Novosibirsk reservoir: Ecological aspects of operation

Abstract

The Novosibirsk reservoir was created as a result of constructing the Novosibirsk hydro development on the Ob River (20 km upstream from Novosibirsk) (Fig. 1). The Ob was dammed at the end of 1956, the reservoir was filled to the normal pool level (NPL) in June 1959. The reservoir parameters (at NPL 113.50 m), original and refined in the "Feasibility Study for Improvement of the Technical State of the Novosibirsk Reservoir Banks in Connectiop with Their Abrasive Reworking" carried out in 1990, are given in Table 1. The seasonal reservoir is located in the Ob valley. The backwater from the dam extends 200 km upstream to Kamen'on-Ob city and 50 km up the Berd' River to Iskitim city. The configuration of the reservoir shoreline is mainly complex, its length is estimated to be 550 km. There are 19 local inflows longer than 10 km. Bays are formed at the mouths of the rivers Berd' (the largest tributary), Mil'tyush, Karakan, Orda, Sharap, and Irmen'. The reservoir is shallow with many islands and has a maximum depth up to 20 m only along the drowned Ob channel. The dominant depths are less than 10 m. The Novosibirsk reservoir stores on average 13.4% of the volume of the annual runoff of the Ob, varying from 9 to 18.8% depending on the wetness of the year. The average annual river runoff at the site of the hydrostation is 54.5 km 3 with a range from 39.8 to 73.7 km 3. The maximum monthly runoff from 6.7 to 18.6 km 3 is observed in May; the minimum from 1.4 to 1.8 km 3, in December. The annual variation of the reservoir water level is determined by three characteristic phases: filling by the surplus spring flood runoff, summer stand of the levels at the NPL with its brief excess during passage of a freshet, and long drawdown of the level. In the ice-free period the drawdown of the water level does not exceed 1.3 m, in the winter it is 4 m and limited by the dead storage level (DSL) of the reservoir. However, in connection with natural dry years in the past decade and markedly increased demands for water resources of the Novosibirsk reservoir downstream by water users and consumers, it was drawn down below the DSL in 1980-1981 by 1.28 m, in 1981-1982 by 1.87 m, in 1989 and subsequent years by up to 0.6 m. The reservoir is divided into three parts according to morphologic characteristics: lower from the hydrostation dam to the site of Zav'yalovo--Novopichugovo, representing a lakelike water area with a width reaching 20-22 kin. This stretch has large depths, especially in the right-bank part, in the region of the drowned Ob channel. The hydrologic regime is lake-sea. The wave height reaches 2.5-3.5 m. Wind denivellation (wind set-up and set-down phenomena) with an increase of the water level up to 50-60 cm is observed; middle from Zav'yalovo village to Ust'-Khmelevka village, representing a long, narrow stretch with a width of not more than 5-6 km with numerous islands and shoals at places of washed-away islands. In the flood period this stretch is characterized by a regime close to river; upper upstream of Ust'-Khmelevka, during a flood it has a regime close to river. At this time the flow velocity here reaches 1.5-2 m/sec. The regime of using the water resources of the reservoir is determined by the requirements of the main water users: power industry, water transport, public water supply. Beginning in 1969 it was decided to increase the NPL by 20 cm, to 113.70 m, in the interests of hydropower and water transport. By 1980 the water users' and water consumers' priorities were ranked in the following order: public water consumption, reclamation water consumption, river transport, hydropower. In recent years reclamation water consumption has been passing to a lower level due to a decrease of the use of irrigation systems.