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Surface-Water Diversion System Seepage Reconnaissance Study, East Maui, Hawaii
Project Chief: Chui Ling Cheng
The East Maui Irrigation Company’s (EMI) surface-water diversion system, which consists of about 75 miles of open ditch and tunnel sections, diverts water from east Maui streams and transports it to central Maui for sugarcane cultivation, general agriculture, and domestic use through the public water system(s). The Hawaii State Commission on Water Resource Management (CWRM) established interim instream flow standards for many of the streams diverted by ditches in the EMI system, but the CWRM decision required that a system efficiency study be conducted to accurately determine system losses and/or gains.
The objective of this 1.5-year study is to assess, at the reconnaissance level, the amount of losses or gains from the four main ditches (Koolau/Wailoa, New Hamakua, Lowrie, and Haiku Ditches) of the EMI system in east Maui by documenting seepage rates for various construction-type sections of the ditches. This study will not address the loss rates from ditches that are tunnels, and reservoirs that receive water from or are part of the EMI system.
Relevance and Benefits
The results from this study are necessary for the proper management of the surface waters in the State and, thus, 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 be useful for determining system efficiency and provide information useful for setting instream flow standards in east Maui streams.
To meet the objectives of this study, the USGS will characterize the four main ditches of the EMI system as open ditch or tunnel. The open ditch sections of the diversion system will be further characterized as lined, partially lined, or unlined. A total of nine representative sections, three sections for each ditch-construction type (lined, partially lined, unlined), will be selected and a series of flow measurements will be made in each section to determine the seepage loss or gain for each construction type. The seepage losses or gains will be estimated from the flow measurements for each ditch-construction type (excepting tunnel), and they will be applied to the unmeasured sections of the system.
Characterized the ditch system by conducting two one-week reconnaissance surveys. Conducted seepage analysis on representative sections to characterize gains and losses between the measurement sites. Completed the study.
Cheng, C.L., 2012, Measurements of seepage losses and gains, East Maui Irrigation diversion system, Maui, Hawai'i: U.S. Geological Survey Open-File Report 2012-1115, 23 p.
Study results presented at the Commission on Water Resource Management meeting, January 23, 2013 (7.2 MB).