A dam is a controlled bank account
A reservoir stores water that arrives from its catchment — the area of land whose rain drains into it — and releases it through turbines, irrigation canals or spillway shutters. Everything JalaNet reports is a snapshot of that balance: what came in (inflow), what went out (outflow), and what is left (storage).
Because dams are operated, not passive, level alone never tells the whole story. A dam held deliberately low before a forecast storm is safer than a dam at the same level with no headroom left and rain arriving.
The levels that matter
Kerala dam reports use a small set of reference elevations, all measured in metres above mean sea level:
- FRL (Full Reservoir Level) — the maximum level at which water is normally stored. Operating above it is exceptional.
- MWL (Maximum Water Level) — the highest level the structure is designed to survive during a flood, above FRL.
- Blue / Orange / Red rule levels — pre-declared warning elevations published by KSEB and the Irrigation Department for each dam.
- Dead storage — water below the lowest outlet. It exists on paper but cannot be released.
Freeboard is the number to watch
Freeboard is simply FRL minus the current water level: how many metres of empty dam remain. JalaNet computes freeboard for every reservoir and treats it as the primary escalation signal, because a 0.3 m freeboard means gates will open within hours regardless of what the percentage says.
Percentage storage can mislead in both directions. A barrage like Pazhassi can sit at 9% while discharging 2,000 cumecs, because it is a shutter-controlled structure with almost no live storage. A high-altitude dam can sit at 95% all summer safely.