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Stephen R. Hinkle

Publications and source records attributed to Stephen R. Hinkle.

22 records · Page 2Linked to original sources
USGS1998

Water quality in the Willamette Basin, Oregon, 1991-95

This report is intended to summarize major findings that emerged between 1991 and 1995 from the water-quality assessment of the Willamette Basin Study Unit and to relate these findings to water-quality issues of regional and national concern. The information is primarily intended for those who are involved in water-resource management. Yet, the information contained here may also interest those who simply wish to know more about the quality of water in the rivers and aquifers in the area where they live.

Oregon↗
USGS1997

Quality of shallow ground water in alluvial aquifers of the Willamette Basin, Oregon, 1993-95

The current (1993?95) quality of shallow ground water (generally, <25 meters below land surface) in Willamette Basin alluvium is described using results from two studies. A Study-Unit Survey, or regional assessment of shallow groundwater quality in alluvium, was done from June through August 1993. During the Study-Unit Survey, data were collected from 70 domestic wells chosen using a random-selection process and located mostly in areas of agricultural land use. An urban Land-Use Study, which was a reconnaissance of shallow urban ground-water quality from 10 monitoring wells installed in areas of residential land use, was done in July 1995. Concentrations of nitrite plus nitrate (henceforth, nitrate, because nitrite concentrations were low) ranged from <0.05 to 26 mg N/L (milligrams nitrogen per liter) in ground water from 70 Study-Unit-Survey wells; concentrations exceeded the U.S. Environmental Protection Agency (USEPA) Maximum Contaminant Level (MCL) of 10 mg N/L in 9 percent of Study-Unit-Survey samples. Relationships were observed between nitrate concentrations and dissolved-oxygen concentrations, the amount of clay present within and overlying aquifers, overlying geology, and upgradient land use. Tritium (3H) data indicate that 21 percent of Study-Unit-Survey samples represented water recharged prior to 1953. Nitrogen-fertilizer application rates in the basin have increased greatly over the past several decades. Thus, some observed nitrate concentrations may reflect nitrogen loading rates that were smaller than those presently applied in the basin. Concentrations of phosphorus ranged from <0.01 to 2.2 mg/L in 70 Study-Unit-Survey wells and exceeded 0.10 mg/L in 60 percent of the samples. Phosphorus and nitrate concentrations were inversely correlated. From 1 to 5 pesticides and pesticide degradation products (henceforth, pesticides) were detected in ground water from each of 23 Study-Unit-Survey wells (33 percent of 69 wells sampled for pesticides) for a total of 51 pesticide detections. Thirteen different pesticides were detected; atrazine was the most frequently encountered pesticide. Although detections were widespread, concentrations were low (generally <1,000 ng/L [nanograms per liter]). (One ng/L is equal to 0.001 mg/L [micrograms per liter].) One detection (dinoseb, at 7,900 ng/L) exceeded a USEPA MCL. Relationships were observed between the occurrence of pesticides and the amount of clay present within and overlying aquifers, overlying geology, and land use. Between 1 and 5 volatile organic compounds (VOCs) were detected at each of 7 Study-Unit-Survey sites (11 percent of 65 sites evaluated), for a total of 14 VOC detections. One detection (tetrachloroethylene, at 29 mg/L) exceeded a USEPA MCL. Other detections were at low concentrations (0.2 to 2.0 mg/L). VOC detections generally were from sites associated with urban land use. Concentrations of arsenic ranged from <1 to 13 mg/L in 70 Study-Unit-Survey wells. Concentrations in 16 percent of samples exceeded the USEPA Risk-Specific-Dose Health Advisory of 2 mg/L. Radon concentrations ranged from 200 to 1,200 pCi/L (picocuries per liter) in 51 Study-Unit-Survey wells. All samples exceeded the USEPA Risk-Specific-Dose Health Advisory of 150 pCi/L. All urban Land-Use-Study samples were well oxygenated; thus, nitrate reduction probably did not affect these samples. Urban Land-Use-Study nitrate concentrations were similar to those of the well oxygenated, agricultural subset of Study-Unit-Survey samples. Pesticides were detected in samples from three urban Land-Use-Study sites, but concentrations were low (1 to 5 ng/L). In contrast, VOCs were detected in ground water from 80 percent of urban Land-Use-Study wells; concentrations ranged up to 7.6 mg/L. Trace-element concentrations in the urban Land-Use Study samples were low. Median concentrations consistently were <10 mg/L and frequently were <1 mg/L

Water-Resources Investigations Report↗
USGS1996

Age of ground water in basalt aquifers near Spring Creek National Fish Hatchery, Skamania County, Washington

Water samples from four springs and five wells in basalt aquifers near Spring Creek National Fish Hatchery in Skamania County, Washington, were collected and analyzed for selected inorganic ions and stable isotopes. Eight samples were analyzed for carbon-14 (14C), carbon-13 ([3C), and either chlorofluorocarbons (CFCs) or tritium. This work was done to estimate the age (residence time, or time elapsed since recharge) of water issuing from springs at the hatchery. If CFCs are present in ground water, the presence of at least a component of modem (post- 1944) water is indicated. CFC-dating suggests that ground water several hundred feet below land surface in the Underwood Heights area noah of the hatchery, including ground water discharging from the hatchery springs, contains modem water. In contrast, CFC-dating suggests that deeper ground water such as that withdrawn from the Hatchery Well may contain little or no modem water. Concentrations of 14C in water can yield 14C-based ground-water ages, termed 14C-model ages. Unadjusted 14C-model ages (14C-model ages unadjusted for carbon mass transfers) for water discharging from the hatchery springs are on the order of several hundred years. Ground-water samples from three wells in the Underwood Heights area yielded 14C-model ages ranging from modem to several hundred years. Unadjusted 14C-model ages for deep ground water pumped by the Hatchery Well indicate an overall age of several thousand years. However, 14C concentrations may be affected by transfers of carbon into and out of solution. The 13C values of the downgradient ground waters ranged from - 16.4 (per mil) to -18.2 per rail, isotopically heavier than expected for ground water that obtains carbon solely from root respiration in a temperate climate and undergoes no subsequent carbon-isotope fractionation or exchange. Such 13C values in the ground water near the hatchery suggest the possibility of carbon mass transfers during the evolution of these waters. Geochemical mass-transfer modeling suggests that carbon dioxide may degas and calcite may dissolve during the evolution of the modeled ground waters, but that degassing of carbon dioxide is the dominant carbon mass transfer in these ground waters. In addition, modeling results also suggest that, although some calcite may dissolve during the evolution of the water produced by the Hatchery Well, and possibly during the evolution of the shallower ground waters, the amount of calcite dissolution is small. Model testing suggests that the quantity of 14C-dead carbon added from calcite dissolution may not be sufficient to greatly affect the 14C-model ages of these ground waters. In other words, the 14C-model ages that were adjusted for various modeled carbon mass transfers are similar to the unadjusted 14C-model ages. A comparison of CFC data with both adjusted and unadjusted 14C data suggests that water discharging at the hatchery springs contains a mixture of modem and old water, where old water is defined as water recharged prior to 1944. The CFC data support a component of modem water, whereas the 14C data suggest a component of old water. Similar results were obtained from a comparison of CFC data with adjusted and unadjusted 14C data for water collected from Well 3. Well 3 is north of the hatchery springs, on a flow path that appears to be parallel to and similar in length to the flow path leading to the hatchery springs. Water from the Hatchery Well, however, may be devoid of modem water and appears to have an overall age on the order of thousands of years.

Washington↗