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Articles 31 - 50 of 50
Full-Text Articles in Water Resource Management
A Method For Computing Infiltration And Redistribution In A Discretized Moisture Content Domain, Fred L. Ogden
A Method For Computing Infiltration And Redistribution In A Discretized Moisture Content Domain, Fred L. Ogden
Fred L. Ogden
A new one-dimensional infiltration and redistribution method is proposed as an alternative to the Richards equation (RE) for coupled surface and subsurface models. The proposed method discretizes soil water content into hypothetical hydraulically interacting bins. The entry and propagation of displacement fronts in each bin are simulated by means of explicit infiltration and drainage approximations based on capillary and gravitational driving forces. Wetting front advances within bins create water deficits that are satisfied by capillary-driven interbin flow. The method inherently provides numerical stability by precluding the need to directly estimate nonlinear gradients through numerical schemes. Comparisons of the performance of …
Bench-Scale Disinfection Of Bacteria And Viruses With Pulsed Arc Electrohydraulic Discharge, L H. Lee, A J. Arnold, C A. Santillan, M B. Emelko, Sarah E. Dickson, J. -S Chang
Bench-Scale Disinfection Of Bacteria And Viruses With Pulsed Arc Electrohydraulic Discharge, L H. Lee, A J. Arnold, C A. Santillan, M B. Emelko, Sarah E. Dickson, J. -S Chang
Sarah E Dickson
Pulsed arc electrohydraulic discharge (PAED) offers concurrent treatment of chemical and microbial target compounds in water by several mechanisms. Here, Escherichia coli, Bacillus subtilis spore, and MS2 bacteriophage inactivation by PAED were investigated using two bench-scale reactors (0.7 and 3 L). A plasma channel was created between a pair of iron electrodes set 0.5 mm apart in these reactors. Pulsed applied voltage was supplied at approximately 0.3 kJ/pulse (~100 ìsec). In the 0.7-L reactor, median E. coli, B. subtilis, and MS2 reductions of 2.4-, 4.6-, and 3.7-log, respectively, were observed after approximately 80 seconds of treatment in water with a …
Expansion Of The Discontinuous Gas Phase And Its Effect On Mass Flux From A Non-Aqueous Phase Liquid (Napl) Pool, Kevin G. Mumford, James E. Smith, Sarah E. Dickson
Expansion Of The Discontinuous Gas Phase And Its Effect On Mass Flux From A Non-Aqueous Phase Liquid (Napl) Pool, Kevin G. Mumford, James E. Smith, Sarah E. Dickson
Sarah E Dickson
The partitioning of non-aqueous phase liquid (NAPL) compounds to a discontinuous gas phase results in the repeated spontaneous expansion, snap-off, and vertical mobilization of the gas phase. This mechanism has the potential to significantly affect the mass transfer processes that control the dissolution of NAPL pools by increasing the vertical transport of NAPL mass and increasing the total mass transfer rate from the surface of the pool. The extent to which this mechanism affects mass transfer from a NAPL pool depends on the rate of expansion and the mass of NAPL compound in the gas phase. This study used well-controlled …
On The Appropriate “Equivalent Aperture” For The Description Of Solute Transport In Single Fractures: Laboratory-Scale Experiments, Qinghuai Zheng, Sarah E. Dickson, Yiping Guo
On The Appropriate “Equivalent Aperture” For The Description Of Solute Transport In Single Fractures: Laboratory-Scale Experiments, Qinghuai Zheng, Sarah E. Dickson, Yiping Guo
Sarah E Dickson
Three distinct definitions of ‘‘equivalent aperture’’ have been used in the literature to describe variable-aperture fractures; however, significant inconsistencies exist in the literature as to which ‘‘equivalent aperture’’ is appropriate for simulating solute transport. In this work, a systematic series of hydraulic and tracer tests was conducted on three laboratory-scale fracture replicas, and the cubic law, mass balance, and frictional loss apertures were calculated. The analytical solution of the one-dimensional advectiondispersion equation was fit to the experimental breakthrough curves. Additionally, one of the experimental aperture fields was measured directly using a light transmission technique. The results clearly demonstrate that the …
Slow Gas Expansion In Saturated Natural Porous Media By Gas Injection And Partitioning With Non-Aqueous Phase Liquids, Kevin G. Mumford, Sarah E. Dickson, James E. Smith
Slow Gas Expansion In Saturated Natural Porous Media By Gas Injection And Partitioning With Non-Aqueous Phase Liquids, Kevin G. Mumford, Sarah E. Dickson, James E. Smith
Sarah E Dickson
The partitioning of volatile non-aqueous phase liquid (NAPL) compounds to a discontinuous gas phase can result in the expansion of that gas phase, and the resulting gas flow can significantly affect the mass transfer from NAPL source zones. This recently reported gas flow generated by the spontaneous expansion of a discontinuous gas phase has not been extensively characterized in the literature. This study measured the expansion rate of a single gas cluster in a 1.1 mm sand above a pool of trans-1,2-dichloroethene (tDCE) in small-scale flow cell experiments. To characterize the gas flow, gas injection experiments in three sizes of …
Spontaneous Expansion And Mobilization Of Gas Above Dnapl, Kevin G. Mumford
Spontaneous Expansion And Mobilization Of Gas Above Dnapl, Kevin G. Mumford
Sarah E Dickson
No abstract provided.
Multivariate Analysis Of Groundwater And Soil Data From A Waste Disposal Site, Kevin G. Mumford, John F. Macgregor, Sarah E. Dickson, Richard H. Frappa
Multivariate Analysis Of Groundwater And Soil Data From A Waste Disposal Site, Kevin G. Mumford, John F. Macgregor, Sarah E. Dickson, Richard H. Frappa
Sarah E Dickson
Environmental site investigations often involve the collection and analysis of hundreds of samples producing data sets that contain thousands of data points, which are difficult and time consuming to analyze. Consequently, investigators often focus on key surrogate parameters for site characterization and remedial action planning and assessment, which results in a large portion of the data collected remaining unused. This study presents the application of principal component analysis (PCA) as an efficient statistical technique to examine large environmental data sets through highlighting patterns in a reduced-variable space. In this work, PCA was applied to ground water and soil data collected …
Removal Of Methyl-Tert Butyl Ether From Water By A Pulsed Arc Electrohydraulic Discharge System, Danielle M. Angeloni, Sarah E. Dickson, Monica B. Emelko, J -S Chang
Removal Of Methyl-Tert Butyl Ether From Water By A Pulsed Arc Electrohydraulic Discharge System, Danielle M. Angeloni, Sarah E. Dickson, Monica B. Emelko, J -S Chang
Sarah E Dickson
The removal of methyl-tert-butyl ether (MTBE) from water by a pulsed arc electrohydraulic discharge (PAED) system was investigated experimentally at the laboratory scale. The effects of arc electrode gap, detention time and initial solution pH on the efficacy of MTBE treatment by PAED were investigated. A 0.3 kJ/pulse spark-gap-type power supply was employed in combination with a 3.0 L flow-through reactor. Experimental results showed that: 1) oxidation reactions are induced by this PAED system; 2) removal efficiency increases with increasing cumulative input energy (kW·h/m3 or kJ/L); 3) removal efficiency decreases with increasing arc electrode gap; and 4) initial solution pH …
Pulsed Electrohydraulic Discharge Characteristics In An Eccentric Electrode Cylindrical Reactor With Pbs, A Yamataki, D M. Angeloni, Sarah E. Dickson, Monica B. Emelko, K Yasuoka, J -S Chang
Pulsed Electrohydraulic Discharge Characteristics In An Eccentric Electrode Cylindrical Reactor With Pbs, A Yamataki, D M. Angeloni, Sarah E. Dickson, Monica B. Emelko, K Yasuoka, J -S Chang
Sarah E Dickson
Pulsed arc electrohydroulic discharge (PAED) has been proposed as a water treatment technology for the removal of chemical and microbial contaminants. In this work, we examined the fundamental characteristics of a PAED system with an eccentric electrode cylindrical reactor. Phosphate-buffered saline (PBS) water was used in lieu of tap water, because the conductivity of PBS is much higher than that of tap water. The results show that the voltage and current waveforms generated in PBS and tap water are very different due to the higher conductivity of PBS. Strong pressure waves and UV emission were also observed in PBS.
Decision Support System For Rural Water Supply In The Nilgris District Of South India, Daniel Olsen, Sarah E. Dickson, Brian Baetz
Decision Support System For Rural Water Supply In The Nilgris District Of South India, Daniel Olsen, Sarah E. Dickson, Brian Baetz
Sarah E Dickson
A considerable amount of knowledge exists for planning, designing, and implementing rural water supply schemes in developing countries around the world. Generalized decision support systems (DSSs) are used to tackle the daunting task of providing water in areas that have poor water resources and limited financial capacity. However, there is a lack of site-specific DSSs that utilise local hydrological and socio-economic data for assessing regionally-based rural water supply schemes. In the Nilgiris District of South India, an organizational structure exists for improving local water resources through watershed management projects, but many of the tools used to make informed decisions are …
A Novel Amendment Delivery System, Erica Ryter
Runoff Production In The Upper Rio Chagres Watershed, Panama, Fred Ogden
Runoff Production In The Upper Rio Chagres Watershed, Panama, Fred Ogden
Fred L. Ogden
Runoff production in tropical watersheds is governed by a wide variety of potential sources and there have been few rigorous studies to date. The 414 km2 upper Río Chagres basin offers a unique opportunity to better understand the runoff production mechanisms in tropical watersheds through data analysis and modeling with rainfall and runoff data. Flow data and tipping bucket rain gage data are available at both the basin outlet (Chico gage) and for an 80.6 km2 internal basin location (Piedras gage). Modeling is performed using the Sacramento Soil Moisture Accounting Model (SAC-SMA), calibrated using data from 2000 and verified using …
Long-Range Downstream Effects Of Urban Runoff And Acid Mine Drainage In The Debed River, Armenia: Insights From Lead Isotope Modeling, Robert Kurkjian, Charles Dunlap, A. Flegal
Long-Range Downstream Effects Of Urban Runoff And Acid Mine Drainage In The Debed River, Armenia: Insights From Lead Isotope Modeling, Robert Kurkjian, Charles Dunlap, A. Flegal
Charles Dunlap
Lead concentrations and isotopic compositions measured along 80 km of the Debed River in the Republic of Armenia provide new insights into the geochemical and physical controls on riparian Pb transport by allowing comparison of the long-range, downstream impacts of acid mine drainage with runoff from an industrialized city. The modern background Pb concentration in Armenian surface waters is estimated to be ~0.01 lg/L, based on analyses of remote alpine rivers in Armenia. The lead concentration in the Debed River is 8 µg/L (800 times background) after passing through Vanadzor, the second largest industrial city in Armenia; it then decreases …
Numerical Investigation Of Saturated Source Area Behavior At The Small Catchment Scale, Fred L. Ogden
Numerical Investigation Of Saturated Source Area Behavior At The Small Catchment Scale, Fred L. Ogden
Fred L. Ogden
The objective of this research is to explore the relationship between small catchment properties and the temporal growth and decay of saturated source areas (SSA). A simple physics-based hydrologic model, which we call the Sandbox model, is developed for this purpose. A thorough sensitivity analysis is undertaken to evaluate model response to variations in model parameters. Sandbox model output is compared to that from the semi-distributed conceptual model, TOPMODEL, a model with a wide spread acceptance. Plotting the temporal evolution of the extent of saturated source area versus catchment average soil water content dur- ing a number of wetting and …
Dissolution Of Entrapped Dnapls In Variable Aperture Fractures: Experimental Data And Empirical Model, Sarah E. Dickson, Neil R. Thomson
Dissolution Of Entrapped Dnapls In Variable Aperture Fractures: Experimental Data And Empirical Model, Sarah E. Dickson, Neil R. Thomson
Sarah E Dickson
An appreciation of the dissolution from entrapped nonaqueous phase liquids (NAPLs) in fractures is essential as we attempt to understand and predict the fate of NAPLs present in fractured rock systems. Eight long-term dissolution experiments using 1,1,1-trichloroethane and trichloroethylene were conducted in two laboratory-scale dolomitic limestone variable aperture fractures under various conditions. Between 560 and 2600 fracture volumes of water were passed through the fractures resulting in the removal of 10−60% of the initial mass trapped. The effluent concentration profiles revealed three distinct and characteristic stages of dissolution: an initial pseudosteady stage, a transient stage, and a tailing stage. On …
The Dissolution Of Dnapls In Variable Aperture Fractures, Sarah E. Dickson
The Dissolution Of Dnapls In Variable Aperture Fractures, Sarah E. Dickson
Sarah E Dickson
No abstract provided.
New Isotopic Evidence For Chronic Lead Contamination In The San Francisco Bay Estuary System: Implications For The Persistence Of Past Industrial Lead Emissions In The Biosphere, Douglas J. Steding, Charles E. Dunlap, A. Russell Flegal
New Isotopic Evidence For Chronic Lead Contamination In The San Francisco Bay Estuary System: Implications For The Persistence Of Past Industrial Lead Emissions In The Biosphere, Douglas J. Steding, Charles E. Dunlap, A. Russell Flegal
Charles Dunlap
Measurements of lead isotope compositions in unfiltered San Francisco Bay waters from 1989 to 1998 have brought new insights into the cycling of anthropogenic lead in estuaries. Isotopic com- positions of lead in the shallow (<2 m) southern reach were essentially invariant (~90% derived from 1960s–1970s leaded gasoline) during the study period because of limited hydraulic flushing and the remobilization of lead from bottom sediments. In contrast, in the northern reach freshwater flushing from the San Joaquin and Sacramento rivers produced seasonal and decadal variations in lead isotope compositions. The seasonal shifts are attributed to advection of soils containing late 1980s gasoline lead into the bay during winter rains. Mass balance calculations indicate that only a small fraction (1–10%) of this leaded gasoline fallout from the late 1980s has been washed out of the San Joaquin and Sacramento rivers’ drainage basin by 1995. Superimposed on this seasonal cycling was a long-term systematic shift in the component of gasoline lead expressed in the river systems, with a small (~5–10%) decrease in the amount of 1960s–1970s gasoline lead in river and North Bay waters. The retention of gasoline lead in the river systems draining into the bay as well as San Francisco Bay sediments indicates that historic gasoline deposits may remain in the combined riparian/estuarine system for decades. Such a persistence is in contraindication to recent reports of rapid (annual) decreases in lead contamination in other environments, and the link between climate and contaminant transport suggests local or global climate change will have an impact on contaminant distribution and fate.
Past Leaded Gasoline Emissions As A Nonpoint Source Tracer In Riparian Systems: A Study Of River Inputs To San Francisco Bay, Charles E. Dunlap, Robin Bouse, A. Russell Flegal
Past Leaded Gasoline Emissions As A Nonpoint Source Tracer In Riparian Systems: A Study Of River Inputs To San Francisco Bay, Charles E. Dunlap, Robin Bouse, A. Russell Flegal
Charles Dunlap
Variations in the isotopic composition of lead in 1995- 1998 river waters flowing into San Francisco Bay trace the washout of lead deposited in the drainage basin from leaded gasoline combustion. At the confluence of the Sacramento and San Joaquin rivers where they enter the Bay, the isotopic compositions of lead in the waters define a linear trend away from the measured historical compositions of leaded gas in California. The river waters are shifted away from leaded gasoline values and toward an isotopic composition similar to Sierra Nevadan inputs which became the predominant source of sedimentation in San Francisco Bay …
Regional Hydrology Of The Dixie Valley Geothermal Field, Nevada: Preliminary Interpretations Of Chemical And Isotopic Data, Gregory Nimz, Cathy Janik, Fraser Goff, Charles Dunlap, Mark Huebner, Dale Counce, Stuart Johnson
Regional Hydrology Of The Dixie Valley Geothermal Field, Nevada: Preliminary Interpretations Of Chemical And Isotopic Data, Gregory Nimz, Cathy Janik, Fraser Goff, Charles Dunlap, Mark Huebner, Dale Counce, Stuart Johnson
Charles Dunlap
Chemical and isotopic analyses of Dixie Valley regional waters indicate several distinct groups ranging in recharge age from Pleistocene (<20 ka) to recent (<50a). Valley groundwater is older than water from perennial springs and artesian wells in adjacent ranges, with Clan Alpine range (east) much younger (most <50a) than Stillwater range (west; most > 1OOOa).Geothermal field fluids (-12-14 ka) appear derived from water similar in composition to non-thermal groundwater observed today in valley artesian wells (also -14 ka). Geothermal fluid interaction with mafic rocks (Humboldt Lopolith) appears to be common, and significant reaction with granodiorite may also occur. Despite widespread occurrence of carbonate rocks, largescale chemical interaction appears minor. Age asymmetry of the ranges, more extensive interaction with deep- seated waters in the west, and distribution of springs and artesian wells suggest the existence …
Green And Ampt Infiltration With Redistribution, Fred L. Ogden
Green And Ampt Infiltration With Redistribution, Fred L. Ogden
Fred L. Ogden
Distributed, physically based watershed and irrigation advance models require robust infiltration estimation capabilities. The empirical Green and Ampt (GA) equation of infiltration is a popular method for estimating infiltration. The GA parameters have physical basis and considerable prior research has focused on relating these parameters to soil textural classification. However, the original GA method is limited in that it is applicable only for a single ponding period. An explicit Green and Ampt redistribution (GAR) technique is developed herein to estimate interstorm redistribution of soil water and allow multiple ponding simulations using the GA methodology. Soil water redistribution during interponding periods …