What a cumec is
One cumec is one cubic metre of water per second — a thousand litres every second. A dam discharging 2,000 cumecs is sending two million litres downstream each second, roughly an Olympic swimming pool every 1.25 seconds.
Over 24 hours, 1 cumec equals about 0.0864 million cubic metres (MCM). That conversion is how a release rate translates into reservoir drawdown.
Reading the balance
If inflow exceeds outflow the reservoir is filling; if outflow exceeds inflow it is drawing down. A dam that is spilling while inflow still exceeds outflow is the classic pre-flood pattern — releases are already at capacity and the level is still climbing.
Shutter notices
Kerala dam reports record gate operations verbatim, for example '12/16 shutters opened @ 500 cm each'. JalaNet surfaces those remarks unedited in the Official alerts strip and the alert timeline, because they are the operator's own statement of intent and are the most actionable line in the whole report for downstream residents.