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Home › Waters › Hawaii › Koolau Reservoir
Reservoir · Honolulu County, a small plantation reservoir against the Koolau foothills east of Wahiawa on the central plateau of Oahu · Hawaii

Koolau Reservoir Fishing Guides

A small plantation reservoir tucked against the Koolau foothills east of Wahiawa, gauged for stage and sitting in the wettest corner of Oahu's central plateau.

A small boat pulled up on a calm reservoir bank at sunset
Gauge location. Map data © OpenStreetMap contributors.

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About the Koolau Reservoir

Koolau Reservoir is one of the cluster of small irrigation impoundments in the gulches at the foot of the Koolau Range east of Wahiawa, on the central plateau of Oahu. Like its neighbours it was built to hold water for plantation agriculture, catching runoff from the windward slopes and releasing it across the plateau to the cane and pineapple fields below. The agriculture that justified the system has gone, but the reservoirs remain as the island’s principal freshwater, and they sit in some of the wettest ground in the state.

Rainfall is the defining variable. The Koolau crest immediately east receives among the heaviest rainfall anywhere in Hawaii, driven by trade winds lifting moist air up the windward face, and the gulches draining that crest deliver water to these reservoirs quickly and in quantity. The gauge here reports reservoir stage, and the stage record is effectively a rainfall record for the slopes above. Levels can move substantially within a day during winter storms and settle just as quickly through the drier summer months.

Every game fish present is introduced, as it is across Hawaii, where the native freshwater fauna runs to small amphidromous gobies rather than to anything an angler would target. Largemouth bass are the main quarry, with channel catfish, tilapia, bluegill and carp filling out the population, and smallmouth bass present in parts of the wider Wahiawa system. This is a small and lightly fished water in a state where freshwater angling is a minority pursuit, and access arrangements to the plantation reservoirs vary and should be confirmed locally before a trip is planned. For a visitor with a day to spare on Oahu the freshwater option is a genuine change from the charter and shoreline saltwater fishing that dominates the island, and the setting against the green wall of the Koolau is worth the drive on its own. Tackle is straightforward bass gear, and the fish are neither large nor heavily pressured compared with mainland waters of similar size.

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Version 1.0, dated 6 September 2026. Applies to every photograph submitted to GuidedFloats through the contact form, a species page, or the community board.

1. What you give us

By ticking the box on the form you grant Guided Floats, LLC (“GuidedFloats”, “we”) a non-exclusive, worldwide, royalty-free license to store, copy, resize, crop and display your photograph on guidedfloats.com, in GuidedFloats’ own social media accounts and mobile apps, and in material that promotes the site itself, in connection with the fish, water or community feature you sent it in for. The license lasts until you withdraw it (section 4).

You keep the copyright. The license is not exclusive, so you can use the photo anywhere else and license it to anyone else. We will not sell your photo, license it on to anyone else on its own, or use it in paid advertising for a third party.

2. What you confirm

You confirm that you took the photograph yourself (or otherwise own the rights to it), that you have the right to grant this license, and that publishing the photo does not infringe anyone else’s copyright, privacy or other rights.

If any person is recognisable in the photo, you confirm that they have agreed to its being published here, and that a parent or guardian has agreed on behalf of anyone under 18. Please do not send photographs of other people’s catches, screenshots, or pictures copied from other websites or social media.

3. Credit

We print the credit name you give us beside the photo wherever it appears on the site, and record it as the photo’s creator in the page’s structured data. If you leave the credit blank we use the name you gave us on the form. Write “Anonymous” if you prefer no name at all. Your email address, phone number and the exact spot the photo was taken are never published.

4. Withdrawing the license

You can withdraw the license at any time by emailing hello@guidedfloats.com, or by using the contact form, and telling us which photo you mean. We will remove the photo from guidedfloats.com within 7 days of receiving your message and stop using it in anything new. Copies that are already outside our control — search-engine caches, social posts that have already gone out, printed material already produced — may take longer to disappear or may not be recallable, and we are not responsible for those.

5. What we may do

We choose which photos to publish and may decline any submission without giving a reason. We may crop, resize, sharpen or colour-correct a photo for display, and we may remove a photo at any time. We will not alter a photo in a way that misrepresents the fish, the water or you.

6. Your details

We keep your name, email address, the credit name, the water and date you gave us, and the network address the submission came from, with the submission record, as our evidence of this license. We hold that record for as long as the photo is published and for the retention period described in our privacy policy. Location data that your camera or phone embedded in the file is removed before the photo is published.

7. Versions

The version of this license you accepted is stored with your submission and printed with the photo. A later version does not apply to a photo you have already sent unless you agree to it.

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Posting to Koolau Reservoir.

JPG, PNG or WebP, up to 12 MB. We resize it and strip the location data out of the file.

The name shown under the photo. Leave blank to stay anonymous.

Reader photo license v1.0 — the short version:

  • You grant Guided Floats, LLC a non-exclusive, royalty-free license to publish, resize and crop your photo on guidedfloats.com and in GuidedFloats’ own social posts and apps. You keep the copyright and can use the photo anywhere else.
  • You confirm that you took the photo yourself, that publishing it does not infringe anyone else’s rights, and that anyone recognisable in it (or a parent or guardian, if they are under 18) is happy for it to appear here.
  • Credit is printed beside the photo wherever it appears on the site, using the credit name you give us. Leave it blank and we use your name; write “Anonymous” for no name. Your email address is never published.
  • Withdrawing is one email to hello@guidedfloats.com naming the photo. It comes off the site within 7 days.
Read the full license

Version 1.0, dated 6 September 2026. Applies to every photograph submitted to GuidedFloats through the contact form, a species page, or the community board.

1. What you give us

By ticking the box on the form you grant Guided Floats, LLC (“GuidedFloats”, “we”) a non-exclusive, worldwide, royalty-free license to store, copy, resize, crop and display your photograph on guidedfloats.com, in GuidedFloats’ own social media accounts and mobile apps, and in material that promotes the site itself, in connection with the fish, water or community feature you sent it in for. The license lasts until you withdraw it (section 4).

You keep the copyright. The license is not exclusive, so you can use the photo anywhere else and license it to anyone else. We will not sell your photo, license it on to anyone else on its own, or use it in paid advertising for a third party.

2. What you confirm

You confirm that you took the photograph yourself (or otherwise own the rights to it), that you have the right to grant this license, and that publishing the photo does not infringe anyone else’s copyright, privacy or other rights.

If any person is recognisable in the photo, you confirm that they have agreed to its being published here, and that a parent or guardian has agreed on behalf of anyone under 18. Please do not send photographs of other people’s catches, screenshots, or pictures copied from other websites or social media.

3. Credit

We print the credit name you give us beside the photo wherever it appears on the site, and record it as the photo’s creator in the page’s structured data. If you leave the credit blank we use the name you gave us on the form. Write “Anonymous” if you prefer no name at all. Your email address, phone number and the exact spot the photo was taken are never published.

4. Withdrawing the license

You can withdraw the license at any time by emailing hello@guidedfloats.com, or by using the contact form, and telling us which photo you mean. We will remove the photo from guidedfloats.com within 7 days of receiving your message and stop using it in anything new. Copies that are already outside our control — search-engine caches, social posts that have already gone out, printed material already produced — may take longer to disappear or may not be recallable, and we are not responsible for those.

5. What we may do

We choose which photos to publish and may decline any submission without giving a reason. We may crop, resize, sharpen or colour-correct a photo for display, and we may remove a photo at any time. We will not alter a photo in a way that misrepresents the fish, the water or you.

6. Your details

We keep your name, email address, the credit name, the water and date you gave us, and the network address the submission came from, with the submission record, as our evidence of this license. We hold that record for as long as the photo is published and for the retention period described in our privacy policy. Location data that your camera or phone embedded in the file is removed before the photo is published.

7. Versions

The version of this license you accepted is stored with your submission and printed with the photo. A later version does not apply to a photo you have already sent unless you agree to it.

Access

Wahiawa - the nearest town, with services, lodging and the closest tackle supply.
Wahiawa Reservoir - the main and most accessible freshwater fishery on Oahu, a short distance west.
Koolau Range - the windward crest above, the source of the rainfall that fills the reservoir.
Schofield Barracks - the adjacent military installation, which affects access in parts of the area.
Haleiwa - the North Shore town, with services, the harbour and saltwater charters.
Honolulu - forty minutes south, with the international airport and the fullest services on the island.
Mililani - south on the plateau, with further lodging, dining and services.

Seasons

Spring: warming with steady trade wind rainfall, and the most active bass fishing of the year.
Summer: the drier season, with stable stage, warm water and fishing best in the early morning.
Fall: rainfall building again, with consistent bass and catfish fishing through the period.
Winter: the wet season proper, with Koolau storms moving stage quickly and conditions changing day to day.

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Questions

What species can you catch on the Koolau Reservoir?

Anglers target Black Crappie, Bluegill, Bullhead, Channel Catfish, Common Carp, Green Sunfish, Largemouth Bass, Redear Sunfish, Smallmouth Bass, Tilapia on the Koolau Reservoir in Hawaii.

Where can you access the Koolau Reservoir?

Wahiawa - the nearest town, with services, lodging and the closest tackle supply. Wahiawa Reservoir - the main and most accessible freshwater fishery on Oahu, a short distance west. Koolau Range - the windward crest above, the source of the rainfall that fills the reservoir. Schofield Barracks - the adjacent military installation, which affects access in parts of the area. Haleiwa - the North Shore town, with services, the harbour and saltwater charters. Honolulu - forty minutes south, with the international airport and the fullest services on the island. Mililani - south on the plateau, with...

When is the best time to fish the Koolau Reservoir?

Spring: warming with steady trade wind rainfall, and the most active bass fishing of the year. Summer: the drier season, with stable stage, warm water and fishing best in the early morning. Fall: rainfall building again, with consistent bass and catfish fishing through the period. Winter: the wet season proper, with Koolau storms moving stage quickly and conditions changing day to day.

Where are the fishing regulations for the Koolau Reservoir?

Regulations change by season and section. Read the current rules on the Hawaii agency site: https://dlnr.hawaii.gov/dar/fishing/fishing-regulations/