Effects of artificial hypolimnetic oxygenation in a shallow lake. Part 2: Numerical modelling

A three-dimensional numerical model is used to simulate the thermal destratification caused by hypolimnetic jets releasing oxygen-rich water for lake restoration. Focussing on the case study described in the companion paper (Toffolon et al., 2013), i.e. the small, relatively shallow Lake Serraia (Trentino, Italy), a specific simplified sub-grid model is developed in the numerical model to reproduce jet entrainment with reduced computational costs, with the aim to simulate the whole lake dynamics along several weeks. The noticeable agreement between numerical results and available measurements suggests that the model can be used to understand the main effects of the hypolimnetic oxygenation in different scenarios. Therefore, different options can be evaluated and guidelines can be proposed for lake management, with the aim to preserve the typical thermal stratification while providing sufficient oxygen mass to proceed with the restoration phase.

► We have studied the hypolimnetic warming caused by artificial oxygenation through horizontal jets. ► A three-dimensional numerical model has been used to simulate the effect of the jets on the thermal stratification of the lake. ► Simplified sub-models have been developed for the turbulent mixing and for the entrainment caused by the jets. ► Simulations concerning different operational scenarios have been analysed. ► Numerical models are valuable tools for a correct management of the oxygenation device.