Waimanalo Irrigation System Water Level


  • 10/16/2020:  57.0 (50.0 MG)
  • 10/15/2020:  57.0 (50.0 MG)
  • 10/14/2020:  57.0 (50.0 MG)
  • 10/13/2020:  57.25 (50.43 MG)
  • 10/12/2020:  57.25 (50.43 MG)
  • 10/9/2020:  57.0 (50.0 MG)
  • 10/8/2020:  57.0 (50.0 MG)
  • 10/7/2020:  57.0 (50.0 MG)
  • 10/6/2020:  57.0 (50.0 MG)
  • 10/5/2020:  57.0 (50.0 MG)
  • 10/2/2020:  56.50 (49.14 MG)

Waimanalo Irrigation System Users:

On March 9, during a routine inspection of the Waimanalo Reservoir, two small disturbances were noticed on the outer edge of the downstream crest.  With health and safety first and foremost as our main concern, a decision to immediately begin lowering the reservoir level was made based on available information.  Dam safety officials were notified and a follow-up inspection was conducted that night with HDOA and dam safety personnel present.  Further discussions led the group to conclude there was no immediate threat, to continue lowering the water level throughout the evening, and to meet again at daybreak.

HDOA and dam safety personnel were joined by a geotechnical engineer on the morning of March 10, and the conditions were reviewed following some slope clearing.  With daylight, a more detailed inspection was completed and shallow root decay was noted as the probable cause of the surface disturbances.  However, a decision to temporarily lower the working level of the reservoir to 45 feet was made in an abundance of caution and to allow staff to further inspect the reservoir and address any unknown conditions.  NO USE RESTRICTIONS ARE BEING REQUESTED AT THIS TIME

As of the morning of March 14, the reservoir level is 45.75 feet and staff has been instructed to balance supply and use to maintain this level until ongoing assessments are completed.  Please call Mr. Keoni Akau at 973-9473 should you have any questions or concerns.  We sincerely thank you for your patience and understanding, and apologize for any inconvenience this has or may cause.


Brian Kau, P.E.
Administrator and Chief Engineer
Agricultural Resource Management Division



TO:         All Irrigation System Customers

FROM:   Brian Kau, P.E,
Administrator and Chief Engineer
Agricultural Resource Management Division

SUBJECT: Summer and Fall 2016 Forecast

The National Weather Service is predicting a continuing trend for development of La Nina conditions around the state.  Traditionally La Nina conditions were favorable for a wetter than normal wet season (October – April).  However, recent La Nina events have not necessarily followed that pattern.  Recent La Nina events (since roughly the 1990s) have been trending toward drier wet seasons with fewer cold fronts and Kona lows. Therefore, the forecast for the 2016 summer and fall has a high degree of uncertainty at this time.  Leeward sides of the islands may experience drier than normal conditions while windward sides may experience slightly wetter conditions.

Although reservoir levels are currently high, a prolonged dry spell can quickly bring the levels down.  Therefore, the Department of Agriculture strongly suggests that all irrigation system customers consider this information when planting for this summer and fall, keeping in mind that irrigation water service may be affected should conservation measures be necessary.

Should you have any questions, please feel free to call 973-9473.

* * * * * * * * * * * * * * *

Upon notification by the Waimanalo Irrigation System, the following restrictions will be implemented in phases as the reservoir levels approach pre-determined levels.  However, implementation of a specific conservation phase is approximate and may be put into effect based on factors such as a significant increase in system-wide consumption or upcoming weather conditions.

PHASE I –  Cautionary Low – Voluntary Water Conservation – 10%

  • Distribution days will be Sundays to Saturdays – 24 hours a day
  • Voluntary reduction of water consumption by 10% is requested.

PHASE I – MODIFIED – Mandatory Water Conservation – 10%

  • Distribution days will be Mondays to Fridays only, no weekends
  • Distribution hours will be 24 hours a day
  • Mandatory reduction of water consumption by 10%.

PHASE II – (±27 ft.)   Mandatory Water Conservation – 20%

  • Distribution days will be Mondays to Fridays
  • Distribution hours will be from 7:30 a.m. to 3:30 p.m.
  • Mandatory reduction of water consumption by 20%

PHASE III – (±20 ft.) Critical Low – Mandatory Water Conservation

  • Distribution days will be Mondays, Wednesdays and Fridays.
  • Distribution hours will be from 7:30 a.m. to 3:30 p.m.

Please contact us at 973-9473, if you have any questions.