Showing papers on "Water flow published in 1997"

Theory of SWAP version 2.0; simulation of water flow, solute transport and plant growth in the soil-water-atmosphere-plant environment

Abstract: This manual describes how the numerical SWAP model Version 2.0.9d can be used to simulate vertical transport of weather, solutes and heat in variably saturated, cultivated soils. A brief theoretical description is followed by a technical description of model structure and general data flow. An extensive explanation is given of program inputs and outputs based on ASCII text files. The manual ends with examples using important features of the model.

Benthic suspension feeders and flow

Abstract: This 1997 book is about those animals found on the sea floor that live by filtering microscopic particles carried to them by water currents. Its purpose is to review what is known about the biology of suspension feeders in relation to their flow environment. The book includes the larval biology, physiology, ethology and ecology of suspension feeders interacting with water flow. It will be of value to marine scientists beginning research in the interdisciplinary field of hydrodynamics and benthic biology, and it is the first attempt to provide a comprehensive overview of this synthesis from the biological viewpoint.

Nonrigid, Nonsubmerged, Vegetative Roughness on Floodplains

Abstract: Individual pine and cedar tree saplings and branches were used to model the resistance to flow in a water flume for nonsubmerged and nonrigid vegetation to determine the amount that streamlining decreases the drag coefficient and reduces the momentum absorbing area. Currently, vegetation on floodplains is commonly assumed to behave as rigid roughness that can lead to large errors in the relationships between velocity and drag force. This presents a basic fluid mechanics problem. An extreme variation of roughness with depth of flow can result due to a large increase in the momentum absorbing area in nonsubmerged vegetation as depth is increased. This deems all the available roughness equations (which generally are based on relative roughness approach) useless for this application. In this paper a dimensional analysis, supported by experimental results, is developed to obtain a relationship between roughness conditions (i.e., density and flexural rigidity) and flow conditions (i.e., velocity and depth) for floodplains and vegetative zones of natural waterways.

Fundamentals of Aquacultural Engineering

Abstract: The Aquatic Environment. Site Selection for Aquaculture. Sources of Water for Aquaculture. Off-Bottom Culture Systems. Ponds and Raceways. Recirculating Aquaculture Systems. Fluid Mechanics. Pumps. Water Flow Measurement. Oxygen and Aeration. Sterilization and Disinfection. Control, Monitoring and Alarm Systems. Appendices.

A land surface model (IAP94) for climate studies part I: Formulation and validation in off-line experiments

Abstract: The IAP (Institute of Atnjospheric Physics) land-surface model (IAP94) is described. This model is a comprehensive one with detailed description for the processes of vegetation, snow and soil. Particular attention has been paid to the cases with three water phases in the surface media. On the basis of the mixture theory and the theory of fluid dynamics of porous media, the system of universal conservational equations for water and heat of soil, snow and vegetation canopy has been constructed. On this background, all important factors that may affect the water and heat balance in media can be considered naturally, and each factor and term possess distinct physical meaning. In the computation of water content and temperature, the water phase change and the heat transportation by water flow are taken into account. Moreover, particular attentionhas been given to the water vapor diffusion in soil for arid or semi-arid cases, and snow compaction. In the treatment of surface turbulent fluxes, the difference between aerodynamic and thermal roughness is taken into account. The aerodynamic roughness of vegetation is calculated as a function of canopy density, height and zero-plane displacement. An extrapolation of log-linear and exponential relationship is used when calculating the wind profile within canopy. The model has been validated against field measurements in off-line simulations. The desirable model’s performance leads to the conclusion that the IAP94 is able to reproduce the main physical mechanisms governing the energy and water balances in the global land surface. Part II of the present study will concern the validation in a 3-D experiment coupled with the IAP Two-Level AGCM.

A sequential uncertainty domain inverse procedure for estimating subsurface flow and transport parameters

Abstract: A parameter estimation procedure, sequential uncertainty domain parameter fitting (SUFI), is presented and has the following characteristics. The procedure is sequential in nature, meaning that one more iteration can always be made before choosing the final estimates. The procedure has a Bayesian framework, indicating that the method operates within uncertainty domains (prior, posterior) associated with each parameter. The procedure is a fitting procedure, conditioning the unknown parameter estimates on an array of observed values. Finally, the procedure is iterative, requiring a stopping rule which is provided by a critical value of a goal function. Performance of the SUFI parameter estimation procedure is demonstrated using three examples of increasing complexity: (1) analysis of a solute breakthrough curve measured in the laboratory during steady state water flow, (2) estimation of the unsaturated soil hydraulic parameters from a transient drainage experiment carried out in a 6-m deep lysimeter, and (3) estimation of selected flow and transport parameters from a hypothetical ring infiltrometer experiment. The procedure was found to be general, stable, and always convergent.

FEMWATER: A Three-Dimensional Finite Element Computer Model for Simulating Density-Dependent Flow and Transport in Variably Saturated Media.

Abstract: : This report presents the user's manual of FEMWATER, A Three-dimensional Finite Element Computer Model for Simulating Density-Dependent Flow and Transport The intended users of the manual will have a wide range of technical experience and have different needs that the model and documentation will fulfill. Sophisticated users will find descriptions of the numerical techniques and a complete set of governing equations that form the theoretical basis of the model. The casual users will find examples of several types of problems that will include their type of application. FEMWATER is a modern implementation of the two older models, 3DFEMWATER (flow) and 3DLEWASTE (transport). FEMWATER was formed by combining the two codes into a single coupled flow and transport model. The improvements implemented in FEMWATER are numerous. First, the entire program structure was changed to allow its integration into the Department of Defense Groundwater Modeling System (GMS). The GMS contains a state-of-the-art graphical user environmental that allows efficient model setup and visualization. Second, a series of new solvers were added to replace the previously used block iterative solver. The new solvers allow an arbitrary node numbering scheme that enables easier graphical user interface connections and still provide improved computational efficient. Their, density-driven (salinity) transport capability was added to allow salinity intrusion studies in coastal aquifers. This required the coupling of flow and transport within a common model, which is the last major improvement.

Freshwater input to a gulf estuary: long‐term control of trophic organization

Abstract: A long-term (9.5 yr) study addressed the relationship of the trophic orga- nization of a river-dominated Gulf of Mexico estuary with interannual trends of freshwater input and biological controlling features. Alluvial river flow characteristics were evaluated with respect to seasonal and interannual changes in physical, chemical, and biological trends in the receiving estuary. Infaunal and epifaunal macroinvertebrates and fishes taken over the period of sampling in the Apalachicola Bay system were transformed into their trophic equivalents. The long-term trophic organization of the bay was then related to observed changes in the physical and chemical conditions in the receiving estuary with particular attention to long-term response to a 2-yr drought. Within limited natural bounds of fresh- water flow from the Apalachicola River, there was little change in the trophic organization of the receiving estuary over prolonged periods. The physical instability of the estuary was actually a major component in the continuation of a biologically stable estuarine system. However, when a specific threshold of freshwater reduction was reached during a prolonged natural drought, we suggest that the clarification of the normally turbid and highly colored river-estuarine system led to rapid changes in the pattern of primary production, which, in turn, were associated with major changes in the trophic structure of the system. Increased light penetration due to the cessation of river flow was an important factor in the temporal response of bay productivity and herbivore/omnivore abundance. There was a dichotomous response of the estuarine trophic organization, with herbivores and omnivores responsive to river-dominated physicochemical factors whereas the carnivores responded to biological factors. Trophic response time could be measured in months to years from the point of the initiation of low-flow conditions. The reduction of nutrient loading during the drought period was postulated as a major cause of the loss of productivity of the river-dominated estuary during and after the drought period. Recovery of such productivity with resumption of increased river flows was likewise a long-term event. Based on the observed trends in the bay, postulated permanent reductions of freshwater flows due to anthropogenous ac- tivities could lead to major reductions of biological productivity in the Apalachicola Bay system. The long-term data indicated that, with reduction of freshwater flow below a level specific for the receiving system, the physically controlled, highly productive river-estu- arine system would become a species-rich, biologically controlled bay with substantially reduced productivity.

Determination of effective air-water interfacial area in partially saturated porous media using surfactant adsorption

Abstract: The effective specific air-water interfacial area (a¯i) in a sand-packed column was measured at several water saturations (Sw) using a surface-reactive tracer (sodium dodecylbenzene sulfonate (SDBS)) and a nonreactive tracer (bromide). Miscible displacement experiments were conducted under steady water flow conditions to quantify the retardation of SDBS resulting from its adsorption onto the air-water interface in a sand-packed column. A consistent trend of increased retardation of SDBS compared with the nonreactive tracer, bromide, was observed with decreasing Sw. The data for air-water surface tension measured at various SDBS concentrations were interpreted using the Gibbs model to estimate the required adsorption parameters. The retardation factors (Rt) for SDBS breakthrough curves were then used in combination with the estimated SDBS adsorption coefficient to calculate the a¯i values at different Sw. For the range of experimental conditions employed in this study, the retardation factor for SDBS ranged from Rt = 1.00 at Sw = 1.00 (Rt < 1 due to SDBS sorption on sand) to Rt = 3.44 at Sw = 0.29 (which corresponds to a¯i = 46 cm2/c/m3). These values are in agreement with theoretical predictions and recently published data. Improvements needed to overcome the experimental limitations of the presented method are also discussed.

A non-invasive measurement of phloem and xylem water flow in castor bean seedlings by nuclear magnetic resonance microimaging

Abstract: A flow-sensitive nuclear magnetic resonance (NMR) microimaging technique was applied to measure directly the in-vivo water flow in 6-d-old castor bean seedlings. The achieved in-plane resolution of the technique allowed discrimination between xylem and phloem water flow. Both the xylem- and the phloem-average flow velocities in the intact seedling could be quantified. Furthermore, the total conductive cross-sectional area of the xylem vessels and the phloem sieve elements could be determined using the non-invasive and non-destructive NMR microimaging technique. Hence, it was possible to calculate the in-vivo volume flow rates for both xylem and phloem water flow. Our non-destructive technique showed that previously used methods to measure phloem water flow affected the flow rate itself. In the intact seedlings we found values of 16.6 μl·h−1, two fold lower than those previously estimated from phloem exudation rates. Finally, our results demonstrate for the first time that water is internally circulated between phloem and xylem, and that water flow within the xylem is maintained by this internally circulated water, even in the absence of any significant transpiration or evaporation.

A liquid-filled microrelay with a moving mercury microdrop

Abstract: A micromechanical relay that switches by moving a mercury microdrop is introduced. While microrelays have been introduced to MEMS on several occasions, all are based on solid-solid contacts, making them subject to contact wear, signal bounce, and general loss of performance with use. The goal of our device is to use mercury to eliminate the common problems of solid-contact switches. Descriptions of the design and fabrication of a micromechanical mercury-contact relay, including the technique for formation of microscale mercury droplets, are presented. The deionized (DI) water-filled microrelay has a mercury droplet, 5-25 /spl mu/m in diameter, placed near a disconnected set of electrodes in a V-groove throat. The throat connects two reservoirs containing suspended heaters. By turning on one heater, we grow a vapor bubble in one reservoir and induce a momentary water flow along the throat, forcing the mercury droplet to move and create the signal conduction path. Heating of the second reservoir can drive the mercury drop back to its original position. A microgasketing technique along with UV-curing epoxy sealing method is introduced to seal a chip containing many microdevices, each filled with liquid, at room temperature. Initial test results of the relay are also provided.

Characterization of Water Channels in Wheat Root Membrane Vesicles.

Abstract: The functional significance of water channels in wheat (Triticum aestivum L.) root membranes was assessed using light scattering to measure vesicle shrinking in response to osmotic gradients rapidly imposed in a stopped flow apparatus. Vesicles were obtained from both a plasma membrane fraction and a plasma membrane-depleted endomembrane fraction including tonoplast vesicles. Osmotic water permeability (Pos) in the endomembrane fraction was high (Pos= 86.0 [mu]m s-1) with a low activation energy (EA= 23.32 kJ mol-1 [plus or minus] 3.88 SE), and was inhibited by mercurials (K1= 40 [mu]M HgCl2, where K1 is the inhibition constant for half-maximal inhibition), suggesting participation of water channels. A high ratio of osmotic to diffusional permeability (Pd) (using D2O as a tracer, Pos/Pd = 7 [plus or minus] 0.5 SE) also supported this view. For the endomembrane fraction there was a marked decrease in Pos with increasing osmotic gradient that was not observed in the plasma membrane fraction. Osmotic water permeability in the plasma membrane fraction was lower (Pos= 12.5 [mu]m s-1) with a high activation energy (EA= 48.07 kJ mol-1 [plus or minus] 3.63 SE) and no mercury inhibition. Nevertheless, Pos/Pd was found to be substantially higher than one (Pos= 3 [plus or minus] 0.2 SE), indicating that water channels mediated water flow in this fraction, too. Possible distortion of the Pos/Pd value by unstirred layer effects was shown to be unlikely.

New piecewise-continuous hydraulic functions for modeling preferential flow in an intermittent-flood-irrigated field

Abstract: Modeling water flow in macroporous field soils near saturation has been a major challenge in vadose zone hydrology. Using in situ and laboratory measurements, we developed new piecewise-continuous soil water retention and hydraulic conductivity functions to describe preferential flow in tile drains under a flood-irrigated agricultural field in Las Nutrias, New Mexico. After incorporation into a two-dimensional numerical flow code, CHAIN_2D, the performance of the new piecewise-continuous hydraulic functions was compared with that of the unimodal van Genuchten-Mualem model and with measured tile-flow data at the field site during a number of irrigation events. Model parameters were collected/estimated by site characterization (e.g., soil texture, surface/ subsurface saturated/unsaturated soil hydraulic property measurements), as well as by local and regional-scale hydrologic monitoring (including the use of groundwater monitoring wells, piezometers, and different surface-irrigation and subsurface-drainage measurement systems). Comparison of numerical simulation results with the observed tile flow indicated that the new piecewise-continuous hydraulic functions generally predicted preferential flow in the tile drain reasonably well following all irrigation events at the field site. Also, the new bimodal soil water retention and hydraulic conductivity functions performed better than the unimodal van Genuchten-Mualem functions in terms of describing the observed flow regime at the field site.

Hydrologic issues in arid, unsaturated systems and implications for contaminant transport

Abstract: Analysis of unsaturated flow and transport in arid regions is important, not only in water resource evaluation but in contaminant transport as well, partic- ularly in siting waste disposal facilities and in remediat- ing contaminated sites. The water fluxes under consid- eration have a magnitude close to the errors inherent in measuring or in calculating these water fluxes, which makes it difficult to resolve basic issues such as direction and rate of water movement and controls on unsaturated flow. The purpose of this paper is to review these issues on the basis of unsaturated zone studies in arid settings. Because individual techniques for estimating water fluxes in the unsaturated zone have limitations, a variety of physical measurements and environmental tracers should be used to provide multiple, independent lines of evidence to quantify flow and transport in arid regions. The direction and rate of water flow are affected not only by hydraulic head gradients but also by temperature and air pressure gradients. The similarity of water fluxes in a variety of settings in the southwestern United States indicates that vegetative cover may be one of the pri- mary controls on the magnitude of water flow in the unsaturated zone; however, our understanding of the role of plants is limited. Most unsaturated flow in arid systems is focused beneath topographic depressions, and diffuse flow is limited. Thick unsaturated sections and low water fluxes typical of many arid regions result in preservation of paleoclimatic variations in water flux and suggest that deep vadose zones may be out of equilib- rium with current climate. Whereas water movement along preferred pathways is common in humid sites, field studies that demonstrate preferential flow are restricted mostly to fractured rocks and root zones in arid regions. Results of field studies of preferential flow in humid sites, generally restricted to the upper 1-2 m because of shallow water tables, cannot be applied readily to thick vadose zones in arid regions.

Subcritical Junction Flow

Abstract: The main flow features of subcritical junction flows are explored, based on an extended hydraulic model study. The flow conditions chosen resulted in flows that are governed by the Froude similarity law. So-called simple junctions with junction angles of 30°, 60°, and 90° were tested. The main emphasis was made in determining the characteristics of the lateral flow and the flow contraction in the tailwater branch. Further, expressions for the momentum correction coefficients, the lateral wall pressure force, and the ratio of flow depths in the lateral and upstream branches were provided. A rational approach for the momentum contribution of the lateral branch is presented and applied for the prediction of the backwater effect across a simple junction. The complex flow pattern is further documented with selected photographs such that a rather complete description of junction flow is now available.

Fuel cell with metal screen flow field

Abstract: A polymer electrolyte membrane (PEM) fuel cell is provided with electrodes supplied with a reactant on each side of a catalyzed membrane assembly (CMA). The fuel cell includes a metal mesh defining a rectangular flow-field pattern having an inlet at a first corner and an outlet at a second corner located on a diagonal from the first corner, wherein all flow paths from the inlet to the outlet through the square flow field pattern are equivalent to uniformly distribute the reactant over the CMA. In a preferred form of metal mesh, a square weave screen forms the flow-field pattern. In a particular characterization of the present invention, a bipolar plate electrically connects adjacent fuel cells, where the bipolar plate includes a thin metal foil having an anode side and a cathode side; a first metal mesh on the anode side of the thin metal foil; and a second metal mesh on the cathode side of the thin metal foil. In another characterization of the present invention, a cooling plate assembly cools adjacent fuel cells, where the cooling plate assembly includes an anode electrode and a cathode electrode formed of thin conducting foils; and a metal mesh flow field therebetween for distributing cooling water flow over the electrodes to remove heat generated by the fuel cells.

Very high single channel water permeability of aquaporin-4 in baculovirus-infected insect cells and liposomes reconstituted with purified aquaporin-4.

Abstract: The insect cell/baculovirus system was used to express the mercurial-insensitive water channel aquaporin-4 (AQP4) for purification and reconstitution. Immunoblot analysis of Sf9 cells infected with recombinant baculovirus showed greatest AQP4 expression at 72 h after infection at a multiplicity-of-infection of 5. Immunostaining and cell membrane fractionation indicated AQP4 plasma membrane expression. Quantitative immunoblot analysis showed approximately 60 microg of AQP4 per milligram of plasma membrane protein (approximately 2 mg of AQP4 protein per liter of Sf9 cell culture). Functional analysis by stopped-flow light scattering indicated that AQP4 functioned as a mercurial-insensitive water-selective transporter. Osmotic water permeability (Pf) in plasma membrane vesicles from AQP4-expressing Sf9 cells was very high (0.053 cm/s at 10 degrees C), weakly temperature dependent (activation energy, 4.5 kcal/mol), and not inhibited by HgCl2. The AQP4 single channel water permeability (p(f)), estimated from Pf and protein amount, was 19 x 10(-14) cm3/s. Purification of AQP4 to a single Coomassie blue-stained protein on SDS-PAGE (1300-fold over homogenate) was achieved by membrane fractionation, carbonate stripping of nonintegral proteins, solubilization in octyl-beta-glucoside, and anion exchange chromatography. AQP4 protein identity was confirmed by mass spectrometry. Reconstitution of purified AQP4 into proteoliposomes increased osmotic water permeability by >40-fold, giving a p(f) of 15 x 10(-14) cm3/s, remarkably greater than that of 4.9 x 10(-14) cm3/s measured in parallel for AQP1. These results establish the first purification of an aquaporin from a heterologous expression system. The high AQP4 p(f) suggests (a) significant functional differences among the aquaporins, (b) inadequacy of existing pore models to account for high water flow and water permselectivity, and (c) possible enhancement of water flow by AQP4 assembly in orthogonal arrays.

Aboveground net primary production along a bog-fen-marsh gradient in southern boreal Alberta, Canada

Abstract: :Total aboveground plant production in a bog, three rich fens and two marshes were determined via the multiple harvest and cranked wire techniques. These peatlands follow a gradient of increasing pH, water flow, and surface water nutrient concentrations from the bog to the rich fens to the eutrophic marshes. The net primary production (NPP) values were as follows: (i) bog, 390 g m-2 year-1, (ii) three rich fens (riverine sedge fen, lacustrine sedge fen, and floating sedge fen), 409 g m-2 year-1, 277 g m-2 year-1 and 356 g m-2 year-1, respectively, and (iii) one riverine and one lacustrine marsh, 323 g m-2 year-1 and 757 g m-2 year-1, respectively. Overall, the bog and the three fens had a similar NPP but they were significantly less productive than the marshes. Along this bog-fen-marsh gradient, moss and shrub production decreased and herb production increased. Herb and moss production exhibited a greater variation between years than among sites within each year. Shrub production remained similar ...

Identification of Monitoring Stations in Water Distribution System

Abstract: The location of water quality monitoring stations in a water distribution system should be such that the network is represented with the minimum number of monitoring stations. The present guideline...