Modelling winter operational strategies of a hydropower system

Abstract

11The ice conditions in regulated rivers can be very complicated due to both intake 12 and release of water to and from hydropower plants. The optimal operational 13 strategies for the hydropower system must involve ice management in the river 14 basin and finding a balance can be a challenge for the hydropower operator. 15Issues with ice occur during both freezeup and breakup, and at certain 16 conditions both situations can occur in a basin at nearly the same time. In this 17 study, a series of modelling tools have been used to investigate the consequences 18 of a forced shutdown of a power plant in the Orkla river. The associated impacts 19 on the stability of the ice cover in a downstream bypass reach and the ice and 20 ecological conditions in the reaches upstream of the power plant have been 21 explored. The reason for this is restrictions on upstream water releases during 22 the shutdown period given in the regulation permit to prevent ice breakup in the 23 downstream bypass reach and subsequent flooding problems downstream. The 24 study demonstrates a wide application of numerical tools for environmental 25 impact assessment, providing knowledge for better decision-making and for 26 optimal operational strategies for hydropower systems during winter. 27In summary, the analysis shows that a shutdown period shorter than the travel 28 time of water from the upstream hydropower plants to the bypassed reach does 29 not guarantee a reduction of the ice problems in the bypass reach. Since the 30 intake pond is too small to store already released water from the upstream 31 power plants, spill and ice breakup will occur. It is rather found that a shutdown 32 of the upstream power plants can induce environmental problems due to the 33 rapid dewatering of the river, and an ice breakup during the restart of the 34 upstream power plants. 35 36

Assessing and Mitigating Ice-Jam Flood Hazards and Risks: A European Perspective

“…Figure3. Ice jam on the Svormo River affecting the operation of a downstream hydro-power generation facility (from[12]). …”