Transport In Streams Research Articles

On the relationship of transient storage and aggregated dead zone models of longitudinal solute transport in streams

The relationship between the distributed transient storage (TS) and lumped aggregate dead zone (ADZ) models of longitudinal solute transport in rivers and streams is examined by a parallel application to tracer data and through an investigation of parameter relationships. Both models accurately describe observed solute transport in a stream where the effects of storage or dead zones significantly affect longitudinal dispersion. A moment matching technique, based on theoretical temporal moments, is used to develop parameter relationships. Tests using the previously calibrated parameters, in addition to simulation experiments, show that the moment matching procedure allows ADZ model parameters to be reliably derived from TS model parameters and vice versa. An investigation of these parameter relationships reveals an important difference between the effective solute transport velocity and the average reach flow velocity in streams subject to transient storage or dead zone processes. A number of practical uses for the derived relationships are suggested, including the ability to utilize powerful methods of system identification in the estimation of TS model parameters.

Practical and Innovative Measures for the Control of Agricultural Phosphorus Losses to Water: An Overview

AbstractInputs of P are essential for profitable crop and livestock production. However, its export in watershed runoff can accelerate the eutrophication of receiving fresh waters. The specialization of crop and livestock farming has created regional imbalances in P inputs in feed and fertilizer and output in farm produce. In many areas, soil P exceeds crop needs and has enriched surface runoff with P. This paper provides a brief overview of P management strategies to maintain agricultural production and protect water quality that were discussed at the conference, “Practical and Innovative Measures for the Control of Agricultural Phosphorus Losses to Water,” sponsored by the Organization for Economic Cooperation and Development and held in Antrim, Northern Ireland, June 1998. The purpose of the conference was to assess current strategies for reducing the loads and concentrations of P from agricultural land to surface waters. Topics discussed at the interdisciplinary conference and reviewed here included sustainable P management in productive agriculture; assessing land application of P; evaluating and modeling P transport and transformations in soil, runoff, streams, and lakes; and implementation of integrated best management practices (BMPs). From these discussions, measures to control agricultural P transfer from soil to water may be brought about by optimizing fertilizer P use‐efficiency, refining animal feed rations, using feed additives to increase P absorption by the animal, moving manure from surplus to deficit areas, and targeting conservation practices, such as reduced tillage, buffer strips, and cover crops, to critical areas of P export from a watershed.

Reactive solute transport in streams: A surface complexation approach for trace metal sorption

A model for trace metals that considers in‐stream transport, metal oxide precipitation‐dissolution, and pH‐dependent sorption is presented. Linkage between a surface complexation submodel and the stream transport equations provides a framework for modeling sorption onto static and/or dynamic surfaces. A static surface (e.g., an iron‐ oxide‐coated streambed) is defined as a surface with a temporally constant solid concentration. Limited contact between solutes in the water column and the static surface is considered using a pseudokinetic approach. A dynamic surface (e.g., freshly precipitated metal oxides) has a temporally variable solid concentration and is in equilibrium with the water column. Transport and deposition of solute mass sorbed to the dynamic surface is represented in the stream transport equations that include precipitate settling. The model is applied to a pH‐modification experiment in an acid mine drainage stream. Dissolved copper concentrations were depressed for a 3 hour period in response to the experimentally elevated pH. After passage of the pH front, copper was desorbed, and dissolved concentrations returned to ambient levels. Copper sorption is modeled by considering sorption to aged hydrous ferric oxide (HFO) on the streambed (static surface) and freshly precipitated HFO in the water column (dynamic surface). Comparison of parameter estimates with reported values suggests that naturally formed iron oxides may be more effective in removing trace metals than synthetic oxides used in laboratory studies. The model's ability to simulate pH, metal oxide precipitation‐dissolution, and pH‐dependent sorption provides a means of evaluating the complex interactions between trace metal chemistry and hydrologic transport at the field scale.

The role of colloids in tracemetal transport and adsorption behavior in New JerseyPinelands streams

Dissolved and colloidal concentrations of Al, Fe, Mn, Cu, Zn, Cd, and Pb were determined in the Mullica River, New Jersey, and its tributaries on nine occasions between August 1994 and September 1995. Cross‐flow filtration (CFF) at a nominal 10 kDa cutoff was used to separate total dissolved (>0.45 μm) riverine metals into colloidal and truly dissolved fractions. Reproducibility tests on full procedural replicates demonstrated CFF's precision and indicated that temporal or spatial differences exceeding 10–15% in colloidal fraction can be resolved using these techniques. For the whole data set, mean colloidal fractions of 0.45‐ μm filtrates were 65% for Al, 82% for Fe, 29% for Mn, 66% for Cu, 31% for Zn, 46% for Cd, and 88% for Pb. The magnitude of the colloidal fraction followed an elemental order that was largely consistent from site to site and among different sampling dates, despite large variations in total dissolved metal concentrations. The order was very similar to that observed previously in rivers of varying geochemical properties, suggesting that the degree of colloidal association is driven by a metal's affinity for humic materials and is relatively insensitive to other riverine properties such as pH, dissolved organic carbon, and suspended mass. The constancy of this elemental pattern in Pinelands streams suggests that the relative fates of metals during estuarine colloid flocculation may be predictable and temporally stable. Iron behavior was distinct from that of the other elements: colloidal Fe fraction was positively correlated with pH (range, 4.3–7.1) and the colloidal Fe/Al ratio showed clear seasonal variation. The other metals did not exhibit these behaviors, which suggests that their colloidal association was distinct from that of Fe. Colloidal metal/Al ratio for Fe, Pb, and Zn was clearly different from that of >0.45 μm particles; that finding is consistent with the distinct compositions and sources for colloidal and particulate fractions. The distribution coefficient (Kd) for Pb was positively correlated with suspended particulate mass (<10‐fold variation) over time at one representative site. This inverse particle concentration effect runs contrary to recent observations in other freshwater and marine systems and suggests that colloidal and particulate size fractions vary independently over the course of the year.

Mercury and Organic Carbon Relationships in Streams Draining Forested Upland/Peatland Watersheds

AbstractWe determined the fluxes of total mercury (HgT), total organic carbon (TOC), and dissolved organic carbon (DOC) from five upland/peatland watersheds at the watershed outlet. The difference between TOC and DOC was defined as particulate OC (POC). Concentrations of HgT showed moderate to strong relationships with POC (R2 = 0.77) when all watersheds were grouped. Although POC only accounts for 10 to 20% of the OC transported, we estimate that it is associated with 52 to 80% of the HgT transported from the five watersheds. Total transport of HgT from the watersheds ranged from 0.70 to 2.82 µg m−2 yr−1. Watershed geometry and hydrology play important roles in determining the influence of OC on HgT transport in forested watersheds. Watershed properties such as peatland area have considerable promise as predictors for estimating HgT transport in streams draining forested watersheds in the Great Lakes States.

Calculation of Bed Changes in Mountain Streams

Simulation of flow and sediment transport in mountain streams is complicated by the presence of high gradients, abrupt changes in geometry, variations in regime of flow, and large roughness elements. Most of the numerical models to predict aggradation and degradation in alluvial channels have been developed for low-gradient rivers. This paper is devoted to the development of a numerical model to calculate bed elevation and grain size distribution changes in mountain streams where the maximum bed material size is in the range of boulders. An attempt is made to validate the model by using observed field data collected upstream from a small retention dam in a Venezuelan stream. After calibration of the sediment transport equation, reasonable agreement is obtained for the variations in the grain size distribution of the bed-surface material. An additional application is presented in the Cocorotico River, a small mountain stream located in the northwest region of Venezuela, which illustrates the adaptability of the model to handle a case of coarsest-bed-material removal from the active channel and to simulate the armoring process.

Relating Transient Storage and Whole-System Metabolism with Nitrogen Uptake in Streams

Streams are important landscape features because they provide an avenue for nitrogen loss from a watershed to downstream ecosystems and eventually the ocean; however, in-stream processes can control nutrient transport and export (e.g. Burns 1998). Nitrogen is an important element because it limits rates of primary production in many terrestrial and aquatic ecosystems. Alteration of the forms, timing, and concentration of nutrients is a central property of lotic systems (Fisher et al. 1998). Understanding controls on both transport and retention are central to predicting how streams influence nutrient loss from watersheds (Hedin et al. 1995, Likens and Bormann 1995, Burns 1998) and nutrient loading to downstream ecosystems (Howarth et al. 1996). With increased global nutrient loading from atmospheric sources and fertilizers, streams may play an important role in the retention, transformation and export of nutrients from the upland landscape. We know little about what controls nutrient uptake and transport in streams. There are many studies that show effects of hydrologic, biologic, and geomorphic influences on nutrient transport, but rarely have all aspects been considered in the same study. One potentially important geomorphic control is transient storage. Transient storage is water that is separated from the main channel flow and therefore, moves downstream more slowly than water in the main stream channel, which should facilitate nutrient uptake. Transient storage has been suggested to play an important role in nutrient retention in streams from both theoretical (Mulholland and DeAngelis 2000) and empirical perspectives (Valett et al. 1996, Mulholland et al. 1997). Additionally no studies have linked whole stream measures of metabolism with stream nutrient uptake, though we expect that greater C fixation or respiration will cause higher demand for nutrients. The objective of our study was to relate nutrient uptake with geomorphic and whole stream metabolism in 8 streams in Grand Teton National Park.

Flow of Oil And Sand In a Horizontal Well

Abstract Despite the increasing acceptance of horizontal wells as a potentially productive means of recovering oil and gas from underground reservoirs, the hydrodynamics of flow inside a horizontal well remains incompletely understood, especially for multiphase flow. Sand production into a horizontal well presents a formidable problem as the sand deposits at the bottom of the horizontal well, and thus reduces the effective size of the flow conduit. This study focusses on the flow of oil and sand in a horizontal well. The model developed in this study treats the flow of oil and sand as that of a monodisperse, dilute suspension. The fluid phase (oil) is assumed to be incompressible and Newtonian. The particulate phase, composed of spherical sand particles, is assumed to behave as a continuum. The diffusive movement of the particulate phase is controlled by gravity force. The model allows for the determination of the axial velocity of the fluid phase and particulate phase, and the particulate phase density distribution at different positions along the horizontal well length. Examination of the dimensionless groups allows for an analysis of the dominant parameters controlling the transport of sand in a horizontal well, including condition(s) promoting sedimentation. The rate of sediment bed buildup is correlated with fluid phase flow and interaction between the fluid phase and the particulate phase. Introduction Solid-liquid multiphase flows encompass many different areas of science and engineering, ranging from transport of colloids in rain water, sediment transport in river streams, waste transport in sewers, bed fluidization, flotation to slurry pipeline transportation, drill cuttings removal, and transport of fracture proppants, etc. As more horizontal wells are drilled to recover oil and gas from oil reservoirs, problems associated with sand production into, and their transport inside these horizontal wells become more prominent- particularly for wells drilled in unconsolidated or fractured formations. Deposition of sand and fines inside these horizontal wells could have adverse impact on their productivity, even negating many of the advantages of horizontal drilling. In particular, the produced sand particles tend to collect in the low spots (doglegs) along the horizontal well, and thus constrict the flow of oil through the well at these points. Sand removal techniques have been successful in fluidizing the settled sand particles and removing them from the wellbores. However, these operations are time consuming, expensive, and require a knowledge of where the sand deposits are. Few studies investigating the hydrodynamic transport of sand and fines in horizontal wells are available in current petroleum literature. This paper attempts to identify parameters governing the flow of oil and sand inside a horizontal well, including conditions promoting sand deposition, as well as the rate of sediment buildup at different positions along the horizontal well length. Hydrodynamic Fundamentals From a hydrodynamic viewpoint, the most important and fundamental aspects of solid-liquid multiphase flow are interphase interaction (i.e., interaction between the fluid phase and the particulate phase) and intraphase interaction (i.e., interaction among solid particles making up the particulate phase).

Braided stream aggradation on an alluvial fan margin: Emerald Lake fan, British Columbia

Evolving bar and channel patterns were observed at the distal margin of an active alluvial fan at Emerald Lake, British Columbia, during peak midsummer flows. At the fan margin, bed slope is 0.024, sediment is predominantly coarse gravel, flow is shallow and fluctuating, and sediment transport and deposition are dominated by chutes and lobes. Flow unconfinement at the exit of rapidly formed shallow scour channels typically results in deposition of sediment lobes 0.2 m thick and 10-250 m2 in area. Closely spaced deposition of a number of these sediment lobes results in aggradation of composite sediment sheets. One such sheet, monitored daily over a 15 day period, deposited 129 m3 of gravel over 710 m2 of adjacent marsh sediment, locally extending the distal fan margin by 39 m. Thickness of the aggraded bed varied up to 0.37 m, depending on surface topography. During active deposition, individual lobe deposits formed simple unit bars that partly projected above the water surface. These bars caused local flow division that, together with avulsion of the dominant channel, initiated a braided stream pattern. Complex braid bars composed of several annealed lobe remnants are gradually exposed as waning discharge becomes confined to adjacent chutes. The newly aggraded fan margin is mainly composed of massive to crudely stratified imbricated gravel with interstratified, discontinuous, centimetre-thick finer grained layers. High-angle cross-stratification was not observed. Since chutes and lobes dominate sediment transport and deposition in streams at the distal margin of this rapidly aggrading fan, it is likely that similar deposits should be present in many ancient alluvial fan sequences, but as yet have gone largely unrecognized.

Hydraulic Estimation of Dispersion Coefficient for Streams

Inclusion of longitudinal dispersion enhances realism in the assessment of transport in streams by accounting for contaminant mixing. Here we revisit the problem of estimating the longitudinal dispersion coefficient D from readily measurable bulk hydraulic variables, which is useful in applications. We develop and calibrate, through field testing, a predictor for the longitudinal dispersion coefficient for streams that is structured after the fundamental formula of G. I. Taylor. Comparison of predicted with observed values of D shows the new optimized formula providing closer estimates than the established formula of Fischer, with respect to both mean accuracy and deviations from the mean, achieving in 14 of the 24 cases studied predictive accuracy of 0.5 ≤Dobserved/Dpredicted≤ 2.

Stochastic sediment transport in soil erosion

A stochastic model governing the downslope transport of a sediment particle during an erosion event is described. Particles alternate between resting on the soil bed and being transported by the overland flow. Probability densities and moments are constructed for the distribution of a particle's position at a given time, and also for time of passage to a given location. We show that a suitable averaging of the stochastic particle motions in our model gives rise to the deterministic erosion differential of Hairsine and Rose (Hairsine, P., Rose, C., 1991. Soil Sci. Soc. Am. J. 55 (2), 320–324). The model generalized H. Einstein's stochastic model (Der Geschiebebetrieb als Wahrscheinlichkeitsproblem, Verlag Rascher, Zurich, 1937) for bedload transport in streams.

A case study of longitudinal dispersion in small lowland rivers

Contaminant transport in natural streams is considered on the basis of tracer studies in Moldovian small lowland rivers. Theories describing the spread of conservative and passive pollutants in the context of a longitudinal dispersion model, as well as attempts to estimate the discrepancy between this model and natural processes, are discussed. It is shown that the model agrees with experimental data, with an accuracy ranging from 15 to 20%, at least in the upper [C(t) > 0.5Cmax] concentration distributions. The process behaves in a quasi‐Fickian manner only at distances greater than 80 to 100 times the river width. Primarily, the nonuniformity of the average velocities over cross sections affects the process. An estimate of the Lagrangian spatial scales was proposed, and it was shown that those scales are as large as two to four times the length of alternate bars.

Dynamics of Wood Transport in Streams: A Flume Experiment

The influence of woody debris on channel morphology and aquatic habitat has been recognized for many years. Unlike sediment, however, little is known about how wood moves through river systems. We examined some dynamics of wood transport in streams through a series of flume experiments and observed three distinct wood transport regimes: uncongested, congested and semi-congested. During uncongested transport, logs move without piece-to-piece interactions and generally occupy less than 10 per cent of the channel area. In congested transport, the logs move together as a single mass and occupy more than 33 per cent of the channel area. Semi-congested transport is intermediate between these two transport regimes. The type of transport regime was most sensitive to changes in a dimensionless input rate, defined as the ratio of log volume delivered to the channel per second (Qlog) to discharge (QW); this ratio varied between 0·015 for uncongested transport and 0·20 for congested transport. Depositional fabrics within stable log jams varied by transport type, with deposits derived from uncongested and semi-congested transport regimes having a higher proportion of pieces orientated normal to flow than those from congested transport. Because wood input rates are higher and channel dimensions decrease relative to piece size in low-order channels, we expect congested transport will be more common in low-order streams while uncongested transport will dominate higher-order streams. Single flotation models can be used to model the stability of individual pieces, especially in higher-order channels, but are insufficient for modelling the more complex intractions that occur in lower-order streams. © 1997 John Wiley & Sons, Ltd.

Dynamics of Wood Transport in Streams: A Flume Experiment

The influence of woody debris on channel morphology and aquatic habitat has been recognized for many years. Unlike sediment, however, little is known about how wood moves through river systems. We examined some dynamics of wood transport in streams through a series of flume experiments and observed three distinct wood transport regimes: uncongested, congested and semi-congested. During uncongested transport, logs move without piece-to-piece interactions and generally occupy less than 10 per cent of the channel area. In congested transport, the logs move together as a single mass and occupy more than 33 per cent of the channel area. Semi-congested transport is intermediate between these two transport regimes. The type of transport regime was most sensitive to changes in a dimensionless input rate, defined as the ratio of log volume delivered to the channel per second (Qlog) to discharge (QW); this ratio varied between 0·015 for uncongested transport and 0·20 for congested transport. Depositional fabrics within stable log jams varied by transport type, with deposits derived from uncongested and semi-congested transport regimes having a higher proportion of pieces orientated normal to flow than those from congested transport. Because wood input rates are higher and channel dimensions decrease relative to piece size in low-order channels, we expect congested transport will be more common in low-order streams while uncongested transport will dominate higher-order streams. Single flotation models can be used to model the stability of individual pieces, especially in higher-order channels, but are insufficient for modelling the more complex intractions that occur in lower-order streams. © 1997 John Wiley & Sons, Ltd.

Post-mine metal transport and attenuation in the Keno Hill mining district, central Yukon, Canada

The Keno Hill mining district in central Yukon was the second largest silver producer in Canada with mines operating from 1913 to 1989 on more than 65 vein silver deposits. The seven and a half decades of mining activities have generated large volumes of mine waste disposed on the land surface, resulting in elevated metal contents in numerous small drainages. To assess the extent of metal mobilization, old mine workings and the associated mine waste were examined and the water courses draining to a major river valley sampled. The results of field observations and an array of water and sediment analyses led to three major conclusions. 1. Acid mine drainage is not widespread because of galvanic protection of pyrite from oxidative dissolution and neutralization by carbonates in the country rock. 2. Mechanisms operative to limit aqueous metal transport in small streams in the district include cryogenic precipitation, coprecipitation and sorption. 3. The near-surface concentration of metals limits the options of waste disposal in future mining developments due to potential metal-leaching problems.

Suspended Particulate Organic Matter Concentration and Export in Streams

Suspended Particulate Organic Matter Concentration and Export in Streams

Solution of the Advection-Dispersion Equation: Continuous Load of Finite Duration

Field studies of solute fate and transport in streams and rivers often involve an experimental release of solutes at an upstream boundary for a finite period of time. A review of several standard references on surface-water-quality modeling indicates that the analytical solution to the constant-parameter advection-dispersion equation for this type of boundary condition has been generally overlooked. Here an exact analytical solution that considers a continuous load of finite duration is compared to an approximate analytical solution presented elsewhere. Results indicate that the exact analytical solution should be used for verification of numerical solutions and other solute-transport problems wherein a high level of accuracy is required.

Nitrogen Transport from Tallgrass Prairie Watersheds

AbstractDischarge and N content of surface water flowing from four Karst watersheds on Konza Prairie Research Natural Area, Kansas, managed with different burn frequencies, were monitored from 1986 to 1992. The goal was to establish the influence of natural processes (climate, fire, and bison grazing) on N transport and concentration in streams. Streams were characterized by variable flow, under conditions that included an extreme flood and a drought during which all channels were dry for over a year. The estimated groundwater/stream water discharge ratio varied between 0.15 to 6.41. Annual N transport by streams, averaged across all watersheds and years, was 0.16 kg N ha−1 yr−1. Annual N transport per unit area also increased as the watershed area increased and as precipitation increased. Total annual transport of N from the prairie via streams ranged from 0.01 to 6.0% of the N input from precipitation. Nitrate and total N concentrations in surface water decreased (P < 0.001, r values ranged from 0.14–0.26) as length of time since last fire increased. Increased watershed area was correlated negatively (P < 0.0001) to stream water concentrations of NO−3N and total N (r values = −0.43 and −0.20, respectively). Low N concentration is typical of these streams, with NH+4‐N concentrations below 1.0 µg L−1, NO−3‐N ranging from below 1.4 to 392 µg L−1, and total N from 3.0 to 714 µg L−1. These data provide an important baseline for evaluating N transport and stream water quality from unfertilized grasslands.

Reactive solute transport in acidic streams

Spatial and temporal profiles of pH and concentrations of toxic metals in streams affected by acid mine drainage are the result of the interplay of physical and biogeochemical processes. This paper describes a reactive solute transport model that provides a physically and thermodynamically quantitative interpretation of these profiles. The model combines a transport module that includes advection-dispersion and transient storage with a geochemical speciation module based on MINTEQA2. input to the model includes stream hydrologic properties derived from tracer-dilution experiments, headwater and lateral inflow concentrations analyzed in field samples, and a thermodynamic database. Simulations reproduced the general features of steady-state patterns of observed pli and concentrations of aluminum and sulfate in St. Kevin Gulch, an acid mine drainage stream near Leadville, Colorado. These patterns were altered temporarily by injection of sodium carbonate into the stream. A transient simulation reproduced the observed effects of the base injection.

Reactive Solute Transport in Streams: 1. Development of an Equilibrium‐Based Model

An equilibrium‐based solute transport model is developed for the simulation of trace metal fate and transport in streams. The model is formed by coupling a solute transport model with a chemical equilibrium submodel based on MINTEQ. The solute transport model considers the physical processes of advection, dispersion, lateral inflow, and transient storage, while the equilibrium submodel considers the speciation and complexation of aqueous species, precipitation/dissolution and sorption. Within the model, reactions in the water column may result in the formation of solid phases (precipitates and sorbed species) that are subject to downstream transport and settling processes. Solid phases on the streambed may also interact with the water column through dissolution and sorption/desorption reactions. Consideration of both mobile (water‐borne) and immobile (streambed) solid phases requires a unique set of governing differential equations and solution techniques that are developed herein. The partial differential equations describing physical transport and the algebraic equations describing chemical equilibria are coupled using the sequential iteration approach.