Construction and application of an eco-hydrological model for assessing watershed wetland water storage capacity

Wetland water storage capacity underpins the diverse wetland hydrological functions, making its quantitative assessment essential for watershed eco-hydrological regulation and integrated water resource management. However, previous studies have focused on estimating the water storage capacity of individual or small-scale wetlands, and a robust technical methodology for accurately assessing wetland water storage capacity at large watershed scales remains underdeveloped. To address this gap, this study improved the wetland module and grid-calibrated soil physical-chemical parameters to construct an eco-hydrological model for the accurate assessment of watershed wetland water storage capacity. The model was applied to simulate the evolution of wetland water storage capacity in the Nenjiang River Basin from 1990 to 2020. The results indicate that: (1) The improved wetland module increased the simulation accuracy of runoff depth, with the Pearson correlation coefficient rising by 2.4% to 9.0%. Grid calibration of soil physical-chemical parameters enhanced the simulation accuracy of surface and deep soil moisture, with the Pearson correlation coefficient rising by 12.5% to 53.9%. The constructed model accurately simulated watershed wetland hydrological processes, achieving a Nash-Sutcliffe efficiency coefficient of 0.78 and a determination coefficient of 0.80. (2) In 1990, the wetland water storage capacity of the Nenjiang River Basin was 33.2 billion m3, with wetland soil water storage capacity about 2.5 times greater than depression storage capacity. By 2015, the cumulative loss of wetland water storage capacity reached 6.4 billion m3, accounting for 27.8% of the basin’s natural annual runoff. By 2020, the wetland water storage capacity had recovered by 1.0 billion m3. The decline was mainly due to large-scale wetland reclamation and ecological degradation. These findings deepen the understanding of wetland hydrological function variability and support wetland restoration and flood control decisions in the Nenjiang River Basin. Furthermore, this study offers a novel methodology for assessing wetland water storage at large scales, with significant implications for global integrated water resource management based on wetland hydrological services.