bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrological and Environmental Modeling of Transport Processes in Rivers and Estuaries
Authors: Lin Binliang , Falconer Roger A
Published: April 2006

Hydroinformatics tools are increasingly being used for predicting hydrodynamic, hydrological, and water quality processes in river and estuarine waters. The numerical solutions of the governing hydrodynamic and solute and sediment transport equations form the basis of these software tools. Details are given herein of the governing equations for three‐, two‐ and one‐dimensional flow‐field predictions and the transport of water quality indicators and sediment transport processes within the water column. Two case studies are then discussed. In the first of these studies linked 1‐D and 2‐D models are used to predict the velocity and fecal coliform distributions for a relatively large river and estuarine system, including the Ribble Estuary, its tributaries, and the Fylde coast. In the second of these studies, the velocity, suspended sediment, and heavy metal concentration distributions are predicted along the Humber Estuary using 2‐D and 3‐D models, with dynamic partitioning coefficients being used to link the metal concentrations and sediments. Details are also given of the hydrological models used to specify the pollutant discharge loads from land used models.
Evolutionary Computing in Hydrological Sciences
Authors: Savic Dragan , Khu Soon‐Thiam
Published: April 2006

With the advent of data acquisition techniques and data processing capabilities (computers + algorithms),
evolutionary computing
(
EC
) has found its way into a wide range of applications in hydrological science as demonstrated in this article. These applications range from the use of EC to assist in the understanding of hydrological processes, to improve the performance of simulation models for almost all aspects of hydrologic applications, and most recently, to quantify risk and uncertainty with the aim of providing decision support.

In this article, an attempt is made to provide a detailed review of the applications of EC in different hydrological science topics. References are divided into six main categories: hydrologic processes research, rainfall‐runoff modeling, reservoir operations and control, groundwater systems, urban water systems, and water quality studies. These are broad categorizations, and many applications of EC span across multiple groupings.

Evolutionary Computing is a continuously and rapidly growing area of academic research for computer science, mathematics, economics and management, engineering, physical science, and many others. As such, it is futile to try to provide a comprehensive overview of the currently available EC tools and techniques and therefore, no such attempt is made in this article.
Artificial Neural Network Concepts in Hydrology
Authors: Minns Anthony W , Hall Michael J
Published: April 2006

The solution of many applied hydrological problems, such as the forecasting of floods, has for several decades been based upon the concepts of linear systems analysis. However, the introduction of informatics tools, such as Artificial Neural Networks (ANNs), with their origins in cognitive sciences and pattern recognition, has made available new lines of investigation. Nevertheless, despite their apparent structural simplicity, the use of ANNs to encapsulate the transformation of rainfall over a catchment into streamflow at its outlet requires at least as much hydrological insight as a conventional physical/conceptual hydrological model. Of particular importance are: the choice of the input data streams; and the maintenance of the ability of the ANN to generalize and extrapolate beyond its training data set. Attention to these aspects invariably provides a model whose goodness‐of‐fit to an independent testing data set is superior to that of parameter‐based hydrological modeling systems.
Network Distributed Decision Support Systems and the Role of Hydrological Knowledge
Authors: Jonoski Andreja
Published: April 2006

This article introduces the hydroinformatics concept of new kinds of environments for supporting decision‐making processes in the fields of water and the environment, under the name of Network Distributed Decision Support Systems(NDDSSs). These environments are designed to enable active participation of large numbers of interested stakeholders including the general public. The platforms for their development and deployment are the electronic networks such as the Internet and the wireless mobile telephony networks. Core components of such systems are instantiated hydrological models, acting as main fact providers for the participants' judgments and evaluations of the proposed courses of actions. For achieving the required performance within NDDSSs, these models need to be distributed (viz. capable of representing spatial variability as encountered in real situations) and capable of simulating integrated physical processes in the hydrological system, and open for wider integration with other kinds of models such as ecological or socioeconomic models. A brief overview of the software agent technology is presented, with its potential for the design and development of these new decision support environments. The manners in which full‐fledged NDDSSs can be implemented into our present societies are also presented.
Atmospheric Boundary‐Layer Climates and Interactions with the Land Surface
Authors: Holtslag Albert AM , Ek Michael B
Published: April 2006

The purpose of this article is to provide an overview of the relevant processes and interactions in the Atmospheric Boundary Layer (ABL) over land. Modeling principles for the ABL are summarized and discussed, including the formulation and role of the surface fluxes. It is shown that both the ABL and the coupled soil‐vegetation‐atmosphere system can be well represented in the well‐defined cases examined. The interactions between the ABL and the land surface are illustrated with the role of soil moisture on boundary‐layer cloud initiation. As such, a new analytical development is discussed and illustrated for the tendency of relative humidity at boundary‐layer top. Typically, increased soil moisture leads to a higher potential for boundary‐layer clouds, but in some cases, the largest potential for boundary‐layer clouds is predicted over dry soils. For readers not familiar with atmospheric turbulence and meteorological definitions, some background is given as well.
Evaporation from Lakes
Authors: Finch Jonathan W , Hall Robin L
Published: April 2006

Lakes are an important part of the hydrological cycle, but quantifying the evaporation rates from them is not a trivial task. The amount of radiant energy captured by a lake is generally the dominant control on the annual evaporation rate. At shorter time periods, the major factors affecting lake evaporation are: the albedo, the heat‐storage term of the energy budget, and the atmospheric diffusion processes. The albedo is a function of the solar elevation angle and the proportion of downward diffuse radiation, and can be predicted from empirical relationships. The heat‐storage term can decouple the evaporation rates from the net radiation, but can be estimated simply in the case of well‐mixed water. However, in the situation where the lake becomes thermally stratified, more complex, hydrodynamic models are required. The three commonly used methods of estimating lake evaporation are: mass transfer, energy balance, and combination equations. There are strengths and limitations to each of these methods.
Ground‐Based and Airborne Lidar
Authors: Hardesty R Michael , Darby Lisa S
Published: April 2006

Lidar remote sensing techniques can be applied to measure a wide variety of atmospheric parameters important in the hydrological sciences, including aerosol distribution, cloud properties, ozone and water vapor concentration, and wind fields. Lidar measurements make use of scattering and extinction of laser radiation in the atmosphere. Instruments are deployed on surface and aircraft platforms to investigate phenomena such as moisture spatial distribution and temporal evolution, ozone sources and transport, boundary‐layer height, aerosol distribution, cloud microphysics, and wind structure. New satellite‐based instruments enable lidar techniques to be applied on a global scale.
Spatially Resolved Measurements of Evapotranspiration by Lidar
Authors: Eichinger William E
Published: April 2006

Spatially resolved estimates of evapotranspiration may be made over an area of about a square kilometer, with relatively fine (25 m) spatial resolution, derived from three‐dimensional measurements of water vapor concentration made by a scanning Raman lidar. The method is based upon the Monin–Obukhov similarity theory applied to spatially and temporally averaged data. The method has been applied at several locations to produce maps of the spatial distribution of evapotranspiration rates at regular intervals throughout the day. The estimates of evapotranspiration rates made compare favorably with estimates made using eddy correlation methods. The method is limited in that it assumes that the surface roughness, friction velocity, and Obukhov length are assumed constant over the examined areas. Values for the friction velocity and Obukhov length are required from conventional point instruments. The three‐dimensional water vapor concentration and the evaporation maps can be used in a wide variety of ways to study the spatial variations in evapotranspiration caused by changes in soil type and moisture content, canopy type, and topography.
Estimation of River and Water‐Body Stage, Width and Gradients Using Radar Altimetry, Interferometric
SAR
and Laser Altimetry
Authors: Birkett Charon , Alsdorf Doug , Harding David
Published: April 2006

Major advances in the application of satellite radar altimetry have led the way to a proven ability to determine surface water height, or stage, for some of the largest rivers, wetlands, and lakes around the world. These developments have come at a time when global water resources are of major concern, and there is a much‐noted decline in ground‐based monitoring networks. Recent interferometric synthetic aperture radar studies have also demonstrated the ability to retrieve stage changes over a wide expanse of inundated floodplain or wetland. While the performance of these radar instruments is continuously being assessed, focus is also on the potential of satellite‐based laser altimetry, which may offer smaller observable targets and improved stage accuracies. With these technological capabilities, we have the capacity to determine inland water stage, and to some degree, river width and gradient.
Freezing and Thawing Phenomena in Soils
Authors: Stähli Manfred
Published: April 2006

More than one‐third of the Earth's land surface is subjected to seasonal or permanent soil frost. The freezing and thawing of the soil may generate severe geotechnical, hydrological, and environmental problems, such as frost heaving, restricted infiltration, and enhanced overland flow. Each soil has its own specific freezing characteristic, primarily depending on texture and the prevailing solute concentration. Fine‐textured soils tend to form ice lenses at freezingthat causes the soil to heave. In coarse‐textured soil, on the other hand, the ice is more regularly distributed within the matrix. The behavior of the soil is always strongly linked to the prevailing meteorological conditions. The hydraulic conductivity of frozen soils is reduced, similar to very dry soils. Locally, this leads to reduced infiltration and delayed recharge to groundwater during snowmelt. For larger areas, for example, watersheds, the effect of frozen ground on infiltration and runoff is ambiguous, as a number of recent studies showed.

This article summarizes current theories and recent investigations on soil freezing and thawing phenomena with a major emphasis on implications for hydrology.
Models for Indirect Estimation of Soil Hydraulic Properties
Authors: Schaap Marcel G
Published: April 2006

This article describes methods for the indirect estimation of soil hydraulic properties, such as soil water retention and hydraulic conductivity characteristics. Indirect methods can be classified into semiphysical methods that are based on mechanical assumptions regarding particle and pore arrangements, and statistical methods that are known as pedotransfer functions. Both classes are described and evaluated on their merits, and some characteristic examples are given. A list of applicable software is described at the end of the article and an extensive reference list provides sufficient material for further background information.
Erosion and Sediment Transport by Water on Hillslopes
Authors: Parsons Anthony John
Published: April 2006

Much of the terminology and many of the concepts within the field of erosion and sediment transport by water on hillslopes, derive from the literature of agricultural engineering. Of particular importance has been the distinction between rills and interrill areas. One definition of the former is that they are channels small enough to be removed by ploughing; gullies, by contrast, are not. The distinction of gullies, rills, and interrill areas is artificial. None the less, it provides a convenient framework for an examination of the processes of hillslope erosion and sediment transport.

In interrill areas, the dominant mechanism of sediment detachment is that of raindrop impact. Sediment detached by raindrops may be split into that which is transported away from the location of detachment in splash droplets (rainsplash), and that which is simply dislodged by the impact of raindrops but which either remains at, or falls back to, the site of detachment. The former is relatively easy to measure; the latter is not, but may be quantitatively much more important. The rate of detachment is a function of the rainfall energy at the soil surface, so that where vegetation intercepts some of the energy of the rainfall, or a layer of surface water exists, some of the energy of the falling rain will be dissipated. The rate of detachment is also affected by surface gradient. Whereas detachment in interrill areas is due to the energy of falling raindrops, sediment transport is mainly controlled by flow energy. Several authors have attempted to apply transport‐capacity equations developed for alluvial rivers even though the hydraulic conditions in shallow overland flow are very different from those in rivers. However, sediment transport by interrill flow needs to consider not only the capacity of the flow, but also its competence.

As threads of interrill flow become deeper and faster, a threshold is reached beyond which significant flow detachment begins to take place. Once this occurs the flow begins to erode definable channels, or rills. As with interrill overland flow, the transport capacity of rill flow has typically been estimated using equations taken from the literature developed for alluvial rivers. However, sediment transport by rill flow is equally determined by the competence of the flow. This is particularly the case for stony soils.

Gullies have been relatively neglected in the agricultural literature, so that, whereas there is considerable qualitative literature on gully growth and development, quantitative information is limited. However, gullies may account for between 10% and 94% of total soil loss on hillslopes.

Modelling of hillslope erosion and sediment transport has been undertaken by both geomorphologists and agricultural engineers. There is a shared history, inasmuch as, through time, both demonstrate increasingly explicit representation of processes in their modelling as understanding of processes has increased and increased computing power has become available.
Erosion Monitoring
Authors: Hasholt Bent
Published: April 2006

First the need for and relevance or erosion monitoring is stated, and then definitions, terms and classifications of the topic are described. The monitoring is treated for active erosive agents under natural conditions and at different scales. Monitoring in controlled systems and in laboratory experiments are treated separately. Special emphasis is on problem encountered in monitoring programs. References on key instrumentation are provided.
Microbial Transport in the Subsurface
Authors: Ginn Timothy R , Camesano Terri , Scheibe Timothy D , Nelson Kirk E , Clement T Prabhakar , Wood Brian D
Published: April 2006

We review the processes involved in the transport of bacteria in the saturated subsurface. Our goal is to communicate priority topics in the basic science of bacterial transport processes, and this leads to a focus on the nanometer to micron scales of observation. The scope of this review is the set of physical, chemical, and biological processes involved in the transport of individual cells, and the constitutive theory underlying conceptual depiction of these processes.
Natural and Constructed Wetlands
Authors: Craft Christopher B
Published: April 2006

Wetlands are characterized by periodic to continuous inundation or saturation with water (wetland hydrology), soils that are periodically deficient in oxygen (hydric soils), and vegetation that is adapted to periods of anaerobic or anoxic soil conditions (hydrophytic vegetation). Wetlands include herbaceous marshes and fens, forested swamps, and Sphagnum‐dominated peat bogs. Wetland plants possess morphological adaptations (aerenchyma, buttressed trunks, pneumatophores, hypertrophied lenticels) to facilitate transport of oxygen to the roots and metabolic pathways to respire anaerobically without toxic effects. Duration, depth, and frequency of inundation, water source (precipitation, surface flow, groundwater), and water quality (fresh, saline, oligotrophic, eutrophic) determine the distribution, productivity, and nutrient cycling characteristics of wetland vegetation. Floodplain swamp forests and estuarine marshes and mangroves receive large quantities of water and nutrients during overbank flooding and tidal inundation that enhances plant productivity and sediment, nutrient, and pollutant retention as compared to wetlands that receive most of their water from precipitation. The ability of natural wetlands to filter pollutants has led to construction of artificial wetlands to treat wastewater, stormwater, acid mine drainage, nonpoint runoff and other sources of pollutants. Wetlands also are constructed to replace important ecological functions (water storage, biological productivity, biodiversity) that are lost when natural wetlands are damaged or destroyed by human activities.
Lake Ecosystems (Stratification and Seasonal Mixing Processes, Pelagic and Benthic Coupling)
Authors: Bade Darren L
Published: April 2006

Seasonal stratification in lakes is caused by the differential heating of surface waters, causing them to become less dense and buoyant above colder, denser water. Other forces oppose stratification, including wind energy and loss of heat from the surface. Wind imparts many types of motions to lake waters, each having distinct patterns, energy, and scales of mixing. Theoretical considerations are presented in detail on the expected response of lakes to physical forcing. In addition, empirical equations are given for diverse regions of the world to predict epilimnetic and thermocline depth and timing of stratification. Lake morphometry along with climatic conditions determines the depth of epilimnetic mixing. The seasonal patterns of mixing and stratification are observed in a northern temperate lake (Sparkling Lake, Wisconsin, USA). The influence of stratification and mixing on the coupling of benthic and pelagic zones through processes of sedimentation, resuspension, eddy diffusivity, and hypolimnetic entrainment are discussed. Through these mechanisms, the hydrodynamics of lakes directly and indirectly influence the chemical and biological environment of lake ecosystems.
Land Use and Land Cover Effects on Runoff Processes: Agricultural Effects
Authors: Burt Timothy P , Slattery Michael C
Published: April 2006

The impact of agriculture on runoff processes cannot be underestimated. The greatest impact is usually on soil surface conditions, specifically infiltration. Undisturbed soils have much higher infiltration capacity than soils in agricultural land. Once cultivated, soils become easily compacted as they are laid bare to the elements until the next crop develops a protective cover. Infiltration can fall to levels where infiltration‐excess overland flow can occur even in rainfall of modest intensity. Successive rainfall events compact the bare soil further and impermeable crusts often form. Heavy machinery used in agriculture exacerbates soil compaction, particularly at depth, via the development of plough pans. These compacted, dense layers have significantly higher bulk density and lower total soil porosity than the soil directly above or below it and frequently become preferential zones of runoff generation. Temporary saturation of shallow topsoil layers leads to topsoil saturation overland flow that, if connected to the channel network, may become a significant contributor to event response. Linear zones of compaction and reduced hydraulic conductivity that occur as a result of vehicular traffic have similar impacts.
Land Use and Landcover Effects on Runoff Processes: Forest Harvesting and Road Construction
Authors: Sampurno Bruijnzeel L A
Published: April 2006

The hydrologic impacts of various forestry operations are reviewed, notably the effects of thinning, selective harvesting, clear‐cutting with and without roads, and removal of understorey or riparian vegetation. Thinning and selective logging have a relatively modest effect on amounts of rainfall reaching the forest floor unless at least 70% of the standing biomass is removed. The effect on soil water and streamflow is smaller still, mostly because of the increased vigor of the remaining vegetation. Removing understorey vegetation produces a similarly small effect. The annual water yield is invariably increased in proportion to the amount of biomass harvested, with the exception of forests subject to high fog incidence or old‐growth forest of low vigor. Cutting riparian vegetation produces a larger increase in streamflow (compared to cuts away from the streams) under subhumid conditions and shallow water tables only. The largest seasonal increases in flow after clear‐cutting are normally observed at times when water deficits in the undisturbed forest are highest. The gains in streamflow after clear‐cutting gradually disappear when regrowth is allowed, the effect lasting longer where soils are deeper and forest regeneration slower. Mechanized harvesting practices and road building both increase stormflow volumes and peak discharges. The relative effect diminishes with storm size in the case of clear‐cutting only, but increases in the case of roads only. Similarly, effects of forest cutting per se on stormflows are “diluted” at larger scales, but the effect of the associated road network is not. Various measures are discussed to minimize the adverse hydrologic impacts of timber harvesting operations.
Landscape Element Contributions to Storm Runoff
Authors: Seibert Jan , McGlynn Brian
Published: April 2006

Hydrological conditions and the corresponding land area contributions to streamflow vary across the landscape. Landscapes are mosaics that can be described in varying levels of detail. This document describes the importance of different landscape elements for storm runoff generation. Since topography is often a first‐order control on hydrological processes, topographic indices can be used to describe the spatial variations of hydrological conditions. Another approach is the delineation of landscape elements. We suggest that riparian and hillslope areas are the two most basic landscape elements that need to be considered; however, additional landscape elements including urban areas, floodplains, croplands, wetlands, and so on, can also be important. Landscape elements can be defined through hydrological analysis. This analysis can further define their lateral connections and organization along the stream network, providing valuable interpretation of the dominant controls on hydrological response across the landscape. Additionally, approaches to represent landscape elements in hydrological modeling are reviewed.
Modeling Recession Curves and Low Streamflows
Authors: Kroll Charles
Published: April 2006

Low streamflow events are critical periods for water quantity and water quality management purposes. During most low streamflow events, the stream is comprised solely of groundwater sources. This section focuses on both theoretical and empirical methods for modeling groundwater discharge to a stream and the resulting streamflow recession. A review is provided of solutions to the Boussinesq equation for hillslope discharge, and methods for determining when specific solutions may be most appropriate. In addition, how to estimate baseflow recession constants that aid in the modeling of groundwater discharge to streams, has been discussed. This involves the presentation of numerous methods to parameterize baseflow recession characteristics, how best to represent error in these models, and experiments that have been performed to determine the most appropriate methodology.
Hydrodynamic Considerations
Authors: Graf Walter H , Altinakar Mustafa S
Published: April 2006

The equations of continuity and of energy are developed for the general case. Subsequently, the specific energy, a concept useful for the understanding of different problems, is introduced.
Computer Modeling of Overbank Flows
Authors: Ervine Alan , Pender Gareth
Published: April 2006

Computational river models are in widespread use for estimating flood extent and the effectiveness of proposed flood mitigation schemes. This paper investigates the application of commonly used computational models to river floods, highlighting the advantages and shortcomings and current research activity. 1D, quasi‐2D, 2D, and 3D computational models are applied to simulate a large‐scale physical model tested in the Flood Channel Facility (FCF), Wallingford, as well as field data from the River Severn near Shrewsbury. The results reveal that commonly used 1D models give a reasonable representation of flood levels and flood extent but do not include floodplain/main channel interaction losses associated with compound flows and can be in error in their predictions. This deficit can be overcome in a straightforward manner by using a modified conveyance at each cross section based on the depth‐integrated turbulent form of the Navier–Stokes equation. This so‐called Lateral Distribution Method (LDM) has been incorporated into a new Conveyance Estimation System (CES) funded by the EA/Defra Joint Research Programme in Flood and Coastal Defence and developed by HR Wallingford Ltd for use with 1D models. Alternatively, 2D models can be more useful when simulation of flood inundation extent is important. The use of 3D models is becoming more common due to their ability to simulate very complex flow patterns over short river reaches. Initial results indicate that the choice of mesh discretization in a 3D model has a significant influence on the ability of the model to reproduce secondary velocity fields correctly. Problems of data requirements, friction and free surface representation still persist in 3D models in general.
Stochastic Modeling of Flow and Transport in Porous and Fractured Media
Authors: Ezzedine Souheil M
Published: April 2006

Estimation of various flow and mass transport parameters can be seen as a problem of spatial statistics. The definition of the properties of porous and fractured media in space and time using the concept of random functions provides means for (i) studying the inherent heterogeneity, (ii) evaluating the spatiotemporal variability of the properties, and (iii) assessing the uncertainty associated with their estimated values. In this chapter, the fundamentals of stochastic subsurface hydrology are presented. Applications include mapping hydrogeological properties, flow and transport in porous and fractured media, and inverse problems.
Unsaturated Zone Flow Processes
Authors: Nimmo John R
Published: April 2006

Water flow in the unsaturated zone is greatly influenced by unsaturated hydrostatics (water content, energy, pressure, and retention) and by unsaturated hydrodynamics (diffuse flow and preferential flow). Important multiphase processes include the transport of gases, nonaqueous liquids, and solid particles. Numerous means are available for determination of unsaturated conditions and properties, both measurement (of moisture state, water retention, and dynamic characteristics) and through various formulas and models that are mostly empirical in nature, but in some cases incorporating insight into unsaturated‐zone physical processes. Applications to practical problems include models and techniques relating to distributions of water and energy, fluxes at the land surface, inputs, outputs, and fluxes within the unsaturated zone, all of which are frequently complicated by heterogeneity and preferential flow. Further scientific advance requires new measurement techniques and theoretical constructs that more adequately represent the important physical processes within practical modeling schemes.
Modeling Glacier Hydrology
Authors: Hock Regine , Jansson Peter
Published: April 2006

Modeling glacier hydrology is essential for many aspects of glacier research and water resources planning. Model complexity has developed in parallel with our increasing understanding of the glacier system. Different models can be used depending on the purpose of the modeled results. Stochastic models constitute the first attempts to model glacier discharge. Use of such models has declined because they require extensive site‐specific calibrations and lack a conceptual basis, which makes them cumbersome to use. Conceptual models are the most widely used models for estimating discharge from glacierized basins. Commonly, the concept of linear reservoirs is applied to route melt and rain water through the glacier. Despite the wide variety of models of differing complexity, common to most conceptual models is that they omit many of the physical processes. Therefore attempts have been made to build physically based models that account for all processes in the glacier hydrological system. Because of the complexity of the modeled system and the wide variety of conditions on, in and under glaciers, the first models are relatively site‐specific. However, despite the inherent difficulties, they still yield good results. Physically based models will likely play an increasingly important role in glaciohydrological research while the conceptual models will continue to dominate the monitoring and forecasting modeling in applied hydrology because of their modest data requirements and ease of use.
Observations of the Global Water Cycle – Global Monitoring Networks
Authors: Lettenmaier Dennis P
Published: April 2006

Until the last few decades, in situ networks were the primary source of information for the estimation of the global water cycle. Such networks provide reasonably good climatological estimates of the major terms in the water cycle over the industrialized parts of the world, but are much less adequate in the lesser‐developed countries and in sparsely populated areas. Furthermore, in situ networks have been in the decline over the last several decades. An ongoing trend is toward greater reliance on satellite remote sensing. In some cases (e.g. soil moisture), satellite estimates have characteristics that cannot reasonably be matched by in situ networks. In others, it is less likely that the needs for global observations can be met from remote sensing. Furthermore, there will remain a need for high quality in situ data for algorithm testing and evaluation, and for evaluation of differences between historic in situ‐based, and satellite‐based, observations. The characteristics of in situ and satellite‐based estimates of the dominant fluxes and storages in the land surface and atmospheric branches of the global water cycle are reviewed.
Observations of the Global Water Cycle – Satellites
Authors: Robertson Franklin R
Published: April 2006

Satellite observations of Earth's climate system have evolved dramatically since the first crude video images of cloud cover taken over 40 years ago. Today, spaceborne measurements of precipitation, cloud attributes, radiative fluxes, and surface properties make crucial contributions to monitoring key processes and the evolving state of the planet's hydrologic cycle. We illustrate how this maturing capability has enabled study of the hydrologic cycle in a global context that goes beyond consideration of local or regional water balance. Remote sensing has become a key technology for addressing such interdisciplinary questions as whether the global hydrologic cycle is changing and if so how? What key processes linking the atmosphere, biosphere, and hydrosphere are at play, and what are the prospects for predicting extreme hydrologic events of significant societal impact? The discussion is motivated first by considering these key science problems. Following a brief overview of key remote sensing concepts, we then survey existing capabilities to determine various quantities such as precipitation, evaporation, soil moisture, turbulent fluxes, cloud cover, water vapor, and the links to radiative fluxes. Both successes and persisting challenges are discussed. An assessment of where we stand in developing an integrated picture of the hydrologic cycle and climate is presented, along with anticipated improvements in the future measurements.

In the context of climate, we demonstrate that in spite of substantial improvements in determining hydrologic variables and processes from space, some key challenges remain. Our examination here of signals in precipitation, evaporation, and radiative fluxes suggests that at present we can detect regional patterns of interannual variability with considerable skill; we can resolve globally integrated signals with only modest certainty; and for the most part, we have little confidence yet in decadal changes or trends. Nevertheless, the situation is encouraging because in many cases these retrievals have been done without regard to intercalibration of sensor data streams, and in the case of operational retrievals, algorithm modifications which result in spurious trends. Careful reprocessing is likely to yield substantial benefits. Future planned missions with active remote sensing at 94 GHz (CloudSat) and interferometric measurements at 1.4 GHz promise to expand our knowledge of hydrologic processes of crucial importance to climate.
Teleconnections in the Earth System
Authors: Chase Thomas N , Pielke Roger A , Avissar Roni
Published: April 2006

This article illustrates the large‐scale connectivity of the atmosphere–ocean coupled system and generalizes the concept to regional scales and to other components of the earth system. Connections at a distance, or teleconnections, can occur by the direct transfer of mass by changes in regular circulations or by propagating waves initiated by a variety of mechanisms. Questions as to what extent recognized teleconnection patterns can be associated with identifiable forcing mechanisms, to what extent these patterns are interrelated and how they might cause, react to, or interact with changing forcing such as changes in atmospheric composition, land cover, or the distribution of sea ice to produce climate changes are examined.
Public Participation in River Basin Planning and Management: Quality‐of‐Life Capital as an Information Aid to Sustainable Decisions
Authors: Newson Malcolm , Chalk Liz
Published: April 2006

The long‐term benefits conveyed by intact ecosystems to human development can be considered as an innate “natural” capital investment. A number of UK environmental management agencies have commissioned a practical realization of this concept, partly as a basis for public participation, successively titled “Environmental Capital” and “Quality of Life Capital”. Hydrological concepts are particularly appropriate to an evaluation of natural goods and services; intact natural systems provide flood and pollution controls which need costly artificial replacement when lost or damaged. There are obvious opportunities, therefore, to incorporate assessments of environmental capital as part of the public participation in river basin planning demanded by the European Water Framework Directive. This contribution examines the effectiveness of “Quality of Life Capital” as an information pool and decision‐support mechanism in two catchment‐scale initiatives (sponsored by the European Union), aimed at community involvement in integrated land and water management. Firstly the conceptual and practical justifications for considering river basins as “multistakeholder platforms” are reviewed, followed by a comparison of the two trial applications in the north of England – to the headwater catchments of the rivers Wharfe and Coquet. What emerges from the comparison and from evaluations of other integrated river basin and coastal zone projects is the importance of information (and its management), continuity and facilitation by project management and a lasting system of monitoring to support adaptive management. The spatial scale of most river basin units defined under the Water Framework Directive is possibly the biggest barrier to widespread adoption of the approach.
Observed Trends in Hydrologic Cycle Components
Authors: Lins Harry F
Published: April 2006

Documentation of change in the Earth's climate is accomplished by assessing the rates, magnitude, and distribution of changes in various elements of the climate system, such as the components of the hydrologic cycle. The present section reviews the general character of changes in precipitation, streamflow, and evaporation as determined using systematically collected data through the end of the twentieth century. Precipitation over global land areas increased about 2% during the century, and streamflow also exhibited widespread increases. There was good agreement regionally between the observed precipitation and streamflow increases. The precipitation increases appear to have occurred most commonly in higher intensity categories (>50 mm per day), while the streamflow increases were overwhelmingly observed in the low to moderate range of flows. No systematic increases were observed in peak streamflows. These findings indicate that a general intensification of the hydrologic cycle occurred during the twentieth century, but that this intensification did not result in increased hydrologic extremes.
Motor Unit
Authors: Enoka Roger M.
Published: April 2006

The activation signal sent by the nervous system to evoke a muscle contraction is discharged by motor neurons in the spinal cord and travels along a peripheral nerve to excite selected muscle fibers. On average, a muscle is innervated by a few hundred motor neurons and each motor neuron connects to several hundred muscle fibers. The functional control element is a single motor neuron and the muscle fibers it innervates, which is known as a motor unit, and all muscle contractions involve grading the amount of motor unit activity. The nervous system can vary muscle force by controlling the number of motor units that are activated and the rate at which each active motor unit discharges an activation signal. Despite considerable diversity in the properties of the both motor neurons and muscle fibers, the activation of a motor unit population proceeds in an orderly sequence from small to large and the discharge pattern of a motor neuron is matched to the mechanical properties of its muscle fibers.
Universal model for intracellular ice formation and its growth
Authors: Zhao Gang , Luo Dawei , Gao Dayong
Published: April 2006

The intracellular ice volume (IIV) term, Vice(c,T), is introduced into the classical water transport model developed by P. Mazur so that the modified model is capable of predicting cell volumetric change even after intracellular ice formation (IIF). By coupling the modified P. Mazur's model, ice nucleation, and the diffusion‐limited ice growth theory, the new model describing IIF and the growth of the intracellular ice (IIG) is developed based on J. O. M. Karlsson's work in 1994. The new model could be used to predict IIF, IIG, the final volumetric fraction of the intracellular ice, and the size distribution of the intracellular ice crystals. The major advantage of the new model is that it can provide reasonable intracellular information for both high cryoprotective agent (CPA) and low CPA concentrations without “Avrami correction”. The new model is then used to study the effect of cooling rate and initial CPA concentration on IIF and IIG. Three interesting phenomena, “hydration of salt ions (Na+ and Cl−)”, “crustaceous vitrification”, and “local vitrification” are presented, and their effects on IIF and IIG are studied in detail. It is found that all three of these factors have significant influences on the predicted critical cooling rate for the vitrification of the intracellular solution. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Bilateral periventricular heterotopias in an X‐linked dominant transmission in a family with two affected males
Authors: Gérard‐Blanluet Marion , Sheen Volney , Machinis Kalotina , Neal Jason , Apse Kira , Danan Claude , Sinico Martine , Brugières Pierre , Mage Katia , Ratsimbazafy Lanto , Elbez Annie , Janaud Jean‐Claude , Amselem Serge , Walsh Christopher , Encha‐Razavi Férechté
Published: April 2006

We report on the case of dizygotic twin boys, born prematurely to an asymptomatic mother. Bilateral periventricular heterotopias with enlarged ventricles were discovered at birth in both twins. One of the twins died prematurely of bronchopulmonary complications, and was shown to have several neuropathological anomalies (microgyria, thin corpus callosum, and reduced white matter). The surviving twin had mental retardation, without epilepsy. MRI of the mother showed asymptomatic periventricular heterotopias without ventricular enlargement. She had two affected daughters also with asymptomatic periventricular heterotopias. A point mutation in the last coding exon 48 of the Filamin A (FLNA) gene (7922c > t) was discovered on sequencing and segregated with the affected individuals. This family has a classical X‐linked dominant BPNH pathology, with greater severity in males than females. The location of the FLNA mutation is discussed in light of the neuropathological anomalies and mental retardation in male patients. © 2006 Wiley‐Liss, Inc.
FBN1, TGFBR1, and the Marfan‐craniosynostosis/mental retardation disorders revisited
Authors: Adès L.C. , Sullivan K. , Biggin A. , Haan E.A. , Brett M. , Holman K.J. , Dixon J. , Robertson S. , Holmes A.D. , Rogers J. , Bennetts B.
Published: April 2006

The recent identification of TGFBR2 mutations in Marfan syndrome II (MFSII) [Mizuguchi et al. (2004); Nat Genet 36:855–860] and of TGFBR1 and TGFBR2 mutations in Loeys–Dietz aortic aneurysm syndrome (LDS) [Loeys et al. (2005); Nat Genet 37:275–281] [OMIM 609192] has provided direct evidence of abnormal signaling in transforming growth factors β (TGF‐β) in the pathogenesis of Marfan syndrome (MFS). In light of this, we describe the phenotypes and genotypes of five individuals. Patient 1 had MFS and abnormal cranial dura. Patient 2 had severe early onset MFS and an abnormal skull. Patients 3 and 4 had probable Furlong syndrome (FS). Patient 5 had marfanoid (MD) features, mental retardation (MR), and a deletion of chromosome 15q21.1q21.3. All patients had a condition within the MFS, MD‐craniosynostosis (CS) or MD‐MR spectrum. The names of these entities may become redundant, and instead, come to be considered within the spectrum of TGF‐β signaling pathway disorders. Two recurrent heterozygous FBN1 mutations were found in Patients 1 and 2, and an identical novel heterozygous de novo TGFBR1 mutation was found in Patients 3 and 4, in whom altered fibrillin‐1 processing was demonstrated previously [Milewicz et al. (2000); Am J Hum Genet 67:279]. A heterozygous FBN1 deletion was found in Patient 5. These findings support the notion that perturbation of extracellular matrix homeostasis and/or remodeling caused by abnormal TGF‐β signaling is the core pathogenetic mechanism in MFS and related entities including the MD‐CS syndromes. © 2006 Wiley‐Liss, Inc.
Lack of meiotic crossovers during oogenesis in an apparent 45,X Ullrich–Turner syndrome patient with three children
Authors: Houge Gunnar , Boman Helge , Lybæk Helle , Ness Gro O. , Juliusson Petur B.
Published: April 2006

A woman with apparent 45,X Ullrich–Turner syndrome was ascertained after the birth of three girls, the last being growth retarded due to a del(X)(p22.11) of grand‐paternal origin. In this woman no del(X)‐chromosome was detectable in blood by FISH or PCR. Fibroblast cultures from four different biopsies of her skin varied from having 45,X only to mosaic 46,X,del(X) to 46,X,del(X) only. In one fibroblast culture, a few cells with two del(X) chromosomes were found, probably remnants of a paternal dicentric X that caused the condition. Her three daughters were born when she was 29, 31, and 39 years old, respectively, indicating that disomy for the distal half of Xp is not required for normal folliculogenesis. When studying the crossover pattern of her daughters' maternal X‐chromosomes, it turned out that one daughter had an X that was exclusively grand‐maternal, one daughter lacked crossovers on Xq, and one daughter lacked crossovers on Xp. This suggests that univalent X‐chromosomes were present in the Ullrich–Turner patient's primordial egg cells, either because there was only a single X‐chromosome present (a 45,X primary oocyte), or because the X‐chromosome was a partially or completely unpaired in pachytene, indicating a problem with chromosome association and synapsis formation. © 2006 Wiley‐Liss, Inc.
NO removal in continuous BioDeNOx reactors: Fe(II)EDTA2− regeneration, biomass growth, and EDTA degradation
Authors: van der Maas Peter , van den Brink Paula , Utomo Sudarno , Klapwijk Bram , Lens Piet
Published: April 2006

BioDeNOx is a novel technique for NOx removal from industrial flue gases. In principle, BioDeNOx is based on NO absorption into an aqueous Fe(II)EDTA2− solution combined with biological regeneration of that scrubber liquor in a bioreactor. The technical and economical feasibility of the BioDeNOx concept is strongly determined by high rate biological regeneration of the aqueous Fe(II)EDTA2− scrubber liquor and by EDTA degradation. This investigation deals with the Fe(II)EDTA2− regeneration capacity and EDTA degradation in a lab‐scale BioDeNOx reactor (10–20 mM Fe(II)EDTA2−, pH 7.2 ± 0.2, 55°C), treating an artificial flue gas (1.5 m3/h) containing 60–155 ppm NO and 3.5–3.9% O2. The results obtained show a contradiction between the optimal redox state of the aqueous FeEDTA solution for NO absorption and the biological regeneration. A low redox potential (below −150 mV vs. Ag/AgCl) is needed to obtain a maximal NO removal efficiency from the gas phase via Fe(II)EDTA2− absorption. Fe(III)EDTA− reduction was found to be too slow to keep all FeEDTA in the reduced state. Stimulation of Fe(III)EDTA− reduction via periodical sulfide additions (2 mM spikes twice a week for the conditions applied in this study) was found to be necessary to regenerate the Fe(II)EDTA2− scrubber liquor and to achieve stable operation at redox potentials below −150 mV (pH 7.2 ± 0.2). However, redox potentials of below −200 mV should be avoided since sulfide accumulation is unwanted because it is toxic for NO reduction. Very low values for biomass growth rate and yield, respectively, 0.043/d and 0.009 mg protein per mg ethanol, were observed. This might be due to substrate limitations, that is the electron acceptors NO and presumably polysulfide, or to physiological stress conditions induced by the EDTA rich medium or by radicals formed in the scrubber upon the oxidation of Fe(II)EDTA2− by oxygen present in the flue gas. Radicals possibly also induce EDTA degradation, which occurs at a substantial rate: 2.1 (±0.1) mM/d under the conditions investigated. © 2006 Wiley Periodicals, Inc.