It does not really look like one, but Bukhtarminsk Reservoir (Bukhtarminskoye vodokhranilishchye) is not only the largest reservoir in Kazakhstan but among the largest of its kind in the world. Only a small slice of land was lost when the Irtysh was diverted to this water basin, 340 kilometres long, 25 kilometres wide and up to 68 metres deep. A valley with rocky subsoil was filled up, resulting in a clean, natural-looking lake.
Formed by damming the Irtysh River to the east of Ust Kamenogorsk, the long Z-shaped Bukhtarma Reservoir, constructed in the 1960s, has a total length of around 600km, and a surface area of 5,490km2, making it the fifth-largest reservoir in the world by surface area. A multi-purpose reservoir, it supports a power plant of 675MW, has a storage capacity of 49.8km3, and accounts for a quarter of Kazakhstan's total freshwater fish production. Sturgeon, sterlet and carp are among the species found here. The local authorities are trying to promote the development of fishing tourism, particularly around Lake Zaisan, a large freshwater lake in the eastern part of the region, fed by the waters of the Black Irtysh from China, and in turn feeding into the main Irtysh. Lake Zaisan found itself incorporated into the Bukhtarma Reservoir, as the southeasternmost component of that body of water, its level rising some 6m in the process.