By COLIN M. STEWART
Tribune-Herald staff writer
Areas in Hilo and Puna closed out 2012 with average to above-average rainfall in December, but it wasn’t near enough to balance out a very dry year.
The National Weather Service’s Honolulu Forecast Office said this week in its monthly roundup of precipitation numbers that rain gauges in North Hilo, South Hilo and the Puna districts received near- to above-average rainfall totals for the month, while gauges elsewhere on the island had below average totals.
The U.S. Geological Survey’s Saddle Quarry gauge recorded the highest total in December, of 18.55 inches, 145 percent of its average, and the highest daily total of 6.52 inches was recorded on Dec. 20 during a period of wet trade wind conditions.
“After starting the month with no measurable rainfall, gauge in the South Hilo and Puna districts recorded rainfall every day from Dec. 8 through the rest of the month,” reads the report. “The Piihonua gauge in upper Hilo had more than an inch of rain on four days.”
However, when looking at rain on the Big Island throughout 2012, it was another below-average year, with severe drought conditions on the leeward side of the island. Earlier this week, the U.S. Department of Agriculture declared Hawaii Island a natural disaster area for the seventh year in a row due to extended drought conditions.
Many of the island’s windward rain gauge sites saw between 50 and 80 percent of the long-term average, while most of the leeward gages had totals below 50 percent of average, the report states.
The USGS’ rain gauge at Kawainui Stream had the Big Island’s highest annual total of 182.63 inches, or 135 percent of average. But Hilo Airport’s reported only 90.39 inches, or 71 percent of average — marking the eighth driest year there on record.
Farmers and ranchers on Hawaii Island have had severe drought conditions with which to contend continuously since July 1, 2008, said Kevin Kodama, senior service hydrologist with the National Weather Service. The conditions have fluctuated over time, but in total, it has added up to a very dry period for the island.
“This drought is a big deal. Prior to this one, one of the bigger benchmarks had been the 1998-2001 drought, and this has lasted longer than that, and this has been longer than that one. … In 2010, it was a really bad year,” he explained, with drought conditions in some parts of the island being classified as “D4,” or “Exception Drought,” the highest level on the classification system used by the USDA’s Drought Monitor. Some farmers and ranchers even reported that springs had dried up on their properties, Kodama said.
“Then, in late summer of 2011, the drought almost went away, but not quite, and then it got worse again,” he said. “You can’t do it overnight. It doesn’t take just one storm. You need several storms so the rainfall can soak through the soil. I’ve talked to some ranchers in Hawaii who’ve said that there will be a big thunderstorm that dumps a bunch of rain, and they’ll go out and dig up some dirt under the top soil, and right below it’s still pretty dry.”
In some cases, he added, periods of severe drought followed by a quick, hard rain can be even worse than no rain at all.
“More damaging rains can cause more problems than good,” Kodama said. It can cause flash flooding, or take away more of the topsoil. What we need are some good, prolonged, multiple rain events that allow the water to soak right through.”
Email Colin M. Stewart at email@example.com.