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Low-Flow Characteristics for Streams in the Lahaina District of West Maui, Hawaii

Project Chief: Chui Ling Cheng
Project Period: July 2011 through June 2014
Cooperator: Hawaii State Commission on Water Resource Management
Location: Island of Maui

Problem

For over a century, streams in the Lahaina District of West Maui, Hawaii, were diverted to provide water for large-scale sugarcane cultivation, other agricultural purposes, and domestic uses. The surface-water diversion systems that diverted the West Maui streams consisted of eight separate collection systems that span eleven watersheds, from the northernmost watershed of Honokohau to the southernmost watershed of Ukumehame. Today, many of the diversion systems remain active and provide water for domestic uses, diversified agriculture, and cultural purposes. The Hawaii State Commission on Water Resource Management (CWRM) desires additional scientific information on the West Maui streams, especially streamflow data, that are needed to establish technically defensible instream flow standards that will support equitable, reasonable, and beneficial allocation of the water resources in West Maui.

Objectives

The objectives of this 3-year cooperative study are to (1) quantify the amount of water available under natural, low-flow conditions upstream of diversions; and (2) characterize the magnitude and frequency of low flows at selected sites downstream of existing surface-water diversions. Included in the study are the main streams within the ten watersheds of Honolua, Honokahua, Kahana, Honokowai, Wahikuli, Kahoma, Kauaula, Launiupoko, Olowalu, and Ukumehame.

Relevance and Benefits

The results from this study are necessary for the proper management of the surface waters in the State. The study is consistent with the mission of the USGS Science Strategy to provide citizens, communities, natural-resource managers, and policymakers with a clearer knowledge of the status of their water resources. This study will provide an understanding of the streams in the western part of West Maui with current surface-water data. It will also provide information to CWRM for determining equitable, reasonable, and beneficial instream and off-stream uses of the surface-water resources in the Lahaina District.

Approach

The following scope will be used to meet the study objectives: (1) compilation and review of existing surface-water diversions in the streams and historical discharge records on the hydrologic conditions of the streams; (2) reconnaissance survey of the streams to identify suitable discharge-measurement sites; (3) seepage analysis of the stream to characterize gains and losses between the measurement sites; and (4) discharge measurements at low-flow partial-record sites established upstream from ditch intakes to characterize surface-water availability. Results from this study will be published in the USGS Scientific Investigations Report series and made available on the internet.

Progress

A reconnaissance survey of the streams to select discharge-measurement sites was completed. Low-flow partial-record sites were established, and discharge measurements taken at these sites between February and September 2012. Seepage analyses were conducted on Kahoma and Honokowai Streams.

Fiscal Year 2013

Conduct additional seepage analyses to characterize seepage gains and losses between the measurement sites. Continue to make discharge measurements at low-flow partial-record sites.