Koolau Reservoir near Wahiawa, Oahu water level

Name: Koolau Reservoir near Wahiawa, Oahu water level (U.S. Geological Survey)
Creator: U.S. Geological Survey
License: https://www.usgs.gov/information-policies-and-instructions/copyrights-and-credits

Reservoir, Koolau Reservoir, Hawaii, United States

Directions

Very high for mid-October

Water level

6.72ft Up 0.16 ft over the last 24 hours

Measured Oct 20, 2026, 10:20 PM HST (33 min ago)

History

What this means

Koolau Reservoir near Wahiawa, Oahu is well above normal at 6.72 ft.

That puts it 0.83 ft above the median of 5.89 ft for mid-October, based on 5 years of readings. A year ago it stood at 5.88 ft (+0.84 ft).

It has risen 0.16 ft over the past 24 hours. In the last month it has stayed between 6.07 ft and 6.72 ft.

Many reservoirs are drawn down through summer and fall; most of the refill comes later, with winter rain or spring snowmelt.

Compared with 5 years of daily readings for this time of year. How to read levels

Key numbers

Median for this date: 5.89 ft0.83 ft above the median for this date
Normal for this date: 5.88 ft – 6.15 ft8 years in 10 fall in this range (5 years of records)
Same day last year: 5.88 ft+0.84 ft
Lowest and highest in 30 days: 6.07 ft – 6.72 ft
Lowest and highest in 12 months: 5.86 ft – 10.73 ft

On the water at Koolau Reservoir near Wahiawa, Oahu

Well above normal, shoreline trees stand in the water and debris floats on the surface. Slow down near the edges.

Wear a life jacket on the water. Most boating deaths involve people who were not wearing one.

Weather at the gauge

Rain in the last 3 days: 0.64 in.

20 Tue 78° 69° 0.19 in, 93% Wind 14 mph

21 Wed 78° 68° 0.02 in, 57% Wind 12 mph

22 Thu 78° 65° 0.04 in, 55% Wind 9 mph

23 Fri 78° 65° 0.03 in, 25% Wind 9 mph

24 Sat 78° 67° – Wind 9 mph

25 Sun 72° 66° 0.17 in, 47% Wind 8 mph

26 Mon 79° 64° 0.02 in, 30% Wind 6 mph

Forecast: Open-Meteo

Sunrise 06:31 AM Sunset 06:04 PM Daylight 11 hr, 33 min Waxing gibbous 76%

Map

Nearby gauges

Gauge	Level	Compared with normal	24 hours	Distance
Ku Tree Reservoir near Wahiawa, OahuReservoir, Ku Tree Reservoir	17.19 ft	Low	±0	0.8 mi
SF Kaukonahua Str at E pump, near Wahiawa, OahuRiver gauge, SF Kaukonahua Str	1.77 ft	Below flood stage	−0.19 ft	1.7 mi
NF Kaukonahua Str above RB, near Wahiawa, OahuRiver gauge, NF Kaukonahua Str	1.78 ft	Below flood stage	−0.16 ft	2.3 mi
Upper Helemano Reservoir near Wahiawa, OahuReservoir, Upper Helemano Reservoir	42.76 ft	Very high	−0.08 ft	4.4 mi
Wahiawa Reservoir at Spillway at Wahiawa, OahuReservoir, Wahiawa Reservoir	55.71 ft	Very low	+0.42 ft	5.1 mi
Opaeula Str near Wahiawa, OahuRiver gauge, Opaeula Str	1.94 ft	Below flood stage	+0.08 ft	5.2 mi
Wahiawa Ditch at Wahiawa, OahuCanal gauge, Wahiawa Ditch	6.3 cfs	Low	−2.9 cfs	5.2 mi
Kaukonahua Stream below Wahiawa Reservoir, OahuRiver gauge, Kaukonahua Stream	52.2 cfs	Normal	+19.8 cfs	5.2 mi

Questions and answers

How does Koolau Reservoir near Wahiawa, Oahu compare with last year?

It is 0.84 ft higher than on the same day last year, when the reading was 5.88 ft.

What is a normal level for Koolau Reservoir near Wahiawa, Oahu in mid-October?

The median for mid-October is 5.89 ft. In 8 years out of 10 the reading falls between 5.88 ft and 6.15 ft, based on 5 years of records.

What is the water level of Koolau Reservoir near Wahiawa, Oahu today?

On Oct 20, 2026, 10:20 PM HST, the water level was 6.72 ft. Up 0.16 ft over the last 24 hours.

Is Koolau Reservoir near Wahiawa, Oahu rising or falling?

Up 0.16 ft over the last 24 hours. Up 0.54 ft over the last 7 days.

Is the level of Koolau Reservoir near Wahiawa, Oahu normal?

Very high for mid-October. Compared with 5 years of daily readings for this time of year.

How often is this data updated?

The U.S. Geological Survey publishes a new reading every 15 minutes. This page refreshes within minutes of each update.

Where does this data come from?

The values come directly from the U.S. Geological Survey, the official operator of this gauge, and are in the public domain. We do not estimate or model live values.

For specialists

Station codes, datum, parameters, data quality and downloads

Operator: U.S. Geological Survey
Station code: usgs:16206600 (Agency page)
Coordinates: 21.49205, -157.97020 (WGS84)
Vertical datum: LMSL
Update interval: every 15 minutes
Licence: Public domain. Data: U.S. Geological Survey (USGS), provisional data subject to revision

Published series

Parameter	Last value	Time (UTC)	Quality
Water level	6.72 ft	2026-10-21 08:20	Provisional

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How to cite

U.S. Geological Survey: Koolau Reservoir near Wahiawa, Oahu (usgs:16206600). Accessed October 21, 2026 via Nivelmap, https://nivelmap.com/en/united-states/hawaii/koolau-reservoir-near-wahiawa-oahu

How we check values

Each reading is stored as published. We hold back values that jump faster than physically plausible and show the measurement time with every value.

Readings are provisional, can be delayed or wrong and are not a flood warning. Read the disclaimer