Koolau Reservoir water level history
Daily records since 2022 · Level today: 6.78 ft
Highest on record
10.73 ft
Mar 21, 2026
Lowest on record
5.86 ft
Jul 10, 2026
Today
6.78 ft
Oct 23, 2026
Years of data
4
since 2022
In short
Across 2 complete years, 2023 had the lowest average level (5.89 ft) and 2024 the highest (5.91 ft).
On average the lake is lowest in December (5.88 ft) and highest in March (6.38 ft).
Koolau Reservoir level, all years
Loading chart…
Measured
Normal range for the date (middle 50% of past years)
Each year's lowest and highest level
Lowest to highest that yearYear average2026 so far
One bar per year from the lowest to the highest daily level, with the year's average. Years with no bar have no daily record in the agency archive.
Lowest years
Years ranked by their lowest daily level.
- 2023
- 2024
Yearly highs and lows
| Year | Average | Low | Low date | High | High date |
|---|---|---|---|---|---|
| 2026 (287 days) | 6.75 | 5.86 | Jul 10 | 10.73 | Mar 21 |
| 2025 (325 days) | 5.89 | 5.88 | Feb 2 | 5.92 | Mar 4 |
| 2024 | 5.91 | 5.88 | Jan 6 | 7.49 | May 18 |
| 2023 | 5.89 | 5.87 | Jan 10 | 5.90 | Jul 15 |
| 2022 (17 days) | 5.88 | 5.87 | Dec 15 | 5.88 | Dec 16 |
Levels in feet. Partial years show the number of days with data.
Monthly averages
| Month | Average | Lowest | Highest |
|---|---|---|---|
| January | 5.88 | 5.87 | 5.89 |
| February | 5.94 | 5.87 | 7.04 |
| March | 6.38 | 5.87 | 10.73 |
| April | 6.38 | 5.88 | 8.53 |
| May | 6.13 | 5.88 | 7.49 |
| June | 6.11 | 5.88 | 7.05 |
| July | 5.90 | 5.86 | 6.08 |
| August | 6.23 | 5.88 | 8.53 |
| September | 6.20 | 5.88 | 7.60 |
| October | 5.96 | 5.88 | 6.75 |
| November | 5.88 | 5.88 | 5.89 |
| December | 5.88 | 5.87 | 5.90 |
Download
Daily levels as CSV (1,335 rows; credit the original agencies listed below)