The national study design for surface water assesses the water quality of streams on the basis of three interrelated components: Water-Column, Bed-Sediment and Tissue, and Ecological Studies. Each component characterizes particular water-quality conditions, and each requires a unique, but closely related sampling design. The differences in spatial and temporal patterns characteristic of different water-quality conditions require that the NAWQA design for assessing water quality balance many factors.
Water-Column Studies focus on assessing physical and chemical characteristics, which include suspended sediment, dissolved solids, major ions and metals, nutrients, organic carbon, and dissolved pesticides, and relating these characteristics to hydrologic conditions, sources, and transport (Gilliom and others, 1995, p. 10). For the ALMN Study Unit, these studies include the Basic Fixed-Site Assessment, Intensive Fixed-Site Assessment, Low-Flow Synoptic Survey of Streams in the Coal Fields of the ALMN Basin, and the Mercury Synoptic.
Bed-Sediment and Tissue Studies are the primary means by which trace elements and hydrophobic organic contaminants are initially assessed in NAWQA. Concentrations and their areal distribution are assessed to identify sources and potential needs for more detailed study (Gilliom and others, 1995, p. 10). For the ALMN Study Unit, this study includes the Bed-Sediment and Tissue Study.
Ecological Studies evaluate the effects of physical and chemical characteristics of water and hydrologic conditions on aquatic biota and how biological and habitat characteristics differ among environmental settings in the study unit (Gilliom and others, 1995, p. 11). For the ALMN Study Unit, these studies include the Fixed-Site Reach Assessments (collected at all Basic and Intensive Fixed Sites).
In the ALMN Basin, surface-water samples were collected at essentially two types of data-collection stations -- fixed and synoptic. Under the fixed and synoptic program, basic and/or intensive site sampling was conducted. Many constituents were measured at the selected stations. Review the Study-Unit Design Summary Table for a complete overview of the surface-water study components. The following surface-water study components were developed and completed as part of the ALMN NAWQA Project: