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Pacific Islands Water Science Center
ABOUT THE PACIFIC ISLANDS WSC
USGS IN YOUR STATE
USGS Water Science Centers are located in each state.
The Oahu National Water-Quality Assessment: Surface water
The NAWQA study design for surface water focuses on water-quality conditions in streams using three interrelated components: water-column studies, bed-sediment and tissue studies, and ecological studies.
Water-column studies monitor physical and chemical characteristics and their relation to hydrologic conditions, sources, and transport. Water column studies are conducted at sites termed either "basic-fixed sites" (BFS) or "intensive-fixed sites" (IFS), according to the frequency of sampling and/or constituents analyzed. The sampling sites are selected to determine the quality of water in relation to important environmental settings in the study unit. Basic and intensive fixed sites can be either indicator or integrator sites. Indicator sites represent relatively homogeneous, small basins associated with specific environmental settings, such as a particular land use that substantially affects water quality in the study unit. Integrator sites are established at downstream points in larger relatively heterogeneous drainage basins with complex combinations of land-use settings. Water samples also are collected at other locations as part of (short-term) synoptic studies of specific water-quality conditions or issues during a specific hydrologic period (for example during low streamflow) to provide greater spatial coverage and to allow investigators to assess whether the basic-fixed site or intensive-fixed sites are representative of streams throughout the study unit.
Island of Oahu showing location of fixed and synoptic sites, drainage areas, and land use (Hawaii State Office of Planning Land Use Districts, 2000).
In March 1999 the Oahu NAWQA study team began a 2-year water-column study at three locations, of which one is a basic-fixed site on Waikele Stream and the other two are intensive-fixed sites on Manoa and Waikele Streams. All sites were sampled for BFS constituents (major ions, nutrients, dissolved organic carbon, suspended organic carbon, and suspended sediment). At the intensive fixed sites, the samples also were analyzed for trace elements and pesticides. In addition, VOC samples were collected at the Manoa intensive fixed site. A continuous record of discharge, specific conductance, and water temperature was measured at all sites. Field measurements done at the time of water-quality sampling included water temperature, specific conductance, pH, dissolved oxygen, and alkalinity. The sampling frequency was monthly plus six event-based samples per year at all sites. Event-based samples were collected using an automatic (point) sampler.
Water-column samples were collected during low streamflow conditions at six additional sites to provide greater spatial coverage and to assess whether the basic fixed-site or intensive fixed-sites are representative of streams throughout the study unit.
A description of each site and available data can be found by selecting the site number on the map or stream name listed in the table below.
For More Information
If you have questions and comments related to the Oahu NAWQA study, contact:
Stephen Anthony (firstname.lastname@example.org)
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