Koolau Reservoir Water Level
Hawaii · updated daily from the U.S. Geological Survey
6.07 ft
Koolau Reservoir is high for this time of year and falling (-0.20 ft in the last 7 days).
Change since yesterday: +0.00 ft
Reading as of 2026-08-14 · higher than 85% of August readings on record
Where Koolau Reservoir sits historically
Today's level compared with every reading in our 3.7-year record for this lake.
Since yesterday
+0.00 ft
7-day change
-0.20 ft
30-day change
-0.20 ft
1-year change
+0.19 ft
Last 30 days
Last 12 months
Full history (3.7 years)
Koolau Reservoir records and averages
| Current level | 6.07 ft |
|---|---|
| Record high | 10.79 ft (2026-03-21) |
| Record low | 5.87 ft (2022-12-15) |
| Average of all readings | 6.07 ft |
| Data span | 3.7 years (1,267 readings) |
Frequently asked questions
Is Koolau Reservoir full right now?
As of 2026-08-14, Koolau Reservoir sits at 6.07 ft, which is high for this time of year.Over the past 30 days the level has fallen 0.20 ft.
What is the water level at Koolau Reservoir today?
The most recent reading is 6.07 ft (2026-08-14), sourced from the U.S. Geological Survey. Readings on this page refresh automatically as the agency publishes new data.
What is the highest Koolau Reservoir has ever been?
The highest level in our records is 10.79 ft on 2026-03-21. The lowest is 5.87 ft on 2022-12-15. Our record covers about 3.7 years of readings.
Is Koolau Reservoir low for this time of year?
Compared with every August in our records, the current level is higher than 85% of them — high for this time of year. Seasonal comparison matters more than the raw number, because most reservoirs draw down predictably through late summer and refill over winter and spring.
Why is Koolau Reservoir low right now?
Reservoir levels move for four main reasons: rainfall and runoff into the basin, releases through the dam for downstream water supply, power generation or flood control, evaporation during hot months, and seasonal drawdown schedules set by the operating agency. Koolau Reservoir has fallen 0.20 ft over the past 30 days. For the operational reason on any given week, check the U.S. Geological Survey directly.
How much has Koolau Reservoir changed over the past year?
The level is +0.19 ft compared with this date last year (6.07 ft today). The full-history chart above covers 3.7 years, with a record high of 10.79 ft and a record low of 5.87 ft.
Nearby lakes in Hawaii
Source: the U.S. Geological Survey. Readings are provisional and subject to revision by the publishing agency. All Hawaii lake levels.