A hydrodynamic-water quality model was established using MIKE21 to analyze the distribution of total nitrogen (TN) and total phosphorus (TP) in the wetland sediments of Liaohe Estuary National Wetland Park. The purpose of this model is to investigate the spatial and temporal variation patterns in wetland sediments and the distribution of pollutant contents. The research determines the applicability of this model in accurately predicting these patterns. The simulated contour map of the water quality concentration displays significant variation characteristics and reflects the actual concentration of pollutants in the wetland sediment of the Liaohe Estuary, proving the coupled model to be reasonable and accurate. The water quality simulation results indicate that water flowing through the wetland aids in purifying pollutants in the sediment, and the purification effect is more significant during the flood season. The MIKE21 model’s treatment reveals that the content of TN in wetland sediments decreases from southwest to northeast in the surface layer, following the flow direction of surface water. As the depth increases, the content of TN also decreases, with the bottom layer showing a decrease from southwest to northeast. The TP in wetland sediments receives surface water runoff and diffuses from upstream to downstream. The content of TP gradually decreases with increasing depth.

Rational allocation and coordinated operation of water resources in arid inland river basins are crucial for sustaining irrigated agriculture, maintaining ecological baseflow and ensuring reservoir safety. To address this need, this study develops and evaluates joint-operation schemes for the Jingou River-Hongshan Reservoir irrigation system in Xinjiang, northwestern China, to improve coordination among irrigation water supply, ecological baseflow maintenance and reservoir safety. A monthly reservoir-canal-irrigation operation model is formulated with irrigation demands, ecological flow constraints and key engineering limits. Using this model, operating schemes are generated to explore trade-offs among three objectives: shortages, reliability and non-beneficial reservoir releases. The non-dominated schemes obtained from multi-objective optimization are then ranked using an entropy-weighted TOPSIS framework, from which representative solutions are selected for further interpretation. The results indicate that the top-ranked schemes deliver comparable and relatively well-balanced performance across the objectives. Under the preferred compromise scheme, annual irrigation shortages amount to about 39% of total demand, the mean satisfaction level of irrigation and ecological requirements reaches roughly 57%, and the combined index of spill losses and end-of-year storage deviation remains low. Schemes that push shortage reduction or reliability enhancement to extremes tend to increase spill losses, compromise storage security or both, thereby degrading overall performance. The proposed optimization-ranking framework offers a transparent basis for identifying robust operating strategies that reflect local management priorities and is transferable to other reservoir-supported irrigation systems in arid regions.

Phosphorus is an essential macronutrient that plays a crucial role in the regulation of the biological productivity and biogeochemical cycling of other biogenic elements. As a large tidal wetland dominated by reeds in Liaoning province, China, the Shuangtai estuary wetland is a unique ecosystem class. To better understand the spatial and temporal distributions of total phosphorus (TP) in the sediments of the Shuangtai estuary wetland during the period of reed growth, eight sampling sites were established within the wetland, approximately 11 to 24 km from Liaohe River. These sites were sampled once a month at multiple sediment depth intervals between April and October in 2018 and 2019, periods of time that corresponded with the reed growth period. An alkali fusion method was used to determine TP in the sediment samples. The results show that sediment TP content of wetland sediments ranged from 0.001 to 0.781 mg/kg, and decreases from southwest to northeast with the increase in sediment depth. The TP content reaches the maximum corresponding to the fastest growth stage of the reeds (June and July), while the minimum occurs in October (i.e., the maturity stage of reeds). The variation law of TP in cross-sectional sediment in the wetland is that the deeper the sediments are, the lower the content; its maximum content occurs in surface soil. The TP content of each site tends to be stable with increasing depth and has a regularly dynamic seasonal variation with the growth of reeds.