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A series of chapters on techniques describes methods used by the U.S. Geological Survey for planning and conducting water-resources investigations. The material is arranged under major subject headings called books and is further subdivided into sections and chapters. Book 5 is on laboratory analyses; section A is on water. The unit of publication, the chapter, is limited to a narrow field of subject matter. "Methods for Determination of Inorganic Substances in Water and Fluvial Sediments" is the first chapter under section A of book 5. The chapter number includes the letter of the section.This chapter was prepared with the assistance of many chemists and hydrolo gists of the U.S. Geological Survey as a means of documenting and making available the methods used by the U.S. Geological Survey to analyze water, water-sediment mixtures, and sediment samples.Any use of trade names, commercial products, manufacturers, or distributors is for descriptive purposes only and does not imply endorsement by the U.S. Geological Survey.This chapter supersedes "Methods for Determination of Inorganic Substances in Water and Fluvial Sediments" by M.

Data on concentrations of environmental tracers, such as chlorofluorocarbons (CFCs), tritium ( 3 H), and other chemical and isotopic substances in ground water, can be used to trace the flow of young water (water recharged within the past 50 years) and to determine the time elapsed since recharge. Information about the age of ground water can be used to define recharge rates, refine hydrologic models of ground-water systems, predict contamination potential, and estimate the time needed to flush contaminants from ground-water systems. CFCs also can be used to trace seepage from rivers into ground-water systems, provide diagnostic tools for detection and early warning of leakage from landfills and septic tanks, and to assess susceptibility of water-supply wells to contamination from near-surface sources.

A Watershed Research Programdisturbances, and non-point source pollution. Efforts at the sites include installation of instrumentation and collection of longterm data for key environmental variables and fluxes. The first phase of the WEBB Program focused on understanding processes at the individual watersheds.The next phase of research will compare and contrast process understanding in these small watersheds and describe processes in larger watersheds so that water, energy, and biogeochemical budgets can be predicted over a wide range of spatial and temporal scales. The three areas that have been identified for increased research efforts are: (1) to understand the effect of the geologic and physiographic framework, land use, landscape characteristics, and climatic setting of a watershed on the generation of streamflow or fluctuations of lake levels by using appropriate modeling techniques, (2) to increase our understanding of temporal and climatic factors that affect solute input, export, and retention, and (3) to estimate the impacts of land-use change on erosion and water/soil resource degradation by developing sediment budgets and comparing carbon inventories and fluxes. Challenges for the coming decade in small watershed investigations will be to improve understanding of the effect of human influences on natural systems and to provide information for the restoration of damaged watersheds.