Oritelgi reservoir

The Oritelgi reservoir (Mirselec Oritelgi ferenalmi) is a large reservoir, formed by damming the Oritelgi river and the resultant expansion and merging of the Oritelgi Ponds, in Province 6. This reservoir is one of the central elements in the Rushalya Channelling Scheme, as a store of water which it then releases into the Fosoge and Raltani rivers.

The Oritelgi reservoir has a total summertime surface area of 4,971km², while in winter freezing expands it by another approximately 3km².

Human & environmental impact

The human impact of the reservoir was minimal as the ideal location for the dam was found to be in a relatively sparsely populated area. Nonetheless to create the Oritelgi reservoir, about 1,000 people had to be resettled and compensated, both for their residences and, as they were mostly farming families, for their land.

Compared to that, the ecological and geological repercussions have been more severe. Only 64km² of the reservoir was originally underwater, and as the area subsequently flooded included many deep mountainside pockets of isolated diversity, an estimated 5,254km² of forest cover was destroyed, affecting as many as 13,000 species of flora and fauna, of which just under 3,000 are expected to have been unique to the area and to be now extinct.

The unexpected wintertime freezeover of much of the upper layers of water has also presented tricky problems to civil engineers, such as an increased rate of soil erosion from the surrounding mountains thanks to the intensified weathering effect in which the autumn-winter-spring freeze-thaw cycle has resulted. The sheer weight and pressure of the water has also led to subsidence in the area of the loose volcanically-deposited soil of which Risevne is made, and infiltration has caused waterlogging and destabilisation in the more permeable soil layers and areas. Due to the potential danger to the structural soundness of the Samelna Dam, the Risevan government is intensively monitoring the situation and in discussions with expert groups over how best to relieve the water load on the land.