Сорбулак-самое большое озеро-отстойник в СНГ. (1990 год)

The largest settling lake in the CIS, one of the largest in the world. Wastewater from Almaty, Talgar, Kaskelen and some other settlements of the Almaty region is discharged here after mechanical and biological treatment. The main functions of the reservoir are deep long-term regulation of wastewater - ensuring their natural self-purification. The owner of the reservoir is the State Enterprise "Vodokanal" (since 2008, the State Enterprise "Tospa Su") - www.almatysu.kz Located in a natural closed basin, located in the northwest of Almaty. The maximum length of Lake Sorbulak is 35 km, the width is up to 15 km, the maximum depth is 22 m, the surface area is 58 sq. km. The bowl and foundation of the Sorbulak reservoir dams are composed of a low-permeability layer of mid-Quaternary sediments to a depth of 55 meters, below which there is a regional aquiclude of clay formations. To monitor the regime and level of groundwater, a section of 21 regime wells is equipped from Sorbulak to the west to the Uzun-Kargaly River, and a hydropost is equipped to record the water level in the reservoir. In September 1969, the government of the Kazakh SSR issued an order to divert wastewater from Almaty to the Sorbulak depression with subsequent use for irrigation. The system of reservoirs-storage reservoirs for wastewater is located in natural depressions on the Karaoi plateau in the semi-desert zone along the southern border of the Ili River valley. Water enters the system after primary mechanical treatment and disinfection through a 49 km long canal, then it undergoes additional treatment naturally. The structure of the reservoir includes two low-pressure earthen dams - dams No. 1 and No. 2, which were built in 1991 to cut off shallow waters and protect the highway from flooding. Every second, up to 5 tons of water are discharged into Sorbulak. The total volume of the wastewater reservoir is 900 million m3. with a NPU mark of 620.5 m. According to the conditions of the existing relief of the basin, its maximum filling is possible up to the mark of 622.0 m. At this mark, the natural depression - the Sorbulak reservoir - can accept 1000 million m3 of wastewater. The filling levels of the reservoir are dangerously close to the maximum permissible level, and a breakthrough of the protective dams may occur in the event of a natural disaster, such as an earthquake. After reaching the maximum NPU (~620 m) and breaking through the dam of the associated Zhamankum reservoir (1988), in 1995 a diversion channel to the Ili River (the Right-Bank Sorbulak Canal) and lakes on it with a capacity of up to 50 million cubic meters were built to relieve Sorbulak. To utilize the accumulated water and reduce the reservoir level, the project envisaged the phased construction of agricultural irrigation fields. In 1990, 10.5 thousand hectares of irrigated land were introduced, and it was planned to increase this to 22.8 thousand hectares by 2000. However, to date, the use of wastewater from the Sorbulak reservoir has not been seriously developed, so in 2000, less than 3.0 thousand hectares of irrigated land remained in the Sorbulak massif. The main functions of the Sorbulak storage tank are deep long-term regulation of wastewater in Almaty, ensuring its natural self-purification. The basis of the incoming part of the water balance (71%) of the Sorbulak storage tank is made up of sewage from Almaty and adjacent satellite cities, 19% is atmospheric precipitation, and the contribution of the underground flow is 9%. Most of the outgoing part - 63% - is due to evaporation. With wind movement of water masses, the process is faster. The height of the wind wave in the reservoir can reach 2.7 m at a wind speed of 30 m / s. The Sorbulak storage tank has a slow water exchange, so the intra-reservoir processes of sedimentation, sorption and desorption of elements by bottom sediments, and the processes of interaction between the bottom and water are active. The content of certain types of heavy metals in bottom sediments is several tens of times higher than their composition in water. According to the State Enterprise "Vodokanal", the average content of oil products in the Sorbulak reservoir is from 3.73 to 5.06 mg/l. The content of oil products decreases in the summer, since they evaporate at elevated temperatures. According to calculations by S.D. Tyumenev, 80,784 tons of suspended solids entered the reservoir from 1973 to 1998: iron - 1,400 tons, copper - 42.1 tons, zinc - 26.2 tons, lead - 28.9 tons, strontium - 26.9 tons, cadmium - 26.9 tons, chromium - 29 tons. If we assume that these substances precipitated uniformly over the entire existing area of ​​the Sorbulak bottom (60.2 km2), then the height of the sedimentary layer will be more than 1.5 meters.