Water Flow System Research Articles

Constructed wetland system for storm water treatment

An eleven year old constructed wetland system for storm water treatment at Stammersdorf near Vienna has to be redesigned. The small sand trap and the usage of loamy material as substrate for the main layer of the reed bed led to a rapid clogging of the system and to a very limited elimination rate. To obtain data for parameters (catchment hydrology, loading rates) for the new design, online measurements at the inlet of the system of water flow and some physical parameters were undertaken as well as sampling and analysis of the inlet water (TSS, TOC, NH4‐N). The new design includes two parallel ditches (each 1380 m3) which are a combination of settling and retention ponds. The regulated outlet of the ditches is now treated in the main treatment zone which is a horizontal subsurface flow constructed wetland (1500 m2) with coarse sand (1/4 mm) as main layer. The final structure is a polishing pond (800 m2) after which the effluent is recharged into the groundwater.

Ownership of Mine‐Tunnel Discharge

AbstractWater discharging from numerous tunnels constructed during mining in the Wasatch Mountains near Salt Lake City, Utah, flows into nearby creeks. Disputes over ownership of water feeding the creeks have resulted in extensive litigation. In the course of a legal dispute over ownership of outflow from the Kentucky‐Utah (K‐U) Tunnel we evaluated the patterns and rates of ground water flow using an integrated study of the geology, chemistry, isotopes, and chlorofluorohydrocarbon (CFC) composition of the water. A sequence of sedimentary rocks with a range of hydraulic conductivity values has been folded, faulted, intruded by igneous rocks, and then eroded to create the rough topography of the Wasatch Mountains. The similarity of composition among tunnel discharge, springs, and base flow in the creek indicates that the creek is fed by ground water circulating in local, shallow flow systems. Results of numerical simulations of ground water flow indicate that the K‐U Tunnel likely intercepts ground water that, in the absence of the tunnel, would ultimately flow in the subsurface to Big Cottonwood Creek. CFC and tritium contents of the water indicate flow weighted average ground water travel times range from four to 23 years and support our conclusion that water discharging from the tunnel is moving within a shallow ground water flow system. Despite sparse data, the scientific understanding was deemed sufficient for the judge to rule that owners of the surface water also own the tunnel discharge because, in the absence of the tunnel, this water would supply the stream.

Ground Water Flow in a Fractured Carbonate Aquifer Inferred from Combined Hydrogeological and Geochemical Measurements

AbstractA conceptual model for ground water flow is presented for a fractured Silurian dolomite in the Niagara Escarpment area of southern Ontario. Such a model is necessary to facilitate remedial efforts of a PCB‐contaminated site located in Smithville, Ontario. Both physical and chemical hydrogeological observations obtained from field investigations were used to deduce the structure of the ground water flow system in the fracture network. The field study was conducted using observations obtained from six bore‐holes drilled in the vicinity of the town of Smithville. The boreholes were diamond cored through the entire thickness of the dolomite formation (approximately 45 m), hydraulically tested using a 2 m packer spacing and then completed using multipacker casing strings. Measurements of hydraulic head were obtained on a weekly basis over a period of two years, and ground water from each borehole interval was collected for geochemical analyses for inorganic and isotopic composition. Transmissivity measurements indicate that the dolomite is divided into two ground water flow systems separated by an extensive unit of low transmissivity that is pervasive throughout the region. The upper flow system is characterized by water enriched in Mg2+ and SO42‐. Below the low transmissivity zone, ground water increases in salinity and is enriched in Ca2+ and SO42‐. Based on the geochemistry, the rate of ground water migration in the lower flow system is surmised to be much less than that in the upper system. Measurements of hydraulic head in conjunction with the results of the analyses of the environmental isotopes (δ18O and δ2H) suggest that ground water flow is mainly horizontal and likely governed by enlarged bedding plane fractures. The isotope geochemistry and topographical features further suggest that ground water recharge is occurring approximately 2 km to the north of Smithville.

THE VULNERABILITY OF WETLANDS TO CLIMATE CHANGE: A HYDROLOGIC LANDSCAPE PERSPECTIVE1

ABSTRACT: The vulnerability of wetlands to changes in climate depends on their position within hydrologic landscapes. Hydrologic landscapes are defined by the flow characteristics of ground water and surface water and by the interaction of atmospheric water, surface water, and ground water for any given locality or region. Six general hydrologic landscapes are defined; mountainous, plateau and high plain, broad basins of interior drainage, riverine, flat coastal, and hummocky glacial and dune. Assessment of these landscapes indicate that the vulnerability of all wetlands to climate change fall between two extremes: those dependent primarily on precipitation for their water supply are highly vulnerable, and those dependent primarily on discharge from regional ground water flow systems are the least vulnerable, because of the great buffering capacity of large ground water flow systems to climate change.

Stable isotope studies of precipitation and river water in the Lake Biwa basin, Japan

The δ18O and δD in 17 river waters flowing into and out of Lake Biwa, the lake water itself and precipitation at 11 locations in the Lake Biwa basin were observed from October 1996 to September 1997, to evaluate the origin of river waters and the effect of irrigation water from the lake on the river waters flowing into Lake Biwa. The regional difference and altitude effect of the stable isotopes in precipitation and river water were found in the basin. The δ18O in the rivers which are located in the eastern and the southern areas in the basin is heavier than that of the other rivers, due to the effect of irrigation for the nearby paddy fields. Evaporation from Lake Biwa and the inflow rate into the lake estimated from the δ18O balance agree well with the results of previous studies which used water balance methods. The stable isotopes can enable us to evaluate not only water balance but also the origin of the water and the water flow system. Copyright © 2000 John Wiley & Sons, Ltd.

Hydrologic Setting of Two Interdunal Valleys in the Central Sand Hills of Nebraska

AbstractThe Sand Hills of Nebraska, one of the largest grass‐stabilized dune regions in the world, has nearly 5000 km2 of wetland environments and is one of the most productive waterfowl regions of the United States. Yet, the hydrology of the region is not well defined. This paper presents the results of a two‐and‐a‐half‐year study to characterize the hydrology of two distinctly different interdunal valleys within the Sand Hills. The valleys, located at the Gudmundsen Sand Hills Laboratory in the central Sand Hills, reflect the two major types of interdunal environments: dry, short grass valleys (the east valley) and subirrigated wet meadows (the west valley). In the west valley, ground water flows from west to east and there are significant, upward vertical gradients (0.005 to 0.045). In contrast, ground water in the east valley predominantly flows from west‐southwest to east‐northeast. Where vertical gradients exist, they are downward (0.0025 to 0.07). Therefore, the east valley is a “recharge” or flow‐through valley. Seasonal ground water table fluctuations indicate that net recharge is greatest between growing seasons. The relatively high topographic relief of the water table on the flanks of the west valley, resulting from higher topographic relief of the adjacent dunes, drives ground water discharge into the valley wetland, developing a local flow system. In contrast, the topography of the water table in the east valley, which is flanked by dunes with lower relief, is insufficient to generate a distinct local ground water flow system.

Chlorinated Decreasing Solvents: Physical‐Chemical Properties Affecting Aquifer Contamination and Remediation

AbstractChlorinated degreasing solvents are multicomponent liquids containing not only the chlorinated hydrocarbons with which their name is associated (e.g., trichloroethylene or |TCE]. perchloroethylene or [PCE], 1,1,1‐trichlorocihane [TCA]) but also a number of organic additives included as corrosion inhibitors and antioxidants. The additives, such as 1,4‐dioxane, are likely to be of significant public‐health importance as ground water contaminants due to their toxicity, solubility, and mobility. Following their use in vapor degreasing systems by industry, chlorinated degreasing solvents will also contain about 25% solubilized oil and grease.A number of physical‐chemical properties become especially important in the light of the multicomponent nature of these solvents. First, the higher aqueous solubility and lower sorption of the additives makes it is reasonable to expect that faster moving plumes of these solvent additives will precede plumes of the chlorinated hydrocarbons. Second, due to high losses of chlorinated hydrocarbons by volatilization from vapor degreasers during years in the middle of the century, it is probable that background concentrations of these hydrocarbons are present in ground water flow systems due to their downwind washout. Finally, the solubilized oil and grease may cause profound changes to the wettability of aquifer materials contacted by the solvents during their subsurface migration. It is argued, therefore, that the wettability of aquifer materials contaminated by chlorinated degreasing solvents needs to be experimentally determined before remediation of DNAPL at each site, rather than being simply assumed as water wet.

Hydrogeochemistry in two adjacent areas in the Pannonian Basin (Southeast-Hungary)

Groundwaters from the Quaternary, Pliocene and Pontian layers in two adjacent basin areas of Hungary (Szeged and Körös) and from the intermediate basement high, all belonging to the central part of the Pannonian Basin, have been investigated chemically and isotopically. Most of the waters are NaHCO 3 type with significant quantitative and qualitative regional differences for the Szeged and Körös areas, the intermediate high, and the deepest studied lithostratigraphic zone (the base of the Pontian stage). Hydrogen and oxygen isotopes indicate that most of the waters have a paleometeoric origin. The period of infiltration for the entire studied depth interval (75–2500 m) was within the last cold period in the Szeged and intermediate areas, and during a preceding warmer period in the Körös area. Over the entire studied region, waters in the deepest lithostratigraphic position are mixtures of paleometeoric waters and deep waters squeezed out from the thick sequence of fine-grained (Pannonian) sediments that underlie the Pontian thermal water aquifer. In the Szeged and intermediate areas, the effect of the upward seepage from the deeper (Pannonian) layers was overprinted by the recharge in the last cold period. In the Körös area, due to the lack of infiltration during the last cold period, the mixing with Pannonian waters is seen up to a depth of 1000 m. Based on 87 Sr/ 86 Sr ratios, water flow systems were separated. In the Szeged and intermediate areas, a shallower and a deeper flow systems were distinguished, one in the Pleistocene and Pliocene formations, and another in the Pontian layers. In the Körös area, most of the waters belong to the same flow system that occupies the depth interval from the base of the Pontian (about 2500 m) up to 1000 m. The two shallowest samples studied (above a depth of 1000 m) show lower 87 Sr/ 86 Sr ratios.

Patterns of contaminant transport in a layered fractured aquifer

We investigated patterns of contaminant transport within the layered and fractured aquifer of a 7.3-km 2 upland agricultural watershed in east-central Pennsylvania, USA. Geometry and hydraulic properties of the aquifer had been characterized by field testing and model calibration. These results were extended to simulate flow pathways and patterns of contaminant transport in both areal and cross-section formats within the watershed. The analyses indicated that the ground water flow system at the larger watershed scale is comprised of smaller units of subsurface flow which are self-contained at the scale of first- or second-order streams. For this scale subwatershed or larger, contaminant inputs to ground water from the mix of land use within the subwatershed should translate directly to the quality of nonstorm streamflow. For illustration, recharge water quality from typical land-use distributions were combined with a simple model of contaminant transport to simulate nitrate concentration patterns in ground water in a cross-section format. Land use in the vicinity of the drainage divides between streams was found to control ground water quality within the deeper layers of the aquifer, while land use over the remainder of the watershed area affected water quality only within the shallower layers of the aquifer. Streamflow nitrate data collected during a baseflow survey on the watershed were examined in context of these simulations and found to support the conclusions. Results of the study demonstrate the potential for localized contamination of ground water and nonstorm streamflow by agricultural land use, as well as the potential for managing stream quality and minimizing contamination within targeted zones of the ground water by controlling land use position.

Phosphate Plume Persistence at Two Decommissioned Septic System Sites

AbstractLong‐term monitoring of two well‐characterized, oxidizing septic system plumes (Langton and Long Point 2 sites) over periods extending two to four years after decommissioning, has revealed that ground water PO 43− concentrations (0.4 to 5 mg/L P) have persisted at levels virtually unchanged from those observed during active sewage loading. In addition, the frontal part of the PO43− plume at the Long Point 2 site can be observed to continue to advance during the decommissioned period. At the Langton site, where an active regional ground water flow system is present, all major plume solutes (Na+, Ca2+, Cl−, NO 3−) returned to background values within one year of decommissioning, with the exception of PO43−.This evidence suggests that phosphate behavior in the ground water zone at these sites is dominated by sorption reactions that are both rapid and reversible. Thus, if septic system phosphorus is not retained in the vadose zone, but is transported into the ground water zone, it has the potential to be persistent and to be mobile enough to constitute a threat to downgradient surface water environments. This evidence also shows that when a septic system is decommissioned, if an oxidizing PO43− plume is present, downgradient P loading is not likely to diminish for many years thereafter.

食塩電気分解水を利用したアルジネート印象材と石膏模型の洗浄消毒について

The purpose of this study was to evaluate the efficacy of disinfection method using a flow water system with electrolytic products of sodium chloride (BK) on alginate impressions and subsequent atone casts contaminated with Candida albicans and blood. The dimensional changes and surface roughness of alginate impression on BK water were evaluated.Each alginate impression from a model of maxillary dental arch was inoculated with eachCandida albicanscell suspension at a density of 1.5 × 107 cell/ml and sheep blood. The impression was disinfected with BK flow water and residual microorganisms were harvested, cultured, and counted. The washing disinfection with BK flow water removed mostCandida albicans. Thus, after the washing disinfection of impressions with the flow BK water, the subsequent stone casts were disinfected again with flow water and then residual microorganisms were counted. The washing disinfection of alginate impression for 30 seconds and subsequent stone casts for 15 seconds with flow BK water removed allCandida albicansinoculated. This infectant technique using flow BK water is effective and simple.

Parameter estimation of two-fluid capillary pressure–saturation and permeability functions

Accurate characterization and modeling of subsurface flow in multi-fluid soil systems require development of a rapid, reproducible experimental method that yields the information necessary to determine the parameters of the capillary pressure–saturation and permeability functions. Previous work has demonstrated that parameter optimization using inverse modeling is a powerful approach to indirectly determine these constitutive relationships for air–water systems. We consider extension of the inverse parameter estimation method to the modified multi-step outflow method for two-fluid (air–water, air–oil and oil–water) flow systems. The wellposedness of the proposed parameter estimation problem is evaluated by its accuracy, uniqueness and parameter uncertainty. Seven different parametric models for the capillary pressure–saturation and permeability functions were tested in their ability to fit the multi-step outflow experimental data; these included the van Genuchten–Mualem (VGM) model, van Genuchten–Burdine (VGB), Brooks–Corey–Mualem (BCM), Brooks–Corey–Burdine (BCB), Brutsaert–Burdine (BRB), Gardner–Mualem (GDM) and Lognormal Distribution–Mualem (LNM) models. The VGB, BCM and BCB models fitted the multi-step outflow data poorly, and resulted in relatively large values for the root-mean-squared residuals. It was concluded that the remaining VGM, LNM, BRB and GDM models successfully characterized the multi-step experimental data for two-fluid flow systems. Although having one parameter less than the other models, the GDM model's performance was excellent. Finally, we conclude that optimized capillary pressure–saturation functions for the oil–water and air–oil could be predicted from the respective air–water function using interfacial tension ratios.

Use of Multiple Isotope Tracers to Evaluate Denitrification in Ground Water: Study of Nitrate from a Large‐Flux Septic System Plume

AbstractThis study explores the use of multiple isotopic tracers to evaluate the processes involved in nitrate attenuation in ground water. δ15N and δ18O are used to provide information about the role of denitrification on nitrate attenuation, and δ34S, δ18O, and δ13C are used to evaluate the role of reduced sulfur and carbon as electron donors for nitrate reduction. The focus of this study is a zone of significant NO3−1 attenuation occurring in a sand aquifer impacted by septic system contamination. The NO3−1 pattern, the ground water flow system, and changes in other chemical parameters suggest that the NO3−1 depletion is caused by denitrification. This is supported by the nitrate δ15N and δ18O data which both show significant isotopic enrichment as NO3−1 depletion proceeds along the flow path. The increase of sulfate and dissolved inorganic carbon observed in the zone of nitrate attenuation suggests that reduced sulfur in addition to carbon is also involved in denitrification. This is supported by a trend toward depleted sulfate δ34S and δ18O values in the zone of sulfate increase, which reflects the input of sulfate formed by the oxidation of biogenic pyrite present in the aquifer sediments. The trend toward depleted δ13 values in the zone of increasing dissolved inorganic carbon reflects the input of organic carbon into this carbon pool. Chemical mass balance indicates that carbon is the dominant electron donor; however, this study demonstrates the effectiveness of using multiple isotopic tracers for providing insight into the processes affecting nitrate attenuation in ground water.

Encapsulated Cell Bioremediation: Evaluation on the Basis of Particle Tracer Tests

AbstractMicroencapsulation of degradative organisms enhances microorganism survivability (Stormo and Crawford 1994). The use of encapsulated cell microbeads for in situ biodegradation depends not only on microorganism survival but also on microbead transport characteristics. Two forced‐gradient, recirculating‐loop tracer experiments were conducted to evaluate the feasibility of encapsulated cell transport and bioremediation on the basis of polystyrene microsphere transport results. The tracer tests were conducted in a shallow, confined, unconsolidated, heterogeneous, sedimentary aquifer using bromide ion and 2 μm, 5 μn, and 15 μm microsphere tracers.Significant differences were observed in the transport of bromide solute and polystyrene microspheres. Microspheres reached peak concentrations in monitoring wells before bromide, which was thought to reflect the influence of aquifer heterogeneity. Greater decreases in microsphere C/Co ratios were observed with distance from the injection wells than in bromide C/Co ratios, which was attributed to particle filtration and/or settling.Several methods might be considered for introducing encapsulated cell microbeads into a subsurface environment, including direct injection into a contaminated aquifer zone, injection through a recirculating ground water flow system, or emplacement in a subsurface microbial curtain in advance of a plume. However, the in situ use of encapsulated cells in an aquifer is probably limited to aquifers containing sufficiently large pore spaces, allowing passage of at least some encapsulated cells. The use of encapsulated cells may also be limited by differences in solute and microbead transport patterns and flowpath clogging by larger encapsulated cell microbeads.

Use of Solute and Isotopic Composition of Ground Water to Constrain the Ground Water Flow System of the Azraq Area, Jordan

AbstractThis study shows that hydrological systems in arid areas where water level data are incomplete can be better understood and constrained by using chemical and isotopic data. These constraints significantly alter the conceptual hydrological model of the Azraq area.Previous studies, based on water level data, suggest that water in the Azraq oasis is derived from two major piezometric highs; the western basalt aquifer to the northwest and the Tulul el Ashaquif highlands to the northeast of the oasis. Water from the Tulul el Ashaquif aquifer is also considered to drain to a piezometric low at Ruwaishid to the east, and then into deeper aquifers.Chemical data from this study show that the northwest basalt aquifer provides most of the water (80‐85 %) to the Azraq oasis. Water from the Tulul el Ashaquif supplies a relatively small proportion, but due to its high solute content, imparts its chemical signature on the oasis water. This study has shown that water from Tulul el Ashaquif are not supplied to the Ruwaishid area, as previously thought.Stable isotopic data show that each piezometric high contains water which originated in a distinct climatic setting. Both water types are poor in tritium. Traces of tritium at the Azraq oasis and at Ruwaishid indicate some recent local recharge.

A prototype radonmeter for seismic surveillance

A new 222Rn monitoring prototype has been designed, assembled and tested at the Istituto Nazionale di Geofisica (ING) specifically addressed to seismic surveillance tasks, exploiting environmental monitoring, etc. It operates with an a scintillation technique (photomultiplier + Lucas Cell) coupled with a water input system, that lets continuous dehumidified gas flow, stripped from groundwater under monitoring. Several laboratory tests have been carried out to check the stability and versatility of the system; moreover statistical tests have been accomplished on several data sets obtained with an 241Am radioactive standard source, to check stability of the photomultiplier. A customised water flow system has been developed to perform both the highest efficiency and lowest influence of external noise parameters. This new prototype is very cheap and will be integrated within the new multiparametric geochemical monitoring system GMS II, that is currently being developed at ING, specifically designed for geochemical surveillance of seismic events.

Inversion of borehole-response test data for estimation of subglacial hydraulic properties

AbstractResponse tests are widely used in ground-water studies to assess the hydraulic properties of sub-surface water-flow systems. The simplicity of such tests also makes them attractive for investigation of subglacial hydraulic conditions. This paper describes a systematic, quantitative approach to the analysis of borehole-response test data. The approach uses the theoretical model of Stone and Clarke (1993), which describes water motion in a coupled borehole—subglacial flow system; this framework provides the basis for an inversion scheme that is focused on quantifying physical properties of the basal-flow system, as it is characterized in the theoretical model. The inversion procedure was applied to response-test data from Trapridge Glacier, Yukon Territory, Canada. Results of the inversions suggest that the subglacial drainage network can be described as a confined layer comprising coarse-sand-to fine-gravel-sized sediments, having a thickness of 0.1 – 0.3 m, and a hydraulic conductivity of about 5 × 10−4ms−1. Based on the water-drainage rates from boreholes, as they connect with the subglacial water-flow system, specific storage of the sediment layer was estimated to be approximately 1 × 10−4m−1. Further consideration of subglacial water-flow conditions suggests that connection drainage test results may tend to underestimate specific storage of the overall glacier substrate.

Inversion of borehole-response test data for estimation of subglacial hydraulic properties

AbstractResponse tests are widely used in ground-water studies to assess the hydraulic properties of sub-surface water-flow systems. The simplicity of such tests also makes them attractive for investigation of subglacial hydraulic conditions. This paper describes a systematic, quantitative approach to the analysis of borehole-response test data. The approach uses the theoretical model of Stone and Clarke (1993), which describes water motion in a coupled borehole—subglacial flow system; this framework provides the basis for an inversion scheme that is focused on quantifying physical properties of the basal-flow system, as it is characterized in the theoretical model. The inversion procedure was applied to response-test data from Trapridge Glacier, Yukon Territory, Canada. Results of the inversions suggest that the subglacial drainage network can be described as a confined layer comprising coarse-sand-to fine-gravel-sized sediments, having a thickness of 0.1 – 0.3 m, and a hydraulic conductivity of about 5 × 10−4ms−1. Based on the water-drainage rates from boreholes, as they connect with the subglacial water-flow system, specific storage of the sediment layer was estimated to be approximately 1 × 10−4m−1. Further consideration of subglacial water-flow conditions suggests that connection drainage test results may tend to underestimate specific storage of the overall glacier substrate.

Experimental study on the discharge coefficients and cavitation of conical orifices

The high pressure drop is frequently required in the by-pass line of the pump or of the heat exchanger in power plants. However, cavitation produced by a high pressure drop could damage the pipe and pump blades. Conical orifices are adopted to reduce cavitation due to high pressure drop. The discharge coefficients of conical orifice plates were measured by weighing method in the standard water flow system. The discharge coefficients were larger when the ratios of thickness of orifice edge to throat diameter were larger. The noise generated from a conical orifice due to cavitation was measured with a sound level meter and a hydrophone. With increasing the bore diameter of the orifice, the sound pressure level or the noise level due to cavitation became higher. The noise level was suddenly increased at the inception of cavitation.

Interpretation of soil features produced by ancient and modern processes in degraded landscapes: V. Development of saline sulfidic features in non-tidal seepage areas

Saline sulfidic soils are usually associated with tidal flushing zones. However, less developed saline sulfidic soils have recently been identified in non-tidal seepage and marsh areas strongly affected by waterlogging, dryland salinity and erosion in the Mediterranean climatic region ( > 600 mm per annum winter rainfall maximum) of the Mt Lofty Ranges, South Australia. A conceptual sub-model is developed to explain the formation of these saline sulfidic soils by using data from detailed pedological, mineralogical, hydrological and physico-chemical investigations. The following three saline sulfidic features were recognised both within the subsurface soil layers and on the soil surface: (i) black sulfidic materials, (ii) iron-rich gelatinous precipitates and (iii) salt-iron crusts. The abundance of these features and their distribution in relation to each other were used to establish a chronological order of formation. For each saline sulfidic feature, specific minerals (e.g. pyrite framboids, ferrihydrite and schwertmannite) were identified and their conditions of formation (e.g. Eh and pH) established. Their development is closely associated with two water-flow systems: a rising saline sulfatic groundwater aquifer and the seasonal discharge of fresh water via a perched water table. The conceptual sub-model shows how these two water-flow systems and three biomineralization processes lead to the formation of these saline sulfidic marsh soils. It illustrates how the following three main conditions control the formation of these non-tidal saline sulfidic marsh soils: (i) the development of aquic and saline conditions throughout the solum, (ii) the accumulation of organic matter from which Fe and S reducing/oxidising bacteria derive their energy, and (iii) a continuous supply of Fe and S in groundwater aquifers. In the Mt Lofty Ranges, such conditions are due to rising saline sulfatic groundwater tables following land clearing since European settlement and contemporary weathering of pyrite lenses in the underlying rock.