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Oahu Groundwater Levels

Oahu’s municipal drinking water is provided by groundwater sources, which are dependent on recharge from rainfall. Groundwater sources are less susceptible to drought and climate variability.

The Board of Water Supply (BWS) continuously monitors rainfall and groundwater levels to ensure the island's drinking water supply is preserved. The BWS maintains wells across the island to track the health of the aquifers from the effects of varying rainfall and pumping trends.

During hot summer months, when rainfall is low and water demand is high, water levels decrease. If water levels drop too low, the source could be harmed, with long-term detrimental impacts. Monitoring low groundwater levels allows the BWS to adjust pumping operations and inform the public that summer water conservation is necessary.

We remind ALL Oahu water customers to please use water efficiently and to not waste it. If we each save a little water, together we will save a lot and ensure water supplies are sustainable for generations to come.

Why Should We Conserve Water?

  • It is a finite resource.
  • Protects the health of the aquifer.
  • Saves energy and reduce your carbon footprint.
  • Reduces need/costs for the BWS to develop additional sources to meet demand.
  • Promotes sustainability of the resource for future users.

Featured Presentations

Pacific Water Conference: Impacts of Climate Change

FEBRUARY 20, 2019 – Watch as Robert C. Renner, P.E. of the Water Research Foundation, and Barry Usagawa, P.E. of the Honolulu Board of Water Supply (BWS) present on a joint research project to assess the vulnerability of Oahu's sources of water supply and coastal infrastructure from climate change and sea level rise during the Pacific Water Conference, which took place in Honolulu, Hawaii, on February 20, 2019. (00:53:18)

Voice of the Sea: Conserving Fresh Water

FEBRUARY 16, 2019 – In this episode of Voice of the Sea, learn about the need to conserve fresh water in Hawaii. Featured experts include Micah Kane and Tim Johns with the Hawaii Community Foundation, Reggie Castanares at the Plumbers & Fitters Training Center, Barry Usagawa of the Honolulu Board of Water Supply, and Rick Barboza of the Hui Ku Maoli Ola gardens.


VOS6-2 Full Episode - Conserving Fresh Water from Voice of The Sea TV on Vimeo.

2019 Groundwater Status Levels Reports

February 2019 Groundwater Levels Status Report

There were no aquifer index wells within low groundwater status for the production month of February 2019. The monthly production average for February 2019 was 123.94 million gallons per day.

The Board of Water Supply rainfall index for the month of February 2019 was 157 percent of normal; with a 5-month moving average of 108 percent. As of March 5, 2019, the Hawaii Drought Monitor shows abnormally dry for the leeward side of Oahu, from Ewa to Kapolei. The National Weather Service is forecasting below normal rainfall for March 2019.

Most monitoring wells are showing static to slightly increasing trends, likely resulting from decreased pumping during the winter months.


January 2019 Groundwater Levels Status Report

There were no aquifer index wells within low groundwater status for the production month of January 2019. The monthly production average for January 2019 was 131.30 million gallons per day.

The Board of Water Supply rainfall index for the month of January 2019 was 50 percent of normal; with a 5-month moving average of 107 percent. As of February 5, 2019, the Hawaii Drought Monitor shows abnormally dry to moderate drought conditions for the leeward side of Oahu, from Ewa to Waianae. The National Weather Service is forecasting below normal rainfall for February 2019.

Most monitoring wells are showing static to slightly increasing trends, likely resulting from decreased pumping during the winter months.


2018 Groundwater Levels Status Reports

December 2018 Groundwater Levels Status Report

There were no aquifer index wells within low groundwater status for the production month of December 2018. The monthly production average for December 2018 was 127.52 million gallons per day (mgd).

The Board of Water Supply rainfall index for the month of December 2018 was 89 percent of normal; with a 5-month moving average of 151 percent. As of January 8, 2019, the Hawaii Drought Monitor shows abnormally dry to moderate drought conditions for the leeward side of Oahu, from Ewa to Waianae.

Most monitoring wells are showing increasing trends, likely resulting from decreased pumping during the winter months.


November 2018 Groundwater Levels Status Report

There were no aquifer index wells within low groundwater status for the production month of November 2018. The monthly production average for November 2018 was 128.33 million gallons per day.

The Board of Water Supply rainfall index for the month of November 2018 was 78 percent of normal; with a 5-month moving average of 150 percent. As of December 4, 2018, the Hawaii Drought Monitor shows abnormally dry conditions for the leeward side of Oahu, from Ewa to Waianae.

Most monitoring wells are showing increasing trends, likely resulting from decreased pumping during the winter months.


October 2018 Groundwater Levels Status Report

There were no aquifer index wells within low groundwater status for the production month of October 2018. The monthly production average for October 2018 was 133.04 million gallons per day.

The Board of Water Supply rainfall index for the month of October 2018 was 164 percent of normal; with a 5-month moving average of 153 percent. As of November 6, 2018, the Hawaii Drought Monitor shows no drought conditions for the Island of Oahu.

Most monitoring wells are showing increasing trends, likely resulting from decreased pumping due to increased rainfall as we approach the winter months.


September 2018 Groundwater Levels Status Report

There were no aquifer index wells within low groundwater status for the production month of September 2018. The monthly production average for September 2018 was 136.11 million gallons per day.

The Board of Water Supply rainfall index for the month of September 2018 was 154 percent of normal; with a 5-month moving average of 141 percent. As of October 9, 2018, the Hawaii Drought Monitor shows no drought conditions for the Island of Oahu.

Like the previous month, most monitoring wells are exhibiting static or increasing trends, likely resulting from decreased pumping due to recent storm events.

Most monitoring wells are exhibiting static or increasing trends, likely resulting from decreased pumping during the month due to storm events.


August 2018 Groundwater Levels Status Report

There were no aquifer index wells within low groundwater status for the production month of August 2018. The monthly production average for August 2018 was 147.51 million gallons per day.

The Board of Water Supply rainfall index for the month of August 2018 was 267 percent of normal; with a 5-month moving average of 144 percent. As of September 2018, the Hawaii Drought Monitor downgraded the drought status for Oahu, showing only "abnormally dry conditions" rather than "abnormally dry to moderate drought conditions" for the leeward side of the island.

Most monitoring wells are exhibiting static or increasing trends, likely resulting from decreased pumping during the month due to storm events.


July 2018 Groundwater Levels Status Report

There were no aquifer index wells within low groundwater status for the production month of July 2018. The monthly production average for July 2018 was 150.05 million gallons per day (mgd).

The Board of Water Supply rainfall index for the month of July 2018 was 85 percent of normal; with a five-month moving average of 111 percent. As of August 7, 2018, the Hawaii Drought Monitor shows abnormally dry conditions for the central plain of Oahu and moderate drought conditions for the Leeward coast to the Waianae mountains.

Most monitoring wells are exhibiting static or declining trends due to the increased pumping during the summer season.


June 2018 Groundwater Levels Status Report

There were no aquifer index wells within low groundwater status for the production month of June 2018. The monthly production average for June 2018 was 146.72 million gallons per day.

The Board of Water Supply rainfall index for the month of June 2018 was 94 percent of normal; with a five-month moving average of 132 percent. As of July 10, 2018, the Hawaii Drought Monitor shows abnormally dry conditions for the Leeward side of Oahu.

Most monitoring wells are exhibiting static or declining trends due to the increased pumping during the summer season.


May 2018 Groundwater Levels Status Report

There were no aquifer index wells within low groundwater status for the production month of May 2018. The monthly production average for May 2018 was 135.89 million gallons per day (mgd).

The Board of Water Supply rainfall index for the month of May 2018 was 105 percent of normal; with a five-month moving average of 124 percent. As of June 12, 2018, the Hawaii Drought Monitor shows abnormally dry conditions for the Leeward side of Oahu.

Most monitoring wells are beginning to exhibit static or declining trends due to the increased pumping during the summer season.


April 2018 Groundwater Levels Status Report

There was one aquifer index well (Waialua) within low groundwater status for the production month of April 2018. The monthly production average for April 2018 was 126.93 million gallons per day (mgd).

The Board of Water Supply rainfall index for the month of April 2018 was 168 percent of normal; with a five-month moving average of 124 percent. As of May 8, 2018, the Hawaii Drought Monitor shows no dry conditions for Oahu.

The National Weather Service forecasting favors above normal rainfall for May 2018.

Most monitoring wells are continuing to exhibit static head level trends due to the decreased pumpage in the spring months. Punaluu and Kaluanui wells continued to exhibit larger increases in head levels for April 2018.


March 2018 Groundwater Levels Status Report

There were no aquifer index wells within low groundwater status for the production month of March 2018. The monthly production average for March 2018 was 129.90 million gallons per day (mgd).

The Board of Water Supply rainfall index for the month of March 2018 was 104 percent of normal; with a five-month moving average of 112 percent. As of April 10, 2018, the Hawaii Drought Monitor shows no dry conditions for Oahu.

The National Weather Service forecasting favors above normal rainfall for April, May and June 2018.


February 2018 Groundwater Levels Status Report

There are no aquifer index wells within low groundwater status for the production month of February 2018. The monthly production average for February 2018 was 125.76 million gallons per day.

The Board of Water Supply rainfall index for the month of February 2018 was 187 percent of normal; with a five-month moving average of 110 percent. As of March 13, 2018, the Hawaii Drought Monitor shows no dry conditions for Oahu.

The National Weather Service is forecasting above normal rainfall for April 2018.

Most monitoring wells are continuing to exhibit slightly increasing head level trends due to the decreased pumpage during the winter months.


January 2018 Groundwater Levels Status Report

There was one aquifer index well within low groundwater status for the production month of January 2018. Punaluu has be in caution status since the week of June 18, 2017. The monthly production average for January 2018 was 134.48 million gallons per day (mgd).

The Board of Water Supply rainfall index for the month of January 2018 was 58 percent of normal; with a five-month moving average of 85 percent. As of February 13, 2018, the Hawaii Drought Monitor shows no dry conditions for Oahu.

The National Weather Service (NWS) is forecasting above normal rainfall for March 2018. Because of the La Nina conditions in the equatorial Pacific Ocean, NWS is forecasting above normal rainfall for March, April,and May 2018. 

Most monitoring wells are continuing to exhibit static or slightly increasing head level trends due to the decreased pumping during the winter months.


Updated: 04/15/19