KOYNA DAM · MONSOON DASHBOARD
Updated July 2026

Filling the reservoir, powering the state

Each year Koyna is drained to near-empty by pre-monsoon, then refilled to its 105 TMC brim in a matter of weeks. The same water then splits two ways — west through the turbines to the Arabian Sea, east to the fields and taps of the Krishna basin.

Maharashtra's energy sources
1,960 MW Small 11% Koyna 57% Other hydro 32% Thermal 46% Solar 32% Koyna 3.2%
Koyna dam generates 3.2% of Maharashtra's 60,905 MW — but over half of all its hydro. Full breakdown ↓
105
TMC gross capacity (Shivsagar Lake)
8.6
TMC pre-monsoon low · 28 Jun 2026
+41
TMC added in ≈12 days of rain
1,960
MW installed hydropower
3,586
GWh avg / yr · peaks in monsoon

Reservoir fill — 2026 monsoon

Higher is fuller · gross storage in TMC, against the 105 TMC ceiling. Slow start, then an explosive climb once the Mahabaleshwar catchment opened up.
0 25 50 75 100 105 TMC — full capacity (typically reached by ≈31 Oct) ≈67.5 TMC — annual westward power quota projected → full by Oct 8.6 27.7 53.0 7 Jul: ~400 mm rain at Mahabaleshwar inflow ≈89,600 cusecs · +8.3 TMC/day 28 Jun 1 Jul 3 Jul 6 Jul 8 Jul 11 Jul

Where the 105 TMC goes

Normal-year allocation. The westward power quota is a fixed inter-state share; east-side splits are approximate and get cut first in drought years.
Hydropowerwestward → Arabian Sea
67.5TMC
Irrigationeastward → Krishna basin
≈20.5TMC
Drinking & otherSatara · Sangli · Solapur
≈17.0TMC

Two directions out of one lake

Koyna's quirk: turbine water leaves the basin permanently. So every unit generated is a unit the east side never sees — hence the fixed quota above.
West · Power

Water drops down the steep Western Ghats escarpment through the powerhouses. Monsoon = abundant water = peak generation season.

Discharges to the Konkan coast → Arabian Sea. Lost to the eastern basin.
East · Water & flood

Released through 6 radial spillway gates for irrigation, drinking, and monsoon flood control — coordinated with Almatti Dam downstream.

Flows into the Koyna → Krishna river → Sangli, Kolhapur, Karnataka.
1,960 MW
Installed capacity
18
Francis turbines · 5 units
1,000 MW
Stage 4 (underground)
Monsoon
Peak-output season

Koyna in Maharashtra's grid

State installed capacity, 60,905 MW (Feb 2026). Koyna is just ~3.2% of the whole — but ~57% of all hydro. Longer = more capacity.
Koyna · 3.2% Thermal · 45.7% Solar · 31.8% Wind the 5.6% hydro slice, unpacked ↓ Koyna · 57.1% Other large hydro · 31.7% Small · 11.2% 1,960 MW 1,087 MW 384 MW
Thermal (coal & gas)45.7% · 27,839 MW
Solar31.8% · 19,364 MW
Wind9.6% · 5,873 MW
Koyna3.2% · 1,960 MW
Other large hydro1.8% · 1,087 MW
Small hydro0.6% · 384 MW
Biopower4.9% · 2,998 MW
Nuclear1.8% · 1,069 MW
Other0.5% · ~330 MW
Hydro/dams are only about 5.6% of the state's capacity, and Koyna alone is over half of that. Maharashtra runs mostly on coal (thermal) with a large paper fleet of solar.

Capacity isn't generation

Share of installed capacity (●) vs share of electricity actually generated (○, est). Low-utilisation sources — solar, hydro — punch below their weight; coal and nuclear punch above.
0% 20% 40% 60% 80% Thermal 45.7% → ~77% ▲ Solar 31.8% → ~11% ▼ Wind 9.6% → ~4% ▼ Hydro (all) 5.6% → ~4% ▼ Koyna 3.2% → ~2% ▼ Nuclear 1.8% → ~4% ▲ Biopower 4.9% → ~3% ▼
share of capacity share of generation (est) ▲ generates more than its capacity share · ▼ less
Method & caveats

Fill curve: gross-storage readings from daily 2026 monsoon reports (28 Jun low → 11 Jul); the dashed segment is an illustrative projection to full capacity, which Koyna typically reaches by 31 October.

Allocation: the ≈67.5 TMC westward power share reflects Koyna's fixed inter-state (Krishna) allocation; the east-side irrigation/drinking sub-split is approximate and directional — actual releases shift year to year, and in drought years drinking water is prioritised while power is cut first.

Grid mix: installed-capacity figures are firm — CEA/MNRE, February 2026 (large hydro 3,047 MW + small hydro 384 MW = 3,431 MW; Koyna 1,960 MW). Segments sum to ~60,574 MW; the ~330 MW "Other" reconciles to the CEA state total of 60,905 MW. The generation shares (○) are estimates — coal does the bulk of actual generation while solar/hydro run at low capacity factors (Koyna ≈21%), and hydro output swings with the monsoon, so its energy share moves year to year.