Monitoring of the Iron Gate Hydropower and Navigation System on the Danube River - page 8

(IV) Monitoring of the ice regime

The problem of ice on the Danube and its tributaries was well known for decades, including relatively frequent critical situations, due to formation of ice jams and increase of water levels. Therefore, the ice defense is an integral part of the flood management on the Danube.

The construction of two dams and the operation of the HPP changed the natural conditions of ice formation and movement. In the deep part of the IG1 reservoir and downstream conditions have improved, while at the upstream sectors of the Danube River the ice conditions are worsened and ice jams may occur on 16 potentially critical locations.

The Jaroslav Cerni Institute has monitored the ice conditions in the IG1 reservoir during cold winters between 1972 and 2012, in order to obtain relevant data and establish appropriate techniques for ice control. Nevertheless, the experiences gained are modest and insufficient for their validation, since during the production period no critical situations occurred due to favorable weather conditions. Only twice, in the winters of 1984/85 and 1986/87, icebreakers were used as a method of ice control. In the very cold winter 2011/12 monitoring was also established (Fig. 16 and 17), but there was no need for emergency measures due to favourable hydrological conditions (low flows on the Danube and its tributaries).

 

Fig16
Fig. 16: Ice cover on the Danube River at km 1142, 20.02.2012.

 

Fig17
Fig. 17: Ice jam on the Danube River at km 1132, 25.02.2012

 

(V) Monitoring of backwater impacts on riparian forests

Before IG1 construction, forests in the riverine areas were periodically flooded, in accordance with relatively stable annual hydrological cycles. The problem of forest degradation due to the changed flooding regime was envisaged already in the IG1 initial planning stage. The Jaroslav Cerni Institute carried out an extensive research of the natural foreland forests along the IG1 reservoir, between 1962 and 1972. Afterwards, the impact of the IG1 reservoir was monitored at a number of points within the range of the reservoir. Forty years of monitoring revealed that a forest can endure prolonged flooding, with only a minor conversion of the species and the use of special irrigation.