Meaning of 7Q10 in English
The period of lowest stream flow during a seven-day interval that is expected to occur once every 10 years. During this time of low flow, the amount of Dissolved Oxygen in the water would be expected to be the lowest encountered under normal conditions. Since such conditions are considered to be the worst natural case, the dissolved oxygen levels during such episodes are used to establish Ambient Water Quality Standards for that stream.
Environmental engineering English vocabulary. Английский словарь экологического инжиниринга. 2012