Water use stable; rainfall still below normal on Maui

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AVERAGE DAILY WATER USE

DistrictAug. 21-27Aug. 14-20Aug. 2007

Central Maui25.22 mgd25.42 mgd27.96 mgd

Upcountry8.00 mgd7.86 mgd7.92 mgd

Lahaina5.55 mgd5.91 mgd6.71 mgd

Hana0.34 mgd0.35 mgd0.30 mgd

Molokai1.18 mgd1.16 mgd1.41 mgd

Total40.29 mgd40.70 mgd44.30 mgd

WAILUKU - While continuing low-rainfall conditions are raising concerns on Windward Oahu, Maui County Water Director Jeff Eng expressed appreciation for water conservation efforts of consumers in Central and South Maui.

"Water usage for the Central system dropped a bit compared to the previous week," he said. "I hope we can continue with our conservation efforts until the rainy season begins, and we appreciate those who take seriously their personal responsibility to conserve water."

There have been regular trade wind showers on Maui watersheds this month, but the rainfall totals remained below normal for August. The Puu Kukui rain gauge on the West Maui summit and the West Wailua Iki gauge in the East Maui watershed each recorded just over 15 inches of rain through Saturday.

Normal rainfall for August at Puu Kukui is 32.5 inches while the West Wailua Iki norm for August is 19.7 inches. Both watersheds have recorded lower-than-normal rainfall since early 2007.

Rainfall in the East Maui watershed directly affects water resources for the Upcountry water system, which relies on stream flows for 80 to 90 percent of the water used in the region.

The Central Maui water system, which serves Central Maui and South Maui, gets most of its supply from the Iao and Waihee aquifers. But continued low rainfall on the West Maui peak can raise long-term concerns.

Rainfall percolating into the West Maui watershed re-charges the Iao and Waihee aquifers, where water levels have been falling under the continuing heavy demand. The Waiehu monitor well has declined from a high of 18 feet in 1989 to between 10 to 12 feet this year.

The Maui County Board of Water Supply is urging voluntary water use cutbacks on both the Central and Upcountry systems.

On Oahu, where groundwater is the source of all of the domestic water, the low rainfall prompted a call for a 10 percent cutback on the windward side of the island.

During a press conference Friday, Honolulu water officials and Kevin Kodama, National Weather Service senior hydrologist, said groundwater sources throughout Windward Oahu are "showing signs of stress" and the water department must cut pumping to protect the sources. While the appeal Friday was for voluntary conservation, the Honolulu water board said that it may be forced to order mandatory conservation.

Kodama said areas of Windward Oahu have recorded less than 50 percent of normal rainfall this year "and the short-term outlook for recovery is not promising."

Two weeks ago, the National Oceanic and Atmospheric Administration's Climate Prediction Center forecast below-normal rainfall in the islands through the remainder of 2008.

The U.S. Drought Monitor, released Thursday, maintained the drought severity report for the islands, rating areas of South Maui, North Hawaii and East Oahu in "extreme drought." The west end of Molokai and the rest of Central Maui remain in severe drought, while other areas of Maui County are rated as in moderate drought or abnormally dry - except Hana, which has achieved normal status.

Eng noted that water use on the Upcountry system has been rising, and spiked to a high of 8.9 million gallons a day Tuesday. But he said water levels in the reservoirs have remained stable, with inflow continuing even as usage was rising.

The Wailoa Ditch, which supplies the Kamole Weir Water Treatment Facility, reflected the sporadic rainfall conditions. When West Wailua Iki recorded 1.13 inches Aug. 22, flows in the ditch spiked to 184 mgd on Aug. 23. Flows continued to peak and fall through the week. When there was just 0.15 inches of rain Thursday, flows on Friday were down to 68 mgd.

For the week ahead, the weather service is forecasting continuing moderate to strong trade winds, which will bring in periodic showers, with an upper level trough affecting the flows.

"Passing trade showers have been brief but also a bit heavier at times," the Saturday forecast said. "The trend is expected to continue as long as the upper trough lingers in the area, keeping the atmosphere slightly unstable . . . through the early part of (this) week."

Edwin Tanji can be reached at citydesk@mauinews.com.