Drought Getting Extreme in Hawaii

(April 8) -- When we think of Hawaii, we typically think of a lush and green island paradise with warm sunshine alternating with frequent showers riding the cooling trade winds.

We don't typically think of a state susceptible to serious drought. But the worst drought conditions in the nation are currently occurring in Hawaii, resulting in water restrictions, posing a threat to crops and even reducing the size of cattle herds.

And it's likely to continue for months.

A large portion of the state is in a drought ranging from "extreme" to "exceptional," even though part of Oahu is not in a drought and trade wind showers during March improved water conditions on the eastern side of the Big Island.

Mandatory water-use reductions of 20 percent are in effect for Maui County, and a 10 percent voluntary reduction is in effect in Oahu County.

The USDA Hawaii Weekly Crop Weather Report notes that heavy irrigation is being used for crops and cattle on the kona (leeward) side of the Big Island. Still, one of Hawaii's most famous crops, coffee, is being threatened by the drought. Not only is this year's crop in danger, but some coffee trees, as old as 100 years, are at risk.

The water problems are not only limited to crops and humans. The drought is also affecting the cattle ranchers on the Big Island. They have been forced to reduce the number of cattle in response to a lack of vegetation for grazing and the expense of feed.

Conditions are not likely to improve anytime soon.

The prevailing easterly trade winds result in a huge natural variance in the amount of rain that falls across the islands. Some windward-facing sections receive more than 200 inches of rain per year; some locations on the other side of the mountains, which rarely receive trade wind showers, average less than 10 inches of rain. With trade winds dominant from spring through fall, these naturally dry areas depend on the occasional winter storm for most of the year's rain.

These naturally dry areas are suffering most from the current drought, and El Nino is at least partially responsible.

El Nino adds moisture and intensity to southern storms moving across the Pacific during the winter months, but the storms often track too far to the north to bring Hawaii rain. When these storms remain to the north, storms need to develop to the west of the state for the western sections of the island to receive significant rain. This occurred rarely during the past winter, leaving these areas with a growing drought problem during the rainiest time of year.

In other words, the drought is very unlikely to break in the coming months unless a tropical storm or hurricane brings tropical rain to the state. Such storms are infrequent in Hawaii (and not the best way to break a drought because of the potential damage and loss of life), so Hawaiian residents might have to wait for next winter and hope for the best.