EXCLUSIVE | Deep Depression: Hirakud Dam May Be Forced to Open 14 Gates to Flush 2.8 Lakh Cusecs Inflow in next 48 hours!

Bhubaneswar: Weakening into Depression this afternoon, the system from satellite view looks positioned over between Koraput and Rayagada Thursday evening, and past the midnight and early morning hours, the system will take an entry into Chhattisgarh as a depression and, as per IMD, will maintain its depression intensity throughout its Chhattisgarh journey.

As a consequence, it will be pounding the neighbouring state of Odisha on Friday, before weakening into a low by Saturday morning. The depression's passage through Chhattisgarh will record copious rainfall in the upper catchment of the Mahanadi basin.

The immediate hydrological consequence is already becoming visible at Hirakud: a sharp increase in the volume of water rushing into the reservoir. With the depression expected to dump substantial rain over the upper Mahanadi catchment across Odisha and Chhattisgarh, the reservoir may soon move from routine water regulation towards active flood-management operations.

The significance is particularly high because Hirakud is already virtually full.

Hirakud has little room left to absorb the next flood pulse

The reservoir level is currently around 629.69 feet, against the Full Reservoir Level (FRL) of 630 feet. In other words, the dam has almost no meaningful storage cushion to accommodate a major fresh runoff pulse.

Current inflow is around 1,300 cubic metres per second (m³/sec), or nearly 45,900 cusecs. But the Central Water Commission's projection points towards a dramatic escalation, with peak inflow around 8,000 m³/sec – nearly 2.82 lakh cusecs – during September 26-27.

That represents an increase of almost six times from the present inflow.

This is why the issue is no longer simply how much rain the depression produces. The critical question is where that rainwater will go after falling over the upper Mahanadi basin.

With the reservoir already close to FRL, a substantial proportion of the runoff will have to be passed downstream rather than retained inside Hirakud.

Hirakud: September 24 vs September 26-27 — why the gates become critical

Parameter

Present: Sept 24

CWC projected peak: Sept 26-27

What it means

Reservoir level

629.69 ft

Controlled around ~629.5 ft

Virtually no storage cushion

Full Reservoir Level

630 ft

630 ft

Reservoir operating at/near FRL

Inflow

~1,300 m³/sec (~45,900 cusecs)

~8,000 m³/sec (~2.82 lakh cusecs)

Nearly six-fold surge

Gates open

1

14-20 likely

Transition to flood-management mode

Outflow

~1,050 m³/sec (~37,000 cusecs)

Potentially ~8,000 m³/sec (~2.82 lakh cusecs)

Discharge must rise sharply to maintain reservoir safety

Primary objective

Regulation

Flood moderation and reservoir safety

Incoming water has to be passed downstream

BREAKING: Hirakud likely to open at least 14 gates

The most immediate operational consequence of the projected inflow surge is the likely opening of at least 14 sluice gates at Hirakud, with the possibility of the number increasing depending on the actual inflow.

The logic is straightforward: a reservoir at nearly 630 feet cannot safely absorb an additional flood pulse of the magnitude being projected by CWC.

Gate operation therefore becomes a balancing exercise. The authorities have to maintain the reservoir below its safe operating threshold while simultaneously preventing a sudden uncontrolled build-up of water inside the dam.

The number of gates will ultimately depend on the actual inflow, reservoir level and downstream river conditions. The projected 14-20 gate operation should therefore be read as a flood-management scenario rather than a fixed final gate count.

But will 2.54 lakh cusecs from Hirakud immediately flood the lower Mahanadi?

Not necessarily.

This is where the Naraj-Mundali hydrological picture becomes critical.

Even if Hirakud eventually releases around 2.54 lakh cusecs, the downstream Mahanadi does not respond instantaneously. The water has to travel through a long river system, while additional runoff from tributaries joins the main channel.

The estimated travel time from Hirakud towards the Mundali/Naraj control point is roughly 36-40 hours. Therefore, a major release from Hirakud would not translate into an immediate corresponding rise at Naraj.

More importantly, Naraj currently has substantial hydraulic headroom.

The Naraj Mahanadi gauge is around 23 metres, while its warning level is 25.41 metres and danger level 26.41 metres. Thus, the present level is roughly 2.4 metres below the warning threshold.

CWC's present projection indicates a gradual rise towards around 24.3 metres, which would still leave Naraj more than a metre below the warning level.

Naraj-Mahanadi indicator	Level
Present observed level	~23.0 m
Forecast peak	~24.3 m
Warning level	25.41 m
Danger level	26.41 m
Cushion below warning at projected peak	~1.1 m

The distinction is important: Hirakud facing an enormous inflow does not automatically mean an immediate flood emergency in the coastal Mahanadi delta.

The dam's gates are designed precisely to manage this time lag and regulate the flood pulse.

The real flood equation lies downstream

However, the Naraj situation cannot be judged by Hirakud discharge alone.

As water moves downstream, the Mahanadi receives additional contributions from tributaries and local rainfall. The combined discharge at Mundali/Naraj can therefore become substantially higher than the volume released directly from Hirakud.

This is why the next 48-72 hours will be critical.

The upper catchment will be receiving fresh rainfall as the depression travels through Odisha and Chhattisgarh. At the same time, Hirakud will be receiving the accumulated runoff from that catchment. The reservoir then has to release water while downstream engineers continuously watch the Mahanadi's response.

The operational challenge is therefore a moving flood pulse:

Deep Depression → heavy rainfall → upper Mahanadi runoff → Hirakud inflow surge → gate opening → downstream travel time → tributary contribution → Naraj/Mundali discharge.

Why the situation is serious, but not yet a lower-Mahanadi flood

The present numbers point to a peculiar hydrological situation.

Hirakud is under pressure because its storage cushion is almost exhausted. Naraj, meanwhile, still has significant channel capacity.

That gives flood managers a window to release water progressively rather than allowing the reservoir to accumulate the entire incoming flood pulse.

The Central Water Commission's projected inflow of nearly 2.82 lakh cusecs therefore makes gate operation unavoidable from the standpoint of reservoir management, but it does not automatically translate into an equivalent flood level at Cuttack, Mundali or the coastal delta at the same time.

The next danger point will be the convergence of three factors: the actual intensity of depression-induced rainfall over the upper Mahanadi basin, the timing and magnitude of the Hirakud release, and the volume of uncontrolled runoff joining the river downstream.

For now, the hydrological message is clear: Hirakud is preparing to pass the flood pulse; Naraj still has a cushion to receive it.
Also Read: EXCLUSIVE| Deep Depression Rain Triggers Flood Calamity In Odisha: Vamsadhara, Baitarani Cross Danger Mark; More Rivers Rising