bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aquifer Recharge
Authors: Nimmo John R , Healy Richard W , Stonestrom David A 
Published: April 2006

AbstractAquifer recharge is important both for hydrologic understanding and for effective water resource management. Temporal and spatial patterns of unsaturated‐zone processes such as infiltration largely determine its magnitude. Many techniques of recharge estimation exist. Water budget methods estimate all terms in the continuity equation except recharge, which is calculated as the residual. Detailed hydrologic models based on water‐budget principles can produce recharge estimates at various scales. Empirical methods relate recharge to meteorologic and geographic parameters for a specific location. Surface‐water methods include stream‐hydrograph analyses to estimate baseflow (groundwater discharge) at lower elevations in a watershed, which is taken to equal the recharge that has occurred at higher elevations. Subsurface methods include analysis of water‐table fluctuations following transient recharge events, as well as diverse unsaturated‐zone methods. The zero‐flux plane method determines the recharge rate from the change in water storage beneath the zero‐flux depth, a boundary between water moving upwards due to evapotranspiration and water moving downward due to gravity. Lysimeter methods use buried containers filled with vegetated soil to mimic natural conditions. Water exiting the bottom is considered to be recharge. Darcian methods for estimating flux densities use unsaturated hydraulic conductivities and potential gradients, indicating recharge rates under appropriate conditions. Chemical mass‐balance methods use conservative tracers that move with recharging water. Tracer concentrations in deep unsaturated‐zone water, together with tracer input rates, indicate recharge rates. Distinct chemical “markers” can indicate travel times, hence, recharge rates. Thermal methods use heat as a tracer. Moving water perturbs temperature profiles, allowing recharge estimation. Geophysical methods estimate recharge based on water‐content dependence of gravitational, seismic, and electromagnetic properties of earth materials.
Snow Cover
Authors: Brown Ross D , Goodison Barry E 
Published: April 2006

AbstractSnow cover is encountered over most of the Northern Hemisphere (NH) mid‐ and high‐latitudes during the winter season and over many mountainous regions of the world for extended periods. Snow cover is an important component of the climate system through its role in modifying energy and moisture fluxes between the surface and the atmosphere, and through its role as a water store in hydrological systems. Snow also plays critical roles in ecological and biological systems, and in nutrient and carbon cycling. This article provides an introductory overview of snow cover including: definition of terms (snowfall, solid precipitation, snow depth, snow density, snow water equivalent); a review of methods for measuring snow cover properties; a discussion of the processes and concepts involved in the spatial and temporal variability of snow cover; a look at avalanches and recent efforts to model these; and finally, a discussion of how snow cover is changing in response to global warming.
Water Flow through Snow and Firn
Authors: Marsh Philip 
Published: April 2006

Abstract
Water flux through snow and firn has important implications for the timing and magnitude of runoff from seasonal snowpacks, glaciers, and ice caps. Studies conducted over the last few decades have greatly improved our understanding of water flux through snow and firn, including knowledge of the development of wetting fronts as meltwater enters dry snow, preferential flow paths, grain growth of wet snow, and the growth of ice layers and ice columns within the snowpack. Such studies have resulted in the development of a variety of analytical and numerical models for calculating runoff from melting snow and firn. Although our understanding of key processes continues to increase, there are major gaps in our knowledge that limit our ability to formulate comprehensive physically based models of snow metamorphism and water flux through snow and firn. Part of the problem is a lack of data, which is due to the great difficulty of conducting experiments on snow near 0°C and our inability to measure the properties of snow required for estimating the value of parameters needed for numerical simulations. In order to overcome these problems, there is a need for the development of new measurement techniques and carefully designed field and laboratory experiments. Comprehensive models are required for predicting not only melt runoff, but also the release of pollutants from the snowcover, the large‐scale properties of the snowcover necessary for understanding large‐scale energy‐balance and global‐change problems, and the release of meltwater from cold glaciers and icecaps under future climate scenarios.
Hydrochemical Processes in Snow‐Covered Basins
Authors: Pomeroy John W , Jones H Gerald , Tranter Martyn , Lilbæk Gro 
Published: April 2006

Abstract
This article reviews several aspects of snow hydrochemistry: the chemistry of snowfall including chemical incorporation in snowfall and snowfall chemistry variability, the chemistry of cold, dry snowcovers including snow redistribution, snow–atmosphere chemical exchange and in‐pack chemical transformations, the chemistry of wet and melting snowcovers including solute leaching, particulate interactions and microbial activity, and snow‐covered basin hydrochemistry with an emphasis on nutrient chemistry. The emphasis is on the processes of chemical transformation in seasonal snowpacks and meltwaters with strong attention to the broad ecosystem view of snow chemistry rather than solely focusing on acidification effects from snowmelt. The seasonal snowcover is shown to be a dynamic hydrochemical system with strong ecological interactions. Besides wet deposition by snowfall and rain, the processes of wind redistribution, dry deposition, volatilization, crystal metamorphism, photolysis, microbial uptake and release, solute elution, and meltwater movement strongly affect the chemistry of both the snowpack and meltwaters. Snowmelt chemistry alone is rarely directly responsible for major chemical fluctuations in water bodies, but meltwater has an important role in transporting ions from soils and organic material to water bodies.
Subglacial Drainage
Authors: Sharp Martin 
Published: April 2006

AbstractSubglacial drainage can occur wherever ice at a glacier bed reaches the pressure melting point. The subglacial drainage system is fed from a mixture of surface, englacial, subglacial, and groundwater sources that differ in terms of their spatial distribution and characteristic patterns of temporal variability. Subglacial drainage systems are not readily accessible, and knowledge of their characteristics is derived from a range of indirect methods including radio‐echo sounding, the use of artificial tracers, monitoring, and manipulation of subglacial conditions via boreholes, and monitoring of glacial runoff properties. Subglacial water flow is driven by gradients in hydraulic potential, and occurs through either fast/channelized or slow/distributed systems located at the ice‐bed interface, or through subglacial aquifers. Water can be stored subglacially in cavities, in the pore space of subglacial sediments, or in subglacial lakes. Drainage system structure evolves continually on various timescales in response to changing water inputs, evolving glacier geometry, and changes in glacier flow dynamics. Major hydrological events in such systems include the spring and fall transitions, outburst floods, and structural changes related to glacier advances and glacier surging. In the absence of variable water inputs from the glacier surface, subglacial drainage systems may be sensitive to forcing by earth, ocean, and atmospheric tides.
River‐Ice Hydrology
Authors: Prowse Terry D 
Published: April 2006

AbstractThe hydrology of almost 60% of rivers in the Northern Hemisphere is affected by ice for at least a portion of the winter. At the higher latitudes, river ice is the major controller of most fluvial processes. Although traditionally the pursuit of hydraulic engineers, hydrologic studies of river ice have broadened greatly over the last decade. Initially, this was driven by recognition that many hydrologic extremes produced by river ice, such as floods and low flows, exceed those of the more intensively studied, open‐water period. Added recognition that river ice strongly influenced other fluvial disciplines, such as geomorphology and aquatic ecology, increased its scientific visibility. This manuscript reviews the basic physics of river ice; evaluates its effect on various hydrologic processes and events from freeze‐up to breakup; and discusses its extended role in affecting sediment transport/erosion, river morphology and a number of key ecological processes including geochemical mixing and habitat modification. Arguments are made for increased focus on river‐ice hydrology given its significance to physical and ecological processes, and the growing need to understand the effects of climate change and flow regulation on cold regions rivers.
Global Water Cycle (Fundamental, Theory, Mechanisms)
Authors: Pagano Thomas C , Sorooshian Soroosh 
Published: April 2006

Abstract
Water cycle is the never‐ending movement of water on Earth. Water continuously cycles through various reservoirs in the ocean, sky, and soil. A variety of measurement systems are necessary to quantify the fluxes between reservoirs, ranging from simple buckets to measure rainfall to sophisticated satellites orbiting the Earth. The hydrologic cycle is mainly characterized by its variability in space and time. The Earth contains an incredible diversity in climates, including rainforests, parched deserts and frozen tundra. Water cycle at any given location changes both rapidly and slowly, with the passing of flash floods to the decadal shifts in ocean patterns. Anticipated impacts of human‐induced climate change on the hydrologic cycle are as yet unknown, but the consequences are potentially severe. Nonetheless, humans have a long history of altering the hydrologic cycle including the diversion and impoundment of streamflow, pumping of groundwater, irrigation of fields and management of forests. While the water cycle has been recognized for ages, many interesting fundamental research questions remain.
The Role of Large‐Scale Field Experiments in Water and Energy Balance Studies
Authors: Shuttleworth W James , Gash John HC 
Published: April 2006

AbstractOver the last two decades, increased awareness of the potential importance of anthropogenic drivers of “global change” and growing interest in predicting climate variability at seasonal to interannual timescales has stimulated the development of new experimental techniques and new modeling methods to upscale conventional observations of land‐surface exchanges to area scales consistent with the grid scales used in General Circulation Models, and large‐scale experiments in important global biomes that had previously been neglected. The nature, purpose, and scale of such large‐scale field experiments, many fostered by international programs such as the World Climate Research Programme (WCRP) and the International Geosphere‐Biosphere Programme (IGBP), has evolved with time. Initial studies focused on exploring the value of remotely sensed data when upscaling or provided data at several sites that sampled the most important vegetation covers across large biomes. One important class of experiments, the Mesoscale Field Experiments, laid emphasis on gathering data over an area comparable with that of a Global Circulation Model (GCM) grid square and explored the nature and significance of mesoscale coupling between the land surface and the overlying atmosphere and, in particular, the response of the atmosphere to heterogeneity in vegetation cover. Subsequently, the spatial scale of studies increased in a suite of Continental‐Scale Experiments (CSEs) which explored the extent to which the atmospheric component of energy and water budgets can be reconciled with the equivalent surface budgets, fostered improvement in the performance of the regional scale–coupled hydrometeorological models, and investigated “land memory” processes that operate at regional scale and at the seasonal timescales. Recently the emphasis has been on seeking to link several CSEs together in a Coordinated Enhanced Observing Period (CEOP) using satellite systems to provide observations at the global scale. This article describes the evolving purpose and developing nature of large‐scale field experiments over the period 1984–2004 and their role in providing improved knowledge and modeling of land‐surface energy exchanges.
Modeling of the Global Water Cycle: Numerical Models (General Circulation Models)
Authors: Koster Randal D 
Published: April 2006

AbstractAtmospheric general circulation models (AGCMs) are powerful tools for exploring climate sensitivity and the global water cycle. The wealth of data provided by an AGCM allows a complete statistical characterization of its water cycle, a far more complete picture than would be allowed from real‐world observations. AGCM numerical experiments have been used to isolate the mechanisms that control water cycle variability, illustrate the potential for water cycle prediction, and quantify water cycle changes resulting from human activities. The AGCM fields can also be merged with observations (via data assimilation) to provide the best estimates possible of the true water cycle. Unfortunately, biases in simulated fields resulting from coarse resolution and inadequate physical parameterizations continue to plague AGCMs, forcing climate modelers to temper their faith in the models' results.
Long‐Term Predictions (Climate Simulation and Analysis)
Authors: Betts Richard A 
Published: April 2006

AbstractThe global hydrological cycle is expected to change over the next century as a consequence of human perturbations to the Earth System. Human activities are modifying the composition of the atmosphere, in particular the concentrations of greenhouse gases such as CO2and the concentrations of aerosols. This exerts a radiative forcing of the climate system, which already appears to be warming the global climate. These changes are predicted to increase in the future, and are expected to modify precipitation and evaporation regimes, and hence impact on hydrology, with streamflow increasing in some regions and decreasing in others. Furthermore, changes in atmospheric composition may also affect ecosystems directly, with plant physiological responses to CO2increasing carbon storage, modifying biogeography, and decreasing evapotranspiration. This may have further effects on hydrology in addition to climate change. Human‐induced changes in land cover, such as deforestation and afforestation, may also directly modify hydrology and climate by perturbing the surface water and energy budgets as well as by contributing to radiatively‐forced climate change through changes in atmospheric composition. This article compares and contrasts the climatic, ecological, and hydrological changes predicted as a result of these three human perturbations to the Earth System, and discusses the key interactions between them.
The Hydrological Cycle in Atmospheric Reanalysis
Authors: Beljaars Anton , Andrae Ulf , Kallberg Per , Simmons Adrian , Uppala Sakari , Viterbo Pedro 
Published: April 2006

AbstractAtmospheric (re‐)analysis is a powerful tool to create data sets that provide a good description of the atmosphere including the hydrological cycle. Atmospheric analysis systems use a numerical weather prediction model to propagate the state of the atmosphere in time. Observations, which are irregular in space and time, are inserted into the system in such a way that an optimal blend is obtained between the background fields (forecast from e.g. 6 hours before) and the observations. Observations range from traditional surface observations and radiosondes, to commercial aircraft observations, cloud track winds from satellites and profiling measurements from infrared and microwave instruments in space. Re‐analyses are performed to benefit from the most recent model improvements, data assimilation improvements and increased computer power and to obtain a time series that does not suffer from system changes as in operational numerical weather prediction. Current re‐analyses have a spatial resolution of the order of 1 degree with a temporal sampling interval of 3 to 6 hours. Re‐analysis products have the advantage of being projected on a global numerical grid and have no gaps.The ECMWF 40‐year Re‐Analysis is described as an example. Its realism is discussed by comparing with observations of precipitation, vertically integrated water vapor, moisture convergence and surface fluxes over land and ocean. It is concluded that re‐analysis products are very useful to study the hydrological cycle in the atmosphere. The synoptic variability is particularly good although biases may exist in some of the parameters.
Integrated Land and Water Resources Management
Authors: Calder Ian R 
Published: April 2006

Abstract
The need for Integrated Land and Water Resources Management (ILWRM), to meet and balance competing demands for food, timber and water, for conservation, amenity, recreation and the environment and for supporting people's livelihoods, is discussed. The principles of ILWRM including notions of sustainability, approaches to the economic valuation of land and water and demand management, are outlined. Also discussed are the differing public and science perceptions of the impacts of land use change, the interactions between land use, climate change, and water resources and how ILWRM can be implemented with stakeholder involvement.
Land Use Impacts on Water Resources – Science, Social and Political Factors
Authors: Forsyth Tim 
Published: April 2006

Abstract
Public perceptions of land‐use impacts on water resources are important because they influence formal environmental policies and popular attitudes about land use. For example, upland agriculture and deforestation are commonly blamed for reducing rainfall levels and for causing lowland water shortages, and some governments have consequently passed logging bans or restrictions on upland agriculture. However, there is intense controversy concerning whether these public perceptions are supported by scientific evidence; whether these policies may actually address underlying problems; and how far hydrological science is itself influenced by social and political factors. This article draws upon debates in social science (rather than hydrological science alone) to discuss linkages between public perceptions and scientific explanations of hydrological change. As examples, the article discusses the cases of so‐called Himalayan environmental degradation; dryland desiccation in the Sahel; and debates concerning the impacts of deforestation and reforestation in watersheds. The article argues that hydrologists should not categorize public perceptions and formal science separately, but see both as mutually evolving. Dominant perceptions, or “narratives”, of hydrological change may occur from various coincidences of historical research and public concern, and reflect the viewpoints and experiences of only selected social groups. It is suggested that hydrologists can help overcome apparent conflicts between public perceptions and scientific explanations by increasing public participation in describing and framing complex environmental problems, and using this information to make existing narratives more diverse and flexible. There is also a need to understand the political and institutional factors that lead to the persistence of contested narratives within different national or organizational contexts.
Environmental Flows: Managing Hydrological Environments
Authors: Gippel Christopher J 
Published: April 2006

AbstractEnvironmental flows refer to the facets of natural flow regimes that are required to sustain riparian and aquatic life in a healthy condition, plus provide for the needs of those human uses that rely on, and do not compromise, stream health values. Environmental flow assessments are required for regulated rivers, where the flow regime has been modified, or flow volumes significantly reduced. The methodological trend has been from narrow studies that catered for a single fish species at one critical life phase to a holistic approach that aims to restore natural river processes. Consideration has also been given to the specific issues of flood flows required for wetland inundation and channel formation, needs of groundwater‐dependent ecosystems, the needs of estuarine ecosystems, and flows required for recreational activities. Holistic methodologies are particularly appropriate in developing countries with strong livelihood dependencies on the goods and services provided by aquatic ecosystems. The number of studies worldwide that report environmental flow recommendations greatly outweighs the number of studies that report scientific evaluation of the results of implementation of these recommendations. However, where implemented environmental flow regimes have been monitored, the results have generally been positive.
Inter‐Institutional Links in Land and Water Management
Authors: Amezaga Jaime M 
Published: April 2006

Abstract
This article reviews the institutional aspects of Integrated Land and Water Resources Management. It explores the definition of what constitutes an institution in the land and water sector and presents several approaches to institutional analysis applicable in this context. It examines land and water interinstitutional linkages at several levels: international, national, river basin, and upstream/downstream. For each of these levels, theoretical approaches and examples are discussed. While institutional constraints such as cross‐sectoral coordination and the conflict between different land‐based administrative structures are still common, there are an increasing number of instruments applicable to this problem at all levels. Ensuring basic human needs and rights associated with water and land and establishing institutional systems to benefit disadvantaged people and improve livelihoods remain the greatest challenges to integrated management.
The Role of Water Vapor and Clouds in the Climate System
Authors: Stephens Grahame 
Published: April 2006

Abstract
The exchanges of water between the different water reservoirs on Earth establishes the so‐called hydrological cycle. The influence of this cycle on the energy budget of Earth is central to understanding and predicting climate change. In fact, those processes that characterize the smallest of the water reservoirs ‐ namely the atmospheric branch of the hydrological cycle ‐ play an especially critical role in regulating climate change through feedbacks processes. Two key feedback processes are described. The first deals with the feedback associated with the relation between water vapor, radiation and temperature and the second concerns feedbacks associated with clouds and radiation.
Role and Importance of Paleohydrology in the Study of Climate Change and Variability
Authors: Ekwurzel Brenda 
Published: April 2006

AbstractPaleohydrology has advanced our understanding of climate by uncovering the variability of the prehistoric water cycle. Various proxy records provide insight into aspects of the hydrologic cycle that occurred before the instrumental record and allow for paleoclimate reconstructions locally or over large regions. For example, geomorphologic methods can quantify megafloods; coral or sediment core methods create paleodischarge records; rodent middens archive changes in precipitation volume and temperature; closed‐basin lake level fluctuations offer quantitative evidence of changes in water balance, and tree‐rings provide a high‐resolution archive of precipitation or drought. This article reviews representative examples from the field of paleohydrology and demonstrates the role each has played in enhancing our understanding of climate variability.