The U.S. Geological Survey (USGS) is committed to providing the Nation with accurate and timely scientific information that helps enhance and protect the overall quality of life and that facilitates effective management of water, biological, energy, and mineral resources (http://www.usgs. gov/). Information on the quality of the Nation's water resources is critical to assuring the long-term availability of water that is safe for drinking and recreation and suitable for industry, irrigation, and habitat for fish and wildlife. Population growth and increasing demands for multiple water uses make water availability, now measured in terms of quantity and quality, even more essential to the long-term sustainability of our communities and ecosystems. The USGS implemented the National Water-Quality Assessment (NAWQA) Program in 1991 to support national, regional, and local information needs and decisions related to water-quality management and policy (http://water.usgs.gov/nawqa). Shaped by and coordinated with ongoing efforts of other Federal, State, and local agencies, the NAWQA Program is designed to answer: What is the condition of our Nation's streams and ground-water? How are the conditions changing over time? How do natural features and human activities affect the quality of streams and groundwater , and where are those effects most pronounced? By combining information on water-chemistry, physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide science-based insights for current and emerging water issues and priorities. From 1991 to 2001, the NAWQA Program completed interdisciplinary assessments in 51 of the Nation's major river basins and aquifer systems, referred to as Study Units (http://water.usgs.gov/nawqa/ studyu.html). Baseline conditions were established for comparison to future assessments, and longterm monitoring was initiated in many of the basins. During the next decade, 42 of the 51 Study Units will be reassessed so that 10 years of comparable monitoring data will be available to determine trends at many of the Nation's streams and aquifers. The next 10 years of study also will fill in critical gaps in characterizing water-quality conditions, enhance understanding of factors that affect water quality, and establish links between sources of contaminants, the transport of those contaminants through the hydrologic system, and the potential effects of contaminants on humans and aquatic ecosystems. The USGS aims to disseminate credible, timely, and relevant science information to inform practical and effective water-resource management and strategies that protect and restore water quality. We hope this NAWQA publication will provide you with insights and information to meet your needs, and will foster increased citizen awareness and involvement in the protection and restoration of our Nation's waters. The USGS recognizes that a national assessment by a single program cannot address all water-resource issues of interest. External coordination at all levels is critical f...
As part of a regional monitoring program, water samples were collected in the San Francisco Bay estuary during 25 cruises from January through December 1998. Conductivity, temperature, light attenuation, turbidity, oxygen, and in-vivo chlorophyll fluorescence were measured longitudinally and vertically in the main channel of the estuary from south of the Dumbarton Bridge in the southern part of the Bay to Rio Vista on the Sacramento River. Discrete water samples were analyzed for chlorophyll a, phaeopigments, suspended participate matter, and dissolved oxygen. Water density was calculated from salinity, temperature, and pressure (depth), and is included in the data summaries. Substances Hydrology Program. Additional support was provided by participants in the Regional Monitoring Program for Trace Substances, including municipal and industrial dischargers, cooling water and storm water dischargers, and dredgers. We thank these participants for their financial support and their foresight in appreciating the need to view the Estuary as a whole and to manage it on a regional basis. We also acknowledge the Regional Water Quality Control Board for its oversight and coordination of the Regional Monitoring Program, and the San Francisco Estuary Institute for its essential role in management of that program. METHODS Sampling System In-situ measurements were made from the USGS Research Vessel Polaris with a high speed data acquisition system. At each station, a Sea-Bird Electronics (SBE) underwater unit (SBE-9) was lowered through the water column. Attached to the data acquisition unit were the following sensors: SBE-4 conductivity sensor, SBE-3 temperature probe, Paroscientific digiquartz pressure transducer, Sea Tech in-vivo fluorometer, SBE-13 oxygen sensor, D&A Instruments OBS-3 optical backscatter sensor, and LiCor Instruments 192S quantum sensor. With this instrument package, vertical distributions of conductivity, temperature, depth (pressure), chlorophyll fluorescence, oxygen concentration, turbidity, and solar radiance (photon flux density) were measured throughout the water column. The instrument package was lowered through the water at about 1.0 meter per second to within 1 meter of the bottom. Signals from the conductivity, temperature, pressure, fluorescence, oxygen, OBS, and light sensors were digitized in the underwater unit (SBE-9) at 24 scans per second, resulting in a vertical sampling interval of about 4 cm. The data were transmitted to a deck unit through a single-conductor armored cable, displayed and stored on a shipboard computer. To conserve space in this report, the data presented in Appendix A are centered averages of about 24 data points collected over each 1-meter depth interval. For example, the one-meter values listed in Appendix A are averages of all measurements made between depths of 0.5 and 1.5 meters. The conductivity sensor was a 2-terminal, 3 electrode (platinum), flow-through sensor. This sensor was accurate within 0.0004 Siemens per meter and had a resolution of 5x10"5 Siemens per met...
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