Geology topics
Publications and source records attributed to James Nickles.
U.S. Geological Survey (USGS) scientists are in the forefront of the effort to understand what causes changes in the hydrology, the ecology and the water quality of the Sacramento-San Joaquin River Delta and the San Francisco Bay estuary. Their scientific findings play a crucial role in how agencies manage the Bay-Delta on a daily basis.
As the regional management agency for two of the most heavily used ground-water basins in California, the Water Replenishment District of Southern California (WRD) plays a vital role in sheparding the water resources of southern Los Angeles County. WRD is using the results of the U.S. Geological Survey (USGS) studies to help more effectively manage the Central and West Coast basins in the most efficient, cost-effective way. In partnership with WRD, the USGS is using the latest research tools to study the geohydrology and geochemistry of the two basins. USGS scientists are: *Drilling and collecting detailed data from over 40 multiple-well monitoring sites, *Conducting regional geohydrologic and geochemical analyses, *Developing and applying a computer simulation model of regional ground-water flow. USGS science is providing a more detailed understanding of ground-water flow and quality. This research has enabled WRD to more effectively manage the basins. It has helped the District improve the efficiency of its spreading ponds and barrier injection wells, which replenish the aquifers and control seawater intrusion into the ground-water system.
The Sonoma County Water Agency (SCWA) and other local water purveyors have partnered with the U.S. Geological Survey (USGS) to assess hydrologic conditions and to quan-tify the county-wide interconnections between surface water and ground water. Through this partnership, USGS scientists have completed assessments of the geohydrology and geochemistry of the Sonoma and Alexander Valley ground-water basins. Now, the USGS is constructing a detailed ground-water flow model of the Santa Rosa Plain. It will be used to help identify strategies for surface-water/ground-water management and help to ensure long-term viability of the water supply. The USGS is also working with the SCWA to help meet future demand in the face of possible new restrictions on its main source of water, the Russian River. SCWA draws water from the alluvial aquifer underlying and adjacent to the Russian River and may want to extend riverbank filtration facilities to new areas. USGS scientists are conducting research to charac-terize riverbank filtration processes and changes in water quality during reduced river flows.
Throughout California, as pressure on water resources continues to grow, water-supply agencies are looking to the state?s biggest ?reservoir? ? its ground-water basins ? for supply and storage. To better utilize that resource, the Sweetwater Authority and other local partners, including the city of San Diego and Otay Water Districts, are working with the U.S. Geological Survey (USGS) to develop the first comprehensive study of the coastal ground-water resources of southern San Diego County. USGS research is providing the integrated geologic and hydrologic knowledge necessary to help effectively utilize this resource on a coordinated, regional basis. USGS scientists are building a real-time well-monitoring network and gathering information about how the aquifers respond to different pumping and recharge-management strategies. Real-time ground-water levels are recorded every hour and are viewable on a project web site (http://ca.water.usgs.gov/sandiego/index.html). Data from the wells are helping to define the geology and hydrogeology of the area, define ground-water quality, and assess ground-water levels. The wells also are strategi-cally placed and designed to be usable by the local agencies for decades to come to help manage surface-water and ground-water operations. Additionally, the knowledge gained from the USGS study will help local, state, and federal agencies; water purveyors; and USGS scientists to understand the effects of urbanization on the local surface-water, ground-water, and biological resources, and to better critique ideas and opportuni-ties for additional ground-water development in the San Diego area.
Concentrations of fecal-indicator bacteria in urban streams and ocean beaches in and around Santa Barbara occasionally can exceed public-health standards for recreation. The U.S. Geological Survey (USGS), working with the City of Santa Barbara, has used multi-disciplinary science to trace the sources of the bacteria. This research is helping local agencies take steps to improve recreational water quality. The USGS used an approach that combined traditional hydrologic and microbiological data, with state-of-the-art genetic, molecular, and chemical tracer analysis. This research integrated physical data on streamflow, ground water, and near-shore oceanography, and made extensive use of modern geophysical and isotopic techniques. Using those techniques, the USGS was able to evaluate the movement of water and the exchange of ground water with near-shore ocean water. The USGS has found that most fecal bacteria in the urban streams came from storm-drain discharges, with the highest concentrations occurring during storm flow. During low streamflow, the concentrations varied as much as three-fold, owing to variable contribution of non-point sources such as outdoor water use and urban runoff to streamflow. Fecal indicator bacteria along ocean beaches were from both stream discharge to the ocean and from non-point sources such as bird fecal material that accumulates in kelp and sand at the high-tide line. Low levels of human-specific Bacteroides, suggesting fecal material from a human source, were consistently detected on area beaches. One potential source, a local sewer line buried beneath the beach, was found not to be responsible for the fecal bacteria.
In January 2006, the U.S. Environmental Protection Agency (USEPA) enacted stringent standards on arsenic in drinking water. The new limitsraised concerns about wells in the Antelope Valley of northern Los Angeles County that had high levels of naturally occurring arsenic. To meet the new standard, Los Angeles County Waterworks District No. 40, part of the Los Angeles County Department of Public Works, considered building arsenic-removal facilities at a cost of nearly $34 million. Instead, the District initiated a well-modification project that was based on the findings of a U.S. Geological Survey (USGS) scientific investigation. Using a well flowmeter and down-hole sampler - invented by USGS scientists ? the study team found that high-arsenic levels were concen-trated in the deepest portions of the wells, 600 feet or more below the land surface. Using this finding, the District implemented a well modification pilot project where the deep portions of five wells were sealed off permanently, while preserving the ability to pump high-quality water from the upper sections. Well screens in the upper sections were first cleaned using an innovative sonic technique to increase the yield of high-quality water. The deeper sections then were sealed using micro-fine cement technology. The District now pumps water that meets the new USEPA standard for arsenic from the affected wells. Arsenic concentrations are lower by an average of 84 percent, while well yield is lower by only 24 percent. The total cost of the modification project for the five wells was $608,580; a one-time net savings of 550 percent over construction of an arsenic-removal facility.