Oxygen‐18 dynamics in precipitation and streamflow in a semi‐arid agricultural watershed,Eastern Washington,USA     

Bryan G. Moravec  C. Kent Keller  Jeffrey L. Smith  Richelle M. Allen‐King  Angela J. Goodwin  Jerry P. Fairley  Peter B. Larson 《水文研究》2010,24(4):446-460

Understanding flow pathways and mechanisms that generate streamflow is important to understanding agrochemical contamination in surface waters in agricultural watersheds. Two environmental tracers, δ¹⁸O and electrical conductivity (EC), were monitored in tile drainage (draining 12 ha) and stream water (draining nested catchments of 6‐5700 ha) from 2000 to 2008 in the semi‐arid agricultural Missouri Flat Creek (MFC) watershed, near Pullman Washington, USA. Tile drainage and streamflow generated in the watershed were found to have baseline δ¹⁸O value of ?14·7‰ (VSMOW) year round. Winter precipitation accounted for 67% of total annual precipitation and was found to dominate streamflow, tile drainage, and groundwater recharge. ‘Old’ and ‘new’ water partitioning in streamflow were not identifiable using δ¹⁸O, but seasonal shifts of nitrate‐corrected EC suggest that deep soil pathways primarily generated summer streamflow (mean EC 250 µS/cm) while shallow soil pathways dominated streamflow generation during winter (EC declining as low as 100 µS/cm). Using summer isotopic and EC excursions from tile drainage in larger catchment (4700‐5700 ha) stream waters, summer in‐stream evaporation fractions were estimated to be from 20% to 40%, with the greatest evaporation occurring from August to October. Seasonal watershed and environmental tracer dynamics in the MFC watershed appeared to be similar to those at larger watershed scales in the Palouse River basin. A 0·9‰ enrichment, in shallow groundwater drained to streams (tile drainage and soil seepage), of δ¹⁸O values from 2000 to 2008 may be evidence of altered precipitation conditions due to the Pacific Decadal Oscillation (PDO) in the Inland Northwest. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

GIS professional development for teachers: lessons learned from high-needs schools     

Jerry T. Mitchell  George Roy  Stephannie Fritch  Brandy Wood 《制图学和地理信息科学》2018,45(4):292-304

University faculty partners from the Departments of Geography and Instruction and Teacher Education at a large, public university collaborated with K-12 teachers and the leadership of a rural school district in order to investigate the crosscutting content of science, mathematics, and geography through the integration of web-based GIS technologies. The project explored the critical connections among technology, pedagogy, and content with a particular emphasis on developing technology-enhanced, inquiry-based lessons in which the teachers and their students used GIS technologies to analyze, visualize, and present data in real-world contexts. The findings highlight the importance of well-structured professional development that builds community, integrates diverse content and pedagogical expertise, provides feedback and coaching, and is of sufficient duration to effect change.  相似文献   

Performance and Analysis of Drillstem Tests in Small-Diameter Boreholes     

Fred Marinelli  Jerry W. Rowe 《Ground water》1985,23(3):367-376

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Ground-Water Problems in the Mesozoic Pax Mountain Fault Zone     

David S. Snipes  Peter R. Manoogian  Michael W. Davis  Laura L. Burnett  Jerry A. Wylie  Steven B. Heaton 《Ground water》1986,24(3):375-381

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Foreword     

Bartholomew Nagy 《Precambrian Research》1983,20(2-4)

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Glacial isostatic adjustment on a rotating earth     

Jerry X. Mitrovica  Glenn A. Milne  James L. Davis 《Geophysical Journal International》2001,147(3):562-578

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Use of LIF for Real-Time In-Situ Mixed NAPL Source Zone Detection     

Mark L. Kram  Stephen H. Lieberman  Jerry Fee  Arturo A. Keller 《Ground Water Monitoring & Remediation》2001,21(1):67-76

The site characterization and analysis cone penetrometer system (SCAPS), equipped with realtime fluorophore detection capabilities, was used to delineate subsurface contaminant releases in an area where plating shop waste was temporarily stored. Records indicated that various nonaqueous phase liquids (NAPLs) were released at the site. The investigators advanced the SCAPS laser-induced fluorescence (LIF) sensor to depths beneath the water table of the principal water-bearing zone. The water table was located approximately 6 feet (1.8 m) below ground surface (bgs) across the site. Fluorescence, attributed to fuel compounds commingled with chlorinated solvents, was observed at depths ranging from 4.0 to 11.5 feet (1.2 to 3.5 m) bgs. Fluorescence, attributed to naturally occurring organic materials (by process of elimination and spectral characteristics) commingled with chlorinated solvent constituents, was observed at depths ranging from approximately 13 to 40 feet (4.0 to 12.2 m) bgs. Fluorescence responses from compounds confirmed to be commingled with chlorinated solvents indicates that the SCAPS fluorophore detection system is capable of indirectly delineating vadose zone and subaqueous chlorinated solvents and other dense nonaqueous phase liquids (DNAPLs) at contaminant release sites. This confirmation effort represents the first documented account of the successful application of LIF to identify a mixed DNAPL/LNAPL source zone.  相似文献   

Sources, distribution and storage of heavy metals in the Río Pilcomayo, Bolivia     

Karen A. Hudson-Edwards  Mark G. Macklin  Jerry R. Miller  Paul J. Lechler 《Journal of Geochemical Exploration》2001,72(3)

The Río Pilcomayo rises on the Cerro Rico de Potosí precious metal-polymetallic tin deposits of Bolivia, and flows in a southeasterly direction for ca. 600 km to Bolivia's southern border with Argentina. Mining of the Potosí deposits has occurred continuously since 1545, generating large quantities of waste materials in the headwater of the basin. In addition, a tailings dam breach at the Porco mine in 1996 released an estimated 235 000 m³ of tailings and fluid into the upper reaches of the Río Pilaya, the largest tributary to the Pilcomayo.Concentrations of As, Sb, Cd, Cu, Pb, Hg, Ag, Tl and Zn in contemporary channel sediments upstream of the Pilaya confluence are significantly elevated above background values. Elevated levels appear to be associated with pyrite- and other sulphide mineral-bearing tailings materials transported more than 200 km downstream of the Potosí mines. Significant downstream declines in elemental concentrations occur within 15 km, and again between 150 and 200 km, from the mines. The initial decrease in concentrations is due to the rapid dilution of nearly pure tailings effluent released to the river from milling facilities near Potosí. The latter decrease results from a combination of geomorphic processes including the storage of sediment-borne metals within the channel bed and the influx of ‘clean’ sediment from several large tributaries. Downstream of the Pilaya confluence, concentrations of Cu, Pb, Hg and Zn are only slightly elevated above background values, and Ag, Cd, Sb and Tl cannot be distinguished from background levels. These data suggest that while the Porco tailings spill may have had a significant short-term impact on sediment and water quality along the lower reaches of the Río Pilcomayo, its longer-term impacts were limited. Metals stored and eroded from alluvial deposits of historical age in upstream reaches appear to be an important source of metals to the river today. An additional, and perhaps more significant source, is the release of tailings effluent to the river from modern milling operations. The transport of these contaminants downstream of Icla (203 km from Potosí) appears to be restricted by aggradational processes occurring in the vicinity of Puente Sucre. In addition, downstream of the confluence of the Río Pilaya, inputs of large amounts of ‘clean’ sediment have caused dilution of the metal contaminants. Data from other studies where similar geomorphic processes have occurred suggest that the metals in the upper Pilcomayo may eventually be moved downvalley as the aggradational processes are reversed and channel stabilisation occurs. Thus, the most significant impacts of metal contamination may not be realised in downstream areas for decades.  相似文献   

Regional estimation of base recharge to ground water using water balance and a base-flow index   总被引：4，自引：0，他引：4  

Szilagyi J  Harvey FE  Ayers JF 《Ground water》2003,41(4):504-513

Naturally occurring long-term mean annual base recharge to ground water in Nebraska was estimated with the help of a water-balance approach and an objective automated technique for base-flow separation involving minimal parameter-optimization requirements. Base recharge is equal to total recharge minus the amount of evapotranspiration coming directly from ground water. The estimation of evapotranspiration in the water-balance equation avoids the need to specify a contributing drainage area for ground water, which in certain cases may be considerably different from the drainage area for surface runoff. Evapotranspiration was calculated by the WREVAP model at the Solar and Meteorological Surface Observation Network (SAMSON) sites. Long-term mean annual base recharge was derived by determining the product of estimated long-term mean annual runoff (the difference between precipitation and evapotranspiration) and the base-flow index (BFI). The BFI was calculated from discharge data obtained from the U.S. Geological Survey's gauging stations in Nebraska. Mapping was achieved by using geographic information systems (GIS) and geostatistics. This approach is best suited for regional-scale applications. It does not require complex hydrogeologic modeling nor detailed knowledge of soil characteristics, vegetation cover, or land-use practices. Long-term mean annual base recharge rates in excess of 110 mm/year resulted in the extreme eastern part of Nebraska. The western portion of the state expressed rates of only 15 to 20 mm annually, while the Sandhills region of north-central Nebraska was estimated to receive twice as much base recharge (40 to 50 mm/year) as areas south of it.  相似文献   

Relative stress variations as determined by b-values from earthquakes in circum-pacific subduction zones     

Jerry A. Carter  Eduard Berg 《Tectonophysics》1981,76(3-4)

Assuming a relation of “b” to stress state, the possibility of globe-wide stress variation and transmission was investigated. The NOAA earthquake data file served to determine the temporal change in “b” of log N = a − bM from 1963 to 1975.Periods of six to eight years are observed in the b-values (stress pattern) for most circum-Pacific areas (South America, Tonga, Kermadec, New Hebrides, Kamchatka and Eastern Aleutians).In the Kurils, fore- and aftershock sequences of large earthquakes seem to mask any characteristic global pattern that might exist. These sequences exhibit low b-values (high stress) through the time of foreshocks and early stages of aftershocks, followed by rapid increase in b-values (decrease in stress).Use of a worldwide earthquake data file clearly yields less resolution of the temporal “b” variation than the use of local network studies published by other authors.Incidental to the study, 1124 earthquakes of the NOAA data file yield the M_s − m_b relations: M_s = 1.16m_b − 0.835 for 4.5 m_b 6 and: log₁₀M_s = 0.1432m_b − 0.0629 form_b > 6 with correlative coefficients of 0.994 and 0.992 respectively.  相似文献