Download or read book Variability of Parameters for Modelling Soil Moisture Conditions written by Jan A. van den Berg and published by . This book was released on 1989 with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Variability of Parameters for Modelling Soil Moisture Conditions written by Jan A. van den Berg and published by . This book was released on 1989 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: The research mainly concerned loamy and silty soils in the Ardèche drainage basin.
Download or read book Extreme Hydrology and Climate Variability written by Assefa M. Melesse and published by Elsevier. This book was released on 2019-07-03 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt: Extreme Hydrology and Climate Variability: Monitoring, Modelling, Adaptation and Mitigation is a compilation of contributions by experts from around the world who discuss extreme hydrology topics, from monitoring, to modeling and management. With extreme climatic and hydrologic events becoming so frequent, this book is a critical source, adding knowledge to the science of extreme hydrology. Topics covered include hydrometeorology monitoring, climate variability and trends, hydrological variability and trends, landscape dynamics, droughts, flood processes, and extreme events management, adaptation and mitigation. Each of the book's chapters provide background and theoretical foundations followed by approaches used and results of the applied studies. This book will be highly used by water resource managers and extreme event researchers who are interested in understanding the processes and teleconnectivity of large-scale climate dynamics and extreme events, predictability, simulation and intervention measures. Presents datasets used and methods followed to support the findings included, allowing readers to follow these steps in their own research Provides variable methodological approaches, thus giving the reader multiple hydrological modeling information to use in their work Includes a variety of case studies, thus making the context of the book relatable to everyday working situations for those studying extreme hydrology Discusses extreme event management, including adaption and mitigation
Download or read book Spatial Variability of Two Different Soil Moisture Regimes written by Charles P. Maule and published by . This book was released on 1984 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Optimization of land management for water conservation, soil salinity and erosion control requires a through understanding of the soil water balance. The adequate design of any water balance study requires that the precision and the spatial variability of the soil parameters be known. The objectives of this study were to quantify the soil water balance components and to determine the precision and spatial variability of soil moisture and related soil properties. The study was conducted during 1983 at the Ellerslie Research Station near Edmonton, Alberta. Soil moisture was measured with a neutron probe at 42 locations, 6.1 m apart, arranged in a six by seven grid. Fallow plots were alternated with barley plots resulting in three replicates of each. Particle size analysis, bulk density, and the moisture characteristic curve were determined at several depths at each location. Due to dry conditions in May and June the barley did not germinate until late June. Heavy rains during late June and early July resulted in near saturated conditions and in a perched water table within 1 m of the surface. Dry, warm weather for the remainder of the growing season resulted in vigorous barley growth. Precipitation for the study period was 284 mm. The total change in soil moisture for the top 1 m of the soil profile was -17 mm and -64 mm for the fallow and barley plots respectively. Evapotranspiration, determined in part from the Penman method and from the field capacity method, was 207 mm and 254 mm for the fallow and the barley plots respectively. Drainage was determined to be 94 mm for both fallow and barley plots. As it was not possible to separate deep drainage from upward flow, the contribution of the water table to evapotranspiration could not be evaluated. An alternate method for evaluating drainage and evapotranspirat ion of the barley plots, the gradient method, yielded only a 2% difference in evapotranspiration from the field capacity method. Discontinuous sand lenses below 60 cm resulted in highly skewed distributions of the particle size, the characteristic curve, and the moisture content during dry conditions. During the near saturated conditions of the heavy rainfalls the skewed moisture conditions normalized. This resulted in soil moisture sample size requirements of 4 to over 20 for a precision of ±5%. Semivariograms of soil moisture and related soil properties showed general spatial independence for distances from 6.1 to 37 m. Spatial dependence could exist at distances less than or greater than those measured. An adequate sampling program for the determination of soil moisture for this site, which is approximately 0.1 ha in area, would require at least 10 to 15 access tubes arranged between 6 and 37 m apart to achieve a precision of ± 5%. For these distances systematic sampling does not offer any increase in precision over random sampling.
Download or read book Space and Time Scale Variability and Interdependencies in Hydrological Processes written by R. A. Feddes and published by Cambridge University Press. This book was released on 1995-08-24 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the integrated contributions of hydrologists, meteorologists and ecologists to the first IHP/IAHS George Kovacs Colloquium in connection with the study of global hydrology and climate change. The atmospherical, hydrological and terrestrial components of the Earth's systems operate on different time and space scales. Resolving these scaling incongruities, as well as understanding and modelling the complex interaction of land surface processes at the different scales, represent a major challenge for hydrologists, ecologists and meteorological scientists alike. This book deals with time and space scale variations with reference to several topics including: soil water balance; ecosystems and interaction of flow systems; and macroscale hydrological modelling. This book will be of great use to researchers, engineers and forecasters with an interest in space and time scale variability.
Download or read book Soil Moisture Dynamics and Soil Moisture Controlled Runoff Processes at Different Spatial Scales written by Thomas Gräff and published by . This book was released on 2011 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soil moisture is a key state variable that controls runoff formation, infiltration and partitioning of radiation into latent and sensible heat. However, the experimental characterisation of near surface soil moisture patterns and their controls on runoff formation remains a challenge. This subject was one aspect of the BMBF-funded OPAQUE project (operational discharge and flooding predictions in head catchments). As part of that project the focus of this dissertation is on: (1) testing the methodology and feasibility of the Spatial TDR technology in producing soil moisture profiles along TDR probes, including an inversion technique of the recorded signal in heterogeneous field soils, (2) the analysis of spatial variability and temporal dynamics of soil moisture at the field scale including field experiments and hydrological modelling, (3) the application of models of different complexity for understanding soil moisture dynamics and its importance for runoff generation as well as for improving the prediction of runoff volumes. To fulfil objective 1, several laboratory experiments were conducted to understand the influence of probe rod geometry and heterogeneities in the sampling volume under different wetness conditions. This includes a detailed analysis on how these error sources affect retrieval of soil moisture profiles in soils. Concerning objective 2 a sampling strategy of two TDR clusters installed in the head water of the Wilde Weißeritz catchment (Eastern Ore Mountains, Germany) was used to investigate how well the catchment stateʺ can be characterised by means of distributed soil moisture data observed at the field scale. A grassland site and a forested site both located on gentle slopes were instrumented with two Spatial TDR clusters that consist of up to 39 TDR probes. Process understanding was gained by modelling the interaction of evapotranspiration and soil moisture with the hydrological process model CATFLOW. A field scale irrigation experiment was carried out to investigate near subsurface processes at the hillslope scale. The interactions of soil moisture and runoff formation were analysed using discharge data from three nested catchments: the Becherbach with a size of 2 kmø, the Rehefeld catchment (17 kmø) and the superordinate Ammelsdorf catchment (49 kmø).Statistical analyses including observations of pre-event runoff, soil moisture and different rainfall characteristics were employed to predict stream flow volume. On the different scales a strong correlation between the average soil moisture and the runoff coefficients of rainfall-runoff events could be found, which almost explains equivalent variability as the pre-event runoff. Furthermore, there was a strong correlation between surface soil moisture and subsurface wetness with a hysteretic behaviour between runoff soil moisture. To fulfil objective 3 these findings were used in a generalised linear model (GLM) analysis which combines state variables describing the catchments antecedent wetness and variables describing the meteorological forcing in order to predict event runoff coefficients. GLM results were compared to simulations with the catchment model WaSiM ETH. Hereby were the model results of the GLMs always better than the simulations with WaSiM ETH. The GLM analysis indicated that the proposed sampling strategy of clustering TDR probes in typical functional units is a promising technique to explore soil moisture controls on runoff generation and can be an important link between the scales. Long term monitoring of such sites could yield valuable information for flood warning and forecasting by identifying critical soil moisture conditions for the former and providing a better representation of the initial moisture conditions for the latter.
Download or read book Spatial Patterns in Catchment Hydrology written by Rodger Grayson and published by CUP Archive. This book was released on 2001-08-06 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: Describes use of observed patterns in understanding and modelling hydrological response, for researchers and graduate students.
Download or read book Model based Geostatistics written by Peter Diggle and published by Springer Science & Business Media. This book was released on 2007-05-26 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is the first book-length treatment of model-based geostatistics. The text is expository, emphasizing statistical methods and applications rather than the underlying mathematical theory. Analyses of datasets from a range of scientific contexts feature prominently, and simulations are used to illustrate theoretical results. Readers can reproduce most of the computational results in the book by using the authors' software package, geoR, whose usage is illustrated in a computation section at the end of each chapter. The book assumes a working knowledge of classical and Bayesian methods of inference, linear models, and generalized linear models.
Download or read book Understanding Soil Moisture Dynamics Using Observations and Climate Models written by Haibin Li and published by . This book was released on 2007 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the objective to improve our understanding of soil moisture and its long term changes, I analyzed and compared climate model simulations with in situ soil moisture observations. Three studies were conducted to investigate soil moisture variations on seasonal to interannual scales and its long term changes. To investigate soil moisture evolutions on seasonal to interannual scales and the capacity of reanalysis systems to capture the observed characteristics, I analyzed newly updated 19 yr of Chinese soil moisture data and evaluated ERA40, NCEP/NCAR reanalysis (R-1), and NCEP/DOE reanalysis 2 (R-2). Over this region, soil moisture seasonality is in general not strong. Seasonal cycles and interannual variations exhibit considerably spatial diversity. R-2 generally exhibits improved interannual variability and better seasonal patterns of soil moisture than R-1 as a result of incorporating observed precipitation. ERA40 produces a better mean value of soil moisture for most Chinese stations and good interannual variability. In terms of temporal scale - an indicator of anomaly persistence, R-2 has a memory about twice that of the observations for the growing season. The unrealistic long temporal scale of R-2 can be attributed to the deep layer of the land surface model, which is too thick and dominates the soil moisture variability. The analysis highlights the importance of correct soil parameters to land surface processes and points out possible directions in which the reanalysis can be continuously improved to provide more realistic soil moisture outputs. Observations from Ukraine and Russia show significant increases in summer for the period from 1958-1999 that seem contradictory to the classic summer drying issue from early modeling studies. To see whether the latest climate models can capture the observed patterns, I calculated trends in soil moisture simulations from Intergovernmental Panel on Climate Change Fourth Assessment climate models. The upward trends in observations, which cannot be explained by precipitation and temperature changes alone, were found to be much larger than most trends in model realizations. Solar dimming is proposed to have played an important role in modulating soil moisture variations for these two regions. Further, a series off-line sensitivity experiments with a sophisticated land surface model were conducted to investigate possible contribution from solar dimming and elevated CO2 to the observed soil moisture trends for Ukraine and Russia. I demonstrate, by imposing a downward trend to shortwave radiation forcing to mimic the dimming, the observed soil moisture pattern can be essentially reproduced. On the other hand, the effects of elevated CO2 are relatively small for the study period. The results support the hypothesis that solar dimming may have played an important role in regional soil moisture changes.
Download or read book Interannual Variability of Summer Mean Soil Moisture Conditions in Switzerland During the 20th Century written by and published by . This book was released on 2004 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Climate Change and Terrestrial Ecosystem Modeling written by Gordon Bonan and published by Cambridge University Press. This book was released on 2019-02-21 with total page 459 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides an essential introduction to modeling terrestrial ecosystems in Earth system models for graduate students and researchers.
Download or read book Modeling and Application of Soil Moisture at Varying Spatial Scales with Parameter Scaling written by Narendra Narayan Das and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The dissertation focuses on characterization of subpixel variability within a satellite-based remotely sensed coarse-scale soil moisture footprint. The underlying heterogeneity of coarse-scale soil moisture footprint is masked by the area-integrated properties within the sensor footprint. Therefore, the soil moisture values derived from these measurements are an area average. The variability in soil moisture within the footprint is introduced by inherent spatial variability present in rainfall, and geophysical parameters (vegetation, topography, and soil). The geophysical parameters/variables typically interact in a complex fashion to make soil moisture evolution and dependent processes highly variable, and also, introduce nonlinearity across spatio-temporal scales. To study the variability and scaling characteristics of soil moisture, a quasi-distributed Soil-Vegetation-Atmosphere-Transfer (SVAT) modeling framework is developed to simulate the hydrological dynamics, i.e., the fluxes and the state variables within the satellite-based soil moisture footprint. The modeling framework is successfully tested and implemented in different hydroclimatic regions during the research. New multiscale data assimilation and Markov Chain Monte Carlo (MCMC) techniques in conjunction with the SVAT modeling framework are developed to quantify subpixel variability and assess multiscale soil moisture fields within the coarse-scale satellite footprint. Reasonable results demonstrate the potential to use these techniques to validate multiscale soil moisture data from future satellite mission e.g., Soil Moisture Active Passive (SMAP) mission of NASA. The results also highlight the physical controls of geophysical parameters on the soil moisture fields for various hydroclimatic regions. New algorithm that uses SVAT modeling framework is also proposed and its application demonstrated, to derive the stochastic soil hydraulic properties (i.e., saturated hydraulic conductivity) and surface features (i.e., surface roughness and volume scattering) related to radar remote sensing of soil moisture.
Download or read book Scale Issues in Hydrological Modelling written by J. D. Kalma and published by John Wiley & Sons. This book was released on 1995-09-11 with total page 518 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is a growing need for appropriate models which address the management of land and water resources and ecosystems at large space and time scales. Theories of non-linear hydrological processes must be extrapolated to large-scale, three-dimensional natural systems such as drainage basins, flood plains and wetlands. This book reports on recent progress in research on scale issues in hydrological modelling. It brings together 27 papers from two special issues of the journal Hydrological Processes. The book makes a significant contribution towards developing research strategies for linking model parameterisations across a range of temporal and spatial scales. The papers selected for this book reflect the tremendous advances which have been made in research into scale issues in hydrological modelling during the last ten years.
Download or read book Hydrological Drought written by Lena M. Tallaksen and published by Gulf Professional Publishing. This book was released on 2004 with total page 634 pages. Available in PDF, EPUB and Kindle. Book excerpt: The majority of the examples are taken from regions where the rivers run most of the year.
Download or read book Spatial Variation of Soil Type and Soil Moisture in the Regional Atmospheric Modeling System written by and published by . This book was released on 2001 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soil characteristics (texture and moisture) are typically assumed to be initially constant when performing simulations with the Regional Atmospheric Modeling System (RAMS). Soil texture is spatially homogeneous and time-independent, while soil moisture is often spatially homogeneous initially, but time-dependent. This report discusses the conversion of a global data set of Food and Agriculture Organization (FAO) soil types to RAMS soil texture and the subsequent modifications required in RAMS to ingest this information. Spatial variations in initial soil moisture obtained from the National Center for Environmental Predictions (NCEP) large-scale models are also introduced. Comparisons involving simulations over the southeastern United States for two different time periods, one during warmer, more humid summer conditions, and one during cooler, dryer winter conditions, reveals differences in surface conditions related to increases or decreases in near-surface atmospheric moisture con tent as a result of different soil properties. Three separate simulation types were considered. The base case assumed spatially homogeneous soil texture and initial soil moisture. The second case assumed variable soil texture and constant initial soil moisture, while the third case allowed for both variable soil texture and initial soil moisture. The simulation domain was further divided into four geographically distinct regions. It is concluded there is a more dramatic impact on thermodynamic variables (surface temperature and dewpoint) than on surface winds, and a more pronounced variability in results during the summer period. While no obvious trends in surface winds or dewpoint temperature were found relative to observations covering all regions and times, improvement in surface temperatures in most regions and time periods was generally seen with the incorporation of variable soil texture and initial soil moisture.
Download or read book Soil Moisture Retrieval From ASAR Measurements Over Natural Surfaces With a Large Roughness Variability written by and published by . This book was released on 2005 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, the accuracy of soil moisture retrieved from ASAR data over bare or sparsely vegetated surfaces is investigated by means of a simulation study. The soil moisture retrieval method is based on an optimization algorithm that appropriately inverts theoretical direct models by assimilating a priori information on surface parameters. In order to account for a large variability of roughness conditions, two complementary models have been used, namely the Integral Equation Method model and the Geometrical Optics model. The performance of the inversion method has been assessed on simulated noisy ASAR data, as a function of different a priori information quality level.
Download or read book Proceedings RMRS written by and published by . This book was released on 1998 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt:
