Publications

No abstract available.

The vertical distribution of hydraulic conductivity in layered aquifer systems commonly is needed for model simulations of ground-water flow and transport. In previous studies, time-drawdown data or flowmeter data were used individually, but not in combination, to estimate hydraulic conductivity. In this study, flowmeter data and time-drawdown data collected from a long-screened...

No abstract available.

No abstract available.

Pesticides in stormwater runoff, within the Sacramento River Basin, California, were assessed during a storm that occurred in January 1994. Two organophosphate insecticides (diazinon and methidathion), two carbamate pesticides (molinate and carbofuran), and one triazine herbicide (simazine) were detected. Organophosphate pesticide concentrations increased with the rising stage of the...

A study was conducted in 1992 to assess the effects of anthropogenic activities and land use on the water quality of the San Joaquin River and its major tributaries. This study focused on pesticides and organic contaminants, looking at distributions of contaminants in water, bed and suspended sediment, and the bivalve Corbicula fluminea. Results indicated that this river system is...

Existing methods for measuring water imbibition rates are inadequate when imbibition rates are small (e.g., clay soils and many igneous rocks). We developed an improved laboratory method for performing imbibition measurements on soil or rock cores with a wide range of hydraulic properties. Core specimens are suspended from an electronic strain gauge (load cell) in a closed chamber while

Oxygen isotope and total inorganic carbon values of cored sediments from the Owens Lake basin, California, indicate that Owens Lake overflowed most of the time between 52,500 and 12,509 carbon-14 (14C) years before present (B.P.). Owens Lake desiccated during or after Heinrich event H1 and was hydrologically closed during Heinrich event H2. The magnetic susceptibility and organic carbon...

[No abstract available]

The mechanisms that resuspend bottom sediments in Hillsborough Bay, a shallow, microtidal, subtropical estuary in West-central Florida, were determined by analysing hydrodynamic and suspended-solids concentration data collected during several instrument deployments made in 1990 and 1991. Large vessels in a dredged ship channel can generate forced solitary long waves that cause large...

The distribution and fate of chlorinated pesticides, biomarkers, and polycyclic aromatic hydrocarbons (PAHs) in surficial sediments along a contamination gradient in the Lauritzen Canal and Richmond Harbor in San Francisco Bay was investigated. Compounds were identified and quantified using gas chromatography-ion trap mass spectrometry. Biomarkers and PAHs were derived primarily from...

Metals enter the Upper Sacramento River above Redding, California, primarily through Spring Creek, a tributary that receives acid-mine drainage from a US EPA Superfund site known locally as Iron Mountain Mine. Waterweed (Elodea canadensis) and aquatic insects (midge larvae, Chironomidae; and mayfly nymphs, Ephemeroptera) from the Sacramento River downstream from Spring Creek contained...