John Selker

Department of Biological and Ecological Engineering
Oregon State University

Distributed fiber-optic temperature sensing for hydrologic systems

ABSTRACT:  Instruments for distributed fiber-optic measurement of temperature are now available with temperature resolution of 0.01 degrees Celsius and spatial resolution of 1 m with temporal resolution of fractions of a minute along standard fiber-optic cables used for communication with lengths of up to 30,000 m. We discuss the spectrum of fiber-optic tools that may be employed to make these measurements, illuminating the potential and limitations of these methods in hydrologic science. There are trade-offs between precision in temperature, temporal resolution, and spatial resolution, following the square root of the number of measurements made; thus brief, short measurements are less precise than measurements taken over longer spans in time and space. Five illustrative applications demonstrate configurations where the distributed temperature sensing (DTS) approach could be used: (1) lake bottom temperatures using existing communication cables, (2) temperature profile with depth in a 1400 m deep decommissioned mine shaft, (3) air-snow interface temperature profile above a snow-covered glacier, (4) air-water interfacial temperature in a lake, and (5) temperature distribution along a first-order stream. In examples 3 and 4 it is shown that by winding the fiber around a cylinder, vertical spatial resolution of millimeters can be achieved. These tools may be of exceptional utility in observing a broad range of hydrologic processes, including evaporation, infiltration, limnology, and the local and overall energy budget spanning scales from 0.003 to 30,000 m. This range of scales corresponds well with many of the areas of greatest opportunity for discovery in hydrologic science.
Citation: Selker, J. S., L. The4venaz, H. Huwald, A. Mallet, W. Luxemburg, N. van de Giesen, M. Stejskal, J. Zeman, M. Westhoff, and M. B. Parlange (2006), Distributed fiber-optic temperature sensing for hydrologic systems, Water Resour. Res., 42, W12202, doi:10.1029/200WR005326.

Stan Leake

Research Hydrologist
USGS Arizona Water Science Center

Use of Models to Map Potential Capture of Surface Water by Ground-Water Withdrawls

ABSTRACT:  In 1940, C.V. Theis pointed out that all ground water pumped is balanced by removal of water somewhere, initially from storage in the aquifer and later from capture in the form of increase in recharge and decrease in discharge. Capture that results in a loss of water in streams, rivers, and wetlands is now a concern throughout the United States. Hydrologists commonly use analytical and numerical approaches to study temporal variations in sources of water to wells for select points of interest. Much can be learned about coupled surface-/ground-water systems, however, by looking at the spatial distribution of theoretical capture for a select time of interest. Development of maps of capture requires 1) a reasonably well-constructed transient model of an aquifer with head-dependent boundaries representing surface-water features or evapotranspiration; and 2) an automated procedure to run the model repeatedly and extract results, each time with a well in a different location. This presentation addresses procedures and considerations for mapping capture, as well as results using models of the upper San Pedro Valley in Arizona, areas along the Colorado River in Arizona and California, Paradise Valley in Nevada, and the Deschutes Valley in Oregon.

Kathy Kuivila

Research Hydrologist
USGS California Water Science Center

Pyrethroids: A Potential Peril?

ABSTRACT:  Pesticide use changes over time as pests become resistant, environmental problems are discovered or new pesticides are developed. In the past, insecticide use shifted from hydrophobic, persistent organochlorines such as DDT to the more hydrophilic and less persistent organophosphates such as chlorpyrifos and diazinon. Now these insecticides are being replaced by pyrethroids which are hydrophobic and moderately persistent. More importantly, pyrethroids are highly toxic to aquatic invertebrates and fish, especially cold-water fish such as salmon. The use of pyrethroids is increasing in urban and agricultural areas and for control of West Nile virus and other mosquito-transmitted diseases. Water sampling can be problematic since these compounds sorb to container walls. Pyrethroids are being detected more and more frequently in surface waters, especially associated with sediments. Complexation with colloids is potentially an important mechanism for facilitated transport of pyrethroids to ground water. Methods to sample and analyze pyrethroids at environmentally-relevant levels in water, sediments, colloids, and tissue will be presented. Important processes controlling the fate and bioavailability of pyrethroids in the environment will be discussed using examples from field and laboratory studies.

Elena Nilsen

Research Chemist
USGS Oregon Water Science Center

Pharmaceuticals and Personal Care Products Detected in Sediments of the Lower Columbia River Basin

ABSTRACT:  One byproduct of advances in modern chemistry is the accumulation of synthetic chemicals in the natural environment. These compounds include pharmaceuticals, synthetic fragrances, detergents, and disinfectants present in wastewater and run-off, and are commonly referred to as "pharmaceuticals and personal care products" (PPCPs). Some are endocrine disrupting compounds (EDCs) that have detrimental reproductive effects in wildlife and in humans. Methods have been developed to screen for large suites of PPCPs in aqueous media, but the role of sediments in exposure of aquatic organisms to these chemicals needs to be considered. The first methods capable of analyzing these compounds in solid media were published in 2005, but have not been applied to the Columbia River. Here we present a small-scale reconnaissance of PPCPs in natural bed sediments of the lower Columbia River Basin. Surficial bed sediment samples were collected from the Columbia River, the Willamette River, the Tualatin River, and several small urban tributaries in Oregon. Forty-three pharmaceuticals and personal care products were detected at concentrations ranging from <1 to >1000 ng g-1 sediment. Concentrations and frequency of detection were higher in tributaries and small urban creeks than in the Columbia River main stem, suggesting that the highest risk of toxicity of these compounds to juvenile salmonids and other aquatic life is present in lower order streams. Thirteen known or suspected EDCs were detected during the study. At least one EDC was detected at 22 of 23 sites sampled; several EDCs were relatively widespread among the sites. This study is the first to document the occurrence of a large suite of PPCPs in the sediments of the lower Columbia River Basin. A better understanding of the fate and effects of these classes of emerging contaminants at environmentally relevant concentrations is needed, especially because their use and discharge into the environment is likely to increase in the future.