Historical Hydrology
Although modern Bolaq has only 2 connections to other reservoirs, both subterranean, once it had a complex hydrology. Bolaq had a tributary, a brook that had flew from a former lake in the modern Paris Commune public garden. In the course of year Bolaq flew from Qaban to Kazanka. During Kazanka's spring tide, that followed Qaban's spring tide, Bolaq flew from Kazanka to Qaban. Then flow course normalized. Ten days later, during Volga's spring tide, Bolaq flown from Kazanka, Volga's tributary to Qaban again. At the south Qaban also became connected with Volga. At the winter's end Bolaq waters had 45 m above sea level, at Volga spring tide 50-53 and even 56 m. At summer the normal level was 49,5 m. As the result of this changing of the course, Bolaq's bottom had little silt. Since 1950s Bolaq silts rapidly.
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