LIHUE — The island of Kauai experienced average rainfall between May and July, according to the latest information from the U.S. Geological Survey.
But, precipitation near the summit of Mount Waialeale — Kauai’s second tallest peak and one of the wettest spots on Earth — was below average 10 of the last 12 months.
“The long-term average (at Waialeale) has been dropping every year since 1990,” said Stephen Gingerich, a research hydrologist at USGS. “Since 1990, only three years have been above average.”
The Waialeale rain gauge sits at an altitude of 5,150 feet and has been in operation since 1910. Monthly totals are available for 1950-54 and 1968 to the present, according to the USGS website.
“The average yearly rainfall at the gauge during those years is about 387 inches, and for the entire available period (1912-present) is about 423 inches,” according to the USGS.
Over the past five years, however, Waialeale has been significantly dryer, averaging 326 inches of rain per year from 2009 to 2012, Gingerich said.
“That’s really low, compared to what everybody thinks,” he said.
The most common number tossed around for the mountain is 460 inches of rain per year.
But that calculation dates back to the 1950s, Gingerich said.
“People throw that (number) around,” he said. “But when you update it with all the new data, it’s been dropping and dropping.”
Gingerich said the last time it rained more than 420 inches during a 12-month period at Waialeale was in 2006. And before that was in 1993.
In 1982 — the same year of Hurricane Iwa — a record 683 inches of rain fell on the summit.
Gingerich said his office continues to post rainfall totals on its website because it is concerned with water resources throughout the state.
From August 2012 to July 2013, rainfall across Kauai was about 75 percent of average, according to USGS. Of the eight water gauge stations on Kauai, four registered below normal stream flows for the month of July. The other four registered normal stream flows.
On Oahu, rainfall was about 94 percent of average between August 2012 and July 2013.
Maui was about 60 percent of average for the same time period, Gingerich said.
“The whole state’s been dryer,” he said. “(But) Kauai and Oahu have been not as dry as Maui and Big Island over the last ten years.”
While rainfall totals for 2013 through the end of July were normal or near average for Kauai and Oahu, they were in the near to below average range on Maui and Big Island, according to the National Weather Service.
• Chris D’Angelo, environment writer, can be reached at 245-0441 or firstname.lastname@example.org.