Explaining ecological quality by using variable vegetation densities in hydrological modelling

• Using a combination of ecological monitoring data, ecological modelling and hydrodynamic modelling is a useful method in assessing the ecological water quality.
• Water distribution influences nutrient levels and thus vegetation density in a water system.
• Water distribution is influenced by vegetation density, especially at structures, such as culverts and weirs.
• Higher connectivity in systems with poor quality inlet water results in a lower ecological water quality.

Interactions between vegetation density, water flow distribution and nutrient availability might explain spatial and temporal variability in ecological quality of aquatic ecosystems. We analysed these interactions by simulating a variable vegetation density in hydrodynamic and ecological models. Simulation results of two vegetation density scenarios were compared and related to ecological quality, determined by ecological tools and based on plant species abundance. Our results show that vegetation density is an important factor in determining the water flow distribution. It further shows that water and nutrient distribution influences the vegetation density. Interactions between vegetation density, water and nutrient distribution continue in a positive feedback loop. With this study we showed that explaining ecological quality with hydrological models is improved when variable vegetation densities are included.