Water transport dynamics in a meadow wetland under different hydrological years: Model simulation and mechanism analysis

The water cycle mechanisms in desertified regions have undergone considerable variation owing to the effects of climate change and human activities. Accurate characterization of the water transport processes in meadow wetlands within such areas is crucial for understanding the underlying hydrological mechanisms and improving water resource management. In this study, a representative meadow wetland located in Horqin Sandy Land was selected as the research site, and an enhanced HYDRUS-1D model was employed to simulate the long-term (2013–2020) water transport process. By incorporating the standardized precipitation index (SPI6), the water transport dynamics across hydrologically distinct years were analyzed. The results indicated that the improved HYDRUS-1D model provided a more accurate simulation of water transport in the meadow wetland, with R2 values exceeding 0.74, RMSE below 0.617 cm3·cm−3, and NSE below 0.751 during model validation. The simulation revealed the persistent capillary rise and deep percolation pulsation, with the average capillary rise reaching approximately 2.54 mm d⁻¹ and deep percolation showing marked downward fluctuation, up to 140.26 mm d⁻¹ , following major precipitation events. The interannual variation in the water cycle was primarily characterized by differences in precipitation regimes, leading to distinct patterns of water redistribution among deep percolation (DP), capillary rise (CR), and evapotranspiration (ET). In dry years, vegetation transpiration (T) contributed to 70.58 % of water loss, with DP accounting for only 16.81 %. In contrast, T dropped to 56.26 % and DP increased to 33.87 % in wet years. Soil evaporation consistently contributed approximately 10.7 %, while the change in soil water storage (ΔSWS) increased slightly in dry years to offset moisture deficits. The precipitation-based classification of hydrological years revealed distinct water balance regimes, indicating that precipitation variability drives the redistribution among ET, DP, and CR in meadow wetlands. These findings could provide a scientific foundation for water resource management and wetland ecological conservation in arid and semi-arid regions.