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Wailuku River Stream Flow to be Suspended for Maintenance

Waterfall in Wailuku River (ʻĪao Stream), courtesy Bob Horcajo.

Waterfall in Wailuku River (ʻĪao Stream), courtesy Bob Horcajo.

The Commission on Water Resource Management will be performing work on the waterfall at the Waihe‘e Ditch siphon where it crosses Wailuku River. (The name has since been restored [1] from previous references as ʻĪao Stream).

The Commission has asked Wailuku Water Company, LLC to reduce the amount of water to Wailuku River, in order to perform the work and provide a safe work environment.

The Commission is performing the work under a grant from the US Fish & Wildlife Service to improve habitat and migratory pathways for native stream fauna. Native Hawaiian ‘o‘opu (goby fish), ‘ōpae (shrimp), and hīhīwai (snails) depend on the connectivity of habitat between headwater streams and the ocean and have evolved the ability to climb wet rocks and up waterfalls.

According to the state Department of Land and Natural Resources, an overhanging concrete lip at the top of a naturally occurring waterfall on the Wailuku River limits their upstream migration. The purpose of the project is to repair the overhang section with grouted rocks from the stream to ensure habitat connectivity. A portion of the stream will also be diverted with sandbags for worker safety.

The tentative start date is Monday, Aug. 8, 2016. On this date, WWC will divert a portion of the flow of the Wailuku River at the upper diversion. This work is expected to take about two weeks and will be subject to the availability of supplies, work completion, and weather conditions.

During this time, the interim in-stream flow standard [2] release of 10 million gallons per day near the Hawai‘i Nature Center will be temporarily suspended. After completion, water will be returned to the stream to meet the IIFS at Kepaniwai Park.

In 2014, a settlement restored partial flows [3] to all four of Nā Wai ‘Ehā, while accommodating HC&S’s ongoing plantation water uses for almost 5,000 acres in Central Maui.

The agreement sought to find a balance between offstream water uses, the health of the streams, traditional and customary rights, and water for the public trust.