Developing a Hydraulic Model for Sustainable Restoration and Management of Anzali Wetland

Wetlands are among the most unique and biologically diverse ecosystems on the planet, playing critical roles in water filtration, carbon sequestration, and supporting rich biodiversity. However, these ecosystems are increasingly under threat from a combination of climate change and anthropogenic pressures. To safeguard these vital systems and ensure their sustainable functioning, the Ramsar Convention, an international treaty for wetland conservation, was adopted by 172 countries. The Anzali Wetland, situated in northern Iran, is one such Ramsar site and represents a significant ecological and hydrological resource. This wetland receives freshwater inputs from over 11 rivers and maintains a dynamic connection with the Caspian Sea. However, a confluence of challenges, including climate change-induced flooding, agricultural and wastewater runoff, declining Caspian Sea levels, and accelerated sediment deposition, has severely threatened the wetland’s integrity and functionality.

Addressing these challenges requires comprehensive management strategies informed by robust scientific understanding. Decision-makers and stakeholders need accurate tools to predict the outcomes of various interventions and develop targeted restoration plans. Hydrological and hydraulic models have become essential tools in this context, providing insights into complex ecosystem dynamics and helping evaluate the effectiveness of proposed management measures before their implementation.

In this study, the HEC-RAS (Hydrologic Engineering Center's River Analysis System) model, a computational fluid dynamics (CFD)-based software, was employed to simulate the hydraulic behavior of the rivers flowing into the Anzali Wetland. This model is particularly well-suited for assessing open-channel hydraulics and has been tailored to represent the unique characteristics of the Anzali Wetland. Given that the wetland’s water levels are predominantly influenced by seasonal river inflows rather than Caspian Sea fluctuations, the model emphasizes the critical role of river hydrology in sustaining wetland productivity, including vegetation health and biodiversity.

The HEC-RAS model was calibrated and validated to cover the vast region and major inflows of the Anzali Wetland. It aimed to assess the effectiveness of existing flood control infrastructure, analyze contamination pathways and their impacts on water quality, and identify areas within the wetland prone to excessive sediment deposition. The model results also provide valuable insights into the interplay between hydrology, sediment transport, and water quality within the wetland. For example, the model highlights areas with severe sediment accumulation, threatening to disrupt aquatic habitats and navigation. Additionally, it identifies critical zones where agricultural and urban runoff introduce contaminants, adversely affecting water quality and wetland health.

The outcomes of this modeling effort serve as a vital decision-support tool for wetland managers and policymakers. By simulating different restoration scenarios, such as improved flood control measures, sediment management strategies, and contamination mitigation efforts, the model enables stakeholders to prioritize actions that will have the most significant impact on preserving and restoring the Anzali Wetland. This study underscores the importance of integrating advanced hydraulic modeling with ecosystem management to safeguard vulnerable wetlands like Anzali, ensuring their ecological, cultural, and economic functions for future generations.