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Ecological Assessment of Wadeable Streams, Oahu

Project Chief: Reuben H. Wolff
Project Period: June 2005 through February 2008
Cooperator: Hawaii Department of Health
Location: Island of Oahu


In 1972, the U.S. Congress enacted the Clean Water Act (CWA) to protect the nation's vital water resources. A critical section of the Clean Water Act calls for periodic accounting to Congress and the American public on the success or failure of efforts to protect and restore the nation's waterbodies. In recent years, a number of groups reviewed the available data and concluded that the U.S. Environmental Protection Agency (USEPA) and state environmental agencies have been unable to provide Congress and the public with adequate information regarding the condition of the nation's waterbodies. In 2000, the General Acounting Office issued a report noting that USEPA and the states could not make statistically valid references about water quality and lacked data to support management decisions. A National Research Council report in 2001 found that a uniform, consistent approach to ambient monitoring and data collection was necessary to support core water programs.


The objective of this study is to collect biological, physical, and chemical information for 40 randomly selected stream sites on the island of Oahu.

Relevance and Benefits

The USEPA and states need comprehensive water quality monitoring and assessment information on environmental conditions and changes over time to help set levels of protection in water quality standards and to identify problem areas that are emerging or that need additional regulatory and non-regulatory actions to support water quality management decisions such as TMDLs, NPDES permits, enforcement, and nonpoint source management. The basic intent of this study is to collect information for a small but statistically unbiased, probablity-based, sample of a larger population of streams on Oahu, so that inferences for the larger population of streams can be extrapolated from the smaller, economically tractable sampling network. Standard operating procedures and a strict quality assurance program will be used to ensure data integrity for the assessments.


The approach for this assessment includes four phases: (1) network design, (2) field sampling, (3) laboratory analysis, and (4) data analysis and report writing. The network design will follow the USEPA randomized (probability-based) monitoring design for wadeable rivers and streams. A total of 40 sites will be selected. Field sampling will include the collection of biological, physical, and chemical information according to procedures described in the USEPA Wadeable Streams Assessment: Field Operations Manual (EPA841-B-04-004). Seasonal cycles in macroinvertebrate reproduction in Hawaii restrict sampling to the months of March through July. All aspects of the work will adhere to the USEPA Environmental Monitoring and Assessment Program Quality Assurance Project Plan, which identifies data quality objectives and describes the methods and procedures that will be used to achieve these objectives.


Work started on this study in June 2005 and since then we have completed the network design and collected habitat information and invertebrate and water-quality samples at 40 randomly selected sites, and 5 additional invertebrate and water-quality samples collected at 5 sites that were sampled in the summer of 2006.


Wolff, R.H., and Koch, L.A., 2009, Ecological assessment of wadeable streams on O'ahu, Hawai'i, 2006-2007; a pilot study: U.S. Geological Survey Scientific Investigations Report 2009-5229, 83 p.

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