of cities in the three urban agglomerations all reached a moderate level and above, except Suining and Xiaogan. Water resources ecological footprint presented an increasing trend, and the proportion of sewage footprint exhibited a spatial pattern of “high in the east and west but low in the center”e. There was a large spatial heterogeneity in threshold effect of green development level in the three urban agglomerations, and the impact of co-agglomeration on green development of the YREB continued to increase. When water resources ecological footprint exceeded 0.379 hm2/cap, the impact of producer service agglomeration of the Chengdu-Chongqing urban agglomeration has an inhibitory effect on green development, and the promotive effect of co-agglomeration in Chongqing was the most evident. Different agglomeration modes all presented an inverted “V” relationship with green development in the midstream urban agglomeration. The co-agglomeration of industrial cities (such as Ezhou) had an inhibitory effect on green development. Green development level in the Delta urban agglomeration had a double threshold effect; manufacturing agglomeration had the highest positive effect on green development (0.272) after water resources ecological footprint reached the second threshold value.