The hydroelectric power plant of Mostarsko Blato uses waters of the Lištica River catchment area. These waters are collected into the reservoir lake situated in the area of the Mostarsko Blato field. The construction of HEPP Mostarsko Blato anticipates construction of a new tunnel with the flowcapacity of 45m3/s. Data on rock massif were taken on three different chain ages, and in this paper for them the geomechanical classification was made and the type of support system was determined. The headrace tunnel is designed with horseshoe-shaped profile, tunnel sides are designed as part of a circular arch that is tangentially connected with the arch of calotte, the bottom of tunnel is planned as a level plate. Thus, the static scheme of the tunnel structure is approximately reduced to a circular arch that is connected with the lower plate in a hinged manner.
The wider area of Mostarsko Blato is often flooded because of small capacity of sinkholes. For that reason, a tunnel through the Varda hill was excavated in late 1950-ies. The tunnel has a horseshoe-shaped profile, cross section area P∼15m2, length∼2200 m, and flow capacity∼40m3/s. The construction of HEPP Mostarsko Blato anticipates construction of a new tunnel with the flow capacity of 45m3/s, with hydro technical regulation of the tailrace system from the HEPP Mostarsko Blato powerhouse. That will provide increased water evacuation and shorter duration of floods in the area of Mostarsko Blato. The tunnel starts with the intake structure, and ends in a chute∼400m in length. The tunnel has partially decreased the scale and duration of flooding in the area of Mostarsko Blato, but the problem of floods in the Mostarsko Blato field still remains unsolved due to small capacity of the Jasenica riverbed.