The combined storage in Sri Lanka’s 74 major reservoirs stood at 33.6% of total capacity on September 13, according to the Irrigation Department’s Water Management Branch, reported by the Daily Mirror.
The 74 reservoirs have a combined gross capacity of 3,114,407 acre-feet. No spilling was reported from any of them.
A slow, steady decline
The figure continues a downward line this site has tracked through the dry season:
| Date | Storage |
|---|---|
| August 22 | 35.9% |
| September 6 | 34.3% |
| September 13 | 33.6% |
That is a fall of 2.3 percentage points in three weeks — a grind rather than a collapse. The September 6 release measured against effective capacity; this one is stated against total capacity, so the two are not perfectly like-for-like, and the real week-on-week drop may be slightly smaller than the headline suggests.
The east is the problem
The spread across the 13 irrigation ranges is wide — the best-supplied range holds more than three times the proportion of the worst.
| Range | Storage |
|---|---|
| Kurunegala | 71.7% |
| Galle | 63.2% |
| Kandy | 60.5% |
| Puttalam | 60.2% |
| Monaragala | 55.1% |
| Anuradhapura | 43.6% |
| Hambantota | 36.7% |
| Polonnaruwa | 35.7% |
| Mannar | 27.7% |
| Trincomalee | 25.8% |
| Batticaloa | 24.6% |
| Ampara | 21.5% |
Ampara, Batticaloa and Trincomalee — the three lowest — are all in the Eastern Province, with Mannar in the north the next worst. The four best-supplied ranges are in the west, the south-west and the hills.
Kurunegala’s lead is unchanged from the September 6 release, when it was the strongest range at 73.3%.
The largest reservoir is nearly empty
Individual reservoirs diverge even more sharply than the ranges. Vakaneri in Batticaloa was full at 100%, and Ambewela in Badulla at 98.9% — both in or beside ranges with some of the lowest aggregate storage. Deduru Oya in Kurunegala stood at 90.6% and Rajangana in Anuradhapura at 83.2%.
Against that, Senanayaka Samudraya — the largest of the 74 by gross capacity — was at just 17.6%, and that was after it recorded 23mm of rainfall, the heaviest of any reservoir in the dataset. A reservoir that large absorbs a day’s rain without registering much change.
Because Senanayaka Samudraya is so large, its 17.6% pulls the national aggregate down more than any other single site. The 33.6% figure is not evenly distributed pressure; it is a handful of very large, very low reservoirs sitting alongside smaller ones that are close to full.
Rainfall was patchy. Several reservoirs recorded none at all, while Mahadivul Wewa took 21.5mm.
The 55% question
These figures sit awkwardly beside others in circulation. Agriculture Minister K. D. Lal Kantha told Parliament on September 11 that reservoirs under the Irrigation Department and the Mahaweli Authority stood at 55% — well above the 33.6% the Irrigation Department’s own branch published two days later.
The likeliest explanation is that the two are not counting the same thing. The minister’s figure includes Mahaweli Authority reservoirs, which are not in this 74-reservoir dataset, and a different denominator — gross versus effective capacity — moves the number again. Neither the minister nor the department has said which basis is being used, and no outlet has reconciled the two. Readers should not treat the gap as one of them being wrong.
Why it matters now
The Maha planting season opens shortly, and the Agriculture Ministry has set a target of 830,000 hectares, with a final decision on the season due on September 18. Storage in the Eastern Province ranges — the ones now at a fifth to a quarter of capacity — will bear directly on what can be irrigated there.
The El Niño conditions behind the dry spell have affected more than 160,000 people across eight districts.
Not reported
The Daily Mirror does not give the present storage in acre-feet, so the 33.6% cannot be checked against the gross capacity figure — a calculation that exposed an inconsistency in the August 22 release. It does not give the comparable figure for the same date last year, or a long-run average for mid-September, without which the decline cannot be judged as unusual.
It does not say whether any range is approaching a threshold for restricting irrigation releases or drinking-water supply, does not report the storage in the Mahaweli Authority’s reservoirs, and does not carry any comment from the Irrigation Department on the outlook for the Maha season.
