Water shortfall checks growth plans on Oahu

A water supply shortage is throwing a curve to development of some areas of Hawaii. Long-term water level decline, rising salinity, and increased pumping are affecting the Pearl Harbor basin, which produces 56 percent of Oahu's ground water. As with other islands in the state, rainfall over the centuries has been percolating down through the porous volcanic rock to create underground reservoirs of fresh water.

The city and county of Honolulu, which covers Oahu, has about 729,000 residents, or about 80 percent of the state's population. Water sales through the honolulu Board of Water Supply swelled to 41.9 billion gallons last year from 19.4 billion 20 years earlier and 33.1 billion in 1969. The peak year, however, was 1977 with 45.1 billion gallons.

Water is the backbone of Oahu because it is the hub of governmental and business activities, including commercial and industrial centers. The Navy base at Pearl Harbor, Hickam Air Force Base and other military installations are in the area. Oahu, despite the influx of visitors to Waikiki, remains a major producer of sugar, pineapple, and other crops.

With the state limiting honolulu city and county to 80 million gallons of water a day from the Pearl Harbor basin, the Board of Water Supply and the State Department of Land and Natural Resources are energetically exploring new water sources outside the control area, including some on the windward side of the island, notes Dr. Thomas K. Hitch, senior vice-president, research division. First Hawaiian Bank, Honolulu.

Reserves are extremely limited in the Pearl Harbor basin area, he continues, and development in central Oahu -- where the city general plan envisions the major part of Oahu's future population growth -- will have to be slowed for a time.

There are some hopeful prospects, however, Dr. Hitch points out new wells in Makaha and Waianae, on the leeward side, may be able to produce as much as 6 million gallons a day. Wells can be drilled to develop additional ground water from the windward side to be transported through a pipeline from Waimanalo on the southeast part of the island, around Makapuu to Hawaii Kai, further relieving the Pearl Harbor basin supply, he adds.

In addition, Oahu Sugar Company has entered into an agreement with honolulu to experiment with using sewage effluent from the Mililani sewage treatment plant for irrigation. If successful, this could eventually free more potable water consumption. Also, Hawaiian Electric Company's Waiai wells, which provide water for cooling in its Waiau power plant, may have some surplus good-quality water that the utility can spare for public use.

Water supply problems are not new to Oahu. Honolulu suffered water shortages throughout the 1920s. The Territorial Legislature in 1929 created the Board of Water Supply which set about modernizing the water system, tapping new sources, sealing leaking artesian wells, and metering consumption to prevent waste -- moves that cut per capita consumption by about half.

Meanwhile, on the northern island of Kauai, the Board of Water Supply has declared a moratorium on construction in the Koloa-Poipu area. The first project to be affected is the 224-unit Keoniloa Bay Villas. It will be allowed to proceed only if the developer pays the cost of drilling a well with a minimum capacity of 1 million gallons a day.

Elsewhere on Kauai, a water shortage has developed in the Wailua-Kapaa district where the Board of Water Supply indicates it will approve projects no larger than 15 units up to a total of 200 units until more water becomes available.