ABSTRACT
Mezhennogo System, with its branchwork pattern, an underground river reaches at depth of about 700 m below the Snezhnaja entrance, the large and long river passage, and many large chambers modified by breakdown. The total volume of the cave is estimated to be about 1.7×106 m3. Most of the known deep caves, located within the southern block drain to the Mchishta Spring, the largest spring in the Caucasus with its average discharge of 9.3 m3 s−l and maximum discharge of 197 m3 s−1. The spring is on the Kaldakhvarsky fault, and its underground catchment is estimated at 160 km2. Tracing tests have shown a direct connection to Mchishta from the Snezhnaja-Mezhennogo System (1930 m above) and Napra (2300 m above). Divers in Mchishta have discovered a large cave of total length 4200 m (of which 780 m are underwater) and a volume of 380 000 m3. The cave starts with a siphon 340 m long and 45 m deep with an underwater shaft in which a depth of 75 m has been reached. The entrance siphon leads to the eastern and western series, which have quite different morphologies. The eastern series is a 3-D maze about 1 km long. The western series is a 1400 m long, linear gallery, 5-20 m high and wide, leading to another siphon 320 m long and 48 m deep. It is hoped that further exploration in Mchishta Cave may give access to the main collector of southern Bzybsky. The northern block of the massif drains to springs in the Bzyb River valley. A tracer injected in Boguminskaya Cave appeared in Pantjukhina Cave at −600 m, and came out at the Bzyb Spring, located just in front of the Goluboje Ozero Spring, which is across the river. The depth of the karstic drainage in this case is 1920 m.
