WAILUKU — All of Central Maui slid into "extreme drought" conditions over the past week despite sporadic showers primarily over the windward slopes, according to the U.S. Drought Monitor and the National Weather Service.

Still, water use in the Central Maui system averaged 24.74 million gallons a day — the lowest average demand on the system since 24.69 mgd in the period of April 24-30, The Maui News reported today.

Water Director Jeff Eng said the department asks its customers "to please continue to be mindful of their water use." He noted that demand through the county remained stable even as rainfall and surface runoff slowed again in the East Maui watershed.

A larger concern is the continuing projection of lower-than-normal rainfall through the rest of 2008, he said.

A Drought Information Statement issued Thursday by weather service senior hydrologist Kevin Kodama cited the spread of extreme drought conditions through Central Maui and noted that the Climate Prediction Center continued to project below-normal rainfall to the end of the year.

In the rating system established by the U.S. Drought Monitor program, "extreme drought" is the second-to-worst drought rating. In extreme drought, there are widespread water shortages or restrictions and a potential for major losses in crops or pastures. It is based on multiple factors, including soil moisture levels at 3 percent to 5 percent of normal as well as a rainfall potential index that for Hawai'i is at minus-1.6 where zero is normal rainfall.

The Drought Monitor places all of west Moloka'i into the extreme drought ranking, with Lana'i and Upcountry Maui rated as in severe drought.

The most severe effects are in the watersheds, with moderate to light trade winds over the past several weeks cutting down the trade showers on the East Maui and West Maui slopes. With flows out of the East Maui watershed falling, Upcountry reservoirs are also rapidly dropping, according to the water department weekly report.

"The Upcountry system and the East Maui watershed are beginning to see the effects of less rainfall," Eng said. "During this seven-day period, the raw water storage in the Upper Kula System's Kahakapao Reservoirs went from 84.2 million gallons to 76.6 million gallons."

Overall storage was down from 131.3 million gallons on Sept. 13 to 117.9 million gallons on Friday. An equal concern is the low flows in the Wailoa Ditch that provides water for Upcountry consumers, the Kula Agricultural Park and Hawaiian Commercial & Sugar Co. fields. The ditch has a capacity of 200 million gallons a day, but was flowing at between 30 and 32 mgd through the week.

Since Sept. 6, the West Wailua Iki rain gauge in the watershed has recorded just over 0.6 inches of rain.

The Central Maui system remains under a drought watch precaution, asking consumers to cut use voluntarily by 10 percent from previous years. Upcountry users are asked to cut consumption by 5 percent. Moloka'i farmers on the Moloka'i irrigation system are under a mandatory 20 percent restriction.