bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sediment Yields and Sediment Budgets
Authors: Walling Desmond E 
Published: April 2006

Abstract
Measurements of sediment transport have been undertaken on many rivers throughout the world. Most of the available data relate to suspended sediment loads and the results provide a wealth of information on the variation of suspended sediment yields in both space and time. This contribution reviews current knowledge regarding land–ocean sediment transfer and sediment fluxes to the oceans, global patterns of sediment yield and their controls, and temporal variability of sediment yields in response to both natural controls and human activity and environmental change. In order to understand the sediment response of a drainage basin, it is important to take account of the complex linkages between sediment mobilisation and sediment output, and particularly the role of both short‐ and long‐term storage. The sediment budget provides a useful conceptual framework for this purpose and current understanding of the structure of catchment sediment budgets is reviewed.
Water Quality
Authors: Meybeck Michel , Peters Norman E , Chapman Deborah V 
Published: April 2006

Abstract
Water quality is the term used to describe the chemical, physical, and biological characteristics of water. Furthermore, the physical, chemical, and biological characteristics of a water body, “its water quality”, determine the suitability of that water for a particular value, for example, potability, ecosystem status, agriculture, industry, recreation. Water‐quality issues have become a rapidly evolving component of the environmental sciences primarily due to the increasing demand on water resources and amenity value and the intricate linkage between water‐quality use and ecosystem health. Water quality varies markedly in time and space. Episodic temporal water‐quality variations can occur in minutes whereas, periodic variations can occur on short timescales from diurnal, associated with variations in light and temperature, to seasonal and longer associated with climatic variations. Spatial variations also vary markedly from millimeters and centimeters in soil profiles to very large‐scale variations (>1000 km), for example, associated with water residence times, lithology, landscape position, land use, and bioclimatic zone. In the absence of the effects of human activities, water quality is primarily controlled by climate (precipitation and temperature) and geology (lithology, geomorphology, soil). The water quality of a given volume of water is derived from the sum of effects of mixing and interactions from all upstream sources including atmospheric deposition (precipitation and dry deposition), soil water (matrix and macropore), groundwater, springs, wetlands, irrigation ditches and canals, streams, ponds, lakes, reservoirs, rivers, and estuaries. In most parts of the world, human activities have now caused multiple and complex changes in background water quality.
Point and NonPoint Source Pollution
Authors: Loague Keith , Corwin Dennis L 
Published: April 2006

AbstractThe information age has ushered in a global awareness of complex environmental problems that do not respect political or physical boundaries: climatic change, ozone layer depletion, deforestation, desertification, and pollution from point and nonpoint sources. Among these global environmental problems, point and nonpoint source pollution represent a perfect example of a complex multidisciplinary problem that exists over multiple scales with tremendous spatial and temporal complexity. A point source of pollution discharges to the environment from an identifiable location, whereas a nonpoint source of pollution enters the environment from a widespread area. The ability to accurately assess present and future point and nonpoint source pollution impacts on ecosystems ranging from local to global scales provides a powerful tool for environmental stewardship and guiding future human activities.
Salinization
Authors: Ruprecht John , Dogramaci Shawan 
Published: April 2006

AbstractSalinization of land and water resources is a major environmental and economic problem facing many parts of the world. Soil salinization and the consequent degradation of agricultural land are proceeding so fast that many countries may not be able to achieve sustainable agriculture to feed their population in the foreseeable future. Furthermore, many important ecosystems and internationally recognized wetlands are under serious threat from the increased salinity.Salinization is the process by which the concentration of total dissolved solids in water or soil is increased because of natural or human‐induced processes.Many aspects of hydrological science underpin the understanding of salinization. The knowledge and understanding of the movement of water and salt from the atmosphere, through landscapes and rivers are essential to understanding salinization.The main approaches to assessing the impacts of land and water salinization and to evaluating potential solutions include process studies, catchment studies, modeling, and statistical analysis. Each of these is discussed in more detail in the article. A summary of the models available for salinity studies is also outlined.
Reservoirs
Authors: Marzolf G Richard , Robertson Dale M 
Published: April 2006

Abstract

Reservoirs are surface water impoundments that result from the construction of dams on streams and rivers. Limnological principles are applicable to understanding reservoir functions and the processes that control them because they exhibit lake‐like characters (see Lake Ecosystems –
Lake Ecosystems (Stratification and Seasonal Mixing Processes, Pelagic and Benthic Coupling)
. The basic water qualities of reservoirs are dependent, however, on the river that was impounded in their formation. The river's inflow dominates the upstream reaches of reservoirs. Lacustrine processes become more controlling as advective forces diminish and wind‐mixing and solar heating become influential forcing factors and as the cross section of the basin widens and deepens downstream. This transition from riverine to lacustrine imposes longitudinal gradients in reservoirs that emerge as their central feature. Designs of dams and their operating schedules have considerable influence on these in‐reservoir patterns and on the effects of the dam in the downstream river downstream. Various models have been developed to describe the physical, chemical, and biological processes in reservoirs. Additional studies will lead to further information to improve the models, which in turn will lead to a better understanding and management of reservoirs.
Paleolimnology and Paleohydrology
Authors: Fritz Sherilyn C , Saros Jasmine E 
Published: April 2006

AbstractThe study of the sedimentary record of nonmarine aquatic systems (paleolimnology) provides a tool for reconstructing the history of the basins themselves, as well as the history of the atmospheric and terrestrial systems that influence them. Such records allow us to understand environmental dynamics over periods longer than that of recorded history. Among inland aquatic systems, lakes have been studied more extensively; therefore, this review focuses on insights regarding environmental structure and function gained from studying lake sediments. Studies of the lacustrine paleolimnological record have been used to describe patterns of long‐term climatic variation and the response of lakes to changes in climate and catchment vegetation and soils. Although ecological literature from the early decades of the twentieth century suggested that lakes became enriched over time (eutrophic), eventually filling with sediment and becoming wetlands, it is now clear that there are multiple developmental pathways for lakes. Some lakes indeed become enriched, whereas others show a long‐term decline in nutrient concentrations and pH. Similarly, succession from lake to bog or wetland is not a universal trend. Paleolimnological studies also have been used to reconstruct the recent history of eutrophication, lake acidification, and atmospheric pollution. In these studies, the history archived in lake sediments provides a tool for measuring the magnitude of human impacts on the environment and for evaluating whether twentieth century patterns fall outside the natural range of environmental variation.
Hyporheic Exchange Flows
Authors: Bencala Kenneth E 
Published: April 2006

AbstractWater having entered a stream channel from the surrounding catchment may continue to have connections with the catchment. In the stream's hyporheic zone, water “in the channel” exchanges with “groundwater” in the bed of the stream. Hyporheic exchange flows typically occur at scales small relative to the length and volumetric transport characteristics of the stream. Nevertheless, it is well documented that hyporheic exchange flows significantly influence nutrient dynamics. Additionally, there is evidence of hyporheic exchange flows similarly influencing the processes establishing the concentrations of major‐ions and metals in stream‐catchment systems. It is within the contexts of (i) solute transport and (ii) the continuing connections of streams to their catchments that the hydrologic aspects of hyporheic exchange flows are studied. The Transient Storage Model (TSM), a pseudo‐two‐dimensional representation of stream and hyporheic zone solute transport, is used to identify characteristics of hyporheic zone, physical size, and solute residence times. The TSM is further extended to simulations of reactive solute transport to understand and interpret the biogeochemical processes of streams influencing the solute dynamics of catchments. Active hydrologic research continues to advance the process basis from which quantitative assessments of the role of hyporheic exchange flows will be made.
Snowmelt Runoff Generation
Authors: Woo Ming‐Ko 
Published: April 2006

AbstractSnowmelt runoff has major influence on water supply and hazards for many temperate and polar regions. The magnitude and timing of runoff depend on the processes of snow accumulation and melt, which are controlled by factors that include latitude, topography, and land use. The amount of runoff production is affected by meltwater loss to evaporation and infiltration, the latter is often limited by frozen soil conditions. Runoff is delivered as flow in the snow, overland flow on bare ground, channeled flow in rills and interhummock cracks, or as subsurface flow in organic soils. The flow may be modified by the presence of snow or river ice in the channels, which often causes runoff delay and amplification of peak flows. Streamflow hydrographs for small basins typically show diurnal cycles with high discharge during warm days and declines in the cool and terminating periods of snowmelt. Hydrographs of large basins are an integration of the runoff patterns of their subbasins. In terms of snow management, the control of snowmelt floods is a consideration, yet many arid regions look to snowmelt runoff as a source of water supply.
Intersite Comparisons of Rainfall‐Runoff Processes
Authors: Jones Julia 
Published: April 2006

AbstractThis article argues that despite the limitations of rainfall‐runoff data, there are compelling reasons for hydrologists to conduct many more intersite comparisons of rainfall‐runoff data. Inferences about hydrologic processes are drawn from an unnecessarily narrow subset of temporal scales, spatial scales, and geographic conditions given the range of data available. In intersite comparison of rainfall‐runoff data, we face the same challenge as hydrologic modelers, namely: how can we discriminate among alternative mechanistic explanations for any given rainfall‐runoff (or runoff‐runoff) dataset? This article (1) provides a justification for additional intersite comparisons given the history and lessons learned from rainfall‐runoff and related studies, (2) demonstrates how intersite comparison helps discriminate among alternative hydrologic mechanisms, and (3) outlines steps involved in conducting intersite comparative analysis with a particular focus on analysis of primary data. The article argues that the best approach to intersite hydrology is (re)analysis of original data, which allows us to (1) expand the sample size to include data not yet analyzed and replicate hypothesis tests; (2) ask new questions, even of old data, posed by the current context for hydrology; (3) make new comparisons among records not formerly juxtaposed; (4) use novel statistical approaches to reveal hitherto obscure features of the data, and (5) use ancillary data to refine hypothesis tests about hydrologic mechanisms. The article provides suggestions for the steps involved in intersite comparison including (!) identifying a question, (2) developing a study design, (3) selecting, accessing, and merging datasets, and (4) choosing statistics for comparison of rainfall and runoff data. The endeavor of intersite comparison of rainfall and runoff data is analogous and complementary to the parallel quest for methods of parameter identification and model structure selection in hydrologic modeling.
Rainfall‐Runoff Modeling: Introduction
Authors: Beven Keith J 
Published: April 2006

Abstract
This section provides an introduction to the theme of rainfall‐runoff modeling in hydrology. It provides a summary of the purposes of rainfall‐runoff modeling; a classification of rainfall‐runoff models; a brief account of process descriptions in rainfall‐runoff models; and a short history of rainfall‐runoff modeling. It also discusses the problem of model choice from the wide range of possibilities available, and the important question of model calibration using different types of observational data before considering the prediction of the effects of future change (when no observations are possible). Finally, a guide is given to the future of rainfall‐runoff modeling. Reference to the other sections in this article are given throughout, as well as to relevant available texts.
Rainfall‐Runoff Modeling: Distributed Models
Authors: Reggiani Paolo , Schellekens Jaap 
Published: April 2006

AbstractThe present article presents a discussion of distributed modeling used in watershed hydrology from a modern perspective. The need for distributed modeling is explained on the basis of situations encountered in hydrological practice. The basic equations governing water and energy transfer in hydrology are introduced at the point‐ or microscale. It is explained how these equations are used in the different approaches through change in spatial scale from the microscale to an intermediate scale, the macroscale, or the megascale, which corresponds to the spatial dimension of some smaller or larger parts of the catchments. The strengths and limitations that have been recognized for the various approaches will be pointed out. As a possible alternative a flux‐based approach, formulated entirely at the megascale, is highlighted. Its potential scope for practical applications will be discussed in the context of the closure problem for mass momentum and energy fluxes in hydrology.
Model Calibration and Uncertainty Estimation
Authors: Gupta Hoshin V , Beven Keith J , Wagener Thorsten 
Published: April 2006

AbstractAll rainfall‐runoff models are, by definition, simplifications of the real‐world system under investigation. The model components are aggregated descriptions of real‐world hydrologic processes. One consequence of this is that the model parameters often do not represent directly measurable entities, but must be estimated using measurements of the system response through a process known as model calibration. The objective of this calibration process is to obtain a model with the following characteristics: (i) the input‐state‐output behavior of the model is consistent with the measurements of catchment behavior, (ii) the model predictions are accurate (i.e. they have negligible bias) and precise (i.e. the prediction uncertainty is relatively small), and (iii) the model structure and behavior are consistent with current hydrologic understanding of reality. This article describes the historic development leading to current views on model calibration, and the algorithms and techniques that have been developed for estimating parameters, thereby enabling the model to mimic the behavior of the hydrologic system. Manual techniques as well as automatic algorithms are addressed. The automatic approaches range from purely random techniques, to local and global search algorithms. An overview of multiobjective and recursive algorithms is also presented. Although it would be desirable to reduce the total output prediction error to zero (i.e. the difference between observed and simulated system behavior) this is generally impossible owing to the unavoidable uncertainties inherent in any rainfall‐runoff modeling procedure. These uncertainties stem mainly from the inability of calibration procedures to uniquely identify a single optimal parameter set, from measurement errors associated with the system input and output, and from model structural errors arising from the aggregation of real‐world processes into a mathematical model. Some commonly used approaches to estimate these uncertainties and their impacts on the model predictions are discussed. The article ends with a brief discussion about the current status of calibration and how well we are able to represent the effects of uncertainty in the modeling process, and some potential directions.
Rainfall‐Runoff Modeling for Assessing Impacts of Climate and Land Use Change
Authors: Bronstert Axel 
Published: April 2006

Abstract
Rainfall‐runoff models are frequently used as a tool to assess the impacts of climate and land‐use changes on the hydrological cycle. This requires that the applied rainfall‐runoff model is able to represent the dynamics of the hydrological cycle of the catchment under study, in particular, if land‐use change is of concern, that is, the effects of land‐use or land‐cover change on the runoff generating processes. This may be accomplished by applying either a process‐based model or a conceptual model if the latter's parameters can be regionalized with respect to land‐use change. Furthermore, the chosen model must be able to “represent” the influence of different climatic/ meteorological boundary conditions. This implies, of course, that we know the main dynamics of the catchment under consideration.
Rainfall‐Runoff Modeling of Ungauged Catchments
Authors: Blöschl Günter 
Published: April 2006

Abstract
Catchments where no runoff data are available are termed ungauged catchments. For these catchments, the parameters of rainfall‐runoff models cannot be obtained by the calibration on runoff data and hence need to be obtained by other methods. Model parameters that require calibration are usually transposed from similar gauged catchments. This article reviews concepts for identifying hydrologic similarity as well as methods for transposing the parameters of both event models and explicit soil moisture accounting (ESMA) models. Model parameters that are physically based are usually measured or inferred from other data within the ungauged catchment of interest. This article summarizes the most important methods and discusses the issues of using point scale field data in rainfall‐runoff models. Alternatives to runoff data for model calibration are suggested. The value of soft data and qualitative field observations is emphasized.
Downward Approach to Hydrological Model Development
Authors: Sivapalan Murugesu , Young Peter C 
Published: April 2006

AbstractThis article presents the top‐down or downward approach to hydrological model development as an alternative to the bottom‐up, reductionist approach, which is the current, dominant paradigm in the hydrological sciences. It discusses the philosophical underpinnings as well as the pros and cons of each approach, and illustrates the application of the downward approach through several examples. These examples variously emphasize three key elements in the application of the downward approach. First, the analysis of identifiable “signatures” or “features” in the available data including the definition of a generic model form that can accommodate these features; second, model development including model structure identification and parameter estimation; and last, model refinement or “fingering down” (Klemes, 1983; Jarvis, 1993), in which the model is improved by the use of additional information or by adding more causal factors. Two main approaches to downward modeling are identified and discussed: the classical stochastic systems approach and the deterministic, conceptual modeling approach. The advantages of the downward approach are highlighted, particularly as they relate to the development of models that have sufficient causal basis to make predictions in basins other than those on which the model was developed.
Transport of Sediments
Authors: Graf Walter H , Altinakar Mustafa S 
Published: April 2006

Abstract
A channel bed, made up of a granular material, is usually of a form which varies in space and time. The movement of the sediments, which make up the bed, represents a rather complex phenomenon. The hydrodynamic equations of the flow over a mobile bed are developed. The different modes of the transport of (noncohesive) sediments as bed load and as suspended load are presented. The formulae for the calculations of the transport of the total load are exposed, as well as their domain of application.
Mountain Streams
Authors: Armanini Aronne 
Published: April 2006

AbstractThis paper illustrates the main features of the hydraulics of mountain streams. The effects of small submergence and riverbed steepness on sediment motion initiation and transport are discussed together with the effect of big roughness elements and pool‐riffle and step‐pool sequences on velocity distribution and flow resistance. Finally, the most used torrent defense techniques are described.
Regulated Lowland Rivers
Authors: de Vriend Huib J 
Published: April 2006

Abstract
The article describes flow, sediment transport, and morphological processes in regulated lowland rivers and the impact of human activities thereon. It gives some elementary examples of the morphological response to deviations from a prismatic straight channel, in an attempt to bridge part of the gap between textbook knowledge and reality. Moreover, it shows that even a regulated river is still to some extent natural, thus variable and unpredictable.
Hydraulics of Wells and Well Testing
Authors: Renard Philippe 
Published: April 2006

AbstractWell testing and well hydraulics play a major role in applied hydrogeology. While well hydraulics aims at modeling the groundwater behavior in response to a perturbation – such as pumping – in a well, well testing aims at using these models in an inverse approach to infer the properties of the aquifer or of the well itself. The history of well hydraulics and well testing started in 1863 with Dupuit, who developed the first analytical solution to model radial flow to a well in steady state. In 1935, Theis published the most important analytical solution. The Theis solution assumes that the aquifer is confined, bidimensional, homogeneous, and isotropic. Subsequently, numerous models have been developed with the aim to enlarge the domain of applications. This article presents a brief review of these various models and describes their behavior in terms of drawdown and log derivative of the drawdown. The log derivative is used as a tool to help in the identification of the most appropriate model when analyzing field data.