Downstream of the Novosibirsk hydroelectric station on the Ob River

Conclusions

• 1. The fluvial processes in the Ob River downstream of the hydro development, which markedly changed after damming the river and creation of the reservoir during the first decade of operation of the hydrostation, were expressed in the natural process of deep erosion of the channel, which had a diminishing character.

• 2. Starting with the second half of the 1960s, quarrying in the Ob channel on the 30-km stretch of the lower pool adjacent to the hydrostation began to have a substantial effect on the natural process of transformation of the channel due to streamflow regulation and retention of sediments by the reservoir.

• 3. During the period between 1966 and 1984 more than 40 million m³ of sand-gravel mixture was removed from the river channel and floodplain in the indicated stretch, as a result of which the decrease of levels relative to the normal, natural values at the site of the Novosibirsk gauging station was 0.9–1.0 m.

• 4. A decrease of the levels downstream led to a deficit of water resources of the reservoir in dry years and, as a consequence, to worsening of the operating conditions of the majority of participants of the Novosibirsk water-management complex.

• 5. After some stabilization of the position of the levels in the river in 1984–1986, the decrease, “slump,” of the levels in the stretch passing through the city subsequently resumed beginning in 1987–1988. The rating curve for the Novosibirsk gauging station in 1988 shifted downward from the analogous 1986 curve along the height axis by 15–20 cm.

• 6. The priority task facing water users and consumers of Novosibirsk is the fastest possible realization of the recommendations of MGU, VNIIG, and ZapSibRNIGMI on partial restoration of the water levels in the stretch between the hydrostation and Novosibirsk city by constructing embankments damming nonnavigable branches and converting the Ob channel here at low-water discharges (less than 2000 cm³/sec) into a single-branch channel.

• 7. For a radical solution of the problem of reliable provision of water consumers of Novosibirsk, it is necessary to reconstruct all intakes located downstream of the hydro development.