Hydraulic Exchange Research Articles

Isotopic evolution of snowmelt: A new model incorporating mobile and immobile water

Isotopic variations of snowmelt provide important information for understanding snowmelt processes and the timing and contribution of snowmelt to catchments in spring. We report a new model for simulating the isotopic evolution of snowmelt. The model includes a hydraulic exchange between mobile and immobile water, and an isotopic exchange between liquid water (mobile and immobile water) and ice within a snowpack. Since this model is based on the mobile‐immobile water conceptualization, which is widely used for describing chemical tracer transport in snow, it allows simultaneous simulations of chemical as well as isotopic variations in snowpack discharge. We also report temporal variations of isotopic composition of a snowpack and snowmelt during artificial rain‐on‐snow experiments and diel snowmelt cycles observed in spring 2003 at the Central Sierra Snow Laboratory, California. These observations are used to test the newly developed model and to understand physical processes in a seasonal snowpack. Our model simulates the isotopic variations reasonably well, and suggests that exchanges of ice with both mobile and immobile water are important for determining the isotopic composition of the discharge.

Vertical hydraulic exchange and the contribution of hyporheic community respiration to whole ecosystem respiration in the River Lahn (Germany)

To quantify the contribution of hyporheic community respiration to whole running-water ecosystem respiration in a cultural landscape setting, we studied the vertical hydraulic exchange in riffle–pool sequences of the River Lahn (Germany). We used flow through curves from four tracer experiments to estimate flow velocities in the surface and subsurface water. Generally, vertical exchange velocities were higher in riffle sections and a high temporal variability was observed (range of values 0.11–1.08 m day−1). We then used (1) the exchange velocities and (2) time series of dissolved oxygen concentration in surface and subsurface water to calculate hyporheic respiration. Hyporheic respiration was estimated in a range of 10–50 mg O2 m−3 day−1 for the upper sediment layer (first 20 cm). It was much lower in the deeper sediment layer (20–40 cm), ranging from 0 to 10 mg O2 m−3 day−1 (volumes are volumes of interstitial water; the average porosity was 20%). We determined primary production and respiration of the biofilm growing on the sediment by modelling dissolved oxygen concentration time series for a 2,450 m long stream reach (dissolved oxygen concentrations with diurnal variations from 8 to 16 mg L−1). Modelled respiration rates ranged from 2 to 21 g O2 m2 day−1. All information was integrated in a system analysis with numerical simulations of respiration with and without sediments. Results indicated that hyporheic respiration accounted for 6 to 14% of whole ecosystem respiration. These values are much lower than in other whole system respiration studies on more oligotrophic river systems.

Unsteady two-layer hydraulic exchange flows with friction

Two-layer exchange flow through a contraction with both friction and barotropic forcing is modelled in terms of three parameters reflecting the friction and the strength and period of the barotropic forcing. In the appropriate limits, the results for steady flow with and without friction, and inviscid barotropically forced flow are recovered. The predicted time-dependent interface position compares well with laboratory experiments, improving on the inviscid formulation. The concurrent effects of friction and barotropic forcing on average exchange flow rate are determined. When friction is weak barotropic forcing increases the exchange rate. However, when friction is high, tidal forcing can result in a reduced exchange rate, a phenomena that we call tidal inhibition. When friction is weak maximal exchange occurs throughout the tidal cycle, but as friction is increased submaximal flow develops for longer and longer periods. As friction is increased even further the flow becomes hydraulically uncontrolled. The parameter range for major sea straits includes tidally enhanced and tidally inhibited flows, as well as maximal, submaximal and uncontrolled flows.

Roe Scheme for Two-layer Shallow Water Equations: Application to the Strait of Gibraltar

The flow trough the Strait of Gibraltar could be analyzed as a problem of two-layer hydraulic exchange between the Atlantic ocean and the Mediterranean sea. The shallow water equations in both layers coupled together are an important tool to simulate this phenomenon. In this paper we perform an upwind schemes for hyperbolic equations based on the Roe approximate Riemann solver, to study the resulting model. The main goal assigned was to predict the location of the interface between the two layers. Therefore the computational results obtained are compared to previous results and experiments.

Tidal modulation of two-layer hydraulic exchange flows

Abstract. Time-dependent, two layer hydraulic exchange flow is studied using an idealised shallow water model. It is found that barotropic time-dependent perturbations, representing tidal forcing, increase the baroclinic exchange flux above the steady hydraulic limit, with flux increasing monotonically with tidal amplitude (measured either by height or flux amplitude over a tidal period). Exchange flux also depends on the non-dimensional tidal period, γ, which was introduced by by Helfrich (1995). When tidal amplitude is characterised by the barotropic flux amplitude, exchange flux is a monotonic function of γ as predicted by Helfrich (1995). However, the relationship between the (imposed) free surface amplitude and flux amplitude is complicated by reflections within the channel and by the baroclinic response of the two layer system, leading to a non-monotonic relationship between the height amplitude and γ.

Endoscopic retrograde cholangiopancreatography catheter and accessory exchange using a short hydrophilic guide wire: a prospective study

Although hydrophilic guide wires can be used to facilitate stricture cannulation during endoscopic retrograde cholangiopancreatography (ERCP), some endoscopists avoid using them because of concerns about wire loss during exchange. There are no data available on the outcomes of using a short hydrophilic guide wire during ERCP. The aim of this study was to assess the outcomes of therapeutic ERCP procedures in which a short, completely hydrophilic guide wire was used exclusively. A total of 100 patients undergoing ERCP were studied prospectively. A 0.035-inch, 260-cm long, angled-tip hydrophilic wire (Terumo Glidewire) was used initially. Hydraulic catheter exchange was performed as follows: during catheter withdrawal the assistant advanced all the available wire into the catheter; a 12-ml syringe was then attached to the catheter and water was flushed under pressure to "float the wire" and maintain its position during catheter removal. Variables evaluated included exchange times and wire loss rates. A total of 223 catheter exchanges were performed, 132 (59%) using the Olympus V-Scope (which held the wire in 62% of cases): 15% of exchanges were with catheters/accessories designed for short-wire use (Boston Scientific Rapid Exchange Biliary System or Rx System), and 85% were with a variety of standard-length accessories. Overall, the mean exchange time was 26 seconds (range 6 - 90 seconds, standard deviation 12 seconds). The mean exchange time was faster with the V-Scope and with non-Rx-System accessories. Wire loss occurred in 5 % of all exchanges. Desired ductal/stricture access was achieved in all the patients. Exchange of short hydrophilic wires is quick and reliable. The Olympus V-Scope is able to hold the wire in some cases. Monorail-type devices and accessories slow catheter exchange down slightly because hydraulic exchange cannot be performed using these systems.

Hydraulic ERCP Catheter and Accessory Exchange Using a Short Hydrophilic Guidewire: Prospective Study of 100 Patients

Hydraulic ERCP Catheter and Accessory Exchange Using a Short Hydrophilic Guidewire: Prospective Study of 100 Patients

Theory of two-layer hydraulic exchange flows with rotation

Two-layer rotating exchange flows through channels of rectangular cross-section are modelled using semi-geostrophic, zero-potential-vorticity theory. For a given channel cross-section the full range of possible flow states is considered. The interface always has a uniform slope across the channel, but may separate from one or both of the sidewalls to attach to the upper or lower boundary. The flow may be subcritical, critical or supercritical. These different states are identified in a pseudo-Froude-number plane analogous to that developed by Armi (1986) for non-rotating flows. If the ratio of the channel width to the Rossby radius is constant along the length of the channel, then the solution may be traced along the entire channel using a single diagram. Several examples of maximal and submaximal exchanges are considered. This graphical method of solution is contrasted with the functional approach of Dalziel (1988, 1990).The exchange flux is determined as a function of the channel geometry, the strength of rotation and the difference in Bernoulli potential between the two layers.

A numerical study of surface‐subsurface exchange processes at a riffle‐pool pair in the Lahn River, Germany

Hyporheic exchange is an ecologically important process, controlling the nutrient supply in the upper sediments and thus benthic habitat quality. Hydraulic exchange at a riffle‐pool sequence in the Lahn River, Germany, was analyzed using HEC‐RAS to simulate the surface water flow as a boundary for the subsurface flow and MODFLOW, MODPATH, and MT3DMS to reproduce the transport in the subsurface. Solute transport and residence times of surface water in the subsurface were simulated after calibrating sediment properties to fit simulated hydraulic head to measured subsurface head from the riffle‐pool pair. Three surface water flow rates were considered. Results indicated that exchange increases with increasing surface water flow. However, the hydraulic conductivity of the riverbed sediments influences the mass transfer more than the surface water flow. The ratio of the infiltration rate to the surface water flow is of the same order of magnitude for all the considered flow conditions. Residence times of surface water in the subsurface varied inversely with the flow rates in the river.

Solids flushing, mixing, and water velocity profiles within large (10 and 150 m3) circular ‘Cornell-type’ dual-drain tanks

The objectives of this research were to evaluate how bottom drain flow rate and water inlet structure affect solids flushing, water mixing, and water velocity profiles within large (i.e., 10 and 150m3) circular ‘Cornell-type’ dual-drain culture tanks. Results show relatively uniform water mixing was achieved in both ‘Cornell-type’ dual-drain culture tanks when tested at high fish densities (90–98kg/m3) and at hydraulic exchange rates of one tank volume every 20–32min. The results of the dissolved oxygen profiles showed that the minimum and maximum dissolved oxygen concentrations ranged from 10.0 to 10.6mg/L across the cross-section of the 10m3 tank and from 9.0 to 11.2mg/L across the cross-section of the 150m3 tank when inlet dissolved oxygen levels were 16–18mg/L. Mixing was not influenced by bottom-drain flow over the range tested, but was influenced by the orientation of the water injection nozzles projecting through the side-wall of the culture tanks.Adjustment of the orientation of the water inlet structure and of the water flow discharged through the bottom-center drain was shown to influence the water rotational velocities throughout the circular tank. Water rotational velocity profiles taken in a vertical plane bisecting the tank indicated that velocities were consistently higher at the tank’s perimeter and that these velocities increased nearly linearly with radial distance from the tank center. Results also show that higher rotational velocities were produced at larger bottom flow rates, i.e., a 12% bottom flow created higher rotational velocities than 6 or 0% bottom flows. Reorienting the direction of the water inlet nozzles also provided a simple method for adjusting rotational water velocities within the culture tank. For example, simply reversing the direction of one of the six 45° flow injection nozzles decreased the rotational velocity about the perimeter of the 10m3 tank from 17.8 to 13.4cm/s.Additional studies with arctic char or rainbow trout present at commercial culture densities showed that the rate that settleable solids are flushed from 10 and 150m3 circular ‘Cornell-type’ dual-drain culture tanks depended strongly on the water flow exiting the bottom-center drain and on the rotational period of the water within the tank. A rotational period of 1.3–1.7min produced optimal water velocities for flushing solids from the ‘Cornell-type’ dual-drain tank. Also, a water flow through the tank’s bottom-center drain of at least 5–6L/min for every 1m2 of tank plan area was found to flush settleable solids within 1–2min and 3–6min from 10 and 150m3 ‘Cornell-type’ dual-drain tanks, respectively.

The rate of inflow and mixing during deep‐water renewal in a sill fjord

We obtained high‐resolution data on a deep‐water renewal in the basin of Gullmar Fjord, Sweden, using an autonomous profiling platform. In the middle of the fjord, where the platform is anchored, renewal starts with the passage of a gravity current front and continues with a steady thickening of the new, oxygen‐rich, low‐nitrate bottom layer and an associated lifting of the old, oxygen‐depleted, high‐nitrate bottom water. The basin continuously fills to sill level during a period of 10 d. At the mouth of the fjord, a three‐layer structure develops. Renewal is driven by the density difference between the intermediate water inside and the new deep water outside the fjord. The volume flux is well predicted by a hydraulic exchange model in which the upper layer plays a passive role. Local upwelling and downwelling of the upper halocline cause fluctuating baroclinic currents during renewal, but these seem to have little influence on the average volume flux of new deep water. Entrainment rates are small, and the associated volume flux increase seems to be balanced by detrainment.

Developments in recirculating systems for Arctic char culture in North America

Arctic char (Salvelinus alpinus) tolerate high-density culture conditions, have an excellent fillet yield, are amenable to niche marketing, and are suitable for production within super-intensive recirculating systems. Much of the North American production of Arctic char has been within recirculating systems, which can provide more optimum water temperatures for fish growth and can also overcome limitations created by a lack of high-quality water resources or strict pollution discharge limits. This paper describes some of the developments that have been made in recirculating systems used to produce Arctic char and examines several North American facilities that have used recirculating systems to produce Arctic char. This description includes several state-of-the-art recirculating systems that are now being used to commercially produce Arctic char and another that has just been built and is about to come on-line. This paper also describes several areas where advances have been made in cold-water recirculating system design in order to improve the water quality that they maintain at high feed loadings and to increase the production capacity of these systems. Several critical process improvements include: increased hydraulic exchange rates through the culture tank, superior culture tank designs, better oxygen control strategies and ozonation, improved design of forced-ventilated cascade aeration columns, full flow drum filtration, and better pipe and sump cleanout designs. Several of the strengths and weaknesses of Arctic char production within land-based recirculating systems are also discussed.

Integrated hydrological modelling of a managed coastal Mediterranean wetland (Rhone delta, France): initial calibration

Abstract. This paper presents a model of a heavily managed coastal Mediterranean wetland. The hydrosystem studied , called ``Ile de Camargue", is the central part of the Rhone river delta. It comprises flat agricultural drainage basins, marshes, and shallow brackish lagoons whose connection to the sea is managed. This hydrosystem is subject to strong natural hydrological variability due to the combination of a Mediterranean climate and the artificial hydrological regime imposed by flooded rice cultivation. To quantify the hydrological balance at different spatial and temporal scales, a simplified model is developed — including the basin and the lagoons — using a time step that enables the temporal dynamic to be reproduced that is adapted to data availability. This modelling task takes into account the functioning of the natural and anthropogenic components of the hydrosystem. A conceptual approach is used for modelling drainage from the catchment, using a GIS to estimate water input for rice irrigation. The lagoon system is modelled using a two-dimensional finite element hydrodynamic model. Simulated results from the hydrodynamic model run under various hydro-climatic forcing conditions (water level, wind speed and direction, sea connection) are used to calculate hydraulic exchanges between lagoon sub units considered as boxes. Finally, the HIC ("Hydrologie de l’Ile de Camargue") conceptual model is applied to simulate the water inputs and exchanges between the different units, together with the salt balance in the hydrosystem during a calibration period. Keywords: water management,conceptual hydrological model, hydrodynamic model, box model, GIS, Rhone delta, Camargue.

Influence of hydrologic exchange patterns on water chemistry and hyporheic invertebrate communities in three gravel‐bed rivers

The influence of hydraulic exchange patterns on hyporheic water chemistry and invertebrate community composition was measured in three gravel‐bed rivers of southern Hawke's Bay, North Island, New Zealand. Based on patterns reported overseas we predict that down‐welling waters will be similar to surface waters in chemical characteristics and epigean animals will be more common in down‐welling waters than in up‐wellings, which would have a different chemical signature to the surface waters and a fauna dominated by hypogean invertebrates. Conductivity, pH, and temperature of hyporheic water were least like those of surface waters at up‐wellings in the groundwater‐fed Makaretu River. Only 6% of the invertebrate fauna of these up‐wellings comprised epigean animals. In contrast, in the groundwater‐recharging Tukituki and Waipawa Rivers, hyporheic water chemistry was similar to that of surface water in down‐wellings and 40% of the community comprised epigean animals by abundance. Significant increases (P < 0.05) in species diversity and taxonomic richness was also identified in down‐welling zones compared with up‐wellings. Species diversity and taxonomic richness were lowest in up‐wellings in the Makaretu where hypogean animals dominated the hyporheic fauna. Species diversity and taxonomic richness were higher in down‐wellings than up‐wellings because more epigean taxa were present.

Rheological Properties and Characteristics of Hydraulic Transportation and Heat-Mass Exchange of Coal-Water Fuels

The procedure is proposed for calculating the characteristics of flow and heat exchange of coal-water fuels as applied to the pipeline hydraulic transport and heat-mass exchange in the apparatus of ecologically clean combustion in the objects of power engineering.

Western Mediterranean sea‐level rise: Changing exchange flow through the Strait of Gibraltar

Sea‐level data from tide gauges and satellite altimetry show a decrease of nearly 40% in the sea‐level drop between the Atlantic and the Mediterranean from 1994 to 1997, coming mainly from a rapid rise of western Mediterranean sea‐level by more than 10 mm/year. A decrease in the sea‐level difference across the Strait, coincident with this Mediterranean rise, indicates that the surface inflow is reduced by an amount dynamically consistent with the change along the strait. These secular changes are accompanied by a seasonal cycle in the sea‐level drop between the Atlantic and the Mediterranean, which indicates a seasonal flipping of hydraulic exchange states in the Strait of Gibraltar. Thus, we suggest the sea‐level rise in the Mediterranean is a consequence of a changing exchange flow through the Strait of Gibraltar, driven indirectly by changing conditions in the Mediterranean.

Multi-layer hydraulic exchange flows

Flows between ocean basins are often controlled by narrow channels and shallow sills. A multi-layer hydraulic control theory is developed for exchange flow through such constrictions. The theory is based on the inviscid shallow-water equations and extends the functional approach introduced by Gill (1977) and developed by Dalziel (1991). The flows considered are those in rectangular–cross-section channels connecting two large reservoirs, with a single constriction (sill and/or narrows). The exchange flow depends on the stratification in the two reservoirs, represented as a finite number of immiscible layers of (different) uniform density. For most cases the flow is ‘controlled’ at the constriction and often at other points along the channel (virtual controls) too. As with one- and two-layer hydraulics, controls are locations at which the flow passes from one solution branch to another, and at which (at least) one internal wave mode is stationary. The theory is applied to three-layer flows, which have two internal wave modes, predicting interface heights and layer fluxes from the given reservoir conditions. The theoretical results for three-layer flows are compared to a comprehensive set of laboratory experiments and found to give good agreement. The laboratory experiments also show other features of the flow, such as the formation of waves on the interfaces. The implications of the results for oceanographic flows and ocean modelling are discussed.

Kaolinite exchange between a stream and streambed: Laboratory experiments and validation of a colloid transport model

Experiments were conducted in a recirculating flume to elucidate the fundamental physical and chemical processes which control the stream‐subsurface exchange of colloids. Results are presented on the rate of exchange of colloids (kaolinite clay) and a conservative solute (lithium) from a stream to a sand streambed covered by stationary bed forms (dunes, ripples). Kaolinite and lithium were added to the recirculating stream, and their exchange with the bed was observed over time. Kaolinite was observed to be much more extensively trapped in the streambed than lithium owing to nonconservative processes. By the end of most experiments, essentially all added kaolinite was taken up by the streambed. The observed exchange rates can be explained by analyzing the solute and particle fluxes through the stream‐subsurface interface and the physicochemical interactions between transported kaolinite and the bed sediment. The colloid pumping model predicts particle exchange based on pumping hydraulics, particle settling in the bed, and filtration by the bed sediments. Observed colloid and solute exchanges were successfully predicted by the process‐based models without the use of fitting coefficients. Hydraulic parameters measured in the flume and particle parameters measured in separate experiments were used as model inputs. The successful prediction of experimental results validates the modeling approach of combining a fundamental hydraulic exchange model with a physicochemical model for colloid transport and filtration in the streambed. Further, because colloid transport behavior was interpreted in terms of basic exchange and trapping processes, the results of this study are expected to be directly applicable to the analysis of fine sediment dynamics in natural streams.

Hydraulic head and tracer experiments — two techniques to examine the hydraulic exchange through a riffle

(2000). Hydraulic head and tracer experiments — two techniques to examine the hydraulic exchange through a riffle. SIL Proceedings, 1922-2010: Vol. 27, No. 1, pp. 460-462.

The Hydraulic Exchanges between the Main Water Reservoirs of the Moroccan Middle Atlas Region Measured by Solid State Nuclear Track Detectors

Uranium and thorium contents were evaluated in water samples collected from different sources of the piedmont of the Middle Atlas mountains by using two types of solid state nuclear track detectors (SSNTD). In addition, the radon (222Rn) and thoron (220Rn) α-activities per unit volume of the water samples were also determined. The influence of the water flow rate and altitude on the radon concentration of the water samples belonging to the piedmont of the Middle Atlas mountains was investigated. The hydraulic exchanges between the Middle Atlas water reservoirs and the Turonian aquifer of the neighbouring Tadla plain have been quantified. The results were compared with data given in literature.