The Hol 1 power plant in Hallingdal has four turbines and is operated as a hydropeaking station. The release from the power plant goes into river Storåne before it reaches the lake Hovsfjorden. The flow regime in Storåne is characterised by frequent flow changes and high ramping rates which has a large influence on the river environment. The effects on dried out areas and the rate of flow change is documented by Juarez et al. (20199, who used a 2D hydraulic model to compute characteristic peaking measures for the river reach. This project will build on the work by Juaez et al. to develop mitigation measures to dampen negative effects of peaking operation. A new operational strategy was also proposed for the power plant, and this will be further developed in this project. The following measures will be investigated:

1. Installing a weir in the outlet channel to dampen the largest flow changes from the turbines. This will be tested both for the current operational strategy and for the new strategy.
2. Measures undertaken in the river to prevent drying of critical areas such as current deflector, small weirs and blocking of critical areas. Measures will be developed and tested in a hydraulic model. The measures will also be combined with the setup in 1)
3. Evaluate the performance of these measures during flood conditions, particularly the weir system in 1.
4. Evaluate cost - benefits of the different measures.

The work will be a cooperation with ECO Energi, and a field trip in the spring of 2020 is possible.