Estimating Surface Energy Fluxes with Remotely Sensed Data

Remote Sensing and Hydrology 2000 Edited by Manfred Owe, Kaye Brubaker, Jerry Ritchie & Albert Rango

IAHS Publication no. 267 (published August 2001) in the IAHS Series of Proceedings and Reports ISBN 1-901502-46-5; 610 + xiv pp.; price £ 80.00

Remote sensing applications in hydrology have progressed considerably since the International Workshop on Hydrologic Applications of Space Technology in 1985. This volume, the proceedings of the International Symposium on Remote Sensing and Hydrology 2000 (Santa Fe, New Mexico, USA, April 2000), is clear evidence of that progress and represents the state of the art at the beginning of the 21st century. Two keynote papers provide overviews: Dr Gert Schultz on: Present and future perspectives of remote sensing in hydrology and water management, and Satellite remote sensing of precipitation: progress and problems, by Dr Eric Barrett, whilst the other 123 papers detail many operational applications as well as attempts to exploit a more varied portion of the electromagnetic spectrum. The papers are grouped into ten sections: Precipitation Snow and Ice Large Area Experiments Evapotranspiration Radar Applications Microwave Soil Moisture Geographic Information Systems General Hydrology Wetlands Hydrological Modelling Contents

Preface by Albert Rango v

1 Precipitation Satellite remote sensing of precipitation: progress and problems Eric C. Barrett 10 Estimation of pixel-scale daily rainfall over Nile River catchments using multi-spectral METEOSAT data Konstantine P. Georgakakos, Dimitris Tsintikidis, Bayoumi Attia & Jozef Roskar 11 Calibration of weather radar data in different space and time scales H. Bergmann, R. Schatzl, H. Pozarnik, C. A. Ruch & T. Harum 16 Monthly oceanic rainfall derived from space-borne microwave data Alfred Chang & Long Chiu 22 Analytical software for validating time synchronous radar and raingauge data Brad Fisher, David B. Wolff & Eyal Amitai 27 Development of a distributed database for precipitation radar through the Internet using Java Toshiyuki Moriyama & Kazuo Matsunga 32 A new heavy precipitation warning aid for Hungary Ágnes Takács, Cecilia M. I. R. Girz, Edward I. Tollerud & Sándor Kertész 35 SSM/I-derived global rainfall statistics and their application in surface hydrology modelling Qihang Li & Ralph Ferraro 38 Quantitative rainfall estimates with radar using a weighted multiple regression Marco Gabella, Giovanni Perona & Juerg Joss 41

Systematic variations of Ze-R relations: implications for hydrology Eyal Amitai, David B. Wolff, Michael Robinson, David A. Marks, Mark S. Kulie & Brad S. Ferrier 43 Enhancing weather radar winter precipitation accumulation estimates S. R. Fassnacht, E. D. Soulis & N. Kouwen 46 Accuracy assessment of temporal and spatial up-scaling of IR rain cloud duration techniques Gorm Dybkjaer 50

2 Snow and Ice Earth Observing System (EOS) Moderate Resolution Imaging Spectroradiometer (MODIS) global snow-cover maps Dorothy K. Hall, George A. Riggs, Vincent V. Salomonson & Greg R. Scharfen 55 Improved snow cover remote sensing for snowmelt runoff forecasting Enrique Gomez-Landesa, Albert Rango & Dorothy K. Hall 61 Operational snowmelt runoff forecasting in the Central Asian mountains Michael F. Baumgartner, Manfred Spreafico & Heinz W. Weiss 66 Remote sensing of UK snow covers using multi-sensor satellite imagery Richard Kelly 72 Operational technology for snow-cover mapping in the Central Asian mountains using NOAA-AVHRR data Timur Qobilov, Felix Pertziger, Ludmila Vasilina & Michael F. Baumgartner 76 Application of the SRM and SLURP models in eastern Turkey using remote sensing and geographic information systems Ünal Şorman, Engin Uzunoğlu & H. Ilgaz Kaya 81 Validation of passive microwave snow algorithms Richard L. Armstrong & Mary J. Brodzik 87 Interpolating sparse surface measurements for calibration and validation of satellite- derived snow water equivalent in Russian Siberia Kaye L. Brubaker, Michael Jasinski, Alfred T. C. Chang & Edward Josberger 93 Modelling runoff from large glacierized basins in the Karakoram Himalaya using remote sensing of the transient snowline Andrew T. Lowe & David N. Collins 99 Precision snow cover and glacier mapping for runoff modelling in a high alpine basin Jesko Schaper, Klaus Seidel & Jaroslav Martinec 105 Use of sub-pixel information from optical sensors to adjust passive microwave based snow water equivalent estimates Richard A. Fernandes, Irene G. Rubinstein & Sebastian Martin 112 Remote sensing and operational snowmelt runoff prediction: the Swiss contribution to HYDALP Hannes Kleindienst, Stefan Voigt & Michael F. Baumgartner 117 Estimation of snow fraction using simulated ASTER image data Jiancheng Shi 120 Observation and modelling of water balance components in Northern Fennoscandia with NOAA-AVHRR and SPOT VEGETATION imagery Rutger Dankers, Hans Middelkoop & Steven M. de Jong 123 Snowmelt mathematical simulation with different climatic scenarios in the Tupungato River basin, Mendoza, Argentina Jorge Maza, Federico CaZorzi, Patricia Lopez, Luis Fornero, Adrian Vargas & Jose Zuluaga 126 Topographic and canopy controls on snow deposition, snow-cover energy balance and snowmelt Danny Marks, Adam Winstral, Steven S. Van Vactor, Dave Robertson & Robert E. Davis 129 Impulse radar surveys: influence of liquid water Angela Lundberg & Hans Thunehed 136 A prototype MODIS-SSM/I snow mapping method Andrew Tait, Jonathan Barton & Dorothy K. Hall 139

3 Large Area Experiments Estimating surface energy fluxes with remotely sensed data John D. Albertson, Todd M. Scanlon, Anthony T. Cahill & William P. Kustas 145 Using remote sensing data in macroscale hydrological modelling Ralph Dubayah, Dennis Lettenmaier, Eric F. Wood & Joshua Rhoads 151 Some scientific results from the SALSA programme Abdel Ghani Chehbouni, Chris J. Watts, David C. Goodrich, Susan Moran, Yann Kerr, Gerard Dedieu, William G. Kepner, W. James Shuttleworth & Soroosh Sorooshian 156 The impact of the structure and composition of shrub-coppice dune landscapes on MASTER reflectance anisotropy M. Chopping, T. J. Schmugge, A. Rango, J. Ritchie, W. P. Kustas & John R. Vande Castle 162 Estimation of surface emissivity for arid lands Thomas J. Schmugge, Andrew N. French, Jerry Ritchie & Albert Rango 168 Scale effects in estimating large eddy-driven sensible heat fluxes over heterogeneous terrain Todd M. Scanlon, John D. Albertson & William P. Kustas 175 Aggregation of a nonlinear land surface model for heterogeneous terrain Henk Pelgrum 181 Heat flux distributions over SGP97 sites Andrew N. French, Thomas J. Schmugge & William P. Kustas 187 Use of remote sensing for validation and assimilation in mesoscale models Patrick Gross, Clemens Simmer, Gisela Müller & Günther Haase 192 Assimilation of surface temperature in a land-surface model Praveen Kumar & Amy L. Kaleita 197 On the accuracy of TOVS surface temperatures: a comparison between measured, modelled, and satellite derived data Matthias Drusch & Eric F. Wood 202 Hydrological implications of remotely sensed thermal inertia Valerio Tramutoli, Pierluigi Claps, Mauro Marella, Nicola Pergola, Carla Pietrapertosa & Canio Sileo 207 Derivation of a dryness index from NOAA-AVHRR data for use in large-scale hydrological modelling Inge Sandholt, Kjeld Rasmussen & Jens Andersen 212 Aggregation rules for sensible heat flux estimates over agricultural fields in Mexico C. J. Watts, A. G. Chehbouni, J. C. Rodriguez, F. Santiago, J. Garatuza-Payan & 217 J. Schieldge Area-average estimates of surface fluxes over a mosaic of agricultural fields Abdel Ghani Chehbouni, Chris J. Watts, Julio Rodriguez, Fausto Santiago, Jaime Garatuza-Payan & John Schieldge 220 PGLIERC: a test of remote sensing of hydrology in a grassland Kenlo Nishida, Atsushi Higuchi, Shin-Ichi Iida, Noriko Niimura & Akihiko Kondoh 223 Iowa’s surface albedo variability in space and time throughout the 1990 growing season D. W. Meek & J. L. Hatfield 225 Simulating surface winds near the Great Salt Lake using the US Army Battlescale Forecast Model Robert E. Dumais, Jr 228 Field experiment design for land surface temperature validation Kevin P. Czajkowski, James Coss, Theresa Mulhern & Venkataraman Lakshmi 231 Monitoring physical and biological properties at the Sevilleta LTER using remote sensing Jerry C. Ritchie, Thomas J. Schmugge, Albert Rango & Frank R. Schiebe 234

4 Evapotranspiration Issues in monitoring evapotranspiration with radiometric temperature observations William P. Kustas, John D. Albertson, Todd M. Scanlon & Anthony T. Cahill 239 Feasibility of evapotranspiration monitoring of riparian vegetation with remote sensing John H. Prueger, Lawrence E. Hipps, William P. Kustas, Christopher M. U. Neale, Jerry L. Hatfield, Salim Bawazir, William E. Eichinger & Daniel I. Cooper 246 Satellite derived actual evapotranspiration and groundwater modelling, Botswana W. J. Timmermans, A. M. J. Meijerink & M. W. Lubczynski 252 Evaporation rates in Tamarisk Lawrence E. Hipps, John H. Prueger, Salim Bawazir & William P. Kustas 259 Evapotranspiration at the basin scale estimated from satellite data and by a hydrological model Geoff Kite, Raoul Granger & Gayathree Jayasınghe 265 A technique for estimating the evaporation from deserts by remote sensing Tetsuo Kobayashi, Wenjun He & Weizhen Wang 271 The effect of emissivity on evaporation Nathaniel A. Brunsell & Robert R. Gillies 276 Using airborne Vis-NIR-TIR data and a surface energy balance model to map evapotranspiration at high spatial resolution Frederic Jacob, Albert Olioso, Xingfa Gu, Jean-François Hanocq, Olivier Hautecoeur, Bernard Seguin & ZhongBo Su 281 Remotely sensed estimates of evaporation for irrigated crops in northern Mexico Jaime Garatuza-Payan, W. James Shuttleworth, Rachel T. Pinker & Christopher J. Watts 286 Scaling-up evapotranspiration from field to regional scale based on optical remote sensing scenes Charlotte Bay Hasager, Niels Otto Jensen, Eva Boegh, Henrik Soegaard, Anton Thomsen & Kirsten Schelde 292 Assessing the relationship between surface temperature and soil moisture in southern Africa Ana C. Pinheiro, Compton J. Tucker, Dara Entekhabi, Jeffrey L. Privette & Joseph A. Berry 296

Seasonal evapotranspiration estimation using canopy reflectance: a case study involving pink beans Harikishan Jayanthi, Christopher M. U. Neale & James L. Wright 302 Evapotranspiration estimates obtained from remote sensing data P. C. Doraiswamy, J. L. Hatfield & J. H. Prueger 306 Spatial mapping of evapotranspiration and energy balance components over riparian vegetation using airborne remote sensing C. M. U. Neale, L. E. Hipps, J. H. Prueger, W. P. Kustas, D. I. Cooper & W. E. Eichinger 311 A simple resistance-based model for use in dual source evaporation equations Bruce E. Main, Lester P. Simmonds & Eleanor J. Burke 316

5 Radar Applications Utilization of Radarsat in integrated catchment management Martine Galarneau, Robert Leconte, François Brissette, Terry J. Pultz & Jean Rousselle 321 SAR imagery used for soil moisture monitoring: the potential Tim Davie, Richard Kelly & Marta Timoncini 327 Estimation of snow cover over large mountainous areas using Radarsat ScanSAR Harold Haefner, David Small, Stefan Biegger, Hilko Hoffmann & Daniel Nüesch 333 Mapping snow with repeat pass synthetic aperture radar Jiancheng Shi, Scott Hensley & Jeff Dozier 339 Operational determination of snow water equivalent using Radarsat data over a large hydroelectric complex in eastern Canada Yves Gauthier, Monique Bernier, Jean-Pierre Fortin, Raymond Gauthier, René Roy & Pierre Vincent 343 Hydrological analysis of high resolution multifrequent, multipolarimetric and interferometric airborne SAR data Volker Hochschild & Martin Herold 349 Including vegetation scattering effects in a radar based soil moisture estimation model Rajat Bindlish & Ana P. Barros 354 Radarsat based monitoring of soil roughness over an agricultural area affected by excessive runoff Judith Coulombe-Simoneau, Stéphane Hardy, Nicolas Baghdadi, Christine King, Ferdinand Bonn & Yves Le Bissonnais 362 Characterization of west African shallow flood plains with L- and C-band radar Nick Van de Giesen 365 Potential retrieval of tillage direction as a runoff indicator using Radarsat data Jill Smyth, Ferdinand Bonn, Stéphane Hardy, Agnès Remond & Pierre Clément 368 Extracting land-cover information from ERS SAR intensity and coherence data for hydrological model parameterization Martin Klenke & Wolfgang-Albert Flügel 371 Developments for snowpack water equivalent monitoring using Radarsat data as input to the Hydrotel hydrological model Richard Turcotte, Jean-Pierre Fortin, Monique Bernier & Yves Gauthier 374

6 Microwave Soil Moisture Soil moisture mapping with passive microwave imagery and geostatistical analysis Anna Oldak, Thomas J. Jackson & Yakov Pachepsky 379 Sub-pixel heterogeneity and the retrieval of soil moisture from passive microwave radiometry Eleanor J. Burke & Lester P. Simmonds 384 Development and validation of TMI algorithms for soil moisture and snow Toshio Koike, Hideyuki Fujii, Tetsu Ohta & Eita Togashi 390 Estimating long term surface soil moisture from satellite microwave observations in Illinois, USA Manfred Owe, Richard de Jeu & Adriaan Van de Griend 394 On the impact of the atmosphere in passive microwave remote sensing of land surface parameters Matthias Drusch, Eric F. Wood & Thomas J. Jackson 400 Large scale soil moisture monitoring using C-band scatterometer data Wolfgang Wagner & Klaus Scipal 405 Remote sensing and estimation of root zone water content Patrick J. Starks & Thomas J. Jackson 409 Estimating soil moisture profiles by microwave radiometry over a wheat field Yuei-An Liou, Yu-Chung Tzeng & Jean-Pierre Wigneron 412 First results and analyses from the SWaMP-L radiometer David Pearson, Eleanor J. Burke, Ian Cartmell, Robert J. Gurney, Mark L. Jarrett & Lester P. Simmonds 415

7 Geographic Information Systems Remote sensing inputs and a GIS interface for distributed hydrological modelling Greg S. Crosby, Christopher M. U. Neale, Mark Seyfried & David Tarboton 421 Multidata analysis for automatic river extraction G. M. Petrie, J. D. Tagestad, K. L. Steinmaus, M. S. Wigmosta & Chung Hye Read 427 Spatio-temporal hydrological modelling in a GIS environment N. D. K. Dayawansa, Ranjith Premalal De Silva & John C. Taylor 433 A real-time flood forecasting system based on GIS and DEM Sandra G. García 439 Satellite remote sensing and GIS used to quantify water input for rice cultivation (Rhône delta, France) Philippe Chauvelon, Alain Sandoz, Vincent Heurteaux & Antoine Berceaux 446 Assessment of the renewable groundwater resources of Wadi El-Arish, Sinai, Egypt: modelling, remote sensing and GIS applications Hazem M. Gheith & Mohamed I. Sultan 451 Flood damage and management modelling using satellite remote sensing data with GIS: case study of Bangladesh Md. Monirul Islam & Kimiteru Sado 455 Development of a GIS-based model to estimate landscape water demand at the urban/rural interface Fayek Farag, Christopher M. U. Neale & Roger Kjelgren 458 Land use in the Connecticut River basin, USA: combining GIS and stable isotopes Thomas A. Douglas & C. Page Chamberlain 462 Geo-spatial tools for monitoring floodplain water dynamics Shawkat Ali, Ahmadul Hassan, Timothy C. Martin & Quazi Khalid Hassan 465

8 General Hydrology Land-cover mapping in the Arno basin, Italy: multispectral classification and neural networks Francesca Caparrini, Enrica Caporali & Fabio Castelli 471 Remote sensing of canopy variables for the application of hydrological models Guido D’Urso & Alessandro Santini 476 A satellite-based rainfall estimation method for the Lake Victoria basin Carlo De Marchi & Aris Georgakakos 481 Precision temperature logging and groundwater flow studies along the eastern side of the Albuquerque basin Marshall Reiter 487 Innovative technologies for scientific wetland management, conservation and restoration D. H. A. Al-Khudhairy, R. Calaon, C. Leemhuis, V. Hoffmann, I. M. Shepherd, J. R. Thompson, H. Gavin, D. Gasca Tucker, H. Refstrup Sørensen, A. Refsgaard, G. Bilas & G. Zalidis 491 Sequential assimilation of SAR/ERS data in a lumped rainfall–runoff model with an extended Kalman filter Arnaud Quesney, Christophe François, Catherine Ottle, Sylvie Le Hegarat, Cecile Loumagne & Michel Normand 495 Dynamics of bar growth using remote sensing data M. M. Hossain, M. K. Hasan & M. A. Mukto 498 Using earth observation for constraining uncertainty in sediment loss predictions Martyn Silgram, Mike Hutchins, Steve Robinson, Jeff Settle, Lester P. Simmonds & Nick Veck 501

9 Wetlands Image and in situ data integration to derive sawgrass density for surface flow modelling in the Everglades, Florida, USA John W. Jones 507 Remote sensing of environmental conditions at wetlands in west-central Florida (USA) using high-resolution multispectral imagery Brian G. Ormiston & Chris Shea 513 Application of a hydrodynamic model in a freshwater delta using remote sensing Alain Pietroniro, Robert Leconte, Daniel L. Peters & Terry D. Prowse 519 Monitoring wetland hydrology in Atlantic Canada using multi-temporal and multi-beam Radarsat data Jennifer Sokol, Terry J. Pultz & Victor Bulzgis 526 Hydrological processes on large flatlands: case study in the northwest region of Buenos Aires Province (Argentina) Eduardo Kruse, Juan Alberto Forte Lay, Jose Luis Aiello, 531 Adriana Basualdo & German Heinzenknecht Summer flood mapping in a northern wetland using a combination of Radarsat and SPOT imagery Jessika Töyrä, Alain Pietroniro & Lawrence W. Martz 536 Mapping riparian resources in semiarid watersheds using airborne multispectral imagery Christina J. May, Christopher M. U. Neale & Norm Henderson 539

10 Hydrological Modelling Present use and future perspectives of remote sensing in hydrology and water management Gert A. Schultz & Edwin T. Engman 545 Comparison of global land-cover databases in the Mackenzie basin, Canada Alain Pietroniro & Eric D. Soulis 552 Distributed hydrological modelling using radar precipitation Theresa M. Carpenter & Konstantine P. Georgakakos 558 ARSGISIP: a European project on the application of remote sensing techniques for the parameterization of hydrological, erosion and solute transport models Wolfgang-Albert Flügel, Bettina Müschen, Volker Hochschild & Klaus Steinnocher 563 A comparison of satellite-derived and modelled snow-covered area for a mountain drainage basin A. P. Barrett, G. H. Leavesley, R. L. Viger, A. W. Nolin & 569 M. P. Clark Combining remote sensing and hydrological models to enhance spatial and temporal variability Peter Droogers & Wim Bastiaanssen 574 Hydrological modelling study with digital image processing of multi-sensor satellite data over a small high mountainous catchment Addala Narayana Swamy & Pietro Alessandro Brivio 580 Application of complex process-based models of land surface processes in the interpretation of remote sensing Lester P. Simmonds & Eleanor J. Burke 583 Flood modelling in a mountain basin using mesoscale meteorological models Stefan Taschner, Ralf Ludwig & Wolfram Mauser 586 Improving the basis for validation of large scale distributed hydrological models using a remotely sensed dryness index Jens Andersen, Karsten H. Jensen, Inge Sandholt & Jens Christian Refsgaard 589 Integration of remote sensing data into hydrological models for flood forecasting C. Loumagne, A. Weisse, M. Normand , M. Riffard, A. Quesney, S. Le Hégarat-Mascle & F. Alem 592 Using remote sensing data to update the simulated snow pack of the HBV runoff model Barbro Johansson, Ron Caves, Rob Ferguson & Owen Turpin 595 Application of a hydrological model with integration of remote sensing and GIS techniques for the analysis of land-use change effects upon river discharge Carsten Jürgens 598 Using public-domain datasets to model the Küçük Menderes basin, Turkey Martin Lacroix, Geoff Kite & Peter Droogers 601

Key words 605

Abstracts Publ. no. 267

Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 145–150.

Estimating surface energy fluxes with remotely sensed data

JOHN D. ALBERTSON, TODD M. SCANLON Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22903, USA e-mail: [email protected]

ANTHONY T. CAHILL Department of Civil Engineering, Texas A&M University, College Station, Texas 77843, USA

WILLIAM P. KUSTAS USDA-ARS Hydrology Laboratory, BARC-W, Beltsville, Maryland 20705, USA

Abstract The relationship between modelled and radiometrically observed surface temperature is explored in this paper. Implied in many assimilation attempts is an equivalence in the definition of modelled and observed state variables. We contend and attempt to demonstrate here that this assumption is not of general validity. The analysis is conducted with a Soil–Vegetation–Atmosphere Transfer model and field data collected during the Southern Great Plains Experiment of 1999 (SGP99). It is shown from supporting equations that the modelled temperature evolves in a dynamic equilibrium with the fluxes, where the radiative flux depends strictly on a radiometric temperature and the sensible and latent heat fluxes depend on an aerodynamic temperature, resulting in a hybrid modelled temperature. It is shown that enforcing an equality between modelled and observed temperatures may result in a logical deterioration in model estimates of latent and sensible heat fluxes. Key words aerodynamic temperature; data assimilation; land surface model; radiometric temperature; regional scale fluxes; SGP99; surface temperature; SVAT

______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 465–468.

Geo-spatial tools for monitoring floodplain water dynamics

SHAWKAT ALI, AHMADUL HASSAN, TIMOTHY C. MARTIN & QUAZI KHALID HASSAN EGIS-II, House 49, Road 27, Banani, Dhaka-1207, Bangladesh e-mail: [email protected]

Abstract Techniques were developed for mapping inundation depth for floodplains in Bangladesh. Data and analysis techniques included: multi-temporal synthetic aperture radar (SAR) Radarsat in fine beam mode, acquired in 24-day intervals for the entire 1998 monsoon season; a detailed Digital Elevation Model (DEM); and relative water levels acquired from water level gauges installed in the floodplain. Overall agreement of computed flood depth with gauge observations is 31 cm. Key words Bangladesh; DEM; flood depth; flood mapping; flood plain; Radarsat SAR

Innovative technologies for scientific wetland management, conservation and restoration

D. H. A. AL-KHUDHAIRY, R. CALAON, C. LEEMHUIS, V. HOFFMANN, I. M. SHEPHERD Institute for Systems, Informatics and Safety, Joint Research Centre, European Commission, I-21020 Ispra (VA), Italy. e-mail: [email protected]

J. R. THOMPSON, H. GAVIN, D. GASCA TUCKER Wetland Research Unit, Department of Geography, University College London, Chandler House, Wakefield Street, London WC1N 1PG, UK.

H. REFSTRUP SØRENSEN, A. REFSGAARD Danish Hydraulic Institute, Agern Allé, 11, DK-2970 Hørholm, Denmark

G. BILAS & G. ZALIDIS Laboratory of Applied Soil Science, Department of Land Reclamation, Soil Science and Agricultural Engineering, School of Agronomy, Aristotle University of Thessaloniki, 54006 Thessaloniki, Greece

Abstract Innovative technologies are being developed within the SHYLOC project, which is partly funded by the European Commission’s Space Technology programme under the 4th Framework Programme, to provide improved tools for wetland modelling and satellite- derived information for wetlands that can be used for calibrating hydrological models. The project comprises three main components: (a) a software tool, SHYLOC, that uses a unique method to combine Landsat-TM images with digitized drainage or irrigation ditch networks to determine surface water storage; (b) a coupled hydrological and hydraulic modelling system that can incorporate hydraulic boundary conditions commonly associated with wetlands; and (c) a comprehensive hydro-meteorological database for four wetland sites in England and Greece. Preliminary results are promising. The SHYLOC software and the coupled hydrological/hydraulic modelling package have been completed and are being applied to the project test sites. There is a correlation between space-borne and ground based measurements of ditch water levels, and water balances are being prepared for two of the wetland sites. Key words coupled MIKE SHE/MIKE 11 modelling package; ditch water levels; Elmley Marshes (north Kent, England); Landsat TM; nonlinear regression; SHYLOC; water level recorders; wetland hydrological modelling

Systematic variations of Ze-R relations: implications for hydrology

EYAL AMITAI University of Maryland Baltimore County/JCET, NASA/Goddard Space Flight Center, Mail Code 912.1, Greenbelt, Maryland 20771, USA e-mail: [email protected]

DAVID B. WOLFF SM & A Corporation, NASA/Goddard Space Flight Center, Mail Code 910.1, Greenbelt, Maryland 20771, USA

MICHAEL ROBINSON, DAVID A. MARKS, MARK S. KULIE & BRAD S. FERRIER University of Maryland Baltimore County/JCET, NASA/Goddard Space Flight Center, Mail Code 902, Greenbelt, Maryland 20771, USA

Abstract Radar estimates of precipitation depend on the relations between the radar observed reflectivity (Ze) and surface rainfall rate (R). The dependence of the relations on the method used to relate Ze to R, and on the rain type was investigated. While probability matching method (PMM) based Ze-R curves demonstrated systematic variation between convective and stratiform rain, power law based Ze-R curves showed no systematic trend, and in a few cases were found to be the same for both rain types. Over a large time–space domain both methods will result in similar rainfall estimates since the radar observations are tuned to the monthly gauge network accumulation. However, for many hydrological applications, where the rain intensities or the rain depth over a small time–space domain is of great concern, the application of a power law based Ze-R will yield systematic estimation errors. Key words PMM; precipitation; radar; rain rate; rainfall classification; rainfall estimates; raingauge; reflectivity; Z-R

Improving the basis for validation of large scale distributed hydrological models using a remotely sensed dryness index

JENS ANDERSEN, KARSTEN H. JENSEN Department of Hydrodynamics and Water Resources (ISVA), Technical University of Denmark, DK-2800 Lyngby, Denmark e-mail: [email protected]

INGE SANDHOLT Institute of Geography, University of Copenhagen, Oestervoldgade 10, DK-1350 Copenhagen K, Denmark

JENS CHRISTIAN REFSGAARD Danish Hydraulic Institute, Agern Alle 5, DK-2970 Hoersholm, Denmark

Abstract A spatially distributed hydrological model, based on the MIKE-SHE code, has been constructed for the 375 000 km2 Senegal River basin in West Africa (Andersen et al., 2001). Calibration and validation results suggest that the spatial resolution of the input data in parts of the area has not been sufficient for satisfactory modelling performance. In order to improve the model results, especially the spatial output, a remotely sensed dryness index (Sandholt et al., 2001) has been visually examined for its relation to model soil moisture for two consecutive days in the wet season of 1990. The visual comparison showed the expected consistency in both root zone soil moisture and dryness index between the two days. An examination of the spatial patterns in model input and output variables revealed the input of precipitation zones to be highly dominating on the pattern of the output variables.

Key words distributed hydrological modelling; soil moisture

Validation of passive microwave snow algorithms

RICHARD L. ARMSTRONG & MARY J. BRODZIK National Snow and Ice Data Center (NSIDC), CIRES, CB 449, University of Colorado, Boulder, Colorado 80309, USA e-mail: [email protected]

Abstract Passive microwave satellite remote sensing can greatly enhance large-scale snow measurements based on visible satellite data alone because of the ability to acquire data through clouds or during darkness as well as to provide a measure of snow depth or water equivalent (SWE). This study develops a validation methodology and provides preliminary results from comparisons of several different passive microwave algorithms, including both mid- and high-frequency channels, vertical and horizontal polarizations and polarization difference approaches. Snow extent derived from passive microwave data is compared with the NOAA Northern Hemisphere snow charts. Results clearly indicate those time periods and geographical regions where the two techniques agree and where they tend to consistently disagree. Validation of SWE derived from passive microwave data is undertaken using measurements from snow course transects in the former Soviet Union. Preliminary results indicate a general tendency for nearly all of the algorithms to underestimate SWE. Key words algorithms; climate change; global; passive microwave; remote sensing; satellite; satellite validation; snow

Satellite remote sensing of precipitation: progress and problems

ERIC C. BARRETT Centre for Remote Sensing, School of Geographical Sciences, University of Bristol, Bristol BS8 1SS, UK e-mail: [email protected]

Abstract Thirty years after satellite data were first used for assessing rainfall it is appropriate to critically review what has been achieved in this field to date, and what has not. Good progress has been made in developing and understanding the capabilities of satellite sensing systems, the physics of the atmosphere and land surfaces of the Earth, and in the development of computers capable of multiple, high-speed operations for near real-time data processing. However, all types of satellite monitoring of falling precipitation are subject to limitations, and progress is still relatively poor in several regards. To make matters worse, there has been a global trend towards the collection of less, not more, in situ data on precipitation over at least half of the last century. Foci for further research and operations are proposed. Some problems will require concentrated effort and significant expenditure if the recent rate of progress in this field is even to be maintained. Key words applications; infrared; microwave; operations; precipitation; progress; remote sensing; research; satellite; visible

A comparison of satellite-derived and modelled snow-covered area for a mountain drainage basin

A. P. BARRETT Cryospheric and Polar Processes Division, Cooperative Institute of Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309, USA e-mail: [email protected]

G. H. LEAVESLEY, R. L. VIGER United States Geological Survey, Box 25046, MS 412, Denver Federal Center, Lakewood, Colorado 80225, USA A. W. NOLIN & M. P. CLARK Cryospheric and Polar Processes Division, Cooperative Institute of Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309, USA

Abstract Gridded satellite-derived maps of snow-covered area produced by the National Operational Hydrological Remote Sensing Center of the US National Weather Service between 1990 and 1998, are compared with snow-covered area simulated by the Precipitation–Runoff Modelling System for the East River drainage basin, a 834 km2 mountain basin in southwestern Colorado, USA. The average agreement between snow-covered grid cells simulated by the model, and satellite snow cover, was 88%. However, the number of successful matches between satellite and modelled snow cover was lower in forested areas. The model generally simulates more snow cover for these forested areas than is estimated by satellite maps. It is suggested that this discrepancy between model- and satellite-derived snow cover maps can be attributed to the omission of a canopy correction from processing of the satellite data. Key words Colorado (USA); forest cover; hydrological modelling; NOHRSC; PRMS; snow-covered area

Operational snowmelt runoff forecasting in the Central Asian mountains

MICHAEL F. BAUMGARTNER MFB-GeoConsulting GmbH, Hauptstrasse 17, CH-3254 Messen, Switzerland e-mail: [email protected]

MANFRED SPREAFICO Swiss National Hydrological and Geological Survey, Bern, Switzerland

HEINZ W. WEISS Basler & Hofmann Engineering, Zurich, Switzerland

Abstract The realization of a snowmelt runoff-forecasting centre at the Hydro- Meteorological Survey of Uzbekistan in Tashkent is described. In the context of World Bank Project 2.1 for the “Saving of the Aral Sea”, the estimation of the amount of snow stored in the Central Asian mountains represents an important economic factor with regard to hydroelectric power generation and irrigation. Based on satellite remote sensing, GIS and database technologies, real-time snowmelt runoff forecasts using SRM (Snowmelt Runoff Model) were performed for several basins in Uzbekistan and Kyrgystan. Key words Central Asia; forecasting; GIS; remote sensing; snowmelt runoff; SRM ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 16–21.

Calibration of weather radar data in different space and time scales

H. BERGMANN Institute for Hydraulics and Hydrology, Technical University of Graz, Mandellstraße 9, A-8010 Graz, Austria e-mail: [email protected]

R. SCHATZL, H. POZARNIK Styrian Government, Fa3a-Hydrographical Service, Stempfergasse 7, A-8010 Graz, Austria C. A. RUCH & T. HARUM Institute for Hydrogeology and Geothermie, Joanneum Research, Elisabethstraße 16/II, A-8010 Graz, Austria

Abstract This paper describes a new method for calibrating weather radar data with raingauge data. Since calibration with raingauges in the hydro-graphical network is a scale problem, data from a high-density raingauge net are used to develop a calibration algorithm. This algorithm is then transferred to the region of interest. In this paper the method is described and applied for an advective event, which is considered at different space and time scales. Key words Austria; calibration; “Einflußfunktionenverfahren”; grid; Pollau basin, Austria; weather radar data; scale; Styria

Including vegetation scattering effects in a radar based soil moisture estimation model

RAJAT BINDLISH SSAI, USDA-ARS Hydrology and Remote Sensing Laboratory, Beltsville, BARC-W, Maryland 20705, USA e-mail: [email protected]

ANA P. BARROS Division of Engineering and Applied Sciences, Harvard University, Boston, Massachusetts, USA

Abstract Previously, the IEM (Integral Equation Model) was successfully used in conjunction with an inversion model to retrieve soil moisture using multi-frequency and multi-polarization data from Spaceborne Imaging Radar C-band (SIR-C) and X-band Synthetic Aperture Radar (X-SAR), without the need to prescribe time-varying land surface attributes as constraining parameters. The retrieved values were compared against in situ observations from the Washita’94 field experiment. The RMS error in the estimated soil moisture was of the order of 0.05 cm3 cm-3, which is comparable to the effect of noise in the SAR data. The IEM was originally developed for scattering from a bare soil surface, and therefore the vegetation scattering effects are not explicitly incorporated in the model. In this study, we couple a semi-empirical vegetation scattering model, modified after the water-cloud model, to the existing radar based soil moisture inversion model. This approach allows for the explicit representation of vegetation backscattering effects without the need to specify a large number of parameters. Although the use of this parameterization resulted in modest improvements (roughly 4% overall), it does provide a general framework that can be used for other applications. Key words inverse modelling; microwave remote sensing; SAR; soil moisture; vegetation

Interpolating sparse surface measurements for calibration and validation of satellite-derived snow water equivalent in Russian Siberia

KAYE L. BRUBAKER Civil and Environmental Engineering, University of Maryland, College Park, Maryland 20742, USA  e-mail: [email protected]

MICHAEL JASINSKI, ALFRED T. C. CHANG Hydrological Sciences Branch, Code 974, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

EDWARD JOSBERGER US Geological Survey, Washington District, 1201 Pacific Avenue, Suite 600, Tacoma, Washington 98402, USA

Abstract Geostatistical methods are used to interpolate and average point snow water equivalent (SWE) measurements to a spatial resolution appropriate for comparison with estimates from Special Sensor Microwave Imager (SSM/I) images. Block kriging, a form of optimal interpolation, is applied to station snow course measurements in and around the Ob’ River basin in Russian Siberia, giving spatially averaged SWE estimates at the resolution of the sensors, 25  25 km cells. For the two dates studied, interpolated station data and SSM/I estimates agree well in flat, low-lying regions. In the Ural Mountains, the SSM/I estimates significantly underestimate SWE, with respect to the station data. In the Altai Mountains, the SSM/I algorithm indicates higher SWE than elsewhere, but comparison is difficult, due to the sparsity of stations there. The results will be used to adjust the SSM/I SWE retrieval algorithm for use in complex terrain, where remotely sensed snow data are particularly needed. Key words kriging; snow water equivalent; SSM/I; Siberia; Russia; Ob’ River

The effect of emissivity on evaporation

NATHANIEL A. BRUNSELL Department of Plants, Soils and Biometeorology, Utah State University, Logan, Utah 84322-4826; USA e-mail: [email protected]

ROBERT R. GILLIES Department of Plants, Soils and Biometeorology and Department of Geography and Earth Resources, Utah State University, Logan, Utah 84322-4826, USA

Abstract The effect of emissivity on the estimation of evaporation is investigated using an emissivity estimate based upon the fractional vegetation coverage. An atmospherically corrected image that does not incorporate emissivity is used for comparison purposes. The evaporation is derived as a function of a scaling of the surface radiant temperature field. The mean difference in evaporation between the emissivity corrected and uncorrected temperature images is 3 W m-2. The evaporation estimates are shown to be insensitive to changes in temperature due to the emissivity effect; this however is likely a result of the way the temperature field is scaled. Key words evapotranspiration; surface emissivity; thermal atmospheric correction; triangle method

Sub-pixel heterogeneity and the retrieval of soil moisture from passive microwave radiometry

ELEANOR J. BURKE Department of Hydrology and Water Resources, University of Arizona, Tucson, Arizona 85721, USA e-mail: [email protected] LESTER P. SIMMONDS Department of Soil Science, University of Reading, Whiteknights, Reading RG6 6DW, UK

Abstract This paper uses a simple semi-empirical model that predicts the effect of soil texture and vegetation (optical depth) on the relationship between near-surface water content and L- band microwave brightness temperature. It was developed from experimentation with a much more complex model (MICRO-SWEAT), a coupled microwave emission, and soil– vegetation–atmosphere transfer scheme. The simple model shows that, given a pixel with variable vegetation, there can be significant errors in the soil moisture retrieved using an area- weighted mean vegetation optical depth. However, an effective mean optical depth can be determined which reduces these errors substantially (to zero for a pixel with uniform soil moisture). In the case of bare soils, given a pixel with variable texture, previous work has shown that there are no significant errors introduced into the retrieved soil moisture. This paper explores a simple method of estimating the within-pixel distribution of soil moisture from the retrieved soil moisture, given knowledge of the within-pixel clay content. Key words disaggregation; heterogeneity; MICRO-SWEAT; passive microwave; SGP97; soil moisture ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 471–475. Land-cover mapping in the Arno basin, Italy: multispectral classification and neural networks

FRANCESCA CAPARRINI, ENRICA CAPORALI & FABIO CASTELLI Department of Civil Engineering, University of Florence, Via di S. Marta 3, I-50139 Florence, Italy e-mail: [email protected]

Abstract Two Landsat Thematic Mapper (TM) images covering the Arno basin, one of the major watersheds in central Italy, have been classified using neural network techniques. The main advantage in using neural network classifiers is that they do not require any a priori assumptions in the statistical distribution of the class, since they are non-parametric classifiers. Further-more, the ability of neural networks to “learn” and adapt to different situations makes them more flexible and capable of recognizing inputs with a higher degree of noise. Different network architectures have been trained and applied, and different levels of discrimination have been tested, i.e. various numbers of target classes. A two-layer feed- forward network with a log-sigmoid transfer function gave the best performance. Results show that the recognition of some classes is excellent with neural networks, while for others there are still a large number of pixels incorrectly classified. Keywords Arno basin, Italy; classification; land cover; Landsat TM; neural networks

Distributed hydrological modelling using radar precipitation

THERESA M. CARPENTER & KONSTANTINE P. GEORGAKAKOS Hydrologic Research Center, 12780 High Bluff Drive, Suite 250, San Diego, California 92130, USA e-mail: [email protected]

Abstract The question of the utility of the operational US National Weather Service Weather Surveillance Radar 1988 Doppler (WSR-88D) is posed. To address this question, this work presents a hydrological model which allows for spatially varying model parameters. This particular distributed model incorporates components that are adaptations of operational models used often in a spatially-lumped manner to produce estimates of soil water, runoff and streamflow. A geographic information system is used to sub-divide the study basin into small subcatchment units with areas of up to a few hundred square kilometres. Soil water accounting and channel routing models are used to generate runoff and streamflow over the network of subcatchments and streams. The application illustrates that operational distributed modelling is feasible with present-day operational data, and that sensitivity analyses are necessary to understand the ramifications of the limitations of such data for operational forecasting with distributed models. Key words distributed modelling; Monte Carlo simulation; parameter estimation; radar hydrology

Monthly oceanic rainfall derived from space-borne microwave data

ALFRED CHANG Hydrological Sciences Branch, Laboratory for Hydrospheric Processes, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA e-mail: [email protected]

LONG CHIU Center for Earth Observing and Space Research, Institute of Computational Sciences and Informatics, George Mason University, Fairfax, Virginia 22030, USA

Abstract A technique for estimating monthly oceanic rainfall rate using multi-channel microwave measurements has been in use for over ten years. A modified version of this algorithm is now being applied to the TRMM (Tropical Rainfall Measuring Mission) Microwave Imager (TMI) data. There are three prominent features to this algorithm. First, knowledge of the form of the rainfall intensity probability density function is used to augment the measurements in rain retrieval. Second, utilizing a linear combination of the 19.4 and 21.3 GHz channels, the effect of water vapour is de-emphasized. Third, an objective technique is used to estimate the rain layer thickness from the 19.4 and 21.3 GHz brightness temperature histograms. One year of rainfall data (January–December 1998) is used in this study. The mean differences of TMI and SSM/I (Special Sensor Microwave/Imager) rain estimates are typically less than 15%. The differences are discussed in the context of radiative transfer calculations and the rainfall estimate algorithm. Key words microwave radiometer; precipitation; SSM/I; TMI; TRMM

Satellite remote sensing and GIS used to quantify water input for rice cultivation (Rhône delta, France)

PHILIPPE CHAUVELON, ALAIN SANDOZ, VINCENT HEURTEAUX & ANTOINE BERCEAUX Fondation Sansouire, Station Biologique de la Tour du Valat, Le Sambuc, F-13200 Arles, France e-mail: [email protected]

Abstract In the Rhône River delta (France), flooded rice cropping requires constant irrigation from April to September. Irrigation volumes used are highly variable, and depend greatly on specific cropping practices. Land use characteristics were digitized, updated with classified satellite images, and placed in a GIS format. The actual irrigation volumes were calculated from estimated pump flows and the distribution of rice area within each irrigation basin. Empirical relationships were obtained between specific irrigation volume and rice area for each monitored pumping station. Thus it was possible to estimate water input for previous years from geo-referenced rice-yield data only. This step is necessary to model the hydrology of the system. Without geo-referenced knowledge of irrigation water input, it is not possible to estimate runoff to the lagoons. Key words GIS; irrigation volumes; land use; Rhone River delta, France; rice

Area-average estimates of surface fluxes over a mosaic of agricultural fields

ABDEL GHANI CHEHBOUNI, CHRIS WATTS, JULIO RODRIGUEZ, FAUSTO SANTIAGO IRD/IMADES, Reyes y Aguascalientes Esq., Col San Benito, Hermosillo, CP 83190, Sonora, Mexico e-mail: [email protected]

JAIME GARATUZA-PAYAN ITSON, Ciudad Obregon, Sonora, Mexico

JOHN SCHIELDGE Jet Propulsion Laboratory, Pasadena, California, USA

Abstract A combination of scintillometer measurements, ancillary meteoro-logical data and an aggregation scheme has been used to derive area-averaged sensible and latent heat flux over a transect spanning three adjacent and contrasting vegetation patches: cotton, wheat and chickpeas. The results showed that modelled area-averaged fluxes compared fairly well with observations. Key words aggregation; eddy correlation; heterogeneous surfaces; scintillometer; semiarid; surface fluxes

Some scientific results from the SALSA programme

ABDEL GHANI CHEHBOUNI, CHRIS J. WATTS IRD/IMADES, Reyes & Aguascalientes, Hermosillo, Sonora 83190, Mexico e-mail: [email protected]

DAVID C. GOODRICH, SUSAN MORAN USDA-ARS, Tucson, Arizona 85719, USA

YANN KERR, GERARD DEDIEU CESBIO (CNES-CNRS-IRD-UPS), F-31401 Toulouse cedex 4, France

WILLIAM G. KEPNER US EPA, Office of Research and Development, Las Vegas, Nevada, USA

WILLIAM J. SHUTTLEWORTH & SOROOSH SOROOSHIAN University of Arizona, Department of Hydrology and Water Resources, Tucson, Arizona 85821, USA

Abstract The objective of this paper is to present an overview of preliminary results obtained during the SemiArid Land–Surface–Atmosphere (SALSA) programme. It highlights some of the findings in the fields of remote sensing and surface–atmosphere interaction. Key words hydrology; land degradation; LAS (large aperture scintillometer); moisture; semiarid; SALSA; SVAT; temperature; vegetation ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 162–167.

The impact of the structure and composition of shrub-coppice dune landscapes on MASTER reflectance anisotropy

M. CHOPPING, T. SCHMUGGE, A. RANGO, J. RITCHIE, W. KUSTAS USDA-ARS Hydrology Laboratory, BARC-W, Beltsville, Maryland 20705, USA. e-mail: [email protected]

JOHN R. VANDE CASTLE Biology Department, University of New Mexico, Albuquerque, New Mexico 87131, USA

Abstract This study assesses the effects of physical structure and composition of shrub- coppice dune landscapes on anisotropy in the NASA MODIS-ASTER Airborne Simulator (MASTER) solar channels, and investigates the viability of simulating multi-angular data sets using off-nadir airborne imaging radiometry from a single overpass by means of data segmentation. Segmentation data are plant density and cover and spectral measures derived from high-resolution aerial photography and classified Landsat 7 Enhanced Thematic Mapper imagery. The directional signal contributes a variation of 5–10% in reflectance, necessitating angular corrections. For most areas the signal appears to differ only slightly with changes in landscape structure and composition because the view/illumination geometry is poor and reflectance is dominated by bright soils. Further work is required to determine whether simple models would be adequate for angular corrections. Key words anisotropy; dunes; landscape; mesquite; multiple view angle; New Mexico; structure

Radarsat based monitoring of soil roughness over an agricultural area affected by excessive runoff

JUDITH COULOMBE-SIMONEAU, STÉPHANE HARDY VIASAT Géo-Technologie Inc., 419 boul. Rosemont #301, Montréal, Québec H2S 1Z2, Canada e-mail: [email protected]

NICOLAS BAGHDADI, CHRISTINE KING BRGM, 3 avenue Claude Guillemin, BP 6009, F-45060 Orléans Cedex 2, France

FERDINAND BONN CARTEL, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada

YVES LE BISSONNAIS INRA, BP 20619 Ardon, F-45166 Olivet Cedex, France

Abstract In order to assess the excess runoff risk from loamy soils in Normandy, Radarsat data from the winters of 1998 and 1999 have been used to measure soil surface roughness in wet conditions. The correlation between radar backscatter (°) and root mean square of surface roughness (rms) is above 80% and has allowed production of a Radarsat based map of bare soil roughness with three classes: rough, intermediate and smooth. The latter corresponds to the highest risk for excess runoff. Key words backscattering coefficient; excessive runoff; flood; FLOODGEN; intensive agriculture; Normandy (France); Radarsat; roughness classification; runoff modelling; soil roughness

Remote sensing inputs and a GIS interface for distributed hydrological modelling

GREG S. CROSBY, CHRISTOPHER M. U. NEALE Department of Biological and Irrigation Engineering, Utah State University, 4105 University Blvd, Logan, Utah 84322-4105, USA e-mail: [email protected]

MARK SEYFRIED USDA-ARS, Northwest Watershed Research Center, Boise, Idaho 83712-7716, USA

DAVID TARBOTON Department of Civil and Environmental Engineering, Utah State University, 4110 University Blvd, Logan, Utah 84322-4110, USA

Abstract High resolution aerial (0.3–3.0 m) multispectral imagery was acquired over several sub-basins of the Reynolds Creek Experimental Watershed (RCEW) in 1996 to provide various spatial resolution imagery for the development of vegetation-related GIS layers (LAI, percent cover, vegetation type, canopy height, root depth, etc.). Thematic Mapper (TM) imagery (30 m) was also collected for the entire RCEW. The imagery will provide data to a remote sensing input driven hydrological model. This paper concentrates on the development of the GIS layers in the ArcView environment to be used with the distributed hydrological model. Key words GIS; LAI; multispectral imagery; remote sensing; NDVI; Reynolds Creek Experimental Watershed; RVI; SAVI; semiarid watershed

Field experiment design for land surface temperature validation

KEVIN P. CZAJKOWSKI, JAMES COSS, THERESA MULHERN Department of Geography and Planning, The University of Toledo, Toledo, Ohio 43606, USA e-mail: [email protected]

VENKATARAMAN LAKSHMI Department of Geological Sciences, The University of South Carolina, Columbia, South Carolina 29208, USA

Abstract Validation of land surface temperature (LST) derived from satellites has shown errors of 3 K with some as large as 6 K. Much of this error can be attributed to field observation techniques used to collect ground LST. We instrumented a cattle pasture in Oklahoma during the Southern Great Plains (SGP99) experiment to observe the temperature variability throughout the field. Vegetation differences within a single field can range over 20C making validation of satellite LST difficult. Key words AVHRR; GOES; infrared radiative thermometer; land surface temperature; Oklahoma; pasture; SGP99; soil moisture; vegetation

Observation and modelling of water balance components in Northern Fennoscandia with NOAA-AVHRR and SPOT VEGETATION imagery

RUTGER DANKERS, HANS MIDDELKOOP & STEVEN M. DE JONG ICG, Centre for Geo-ecological Research, Faculty of Geographical Sciences, University of Utrecht, PO Box 80115, 3508 TC Utrecht, The Netherlands e-mail: [email protected]

Abstract NOAA-AVHRR and SPOT VEGETATION imagery is being used for parameterization and validation of a large-scale hydrological model of Northern Fennoscandia. Due to SPOT VEGETATION’s spectral observations at 1.6 µm, snow can easily be discriminated from clouds. The thermal bands of the NOAA satellites will be used to assess spatial patterns of evapotranspiration. Key words climate change; evapotranspiration; hydrological modelling; NOAA-AVHRR; Scandinavia; snow; SPOT VEGETATION

SAR imagery used for soil moisture monitoring: the potential

TIM DAVIE Department of Geography, Queen Mary, University of London, Mile End Road, London E1 4NS, UK e-mail: [email protected]

RICHARD KELLY Department of Geography, Birkbeck College, University of London, 7–15 Gresse Street, London W1P 2LL, UK

MARTA TIMONCINI Department of Geography, Queen Mary, University of London, Mile End Road, London E1 4NS, UK

Abstract A series of soil moisture measurements were taken in a 15 ha unvegetated field on the Essex coast (UK) at times to coincide with seven ERS-1 overpasses during a wetting period in autumn and winter. The results show that the calibrated SAR values have a strong correlation with soil moisture. Analysis of the spatial variability (using semi-variograms) suggests that the SAR data are able to distinguish spatial continuity of soil moisture that the field programmes could not detect. Analysis suggests that the optimum spatial resolution of the SAR data for soil moisture assessment is approximately 1 ha. One-hectare spatial resolution is of great use in hydrology as it is well within the scale of catchment modelling schemes. The paper discusses how such data may be made operational by hydrologists using new satellite platforms and combined modelling approaches. Key words ERS-SAR; Essex, UK; semi-variograms; soil moisture variability

Spatio-temporal hydrological modelling in a GIS environment

N. D. K. DAYAWANSA, RANJITH PREMALAL DE SILVA Department of Agricultural Engineering, University of Peradeniya, Peradeniya, Sri Lanka e-mail: [email protected]

JOHN C. TAYLOR Silsoe College, Silsoe, Bedford MK45 4DT, UK

Abstract An attempt was made to combine the spatial capabilities of GIS and the temporal strengths of hydrological modelling to simulate the hydrological dynamics of a drainage basin. Land use information derived from IRS LISS II data was linked with the hydrological information to provide model parameters based on hydrological significance. The time dimension was incorporated into the spatial modelling through a series of REXX programs. The model is found to be sensitive to land use changes in the drainage basin and it shows a 15–35% annual increase of runoff when forests are converted to grasslands. Key words drainage basin; GIS; hydrological modelling; precipitation; runoff; simulation; spatial diversity; spatio-temporal; supervized classification; water balance

A satellite-based rainfall estimation method for the Lake Victoria basin

CARLO DE MARCHI & ARIS GEORGAKAKOS Georgia Water Resources Institute and School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0355, USA e-mail: [email protected]

Abstract This article describes a method for estimating precipitation over the Lake Victoria basin in East Africa using Meteosat images. The method identifies infrared and visible signals characteristic of convective storms and associates their features with ground rainfall measurements. These temporal patterns are recognized at the pixel level via a neural network model, while mean areal precipitation (MAP) is estimated at larger spatial scales. The method successfully identifies convective cells and provides reliable MAP for daily time steps, and even better for longer time intervals. The procedure is implemented within the Lake Victoria Decision Support System (LVDSS), which addresses planning as well as operational applications for water resources, agriculture and hydropower management in the Lake Victoria basin. LVDSS is presently used by several water resources agencies in Kenya, Tanzania and Uganda. Key words bispectral analysis; convective storms; decision support system; East Africa; Lake Victoria; Meteosat; neural networks; rainfall estimation

Evapotranspiration estimates obtained from remote sensing data

P. C. DORAISWAMY USDA-ARS Hydrology and Remote Sensing Laboratory, Beltsville Agricultural Research Center, Beltsville, Maryland 20705, USA e-mail: [email protected]

J. L. HATFIELD & J. H. PRUEGER USDA-ARS National Soil Tilth Laboratory, Ames, Iowa 50011, USA

Abstract The ability to reliably assess effects of global climate change on water resources for agricultural production on regional scales requires appropriate integration of remotely sensed data and ground observations. A semi-empirical model coupling AVHRR data with surface climate data is evaluated to assess regional estimates of evapotranspiration (ET) in central Iowa, USA. Results show ET estimates from the model to be consistent with the magnitudes of measurements at local scales. Key words AVHRR; energy balance; evapotranspiration; Iowa, USA; NDVI

Land use in the Connecticut River basin, USA: combining GIS and stable isotopes

THOMAS A. DOUGLAS & C. PAGE CHAMBERLAIN Dartmouth College Earth Sciences, 6105 Fairchild, Hanover, New Hampshire 03755, USA e-mail: [email protected]

Abstract Stable isotopes of nitrogen have been successfully employed to quantify the extent of non-point source nitrogen contamination in natural waters (Ostrem et al., 1998). Major nitrate sources include atmospheric deposition, fertilizers, animal waste and nitrification of soils and snow. Variations in 15N have been successful in defining these sources in waters (Kendall, 1998). GIS techniques were combined with nitrate concentrations and hydrogen and nitrogen isotopic ratios of river waters to investigate the effect of land use on the water chemistry of the Connecticut River basin in northeastern USA. The results suggest urban development in the southern portion of the basin increases runoff rates and decreases soil residence times. Key words Conneticut River, USA; GIS; hydrogen isotopes; nitrate; nitrogen isotopes

Combining remote sensing and hydrological models to enhance spatial and temporal variability

PETER DROOGERS & WIM BASTIAANSSEN International Water Management Institute, PO Box 2075, Colombo, Sri Lanka e-mail: [email protected]

Abstract The development of water saving measures requires a thorough understanding of the water balance at a high spatial and temporal resolution. Remote sensing is strong in producing information at a high spatial scale, while simulation models are strong in producing water balance estimates at a high temporal resolution. Actual evapotranspiration for an irrigated area in western Turkey was calculated using the SEBAL remote sensing land algorithm using two Landsat images. The hydrological model SWAP was set up to simulate the water balance for the same area, assuming a certain distribution in soil properties, planting dates, and irrigation practices. A comparison between evapotranspiration determined from SEBAL and from SWAP was made, and differences were minimized by adapting the stochastic input in planting date and irrigation practice. The optimized stochastic input data for SWAP was used to simulate all terms of the water balance for the entire irrigation scheme. Key words evapotranspiration; SEBAL; simulation models; SWAP; Turkey

On the accuracy of TOVS surface temperatures: a comparison between measured, modelled, and satellite derived data

MATTHIAS DRUSCH & ERIC F. WOOD Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, USA e-mail: [email protected]

Abstract Surface temperatures from the TOVS Pathfinder Path A dataset were compared with in situ measurements for the Little Washita (1996–1998) and the FIFE study sites (1987). It was found that the uncertainties of the daily values calculated from TOVS data were too high for calibration/validation applications with hydrological models. Surface temperatures obtained from the VIC-3L model (FIFE 87) exhibited good agreement compared to the in situ measurements. Key words FIFE; surface temperature; TOVS; VIC

On the impact of the atmosphere in passive microwave remote sensing of land surface parameters

MATTHIAS DRUSCH, ERIC F. WOOD Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, USA e-mail: [email protected] THOMAS J. JACKSON USDA-ARS Hydrology Laboratory, BARC-W, Beltsville, Maryland 20705, USA

Abstract Data from the SGP97 Experiment and a coupled soil emission–atmosphere radiative transfer model were used to quantify the atmospheric effects on land surface parameter retrieval. Using vertical profiles of air temperature and humidity obtained from radiosonde ascends, the atmospheric contributions to the top of the atmosphere (TOA) brightness temperatures for frequencies ranging from 1.4 to 37 GHz were calculated. In order to derive surface emissivities, the solution of the radiative transfer equation was inverted. Surface emissivities obtained from SSM/I and ESTAR measurements were compared to in situ measurements of volumetric soil moisture. It was found that SSM/I measurements over sparsely vegetated areas could be used to discriminate wet, normal, and dry soil moisture conditions. Atmospheric corrections did not improve the retrieval. Moreover, it was shown that for the retrieval of cloud and atmospheric parameters from 19 GHz measurements, the surface emissivity and therefore soil moisture have to be accurately known. Key words atmospheric water vapour; ESTAR; SGP97; soil moisture; SSM/I

______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 151–155. Using remote sensing data in macroscale hydrological modelling

RALPH DUBAYAH Department of Geography, University of Maryland, College Park, Maryland 20742, USA e-mail: [email protected]

DENNIS LETTENMAIER Department of Civil and Environmental Engineering, University of Washington, Seattle, Washington 98195, USA

ERIC F. WOOD Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, USA

JOSHUA RHOADS Department of Geography, University of Maryland, College Park, Maryland 20742, USA

Abstract There has been considerable focus on the estimation of the spatial and temporal variability of the hydrological and energy budgets of the land surface using macroscale hydroclimatic models. However, performing large-scale applications is greatly complicated by the scarcity of land surface observations needed to force them. Remote sensing offers a potentially powerful alternative to the use of ground observations that historically have provided the sole forcings. In addition, the use of remotely sensed information for data assimilation in such models has begun. In this paper we summarize our experience using a predominantly remote sensing approach to hydrological modelling. Results are presented from the recent NASA EOS Interdisciplinary Science project whose main objectives were to: (a) develop and test a land surface hydroclimatic model, the VIC model, capable of using remotely sensed data for forcing and assimilation; and (b) develop and test remote sensing algorithms appropriate for hydroclimatic modelling. We also present results from a modelling experiment run over the Ohio River basin where the VIC model is driven first by ground- based data, and then by remotely sensed data. Lastly variability comparisons of satellite- derived vs modelled land surface temperature are discussed. Key words distributed modelling; energy balance; forcing variables; hydroclimatology; Ohio River basin; Red- Arkansas River basin; remote sensing; surface temperature; SVATS (soil–vegetation–atmosphere transfer schemes); validation

Simulating surface winds near the Great Salt Lake using the US Army Battlescale Forecast Model

ROBERT E. DUMAIS, JR US Army Research Laboratory, White Sands Missile Range, New Mexico 88002, USA e-mail: [email protected]

Abstract The ability of a mesoscale model to forecast local diurnal winds is largely determined by horizontal resolution and treatment of local surface feature data. The US Army Battlescale Model (BFM) reproduces these types of local surface flow patterns. The current effectiveness of the model is restricted due to lack of high-resolution surface data (albedo, soil moisture, snow cover). A 2 km grid has been created near the Great Salt Lake, and two 7-h model simulations generated. The day is in late May, during a time of weak synoptic flow, with each run initializing at 1200 h UTC (0500 h LST). One run initializes the surface fields with uniform values, while the other uses more realistic values over the regions of the salt flats and Great Salt Lake. Key words albedo; army; BFM (Battlescale Forecast Model); mesoscale; meteorological; moisture; numerical; temperature; Utah (USA); winds

Remote sensing of canopy variables for the application of hydrological models

GUIDO D’URSO & ALESSANDRO SANTINI Department of Agricultural Engineering and Agronomy, University of Naples “Federico II”, Via Università 100, I-80055 Portici (Naples), Italy e-mail: [email protected]

Abstract The integration of hydrological simulation models with satellite data is presented. Semi-empirical algorithms for retrieving biophysical parameters of land cover, such as leaf area index, surface albedo and canopy roughness, from remote sensing data with different spatial and temporal resolution are available. The spatial distribution of leaf area index (LAI), surface albedo and canopy roughness, derived from satellite images, can be used in conjunction with ground-based meteorological data for mapping the potential fluxes of soil evaporation and canopy transpiration. This information, together with soil properties data, provides the input data for the numerical simulation of soil and crop water flow processes. Key words albedo; canopy; evapotranspiration; hydrological simulation model; Landsat TM; leaf area index; soil water flow; WDVI

Accuracy assessment of temporal and spatial up-scaling of IR rain cloud duration techniques

GORM DYBKJAER Institute of Geography, University of Copenhagen, Oester Voldgade 10, DK-1350 Copenhagen, Denmark e-mail: [email protected]

Abstract Analysis of spatial and temporal sensitivity of the IR rain cloud duration (RCD) methods are presented. It is shown that the remote sensing based rainfall algorithms provide the best fit to aggregated rainfall data over periods of approximately six days inside user defined areas of homogenous climatic zones. Also presented is a simple use of microwave brightness- temperature data, to separate large areas into homogenous climatic zones and improve RCD rainfall estimates significantly. Key words climatic variability; rain cloud duration; rainfall; west Africa

Development of a GIS-based model to estimate landscape water demand at the urban/rural interface

FAYEK FARAG, CHRISTOPHER M. U. NEALE Department of Biological and Irrigation Engineering, Utah State University, Logan, Utah 84322, USA e-mail: [email protected] ROGER KJELGREN Plants, Soils and Biometeorology Department, Utah State University, Logan Utah 84322, USA

Abstract In the arid west of the United States, there has been a redistribution of water from agriculture to municipal, industrial, recreational, and environ-mental uses due to population growth. A growing municipality in search for new water resources usually leads to a rural-to- urban conversion of water uses, affecting irrigated agriculture. Multispectral airborne digital images at one-metre resolution were collected over agricultural and urban landscaped areas in the City of Layton, Utah. Spectral signatures were extracted from the image representing the classes of interest. Water demand in the urban areas was calculated as the volume of water consumed by each house for irrigated landscape areas. Comparison between the estimated volume of water used for irrigation purposes and the actual water use obtained from the water billing data was studied. This study demonstrated the ability to use high-resolution airborne imagery in a GIS environment to estimate landscape water demand for individual houses or subdivisions. This allows the water supplier to identify and target particular end users with water conserving measures. Key words GIS analysis of irrigated urban landscape; Utah, USA; urban landscape water demand; urban study area

Enhancing weather radar winter precipitation accumulation estimates

S. R. FASSNACHT Department of Hydrology and Water Resources, University of Arizona, Tucson, Arizona 85721-0011, USA e-mail: [email protected]

E. D. SOULIS & N. KOUWEN Department of Civil Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada

Abstract Snowfall estimates for weekly, monthly, and seasonal accumulation periods have been compared to measured Nipher-shielded Belfort precipitation gauge quantities. A local scaling issue that caused overestimates is discussed. To enhance the accumulation estimates, the conventional scan radar images were adjusted using the near surface air temperatures. The adjustment for mixed precipitation improved the accumulation estimates, while the subsequent particle shape adjustment for snow crystal shape did not further enhance the radar estimates. Key words mixed precipitation; precipitation measurement; radar; rainfall; snowfall

Use of sub-pixel information from optical sensors to adjust passive microwave based snow water equivalent estimates

RICHARD A. FERNANDES, IRENE G. RUBINSTEIN Department of Mathematics and Statistics, Centre for Research in Earth and Space Technology, York University, North York, Ontario M3J 3K1, Canada e-mail: [email protected]

SEBASTIAN MARTIN Department of Applied Physics and Electronics and Mechanical Engineering, University of Dundee, Dundee DD1 4HN, Scotland, UK

Abstract A relationship between the microwave loss factor and leaf area index is defined using airborne microwave and optical data over a boreal conifer stand. Stand brightness temperature is simulated for winter and melt periods using high resolution (2 m to 30 m) leaf area maps and specified snow cover conditions. Coarser resolution images (30 m to 1 km) are used to map leaf area index and snow cover with existing spectral indices and with the FLIM- CLUS model. Both approaches overestimate winter snow water equivalent (SWE) on the order of 20% and underestimate spring SWE on the order of 35%. Only minor differences were noticed when changing the resolution of the optical data. Key words canopy reflectance model; data fusion; forest brightness temperature; leaf area index; microwave loss factor; passive microwave; scaling; snow water equivalent; spectral index ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 27–31.

Analytical software for validating time synchronous radar and raingauge data

BRAD FISHER, DAVID B. WOLFF SSAI Corporation, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, USA e-mail: [email protected]

EYAL AMITAI University of Maryland Baltimore County/JCET, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

Abstract Validation studies that compare radar and gauge data are often skewed due to poor data quality. The Tropical Rainfall Measuring Mission (TRMM) Global Validation (GV) Programme uses regional gauge networks to compute corrections to a standard reflectivity- rain rate (Z–R) relationship. This bulk adjustment scheme requires quality gauge and radar data as input. In support of this operational effort, a software package called the Radar Rain Gauge Analysis Tool (RRGAT) was developed to ingest gauge time series data and full radar volume scans for graphical analysis. RRGAT was designed to allow users to compare individual gauge time series with the radar data over a small areal region (6 km  6 km) centred on the gauge. Keywords bulk-adjustment; radar-gauge quality control; radar-gauge validation; RRGAT

ARSGISIP: a European project on the application of remote sensing techniques for the parameterization of hydrological, erosion and solute transport models

WOLFGANG-ALBERT FLÜGEL, BETTINA MÜSCHEN, VOLKER HOCHSCHILD Institute for Geography, Department of Geoinformatics, Hydrology and Modelling, Friedrich-Schiller-University of Jena, Löbdergraben 32, D-07743 Jena, Germany e-mail: [email protected]

KLAUS STEINNOCHER Systems Research Division, Environmental Planning Department, Austrian Research Centers, A-2444 Seibersdorf, Austria

Abstract The overall objective of the EU project ARSGISIP is to promote the application of remote sensing techniques and GIS integration for the parameterization of hydrological, erosion, and solute transport models. Activities of the first project stage are presented, emphasizing the common environmental problem of nutrient leaching within two representative basins located in Germany and Austria. The scientific approach is focused on physical parameters describing soil and vegetation cover by means of multi-resolution and multi-spectral land-use classifications using Landsat-5 TM and IRS-1C PAN data. The results obtained clearly demonstrate the advantage of Earth Observation (EO) data for model parameterization when compared with traditional methods of field mapping. Key words classification; hydrological modelling; Innbach (Austria); parameterization; PRMS; solute transport modelling; WASMOD; Zeulenroda (Germany)

Heat flux distributions over SGP97 sites

ANDREW N. FRENCH, THOMAS J. SCHMUGGE & WILLIAM P. KUSTAS USDA-ARS Hydrology Laboratory, BARC-W, Beltsville, Maryland 20705, USA e-mail: [email protected]

Abstract The ability to reliably estimate the spatial distribution of surface energy fluxes using remotely sensed data is investigated using information collected during the Southern Great Plains 1997 Experiment (SGP97) campaign in Oklahoma, USA. The SGP97 data set is especially valuable because it contains four consecutive cloud-free days of simultaneous remote sensing and ground observations. The remote sensing data primarily consist of aircraft based multi-band thermal and visible-near infrared sensors combined with ground observations to predict surface sensible and latent heat fluxes. These energy fluxes were computed using a two-source model, which is a method requiring relatively few input parameters. The most important of these are surface temperatures and vegetation cover derived from remote sensing data, and near surface meteorological data, which include surface wind speed, air temperature and humidity. Energy fluxes were computed from SGP97 sites at El Reno, Oklahoma at mid-morning times on 29 June to 2 July 1997. These days correspond to a dry-down period immediately following a 61 mm rainfall on 28 June. When compared with surface based measurements, modelled evaporative fractions were generally in good agreement. Evaporative fractions over vegetated fields showed small changes over the period, while the evaporative fraction markedly decreased over bare soil. Key words El Reno; heat flux; Oklahoma; SGP97; Southern Great Plains 1997 Experiment; spatial distribution of flux; two source; TIMS

Quantitative rainfall estimates with radar using a weighted multiple regression

MARCO GABELLA, GIOVANNI PERONA Dipartimento Elettronica, Politecnico di Torino, C. so Duca degli Abruzzi 24, I-10129 Torino, Italy e-mail: [email protected]

JUERG JOSS Osservatorio Ticinese, Swiss Meteorological Institute, Via ai Monti 142, CH-6605 Locarno Monti, Switzerland Abstract A technique to mitigate the hostile effects of a complex orography on precipitation estimated by radar is analysed. The corrections are derived as a function of the distance from the radar, the height of visibility and the height of the ground, at each pixel. Two C-band radars, 140 km apart are analysed: two  60 radar–gauge data pairs in an Alpine region are used for training a correction scheme based on weighted multiple regression. Furthermore, about 2500 radar-derived pairs of precipitation amounts are compared in a “mutual coverage” area (10 000 km2). The correction adjusts the bias of the radar’s values and reduces the standard deviation by a factor of three. Key words adjustment; errors; precipitation over complex orography; precipitation; radar rainfall estimates; weighted multiple regression ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 321–326.

Utilization of Radarsat in integrated catchment management

MARTINE GALARNEAU, ROBERT LECONTE, FRANÇOIS BRISSETTE ARDEM Research Group, École de Technologie Supérieure, Université du Québec, 1100 Notre-Dame West, Montréal, Québec H3C 1K3, Canada e-mail: [email protected]

TERRY J. PULTZ Applications Division, Canada Centre for Remote Sensing, 588 Booth Street, Ottawa, Ontario K1A 0Y7, Canada

JEAN ROUSSELLE Department of Civil Engineering, École Polytechnique de Montréal, CP6079 Succursale Centre-Ville, Montreal, Québec H3C 3A7, Canada

Abstract This paper discusses the development and validation of an algorithm for extracting soil moisture data from Radarsat images in a form suitable for hydrological simulations and forecasts. A total of seven ascending Radarsat images of the Châteauguay River basin were acquired approximately at 18:00 h local time, between 2 May and 10 November 1998. Soil moisture information was extracted at the field level from Radarsat C-Band SAR using a semi-empirical radar backscatter model. Soil surface roughness was evaluated at the basin scale using a test image and assuming known soil moisture conditions. Soil moisture maps were then produced at the basin scale. These maps are then extended to the root zone using correlation functions obtained from the Richards equation, thus producing basin-scale soil moisture maps suitable for hydrological modelling purposes. Key words basin scale; hydrological modelling; Quebec, Canada; Radarsat; SAR; soil moisture; soil roughness ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 286–291.

Remotely sensed estimates of evaporation for irrigated crops in northern Mexico

JAIME GARATUZA-PAYAN Instituto Tecnologico de Sonora, 5 de Febrero 818 Sur, Ciudad Obregon, Sonora 85000, México e-mail: [email protected]

W. JAMES SHUTTLEWORTH Department of Hydrology and Water Resources, Harshbarger Building 11, The University of Arizona, Tucson, Arizona 85721, USA

RACHEL T. PINKER Department of Meteorology, Space Sciences Building, University of Maryland, College Park, Maryland 20742, USA

CHRISTOPHER J. WATTS Instituto del Medio Ambiente y Desarrollo de Sonora, Reyes y Aguascalientes, Hermosillo, Sonora, México

Abstract Hourly estimates of solar radiation were derived from satellite data for the Yaqui Valley in Mexico, made on a 50 km grid using the GEWEX/SRB algorithm applied with GOES-East data and, on a 4 km grid, using a high-resolution development of the algorithm with GOES-West data. On average, values derived from GOES-East are 18% greater, while those from GOES-West are 9% lower than field measurements. After re-calibration, random differences between hourly satellite estimates and surface observations remained. These were markedly reduced when daily-average values were compared. Root mean square error (RMSE) between the satellite and the surface measurements is lower for the high-resolution satellite estimates than it is for the low-resolution estimates, and there is a noticeable increase in apparent structure with the high-resolution data. Finally, the application of the high- resolution estimates of solar radiation to calculate daily estimates of crop evaporation for wheat and cotton fields is demonstrated. Key words cotton; evapotranspiration; GOES; Makkink equation; Mexico; remote sensing; solar radiation; Sonora; wheat

A real-time flood forecasting system based on GIS and DEM

SANDRA G. GARCÍA UTE SEGURA 2000, Plaza Fontes 1, E-30001 Murcia, Spain e-mail: [email protected]

Abstract A real-time operative decision support computer system named Shyska is presented. The system applies the potential of GIS to processing information to different space–time scales. It integrates spatially-distributed hydrological models, oriented to runoff simulation and prediction, using topographical attributes extracted from a DEM. Its final aim is to assist Hydrological Information Automatic Systems (SAIH) in Spain, facilitating information management and use in real-time during alert and flash-flood situations typical of Mediterranean environments. Shyska has been applied to semiarid basins in southeast Spain, using pluviometric information from telemetric networks and the products of remote sensing, presenting satisfactory results. The sensitivity of results, both the spatial distribution of geomorphological and hydrodynamic parameters, to DEM resolution is investigated. Key words DEM; distributed hydrological models; flash flood forecasting; GIS; Spain

Operational determination of snow water equivalent using Radarsat data over a large hydroelectric complex in eastern Canada

YVES GAUTHIER, MONIQUE BERNIER, JEAN-PIERRE FORTIN INRS-Eau, Université du Québec, 2800 rue Einstein, CP 7500, Sainte-Foy, Québec G1V 4C7, Canada e-mail: [email protected]

RAYMOND GAUTHIER, RENÉ ROY Prévisions et Ressources Hydriques, Hydro-Québec, 75 René-Lévesque Ouest, 9ième étage, Montréal, Québec H2Z 1A4, Canada

PIERRE VINCENT Viasat Géo-Technologie , 419 boulevard Rosemont, Montréal, Québec H2S 1Z2, Canada

Abstract The operational feasibility of using Radarsat ScanSAR data to estimate the spatial distribution of snow water equivalent (SWE) in the La Grande River basin, a large hydroelectric complex located in a subarctic climatic region (Northern Québec, Canada), is demonstrated for the 1998–1999 winter season. The methodologies developed for this project have been implemented within a MapInfoTM application that has been named EQeau. Analysis of ScanSAR images has shown that they can yield results similar to wide mode images, despite their lower resolution. On a sub-basin level, EQeau and ScanSAR images have given similar SWE ( 1–12%) to those derived from Hydro-Quebec snow lines for January and March 1999. Key words Radarsat; operational; ScanSAR mode; snow water equivalent

Estimation of pixel-scale daily rainfall over Nile River catchments using multi-spectral METEOSAT data

KONSTANTINE P. GEORGAKAKOS, DIMITRIS TSINTIKIDIS Hydrologic Research Center and Scripps Institution of Oceanography, 12780 High Bluff Drive, Suite 250, San Diego, California 92130, USA e-mail: [email protected]

BAYOUMI ATTIA Ministry of Water Resources and Irrigation, Planning Sector, Cairo, Egypt

JOZEF ROSKAR Food and Agriculture Organization of the United Nations, Cairo, Egypt

Abstract Visible, infrared and water vapour data from METEOSAT are used in a multispectral methodology to estimate small-scale daily rainfall over the Nile River basin. Rainy areas are first delineated every half hour and then daily linear regression is used to estimate daily rainfall amounts from half-hourly delineated areas and observed daily raingauge rainfall. Validation tests of the consistency of the rainfall estimates were based on reproduction of spatial averages over large domains of the Nile River and temporal averages at raingauge sites. Use with a distributed hydrological model for the Blue Nile basin with outlet at Diem, Sudan, shows good performance in simulating daily flows. The methodology is used at the Nile Forecast Center in Cairo as part of the operational Nile Forecast System. Key words Nile River; satellite hydrology; satellite rainfall estimation

Assessment of the renewable groundwater resources of Wadi El-Arish, Sinai, Egypt: modelling, remote sensing and GIS applications

HAZEM M. GHEITH EMH&T, South East Building, 140 North High Street, Gahanna, Ohio 43230, USA e-mail: [email protected] MOHAMED I. SULTAN Argonne National Laboratory, Environmental Research Division, 9700 South Cass Avenue, Argonne, Illinois 60439, USA

Abstract Recharge of the alluvial aquifers flooring Wadi El-Arish in central and northern Sinai, Egypt was investigated. A hydrological model that combined the spatial and temporal distribution of rainfall, suitable infiltration parameters, and appropriate sub-basin unit hydrographs to estimate rainfall excess, transmission losses along stream networks, and downstream runoff was developed. The Wadi El-Arish watershed receives an annual average rainfall of 981.3  106 m3 in the rainy season (November–March) of which our model indicates that 938.7  106 m3 is the initial upstream loss, 32.5  106 m3 is the transmission loss recharging the alluvial aquifers flooring the stream network, and 10.1  106 m3 is downstream runoff. Key words alluvial aquifer; arid region; groundwater recharge; Landsat TM; remote sensing; Sinai, transmission losses

Improved snow cover remote sensing for snowmelt runoff forecasting

ENRIQUE GOMEZ-LANDESA, ALBERT RANGO USDA-ARS Hydrology Laboratory, Beltsville, Maryland 20705, USA. e-mail: [email protected]

DOROTHY K. HALL NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

Abstract A system based on satellite remote sensing has been developed for snow cover monitoring of a number of basins in the Spanish Pyrenees. The snow covered area is used as an input for snowmelt runoff forecasts on 42 basins using the Snowmelt Runoff Model (SRM). The forecast snowmelt volume accumulated from May to September is sent to the hydropower companies for water resources management. A sub-pixel analysis is carried out to map the snow cover with Advanced Very High Resolution Radiometer (AVHRR) data on board the National Oceanic and Atmospheric Administration (NOAA) satellites. Two mapping methods are compared: a linear combination of visible and near infrared channels, and a snow classification based on the normalized difference snow index (NDSI) and the normalized difference vegetation index (NDVI). Key words AVHRR; Spanish Pyrenees; remote sensing; snow mapping; snowmelt runoff; streamflow forecasting; sub-pixel analysis; water resources

Use of remote sensing for validation and assimilation in mesoscale models

PATRICK GROSS, CLEMENS SIMMER, GISELA MÜLLER & GÜNTHER HAASE Meteorological Institute, University of Bonn, Auf dem Hügel 20, D-53121 Bonn, Germany e-mail: [email protected] Abstract Radar derived precipitation and satellite derived cloud characteristics are assimilated into the SVAT module of a mesoscale atmospheric model. The radar data are additionally used to initialize the vertical wind field of the model forecast. The validation of the model results shows that the simulated hydrological cycle is better represented by means of the assimilation. Key words assimilation; hydrological modelling; mesoscale modelling; remote sensing; validation

Estimation of snow cover over large mountainous areas using Radarsat ScanSAR

HAROLD HAEFNER, DAVID SMALL, STEFAN BIEGGER, HILKO HOFFMANN & DANIEL NÜESCH Remote Sensing Laboratories, Department of Geography, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland e-mail: [email protected]

Abstract As part of our general objective to develop and operationalize methods for snow monitoring in high mountain terrain, the possibilities of snow cover mapping over large mountainous areas—e.g. almost the entire Swiss Alps and Pre-Alps—using Radarsat ScanSAR, and NOAA-AVHRR for comparison, are evaluated. The generation of snow masks in AVHRR scenes is achieved using a simple threshold-based method. A change detection approach is employed to compare the two SAR-scenes. It is expected that the most important differences will result from vast changes in the snow cover. Since large parts of the Swiss Plateau were also snow covered in the winter scene, other changes in land cover are expected to have only minor influence. Hence, it will be possible to assess the total snow cover by combining the information gained from the SAR ratios with the relief information from the DEM. Results from the two sensors are compared with each other, and with ground-based meteorological observations. Verification using a finer temporal resolution is desirable. Key words change detection; monitoring of large mountainous areas; NOAA-AVHRR; Radarsat ScanSAR; snow cover estimation; Swiss Alps

Earth Observing System (EOS) Moderate Resolution Imaging Spectroradiometer (MODIS) global snow-cover maps

DOROTHY K. HALL Hydrological Sciences Branch, Code 974, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, USA e-mail: [email protected]

GEORGE A. RIGGS Research and Data Systems Corporation, Greenbelt, Maryland 20770, USA

VINCENT V. SALOMONSON Earth Sciences Directorate, Code 900, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

GREG R. SCHARFEN National Snow and Ice Data Center, University of Colorado, Boulder, Colorado 80309, USA Abstract Following the 1999 launch of the Earth Observing System (EOS) Moderate Resolution Imaging Spectroradiometer (MODIS), the capability exists to produce global snow-cover maps on a daily basis at 500 m resolution. Eight-day composite snow-cover maps are also available. The snow maps are also produced at a spatial resolution of 1/4  1/4, and enhancements are available that provide information on sub-pixel (fractional) snow cover. MODIS snow-cover products are produced at Goddard Space Flight Center and archived and distributed by the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado. The products are produced in both orbital and gridded formats. An online search and order tool and user-services staff are available at NSIDC to assist users with the snow products. Pre- launch validation work has shown that snow-mapping algorithms perform best under conditions of continuous snow cover in low vegetation areas, but can also map snow cover in dense forests. Post-launch validation activities are being performed using field and aircraft measurements from a March 2000 validation mission, as well as from existing satellite- derived snow-cover maps from NOAA and Landsat-7 Enhanced Thematic Mapper Plus (ETM+). Key words Earth Observing System; satellite snow mapping; snow cover

Scaling-up evapotranspiration from field to regional scale based on optical remote sensing scenes

CHARLOTTE BAY HASAGER, NIELS OTTO JENSEN Atmospheric Physics, Wind Energy Department, Risoe National Laboratory, DK-4000 Roskilde, Denmark email: [email protected]

EVA BOEGH, HENRIK SOEGAARD Institute of Geography, University of Copenhagen, Oester Voldgade 10, DK-1350 Copenhagen K, Denmark

ANTON THOMSEN & KIRSTEN SCHELDE Danish Institute of Agricultural Sciences, PO Box 50, DK-8830 Tjele, Denmark

Abstract Evapotranspiration is modelled by a surface-flux aggregation model for a landscape with field patches of the size order of tens of metres to a kilometre. The model results of friction velocity and sensible heat flux are compared at the local scale to field data collected at 3 m height in five different crops and at the regional scale to data from a 48 m tall mast. At the local scale the model prediction is good for friction velocity but for sensible heat the model results still have some problem. At the regional scale both friction velocity and sensible heat flux are modelled with good results. Key words aggregation; heterogeneous terrain; nonlinear processes; surface fluxes

Evaporation rates in Tamarisk

LAWRENCE E. HIPPS Plants, Soils and Biometeorology, Utah State University, Logan, Utah 84322, USA e-mail: [email protected]

JOHN H. PRUEGER USDA-ARS National Soil Tilth Laboratory, Ames, Iowa 50011, USA SALIM BAWAZIR Civil and Geological Engineering, New Mexico State University, Las Cruces, New Mexico 88003, USA

Abstract The evaporation rates and energy balance for Tamarisk vegetation along the Rio Grande in New Mexico are examined. The main objective is to generate knowledge of the key biophysical factors that control the water use by this vegetation community. Current results indicate that evaporation is often energy limited and close to the equilibrium rate, which reflects the fairly large extent of the vegetation corridor. However, there are times when the evaporation is largely controlled by saturation deficit, reflected in small values of the omega or coupling factor. This is most commonly observed during afternoons. The increase in saturation deficit during these times can result from horizontal advection of warm, dry air when winds blow across the corridor. Or it can result from the imposition of drier air from the mixed layer during the afternoon hours, when the ABL is strongly coupled to the surface. The results will be integrated with other physiological measurements made at the site. The findings will provide the direction for development of appropriate models for water use of this important ecosystem. Key words energy balance; evapotranspiration; New Mexico; riparian vegetation; Tamarisk

Hydrological analysis of high resolution multifrequent, multipolarimetric and interferometric airborne SAR data

VOLKER HOCHSCHILD & MARTIN HEROLD Institute for Geography, Department of Geoinformatics, Hydrology and Modelling, Friedrich-Schiller-University of Jena, Löbdergraben 32, D-07743 Jena, Germany e-mail: [email protected]

Abstract Hydrological applications, i.e. physically-based, distributed hydrological modelling, require areal input for parameterization and validation of water cycle components. Active microwave remote sensing research shows the eligibility of multifrequent, multipolarimetric and interferometric SAR data to retrieve land use, topography, soil moisture and vegetation information. In this study, data of the multifrequent, multipolarimetric and interferometric airborne Experimental Synthetic Aperture Radar (E-SAR) were evaluated and analysed to derive land use information, surface soil moisture and plant water content using a standardized scheme. Topographic information was derived using X-band single pass interferometry. Multipolarimetric L-Band data show the highest information content of hydrologically relevant parameters. The hydrological parameters of land use and vegetation features (plant water content, biomass, plant height) were derived with satisfying accuracy. Problems were encountered during the soil moisture calculation as a result of the influence of vegetation on the L-band backscatter and the large incidence angles. Key words German mid-mountain range; hydrological parameters; land cover; level approach; multifrequent airborne SAR; soil moisture; vegetation parameters

Dynamics of bar growth using remote sensing data

M. M. HOSSAIN, M. K. HASAN & M. A. MUKTO Department of Water Resources Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh e-mail: [email protected]

Abstract The dynamics of bar growth in alluvial rivers may be studied using remote sensing and hydrological data. Results of a study conducted to examine the morphological features of two characteristic bars of the Jamuna River in Bangladesh for the period from 1973 to 1997 based on PC ARC/INFO and ArcView GIS are presented. The study revealed that the area, average width and average length of the selected bar had an overall diminishing trend. A comparison of the common bar area in 1997 with that of 1973 showed the existing bar area reduces to about 2.5%. The study showed that the inundation of the selected bars increased from 271 ha to 418 ha due to a change in water level from 7.33 m to 9.05 m, whereas it increased from 418 ha to 2218 ha with a rise of water level from 9.05 m to 12.07 m. When the water level was at 17.5 m, the bars were completely submerged. Key words bar dynamics; Ganges-Bhramaputra-Meghna basin; GIS; Jamuna River, Bangladesh; satellite imagery; morphology; PC ARC/INFO and Arc View

Flood damage and management modelling using satellite remote sensing data with GIS: case study of Bangladesh

MD. MONIRUL ISLAM Tropical Marine Science Institute, National University of Singapore, 14 Kent Ridge Road, Singapore 119223 e-mail: [email protected]

KIMITERU SADO Department of Civil Engineering, Kitami Institute of Technology, 165 Koen-cho, Kitami 090-8507, Japan

Abstract Physiographic divisions, geological divisions, land cover categories and drainage network data were used as GIS components. Flood frequency and floodwater depth were estimated using NOAA AVHRR data for the development of a flood hazard map. The flood hazard map provides information for the development of counter measures and preparation of high risk areas, on a priority basis, against flood damage. It is concluded that the flood hazard map, which was developed by considering the interaction of floodwater depth and flood frequency, gives good results for other events. Key words elevation height; flood affected frequency; flood hazard map; floodwater depth; geological division; hazard rank; land cover classification; physiographic division; ranking matrix

Using airborne Vis-NIR-TIR data and a surface energy balance model to map evapotranspiration at high spatial resolution

FREDERIC JACOB, ALBERT OLIOSO, XINGFA GU, JEAN-FRANÇOIS HANOCQ INRA-Bioclimatologie, Site Agroparc, F-84914 Avignon Cedex 9, France e-mail: [email protected]

OLIVIER HAUTECOEUR CESBIO, 18 avenue E. Belin, F-31055 Toulouse, France BERNARD SEGUIN INRA-Bioclimatologie, Site Agroparc, F-84914 Avignon Cedex 9, France

ZHONGBO SU DLO Winand Staring Center, PO Box 125, 6700 AC Wageningen, The Netherlands

Abstract This paper presents the mapping of surface energy fluxes in a Mediterranean agricultural region using two original tools. The first one is a set of high spatial resolution remote sensing data, allowing the consideration of 100 m size agricultural fields, and the second is a surface energy balance model that retrieves some variables of interest through the spatial variability depicted by the study area. The proposed approach was tested using field measurements on different crops during one year. The comparison showed that the key points of the model gave realistic results and that the energy flux estimates were in agreement with experimental reference measurements. Key words high spatial resolution; single layer model; spatial variability; surface energy balance; validation; VIS-NIR-TIR multidirectional remote sensing

Seasonal evapotranspiration estimation using canopy reflectance: a case study involving pink beans

HARIKISHAN JAYANTHI, CHRISTOPHER M. U. NEALE Biological and Irrigation Engineering Department, Utah State University, Logan, Utah 84322-4105, USA e-mail: [email protected]

JAMES L. WRIGHT Northwest Irrigation and Soils Research Laboratory, USDA-ARS, Kimberly, Idaho 83341, USA

Abstract In the estimation of crop evapotranspiration (ET) crop coefficients are employed to simulate soil moisture in the crop root zone. Remote sensing offers an excellent means of determining near real time crop coefficients for most irrigated crops. In the absence of prior knowledge of planting, emergence and/or full effective cover dates, canopy reflectance can be used to establish the growth rate of the crop, and subsequently can be used to fractionalize the reference ET for irrigation scheduling. This paper presents the results of extending the reflectance-based crop coefficient methodology, initially developed for corn, to pink beans. Simulation results indicate that the reflectance-based coefficients follow the actual crop growth in the field, and thus can simulate the measured soil moisture content. Key words basal crop coefficient; evapotranspiration; Kimberly, Idaho; pink beans; reflectance-based crop coefficient; root zone soil water balance; Soil Adjusted Vegetation Index (SAVI)

Using remote sensing data to update the simulated snow pack of the HBV runoff model

BARBRO JOHANSSON Swedish Meteorological and Hydrological Institute, SE-601 76 Norrköping, Sweden e-mail: [email protected] RON CAVES Sheffield Centre for Earth Observation Science, The University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, UK

ROB FERGUSON & OWEN TURPIN Sheffield Centre for Earth Observation Science, The University of Sheffield, Department of Geography, Winter Street, Sheffield S10 2TN, UK

Abstract The conceptual HBV model is widely used in Scandinavia for operational runoff forecasts. Snow accumulation and snowmelt are modelled from point observations of precipitation and temperature. A method has been developed within the Hydalp Project to use remote sensing to correct errors in simulated snow cover. The method was tested in real-time forecasts during the spring of 1999. The results only represent one season and one catchment, but they clearly show that remote sensing data can be used to improve HBV forecasts. Key words HBV; Hydalp; runoff forecasts; runoff modelling; Scandinavia; snow

Image and in situ data integration to derive sawgrass density for surface flow modelling in the Everglades, Florida, USA

JOHN W. JONES US Geological Survey, Reston, Virginia 20192, USA e-mail: [email protected]

Abstract The US Geological Survey is building models of the Florida Everglades to be used in managing south Florida surface water flows for habitat restoration and maintenance. Because of the low gradients in the Everglades, vegetation structural characteristics are very important and greatly influence surface water flow and distribution. Vegetation density is being evaluated as an index of surface resistance to flow. Digital multispectral videography (DMSV) has been captured over several sites just before field collection of vegetation data. Linear regression has been used to establish a relationship between normalized difference vegetation index (NDVI) values computed from the DMSV and field-collected biomass and density estimates. Spatial analysis applied to the DMSV data indicates that thematic mapper (TM) resolution is at the limit required to capture land surface heterogeneity. The TM data collected close to the time of the DMSV will be used to derive a regional sawgrass density map. Key words biomass; Florida Everglades, USA; multispectral; NDVI; sawgrass; spatial autocorrelation; vegetation quadrats

Application of a hydrological model with integration of remote sensing and GIS techniques for the analysis of land-use change effects upon river discharge

CARSTEN JÜRGENS Department of Geography, University of Regensburg, D-93040 Regensburg, Germany e-mail: [email protected]

Abstract This investigation compares how two adjacent mesoscale catchments with suburban development activities react to land-use changes. It is very likely that an increasing percentage of impervious area affects the size of peak discharge in a river. To prove this remote sensing was used to determine the actual land use in two catchments at two different dates, and the land-use changes that occurred between these dates. The results and additional spatial data were stored and processed in a GIS system to facilitate data input to the hydrological catchment model ANSWERS (Beaseley & Huggins, 1991). The calculations demonstrated that due to continuous construction activities, the increased impervious land area causes higher peak discharges than earlier when the impervious area was smaller. Further simulation scenarios give guidance for future land-use planning within the study area. The model used proves to be an efficient tool for mesoscale modelling using GIS datasets. Key words ANSWERS; Germany; GIS; simulation

Remote sensing of UK snow covers using multi-sensor satellite imagery

RICHARD KELLY School of Geography, Birkbeck College, 7–15 Gresse St, London W1P 2LL, UK e-mail: [email protected]

Abstract At global scales, the Special Sensor Microwave Imager (SSM/I) can provide frequent information about snow cover area and snow water equivalent of liquid free snow under all but the thickest cloud. Continuous, liquid-free snow over an entire SSM/I footprint can be identified by its electromagnetic scattering properties at high frequencies (>25 GHz) with the degree of scattering proportional to the snow water equivalent of the snow layer. However, high frequency microwave radiation also can be scattered by discontinuous snow cover at regional/local scales (e.g. UK). Analysis of multi-temporal coincident AVHRR and SSM/I data reveals that the degree of microwave scattering is related to the percentage cover of snow within the footprint. Thus, for UK studies, unqualified application of snow monitoring algorithms calibrated for global applications can lead to ambiguities when applied at regional/local scales. Key words monitoring; passive microwave; remote sensing; resolution; snow, snow depth; snow water equivalent; spatial resolution; temporal resolution; visible/infra-red

Evapotranspiration at the basin scale estimated from satellite data and by a hydrological model

GEOFF KITE Hydrologic-Solutions, 1 Metcalfe Close, Abingdon, Oxfordshire OX14 5TH, UK e-mail: [email protected]

RAOUL GRANGER National Water Research Institute, Saskatoon, Canada

GAYATHREE JAYASINGHE International Water Management Institute, Colombo, Sri Lanka

Abstract Evaporation and transpiration are important components of the hydrological cycle from both a research and a practical point of view. Measures of irrigation productivity regard transpiration as a measure of crop growth and evaporation as an indicator of un-utilized water. Evapo-transpiration (ET) may be estimated at a point from climate station data but estimating evapotranspiration over large areas such as irrigation schemes or river basins is more difficult. This paper compares two recent methods, remote sensing and hydrological modelling, that are able to compute areal estimates of evapotranspiration. First, estimates of evapotranspiration for the 17 200 km2 Gediz Basin in western Turkey are made for a series of days in 1998 based on a feedback algorithm using data from the NOAA-AVHRR satellite sensor. Second, a distributed hydrological model is applied to the same basin and, as part of the daily vertical water balance, derives estimates of actual crop transpiration and soil evaporation for the 1998 irrigation season. Both methods estimate evapotranspiration for each land cover and location within the basin. Results show that remote sensing and model estimates of ET are in reasonable agreement. Key words evapotranspiration; modelling; remote sensing; Turkey

Remote sensing and operational snowmelt runoff prediction: the Swiss contribution to HYDALP

HANNES KLEINDIENST, STEFAN VOIGT & MICHAEL F. BAUMGARTNER Department of Geography, University of Bern, Hallerstrasse 12, CH-3012 Bern, Switzerland e-mail: [email protected]

Abstract Within the HYDALP project, methods were developed for real time operational snowmelt runoff prediction using combined NOAA-AVHRR data, meteorological forecasts, and hydrological modelling. During the snowmelt season of 1999 the system was applied in real-time and on an operational basis. On 79% of the forecast days, prediction errors of less than 20% were achieved, with a total volume difference of –4.9% compared to the observed stream flow and an R2 value of 0.88. Key words HYDALP; Inn basin; NOAA-AVHRR; runoff forecast; snow cover; snowmelt; SRM-Java; Switzerland

Extracting land-cover information from ERS SAR intensity and coherence data for hydrological model parameterization

MARTIN KLENKE Alfred Wegener Institute for Polar and Marine Research, Bathymetry and Geodesy Group, PO Box 12 01 61, D-27515 Bremerhaven, Germany e-mail: [email protected]

WOLFGANG-ALBERT FLÜGEL Department of Geoinformatics, Hydrology and Modelling, Institute of Geography, Friedrich-Schiller-University Jena, Löbdergraben 32, D-07743 Jena, Germany

Abstract Multi-temporal SAR data from the ERS-1/2 Tandem Mission (1995–1996) was used to extract land cover information in a mesoscale basin. The actual land cover plays a key role in the parameterization of distributed, physically-based watershed models. For land cover classification both SAR intensity and coherence information were utilized. Principal Components Analyses (PCA) were used to reduce the strong radiometric terrain effect in the intensity data. It was possible to separate main land cover classes with accuracies sufficient for model parameterization. Moreover the results show that coherence information is valuable additional information complementary to the frequently analysed SAR backscatter intensity. Key words land-cover classification; model parameterization; SAR data analysis

A technique for estimating the evaporation from deserts by remote sensing

TETSUO KOBAYASHI Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan e-mail: [email protected]

WENJUN HE Arid Land Research Center, Tottori University, 1390 Hamasaka, Tottori 680-0001, Japan

WEIZHEN WANG Division of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan

Abstract Evaporation from a hot, dry soil surface cannot be regarded as an isothermal process and its rate is not proportional to the difference in water vapour density between the soil surface and the overlying air. Therefore, a method was formulated to estimate the upward flux of water vapour through the dry surface layer of soil (DSL) from the difference in water content between its top and bottom surfaces; it is called the DSL method. The DSL bulk method is a simplified version of the DSL method, which needs only the measurements of soil surface temperature and mean volumetric water content for the 0–5 cm surface layer, both of which can be measured by remote sensing. This paper describes the formulation of the DSL method and a technique for estimating the daily evaporation from an instantaneous flux measured by the DSL bulk method in the afternoon. Key words desert; DSL; DSL bulk method; evaporation; non-isothermal evaporation; remote sensing

Development and validation of TMI algorithms for soil moisture and snow

TOSHIO KOIKE, HIDEYUKI FUJII, TETSU OHTA & EITA TOGASHI Department of Civil Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan e-mail: [email protected]

Abstract Land surface hydrological conditions are considered to play an important role in global and regional climate variability. Soil moisture and snow are especially key parameters, which should be observed at the global scale and included in global and regional models. In this study, new algorithms based on radiative transfer theory are developed for soil moisture and snow using passive microwave sensors. These are applied to data from the TRMM Microwave Imager and evaluated by using the field data obtained during the GAME-Tibet Intensive Observing Period. The estimated hydrological parameters, surface soil moisture, soil surface temperature and water content of vegetation and snow temperature show good correspondence to the observed data. Key words Asian monsoon; GEWEX; microwave radiometer; passive microwave remote sensing; snow; soil moisture; surface temperature; Tibetan Plateau; TMI; TRMM

Hydrological processes on large flatlands: case study in the northwest region of Buenos Aires Province (Argentina)

EDUARDO KRUSE Universidad Nacional de La Plata and CONICET, Facultad de Ciencias Astronómicas y Geofísicas, Paseo del Bosque, La Plata 1900, Argentina e-mail: [email protected]

JUAN ALBERTO FORTE LAY CONICET, Avenue Paseo Colón 751, Buenos Aires, Argentina

JOSE LUIS AIELLO CONAE and Universidad Nacional de La Plata, Avenue Paseo Colón 751, Buenos Aires, Argentina

ADRIANA BASUALDO & GERMAN HEINZENKNECHT FECEACOP, Avenue Corrientes 119, Buenos Aires, Argentina

Abstract. The main features of the northwest region of Buenos Aires Province (Argentina) are its small topographic slope, the lack of a drainage network and the presence of permeable sediments near the surface. As a consequence, there is no fluvial network and the lagoons or ponds located in the depressions are important. Landsat 5 TM images have shown good contrast between water and land areas. All available scenes between August 1998 and August 1999 were used in a multitemporal analysis. The areas of the lagoons, obtained by satellite images, in each period were compared with hydrological variables measured in situ. The results show a relationship between variations of the water balance (precipitation – evapotranspiration) and fluctuations of the water table and lagoon areas. Key words agricultural system; Buenos Aires Province (Argentina); flatlands; hydrological processes; image classification; image geo-referencing;lagoon areas; Landsat; water table fluctuations ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 197–202.

Assimilation of surface temperature in a land-surface model

PRAVEEN KUMAR & AMY L. KALEITA Environmental Hydrology and Hydraulic Engineering, Department of Civil and Environmental Engineering, University of Illinois, Urbana, Illinois 61801, USA e-mail: [email protected]

Abstract An extended Kalman filter (EKF) scheme, for the assimilation of near-surface temperature observations in a hydrological model, is developed. The formulation is based on the modification of the diffusion equation of heat flux into the ground. Both model and measurement uncertainties are incorporated. It is found that, in addition to the model error, the accuracy in specification of the initial error covariance has an important bearing on the performance of the assimilation scheme. An inadequate specification can result in decreased rather than enhanced model performance. Study suggests that an “equilibrium” error covariance, arrived at by allowing the model to run with an arbitrary value for a long enough time such that the resulting perturbations subside, can capture the basic correlation structure between the different layers. An arbitrarily scaled equilibrium error covariance, to capture the large initial uncertainty, provides significantly improved performance. Key words AVHRR; data assimilation; error covariance; land-surface model; SGP97; surface temperature

Issues in monitoring evapotranspiration with radiometric temperature observations

WILLIAM P. KUSTAS USDA-ARS Hydrology and Remote Sensing Laboratory, BARC-W, Beltsville, Maryland 20705, USA e-mail: [email protected]

JOHN D. ALBERTSON, TODD M. SCANLON Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22903, USA

ANTHONY T. CAHILL Department of Civil Engineering, Texas A&M, College Station, Texas 77843, USA

Abstract Use of radiometric surface temperature in standard bulk transport equations for computing heat fluxes has not been successful in general. This has been attributed to the significant differences existing between the radiative and the so-called “aerodynamic” temperature of the surface. Numerous studies have explored ways of accounting for the discrepancies between radiometric and aerodynamic temperatures. Radiometric temperature and surface flux observations collected during the 1999 Southern Great Plains Experiment (SGP99) over four field sites comprising the major land cover types for this region are used to evaluate these approaches. The results suggest correction schemes require site-specific calibration and therefore are not useful for regional applications. A more general approach, which accounts for the main factors affecting radiometric and aerodynamic temperatures and reduces the impact of errors in radiometric temperature observations, is presented. Key words aerodynamic and excess resistance; aerodynamic temperature; evapotranspiration; radiometric surface temperature; sensible heat flux; SGP99; single- and two-source models; Southern Great Plains

Using public-domain datasets to model the Küçük Menderes basin, Turkey

MARTIN LACROIX Aquatic Ecosystem Impacts Research Branch, National Water Research Institute, National Hydrology Research Centre, 11, Innovation Boulevard, Saskatoon, Saskatchewan S7N 3HF, Canada e-mail: [email protected]

GEOFF KITE & PETER DROOGERS International Water Management Institute, PO Box 2075, Colombo, Sri Lanka

Abstract Distributed hydrological models used to investigate basin water resources generally require large numbers of data which are not always available. However, data from satellites and global datasets of elevation, land cover and climate are available from the Internet. The paper describes the application of a distributed hydrological model using only data from satellite and the Internet and discusses the results. Key words digital elevation model (DEM); distributed hydrological model; land classification; public-domain datasets; SLURP; TOPAZ; Turkey; water management; water resources

SSM/I-derived global rainfall statistics and their application in surface hydrology modelling

QIHANG LI & RALPH FERRARO NOAA/NESDIS/Office of Research and Application, 5200 Auth Road #703, Camp Springs, Maryland 20746, USA e-mail: [email protected]

Abstract A new global 2.5 monthly rainfall statistics dataset has recently been produced by the NOAA/NESDIS/Office of Research and Applications. This dataset is based on the SSM/I rainfall algorithms and covers the period from July 1987 to the most recent month. It includes the following parameters: monthly rain estimates, sampling and algorithm errors associated with the monthly rain estimates, variance and auto-correlation at 4-h and 8-h lag times of instantaneous rain rate, frequency of rain, fractional coverage of rain, and the number of available samples. This dataset provides, on the global scale, more detailed information about rainfall beyond simple monthly rainfall amount, and will be useful to the hydrology and climatology communities. The utilization of this dataset is demonstrated through a simulation of the effects of the fractional coverage of rainfall on evapotranspiration. Key words algorithm; correlation; error; fraction; frequency; global; monthly; rainfall; SSM/I; variance

Estimating soil moisture profiles by microwave radiometry over a wheat field

YUEI-AN LIOU Center for Space and Remote Sensing Research, National Central University, Chung-Li 320, Taiwan e-mail: [email protected].

YU-CHUNG TZENG Department of Electronics Engineering, National Lien-Ho Institute of Technology and Commerce, Miao-Li, Taiwan

JEAN-PIERRE WIGNERON C.S.E., Avignon, France

Abstract This paper demonstrates the use of microwave radiometry in sensing soil moisture profiles over a wheat field. Field measurements of brightness temperatures collected by the PORTOS radiometer operating at 1.4, 5.05 and 10.65 GHz, and concurrent measurements of soil moisture profiles to a depth of 10 cm over a wheat field during a 2.5-month complete growing cycle in 1993 (PORTOS-93 experiment), were used. A Dynamic Learning Neural Network (DLNN) was applied to manage nonlinear mapping from brightness temperatures to soil moisture profiles. Key words brightness temperature; microwave radiometry; neural network; soil moisture ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 592–594.

Integration of remote sensing data into hydrological models for flood forecasting

C. LOUMAGNE, A. WEISSE, M. NORMAND, M. RIFFARD Cemagref, Parc de Tourvoie, BP 44, F-92163 Antony, France e-mail: [email protected]

A. QUESNEY, S. LE HÉGARAT-MASCLE & F. ALEM CETP/CNRS, 10–12 avenue de l’Europe, F-78140 Vélizy, France

Abstract The purpose of this paper is to present the methodology set up to derive catchment soil moisture from Earth Observation (EO) data using microwave spaceborne Synthetic Aperture Radar (SAR) images from ERS satellites, and to study the improvements in flood forecasting introduced by an assimilation of this information into hydrological models. This methodology has been put forward for use in the European AIMWATER project on the Seine catchment upstream of Paris (France) and on the Arade catchment in southern Portugal. Key words flood forecasting; SAR; Seine basin (France); sequential assimilation; soil moisture; variational assimilation

Modelling runoff from large glacierized basins in the Karakoram Himalaya using remote sensing of the transient snowline

ANDREW T. LOWE Cold Regions Research Centre, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada

DAVID N. COLLINS School of Environment and Life Sciences, University of Salford, Salford Crescent, Manchester M5 4WT, UK e-mail: [email protected]

Abstract A glacier runoff model has been developed with a view to forecasting discharge from large remote glacierized basins in the Karakoram Himalaya. The model requires modest data input. Energy inputs are represented by positive degree-days, determined for various elevations from lapse rates, and depletion of snow cover and consequent rise of the transient snowline (TSL) during summer are determined from close-interval satellite monitoring by the Advanced Very High Resolution Radiometer (AVHRR) sensor. Coupled with a digital elevation model, position of the TSL is used to partition glacierized areas into snow-covered and exposed ice portions, to which differential melt rates are then applied. The degree-day factor applied over bare ice is substantially higher than that over snow. Model performance evaluations indicated a good fit between measured and simulated runoff for the Hunza River at Danyore Bridge for both spring and summer of 1989. Both the model and the spatial and temporal resolution of the satellite platforms are well suited to and appropriate for the scale of the large glacierized high mountain basins of the Himalaya. Key words AVHRR; glacier hydrology; glacierized basin; Karakoram mountains; runoff modelling

______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 136–138. Impulse radar surveys: influence of liquid water

ANGELA LUNDBERG Water Resources Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden e- mail: [email protected]

HANS THUNEHED Applied Geophysics, Luleå University of Technology, SE-971 87 Luleå, Sweden

Abstract Snow water equivalent (SWE) of snow is of great importance for hydropower production in areas where a large proportion of the reservoir water comes from snow. Impulse radar to estimate the SWE is now in operational use in some Scandinavian basins. With radar technology the radar wave propagation time in the snow pack is converted into SWE with the help of a parameter usually termed the a value. Use of radar technology during late winter brings about risk for measurements of wet snow. The a value for dry snow cannot be used directly for wet snow. A liquid-water content of 5% (by volume) reduces the a value by 20%. Key words dielectric model; GPR (ground penetrating radar); laboratory study; snow wetness

A simple resistance-based model for use in dual source evaporation equations

BRUCE E. MAIN, LESTER P. SIMMONDS Department of Soil Science, University of Reading, Reading RG6 6DW, UK e-mail: [email protected]

ELEANOR J. BURKE Department of Hydrology and Water Resources, University of Arizona, Tucson, Arizona 85721, USA

Abstract A procedure is described for estimating soil surface resistance for use in evaporation equations from passive microwave remote sensing. The procedure is based on analyses using a physically-based model of microwave emission from soils (MICRO- SWEAT). It accounts for the influence of soil type and the effect of the prevailing evaporative demand, both of which effect the interrelations between near-surface water content, evaporative demand and soil surface resistance. Key words MICRO-SWEAT; microwave remote sensing; modelling; soil resistance

Topographic and canopy controls on snow deposition, snow-cover energy balance and snowmelt

DANNY MARKS, ADAM WINSTRAL, STEVEN S. VAN VACTOR, DAVE ROBERTSON USDA Agricultural Research Service, Northwest Watershed Research Center, Boise, Idaho 83712, USA e-mail: [email protected] ROBERT E. DAVIS US Army Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire 03755-1290, USA

Abstract Significant differences in snow deposition, development of the seasonal snow cover, and the timing of melt, occur between two experimental sites located in a headwater sub-drainage of the Reynolds Creek Experimental Watershed (RCEW) in the Owyhee Mountains of southwestern Idaho, USA. Snow, climate and stream discharge data were used to drive and verify a point snow-cover energy and mass balance model, SNOBAL, to evaluate these differences for three water years: 1984, the largest discharge year on record (204% of average), 1992, the smallest discharge year on record (36% of average), and 1999 (140% of average). The simulations showed that wind differences between sites are the most important cause of the snow cover differences between the sites. Though differences do occur in the snow-cover energy balance, these are primarily caused by the fact that reduced precipitation causes melt-out to occur earlier at site 176. This analysis shows the importance of understanding and accounting for variable patterns of snow deposition and redistribution of snow in semiarid regions. Key words snow; snow cover modelling; terrain and canopy effects

Mapping riparian resources in semiarid watersheds using airborne multispectral imagery

CHRISTINA J. MAY, CHRISTOPHER M. U. NEALE Department of Biological and Irrigation Engineering, Utah State University, Logan, Utah 84322-4105, USA e-mail: [email protected]

NORM HENDERSON National Park Service, Glen Canyon National Recreation Area, Utah, USA

Abstract This research quantifies remotely sensed airborne data into physical and ecological variables, obtaining an improved spatial and temporal representation of the dynamics of native and exotic plant communities within the Escalante River corridor, Utah, USA. Key words airborne multispectral imagery; atmospheric correction; Escalante River (Utah, USA); exotic species; riparian vegetation

Snowmelt mathematical simulation with different climatic scenarios in the Tupungato River basin, Mendoza, Argentina

JORGE MAZA INA Centro Regional Andino, Belgrano (oeste), 210-5500 Mendoza, Argentina e-mail: [email protected]

FEDERICO CAZORZI Dipartamento Territorio e Sistemi Agro-Forestali, University of Padova, Via Romea, I-35020 Legnaro, Padova, Italy

PATRICIA LOPEZ, LUIS FORNERO, ADRIAN VARGAS & JOSE ZULUAGA INA Centro Regional Andino, Belgrano (oeste), 210-5500 Mendoza, Argentina

Abstract The impact of climate change on water resource availability in the Mendoza River oasis, Argentina where 1 000 000 inhabitants live and 80 000 ha of crops are irrigated was assessed. The snow coverage depletion curve was obtained from the NEVE model using Landsat-TM images for calibration. The possible evidence of climate change and its severity was analysed. The results obtained from the SRM model showed an important peak flow and runoff volume variation. Key words Argentina; climate change; NEVE model; snowmelt; SRM model ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 225–227.

Iowa’s surface albedo variability in space and time throughout the 1990 growing season

D. W. MEEK & J. L. HATFIELD USDA-ARS-MWA National Soil Tilth Laboratory, 2150 Pammel Dr., Ames, Iowa 50011, USA e-mail: [email protected]

Abstract Variability of albedo has important implications for the regional energy balance. Assessments of albedo changes throughout a year over large areas are scarce. Surface albedo data for Iowa were constructed from AVHRR data for 16 biweekly 1990 datasets. Data were examined with spatial and time series statistics. The study assessed the temporal changes in spatial trends and correlation scales. Each dataset generally exhibited large scale trend especially in the north–south direction until full crop cover occurred. Areal correlation scales for non-harvest periods varied greatly over the growing season and showed a correlation with the previous period’s estimate. They ranged from 340 to 2010 km2, suggesting averaging areas for reliable, independent areal albedo estimates that are double those of the correlation scales. The utility of conducting large scale spatial and temporal analysis is shown, demonstrating that albedo values used in regional energy balance models are improved. Key words correlated data; EROS dataset (1 km2 areas); geostatistics; scale of fluctuation

Development of a distributed database for precipitation radar through the Internet using Java

TOSHIYUKI MORIYAMA & KAZUO MATSUNGA Sojo University, 4-22-1 Ikeda Kumamoto City, Japan e-mail: [email protected]

Abstract Except for NEXRAD or TRMM, most precipitation data observed by radar are only recorded without compilation. But some of the archived data are only available as an off-line distribution. Many researchers hope to find and retrieve the required data easily through the Internet. In this study, we developed a database system using the Java language. Java has the best portability through heterogeneous operating systems and a good fit with the Internet. We made a database file of data observed by radar which belongs to the Ministry of Construction, Japan. With the applet, servlet and agent made in Java, we can find the required data from an object-oriented database system. The applet–servlet–database system can be accessed via an Internet web browser. In addition, we produced a distributed-database system using multiple WWW and database servers through the Internet. This system does not require much financial support or manpower, because the unit of a distributed server is fast enough to use an old personal computer with a PC-Unix operating system or the Java compatible operating system. Key words distributed database; Java; object oriented database system; precipitation radar; servlet

Spatial mapping of evapotranspiration and energy balance components over riparian vegetation using airborne remote sensing

C. M. U. NEALE, L. E. HIPPS Departments of Biological and Irrigation Engineering, and Plants, Soils and Biometeorology, Utah State University, Logan, Utah 84322-4105, USA e-mail: [email protected]

J. H. PRUEGER, W. P. KUSTAS USDA-ARS National Soil Tilth Laboratory and National Hydrology Laboratory, USA

D. I. COOPER Los Alamos National Laboratory, Los Alamos, New Mexico, USA

W. E. EICHINGER University of Iowa, Iowa City, Iowa, USA

Abstract High resolution, airborne multispectral imagery of a riparian system dominated by salt cedar (Tamarix spp) along the Rio Grande in New Mexico, USA, was used to determine the instantaneous evapotranspiration rates and spatially distributed energy balance components over the system. Comparisons of instantaneous spatially distributed upwind fluxes with values of ground-based measured fluxes using eddy correlation techniques and other micrometeorological instruments, were conducted for two different dates. Results show considerable differences between the fluxes that can be attributed to advection, canopy heat storage and wind variability. A careful footprint analysis will need to be conducted in the future to better match the ground-based and aircraft measurements. Key words advection; airborne multispectral imagery; canopy reflectance; energy balance fluxes; eddy correlation; evapotranspiration; footprint analysis; Rio Grande; Tamarisk; upwind fetch

PGLIERC: a test of remote sensing of hydrology in a grassland

KENLO NISHIDA Institute of Agricultural and Forest Engineering, University of Tsukuba, Ibaraki 305-8572, Japan e-mail: [email protected]

ATSUSHI HIGUCHI Institute for Hydrospheric-Atmospheric Sciences, Nagoya University, Nagoya 464-8601, Japan

SHIN-ICHI IIDA, NORIKO NIIMURA Environmental Research Center, University of Tsukuba, Ibaraki 305-8577, Japan

AKIHIKO KONDOH Center for Environmental Remote Sensing, Chiba University, Chiba 263-8522, Japan

Abstract A field experiment over a grassland surface was conducted with flux observations, biomass measurements, and ground remote sensing. Seasonal changes of the grassland were characterized in terms of phenology, flux, and optical characteristics. Optical signals that correspond to the phenology and hydrological state of the grassland were identified. Key words albedo; BRDF; evapotranspiration; grassland

Soil moisture mapping with passive microwave imagery and geostatistical analysis

ANNA OLDAK, THOMAS J. JACKSON & YAKOV PACHEPSKY USDA-ARS Hydrology Laboratory, BARC-W, Beltsville, Maryland 20705, USA e-mail: [email protected]

Abstract Remote sensing, and in particular passive microwave, has a great potential for providing areal estimates of soil moisture. It can be implemented with aircraft-based sensors as described here. The result of the measurements, the brightness temperature images, can be converted into volumetric soil moisture maps using additional environmental information. These maps display information on soil moisture distribution over space and time. Semi- variogram analysis was performed to investigate spatial variation of soil moisture and its scale dependence with the environmental features. Analysis revealed a dependency of soil moisture distribution at two scales. On the regional scale, rainfall is the dominant factor influencing soil moisture distribution. On the local scale, soil texture dominates. Key words geostatistical analysis; GIS; Oklahoma, USA; passive microwave; semivariograms; SGP97; soil moisture; spatial scale

Remote sensing of environmental conditions at wetlands in west- central Florida (USA) using high-resolution multispectral imagery

BRIAN G. ORMISTON Ecological Consultant, 1606 Huntington Lane, Safety Harbor, Florida 34695, USA e-mail: [email protected]

CHRIS SHEA Tampa Bay Water, 2535 Landmark Drive, Suite 211, Clearwater, Florida 33761-3930, USA

Abstract High resolution multispectral Compact Airborne Spectrographic Imager (CASI) imagery was evaluated for suitability to conduct environmental monitoring of wetland, surface water and land cover changes at a public water supply wellfield in Florida, USA. CASI imagery covering the visible and near-infrared wavelengths (430–796 nm) was acquired for a 23 km2 test area at the Starkey wellfield in Pasco County, Florida. Moderately to severely stressed (i.e. dewatered) cypress domes exhibited various degrees of tree mortality and canopy-thinning gaps, which were indicated by significantly lower NDVI values. Classification of cypress domes using CASI imagery accurately (98%) identified areas of intact cypress canopy, canopy gaps, standing water, wet prairies, and successional change in the understory. The results indicate that high resolution multispectral imagery could be used to remotely sense and map relevant ecological and hydrological indicators of wetland condition. Key words CASI; cypress; Florida (USA); maximum likelihood classification; multispectral; NDVI; tree canopy; water supply wellfield; wetland impact monitoring

Estimating long term surface soil moisture from satellite microwave observations in Illinois, USA

MANFRED OWE MC 974, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, USA e-mail: [email protected]

RICHARD DE JEU & ADRIAAN VAN DE GRIEND Faculty of Earth Sciences, Vrije Universiteit, Amsterdam, The Netherlands

Abstract A database of long-term soil moisture was compared to satellite microwave observations over a test site in the midwestern United States. Night-time microwave brightness temperatures were observed at a frequency of 6.6 GHz by the Scanning Multichannel Microwave Radiometer (SMMR). At 6.6 GHz, the instrument provides a spatial resolution of approximately 150 km, and a temporal frequency over the test area of about two to three night-time orbits per week. Vegetation radiative transfer characteristics, such as the canopy transmissivity, were estimated from vegetation indices such as the NDVI and the MPDI. Because the time of satellite coverage does not always coincide with the ground measurements of soil moisture, the existing ground data were used to calibrate a water balance for the top 10 cm surface soil layer in order to interpolate daily surface moisture values. Passive microwave remote sensing presents the greatest potential for providing regular spatially representative estimates of surface soil moisture at global scales. Key words microwave; optical depth; remote sensing; SMMR; soil moisture

First results and analyses from the SWaMP-L radiometer

DAVID PEARSON Environmental Systems Science Centre, The University of Reading, Reading RG6 6AL, UK e-mail: [email protected]

IAN CARTMELL Sula Systems Ltd, 8 Long Street, Wotton under Edge GL12 7ES, UK

ROBERT J. GURNEY Environmental Systems Science Centre, The University of Reading, Reading RG6 6AL, UK

MARK L. JARRETT Sula Systems Ltd, 8 Long Street, Wotton under Edge GL12 7ES, UK LESTER P. SIMMONDS Department of Soil Science, The University of Reading, Reading RG6 6DW, UK

Abstract The design and performance of an L-band passive microwave radiometer (SWaMP- L), built for hydrological studies, and containing a number of novel features, is described. Preliminary results from field tests are presented, showing that brightness temperature measurements are qualitatively consistent with expectations during rainfall, changes in roughness, and dry-down. Angular pointing stability is good. Key words brightness temperature; L-band; passive microwave radiometry; roughness; soil moisture

Aggregation of a nonlinear land surface model for heterogeneous terrain

HENK PELGRUM ESTEC, PO Box 229, 2200 AG, Noordwijk, The Netherlands e-mail: [email protected]

Abstract The aggregation of a nonlinear land surface model for heterogeneous terrain from the pixel-scale to the scale of a large-scale atmospheric model is investigated. The aggregation process is quantified using a linearization approach based on Taylor expansion. A test case with remote sensing data from the Barrax site applied to the land surface model SEBI is presented. The error due to aggregation is 8% and can be approximated by the linearization approach. Key words aggregation; EFEDA; energy balance; evaporation; linearization; SEBI; wavelets

Multidata analysis for automatic river extraction

G. M. PETRIE, J. D. TAGESTAD, K. L. STEINMAUS, M. S. WIGMOSTA Pacific Northwest National Laboratory, PO Box 999, Richland, Washington 99352, USA e-mail: [email protected]

CHUNG HYE READ National Imagery and Mapping Agency, 12310 Sunrise Valley Drive, Reston, Virginia 20191-3449, USA

Abstract To meet demanding geospatial map generation requirements, the National Imagery and Mapping Agency (NIMA) is developing new tools to automatically extract critical spatial information needed to populate sophisticated global digital databases. Accurate identification, delineation, attribution, and vectorization of rivers are particularly challenging tasks given the need for global coverage, accurate positioning, and sophisticated attribution. To meet these challenges, the Pacific Northwest National Laboratory (PNNL) has been tasked by NIMA to develop computer-assisted methodologies to extract rivers using a combination of Digital Elevation Model (DEM) and multisensor imagery. This multidisciplinary approach includes remote sensing, geology, meteorology, artificial intelligence, and vision technology; however, the main emphasis is on fusing methodology from image processing and hydrological modelling. The hydrological methodology is based on modelling river locations from DEM data. Satellite imagery provides direct evidence of river and lake locations and is used to complement and/or supersede locations derived from DEM. While this methodology was developed to exploit the “orthogonal” information on rivers from each dataset to meet NIMA’s specialized geospatial information generation needs, this data fusion approach also has broad application to the hydrological community in general. Key words data fusion; DEM; feature extraction; hydrology, NIMA; remote sensing; river extraction; satellite; stream; terrain analysis

Comparison of global land-cover databases in the Mackenzie basin, Canada

ALAIN PIETRONIRO National Water Research Institute, Environment Canada, Saskatoon, Saskatchewan S7N 3H5, Canada e-mail: [email protected]

ERIC D. SOULIS Department of Civil Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada

Abstract The objective of the work was to consider the applicability of emerging global medium-resolution land-cover datasets to determine their suitability for modelling applications in the Mackenzie basin GEWEX Study (MAGS). This is both to take advantage of the datasets and to ensure the applicability of the results. Suitable global medium- resolution datasets were selected for evaluation and to assess their accuracy by a comparison with the high resolution Landsat derived datasets. It was concluded that generalized land- cover types were drastically different when the global datasets were compared for the Mackenzie basin. Accuracy assessments on a per pixel basis, when compared to Landsat derived products, were on the order of 30%. Key words global; land use; Mackenzie River (Canada); NOAA; vegetation ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 519–525.

Application of a hydrodynamic model in a freshwater delta using remote sensing

ALAIN PIETRONIRO National Water Research Institute, Environment Canada, Saskatoon, Saskatchewan S7N 3H5, Canada e-mail: [email protected]

ROBERT LECONTE Ecole de Technologie Supérieure, Montréal, Québec H3C 1K3, Canada

DANIEL L. PETERS Trent University, Peterborough, Ontario K9J 7B8, Canada

TERRY D. PROWSE National Water Research Institute, Environment Canada, Saskatoon, Saskatchewan S7N 3H5, Canada

Abstract The Peace-Athabasca delta (PAD) is located in the northern extreme of Alberta, Canada and is one of the world’s largest freshwater inland deltas. Inland areas surrounding the main flow system comprise a myriad of small lakes and wetlands, of which a large percentage are hydrologically disconnected or “perched” at elevations higher than adjacent lakes or channels. This large, complex and dynamic ecosystem has undergone substantial changes over the last 25 years. The remoteness of this site, along with a shortage of hydrological and ecological information, has necessitated the development of innovative methods to assess these changes. These methods include the analysis of Landsat, Radarsat and SPOT satellite imagery for verification and calibration of a hydrodynamic model to observed flood conditions. This unique coupling of imagery and a hydrodynamic model provides key validation points and initial conditions for model runs. The results of the techniques outlined in this paper provide a starting point to assess changes produced by flow regulation and climatic change. Key words delta; flood mapping; hydraulic modelling; northern; Peace-Athabasca delta (Canada); wetland

Assessing the relationship between surface temperature and soil moisture in southern Africa

ANA C. PINHEIRO, COMPTON J. TUCKER NASA/Goddard Space Flight Center, Code 923, Greenbelt, Maryland 20771, USA e-mail: [email protected]

DARA ENTEKHABI Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

JEFFREY L. PRIVETTE NASA/Goddard Space Flight Center, Code 923, Greenbelt, Maryland 20771, USA

JOSEPH A. BERRY Department of Plant Biology, Carnegie Institution of Washington, Stanford, California 94305, USA

Abstract Droughts have important implications for the natural and socio-economic environments of southern Africa. An understanding of the relation-ship between soil moisture content and vegetation condition is necessary to predict the impact of those events. In this paper we explore a methodological approach for early drought prediction. We hypothesize that the amplitude of the diurnal temperature cycle of a vegetated surface, determined using remote sensing measurements, can indicate soil moisture content and vegetation condition. We present a preliminary analysis of three months of soil moisture and temperature data collected at Skukuza, South Africa. The results support our basic hypothesis yet suggest that further work is required to better understand the coupling of these parameters. The SiB2 model will be adapted for this purpose. Key words SAFARI 2000; SAVE, soil moisture; southern Africa; surface temperature; thermal inertia

Feasibility of evapotranspiration monitoring of riparian vegetation with remote sensing

JOHN H. PRUEGER USDA-ARS National Soil Tilth Laboratory, Ames, Iowa 50011, USA e-mail: [email protected]

LAWRENCE E. HIPPS Utah State University, Logan, Utah 84322-4820, USA

WILLIAM P. KUSTAS USDA-ARS National Hydrology Laboratory, BARC-W, Beltsville, Maryland 20705, USA

CHRISTOPHER M. U. NEALE Utah State University, Logan, Utah 84322-4105, USA

JERRY L. HATFIELD USDA-ARS National Soil Tilth Laboratory, Ames, Iowa 50011, USA

SALIM BAWAZIR New Mexico State University, Las Cruces, New Mexico 88003-8001, USA

WILLIAM E. EICHINGER University of Iowa, Iowa City, Iowa, 52242 USA

DANIEL I. COOPER Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA

Abstract Quantification of evapotranspiration (ET) continues to be challenging especially when attempting to evaluate ET at basin scales. Extending approaches to whole basins or larger regions is difficult due to issues related to landscape heterogeneity and scale. Reliable areal estimates of ET are essential for accurate modelling of the hydrological cycle and for assessing water-use of different ecosystems. A riparian corridor along the Rio Grande (USA) dominated by Tamarisk (salt cedar) is being studied to determine daily and total seasonal water-use. Local estimates of ET in the Tamarisk were made using eddy covariance instrumentation mounted on two towers. Radiometric temperature at the top of the canopy was also measured using a fixed-head infrared thermometer. The combination of these data will be used to evaluate evapotranspiration estimates along the corridor using data remotely sensed from an aircraft platform that have been acquired periodically for a large extent of the riparian zone. Key words eddy covariance; evapotranspiration; radiometric temperature; remote sensing; riparian; salt cedar; Tamarisk

Operational technology for snow-cover mapping in the Central Asian mountains using NOAA-AVHRR data

TIMUR QOBILOV, FELIX PERTZIGER, LUDMILA VASILINA National Hydro-Meteorological Survey of Uzbekistan, GLAVGIDROMET, 72 K. Makhsumov St, Tashkent 700052, Uzbekistan e-mail: [email protected]

MICHAEL F. BAUMGARTNER MFB-GeoConsulting, Hauptstrasse 17, CH-3254 Messen, Switzerland

Abstract An important problem in the evaluation of snow in mountains, is that of the observation and mapping of snow cover variations which is required for snowmelt runoff forecasting in mountain river basins. Satellite data are an efficient tool for these purposes, especially for large and remote river basins. The Snowmelt Runoff Model (SRM) is one of the few snowmelt runoff forecasting models using snow cover information derived from satellite data (or any other remote sensing system). Today, SRM is used operationally in the Main Administration of the Hydro-Meteorological Survey of the Republic of Uzbekistan for forecasting snowmelt runoff in several Central Asian river basins. The Swiss-American SRM is based on the degree-day method and requires daily information on temperature, precipitation and snow-covered areas within several elevation zones. In this context, an extremely important question concerns the accuracy of snow cover classification of satellite data. This paper describes locally developed software tools for increasing the accuracy of snow cover estimation and for operational processing of satellite data. Key words Aral Sea; AVHRR; brightness normalization using DEM; Central Asia; geometric correction; GIS; NOAA; SRM

Sequential assimilation of SAR/ERS data in a lumped rainfall–runoff model with an extended Kalman filter

ARNAUD QUESNEY, CHRISTOPHE FRANÇOIS, CATHERINE OTTLE, SYLVIE LE HEGARAT CETP-CNRS 10 Avenue de l’Europe, F-78140 Vélizy, France e-mail: [email protected]

CECILE LOUMAGNE & MICHEL NORMAND CEMAGREF, Parc de Tourvoie, BP44, F-92163 Antony Cédex, France

Abstract A first attempt of sequential assimilation of SAR/ERS estimates of surface soil moisture in a lumped rainfall–runoff model has been conducted. The methodology is based on the use of an extended Kalman filter to assimilate the SAR retrievals in the two-layer surface scheme. This study has been done on the Orgeval agricultural catchment (104 km2, east of Paris, France). The assimilation has been tested on a two-year period (1996–1997) corresponding to 25 SAR measurements. Key words assimilation; Kalman filter; radar data; rainfall–runoff modelling; SAR/ERS; soil moisture

Precision temperature logging and groundwater flow studies along the eastern side of the Albuquerque basin

MARSHALL REITER New Mexico Bureau of Mines and Mineral Resources, New Mexico Tech, Socorro, New Mexico 87801, USA e-mail: [email protected]

Abstract Subsurface temperature gradients, which are often linear in undisturbed regimes, demonstrate a variety of nonlinear characteristics when perturbed by groundwater flow. This property of subsurface temperatures is used to examine the groundwater flow pattern at four sites in the Albuquerque basin along the eastern edge of the Rio Grande flood plain. Two sites demonstrate appreciable groundwater flow, although quite different in nature; and two sites demonstrate little if any groundwater movement. The two sites demonstrating groundwater flow are in areas showing vegetation on a Landsat thematic map of the area; one site is located beside a major arroyo drainage. The two sites showing little if any groundwater flow are away from any large drainage structures and show no vegetation on the Landsat thematic map. Key words Albuquerque basin (USA); groundwater flow; recharge; subsurface temperatures

Monitoring physical and biological properties at the Sevilleta LTER using remote sensing

JERRY C. RITCHIE, THOMAS J. SCHMUGGE, ALBERT RANGO USDA-ARS Hydrology Laboratory, BARC-W, Beltsville, Maryland 20705, USA e-mail: [email protected]

FRANK R. SCHIEBE SST Development Group Inc., 824 North Country Club Road, Stillwater, Oklahoma 74075, USA

Abstract In 1997 the USDA Agriculture Research Service (ARS), Hydrology Laboratory began collecting remotely sensed ground, aircraft, and satellite data on the physical and biological states of two semiarid ecosystems (grass and shrub) typical of the Sevilleta Long- Term Ecological Research (LTER) site (New Mexico, USA). Remote sensing measurements were made at Sevilleta in May/June and September/October of 1997, 1998, and 1999. Radiance measured at ground and aircraft platforms was 12 to 40% higher for a 30  30 m area at the shrub site when compared with the grass site. Land-scape surface temperatures that were similar in the morning were 3 to 5C higher under the shrub when compared with the grass site by 1300 h local time. The shrub site had a lower LAI indicating less surface cover and giving a greater soil contribution to the total radiance measured. These differences could have significant effects on the energy and water balances of the Sevilleta if shrubs continue to expand at the expense of the grassland. Key words arid land; Chihuahuan Desert; desert grassland; grass; Landsat; leaf area index; radiance; shrubs; surface temperature

Derivation of a dryness index from NOAA-AVHRR data for use in large-scale hydrological modelling

INGE SANDHOLT, KJELD RASMUSSEN Institute of Geography, University of Copenhagen, Østervoldgade 10, DK-1350 Copenhagen K, Denmark e-mail: [email protected]

JENS ANDERSEN Department of Hydrodynamics and Water Resources (ISVA), Technical, University of Denmark, DK-2800 Lyngby, Denmark

Abstract Modelling of soil moisture for large river basins relies on the spatial resolution of the input data. Therefore, in areas where spatial information on hydrological variables is sparse, remotely sensed information can be of great importance. The surface temperature/vegetation index (Ts/NDVI) space, based on NOAA-AVHRR data covering the Senegal River basin, has been analysed in this study. The approach evaluates the shape of the Ts/NDVI-space for each available image acquisition, which makes this simple approach robust to atmospheric attenuation of the signal and to changes in, for instance, atmospheric forcings or net radiation that may determine the shape of the Ts/NDVI space. It has been shown that global parameters for estimation of a dryness index in the river basin can be used for various surface cover types, and that the approach can be applied for sparsely vegetated areas as well as for more dense vegetation covers. Key words hydrological modelling; NOAA-AVHRR; soil moisture, Ts/NDVI space; West Africa ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 175–180.

Scale effects in estimating large eddy-driven sensible heat fluxes over heterogeneous terrain

TODD M. SCANLON, JOHN D. ALBERTSON Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22903, USA e-mail: [email protected]

Abstract Remotely sensed surface temperatures from the Monsoon 1990 experiment in Arizona were used as boundary conditions for a large eddy simulation (LES) model in order to compute surface sensible heat fluxes (H). The LES model takes into account the dynamic effects of surface hetero-geneity. Model runs were conducted over boundary condition resolutions of 200 m, 400 m, and 800 m. Regional averages of H determined by the LES model did not vary significantly over the differing scales of surface resolution and were similar to values derived by an “offline” method, in which average meteorological variables of air temperature and wind speed were used as inputs. However, localized differences in H calculated by the two methods over the surface were as high as 36.75 W m-2, reflecting the surface heterogeneity induced feedbacks present in a dynamic atmospheric boundary layer, as captured by the LES model. Key words large eddy simulation; Monsoon 1990; sensible heat flux; spatial resolution; surface heterogeneity; surface temperature

Precision snow cover and glacier mapping for runoff modelling in a high alpine basin

JESKO SCHAPER, KLAUS SEIDEL & JAROSLAV MARTINEC Communication Technology Laboratory, Image Science Group, Swiss Federal Institute of Technology ETHZ, Gloriastrasse 35, CH-8092 Zürich, Switzerland e-mail: [email protected]

Abstract The runoff regime of high alpine basins will be affected by the response of both the seasonal snow cover and the glaciers to global warming. Runoff peaks due to snowmelt will be partially shifted from the summer to the winter. Glacier melt will supply a larger amount of meltwater until the glaciers finally disappear, if the temperature keeps rising. In order to evaluate this effect quantitatively, a method is presented for separately mapping the snow cover area, the gradually decreasing snow coverage on a glacier, and the area of the exposed ice. The test basin Rhône-Sion (3371 km2, 491–4634 m a.s.l.) has been divided into seven elevation zones due to the large altitude range. Periodic satellite monitoring of snow and ice areas was carried out separately for each zone using high resolution optical remote sensing data which provide the capability to distinguish between snow and ice. The paper demonstrates the necessity of accurate glacier and snow cover mapping by adequate satellite sensors for prediction of snow and glacier conditions as well as the changing runoff regime in high alpine basins in the twenty-first century. Key words ice melt runoff; runoff; satellite remote sensing; snowmelt runoff; Swiss Alps ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 168–174.

Estimation of surface emissivity for arid lands

THOMAS SCHMUGGE, ANDREW FRENCH, JERRY RITCHIE & ALBERT RANGO USDA ARS Hydrology Laboratory, BARC-W, Beltsville, Maryland 20705, USA e-mail: [email protected]

Abstract Knowledge of surface emissivity is important for determining the radiation balance at the land surface. For heavily vegetated surfaces there is little problem since the emissivity is relatively uniform and close to one. For arid lands with sparse vegetation the problem is more difficult because the emissivity of the exposed soils and rocks is highly variable. With multispectral thermal infrared (TIR) observations it is possible to estimate the spectral emissivity variation for these surfaces. The data presented is from the TIMS (Thermal Infrared Multispectral Scanner) instrument which has six channels in the 8 to 12 m region. TIMS is a prototype of the TIR portion of the ASTER (Advanced Spaceborne Thermal Emission and Reflection radiometer) instrument on NASA’s EOS-TERRA satellite. The approach is to use the Temperature Emissivity Separation (TES) algorithm developed for use with ASTER data to extract the temperature and six emissivities from the six channels of TIMS data. The algorithm makes use of the empirical relation between the range of observed emissivities and their minimum value. This approach was applied to the TIMS data acquired over the USDA/ARS Jornada Experimental Range in New Mexico. The Jornada site is typical of a desert grassland where the main vegetation components are grass (black grama) and shrubs (primarily mesquite) in the degraded grassland. The data are from an altitude of 800 m yielding a pixel resolution of approximately 2 m. The result-ing spectral emissivities are in qualitative agreement with laboratory measurements of the emissivity () for the quartz rich soils of the site with  < 0.8 for the 8–9.5 m channels. For the longest wavelength channel little spatial variation of  was observed with values of 0.96 ± 0.005 over large areas. Key words arid lands; ASTER; Chihuahuan Desert; emissivity; Jornada; multispectral; surface temperature; thermal infrared; TIMS

Present use and future perspectives of remote sensing in hydrology and water management

GERT A. SCHULTZ Institute of Hydrology, Water Resources Management and Environmental Techniques, Ruhr University Bochum, D-44780 Bochum, Germany e-mail: [email protected]

EDWIN T. ENGMAN Hydrological Science Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

Abstract This paper starts with discussion of the availability of remote sensing data, their resolution in time, space and spectral bands. Possibilities of integration of remote sensing (RS) and other data are presented along with an example of merging Landsat data and a digital soil map to generate spatially distributed soil storage capacity. This serves as a basis for the use of the entropy concept in order to generate Hydrological Response Units. The potential of RS data to be used in real time is demonstrated for the problem of flood forecasting and control. The use of RS data for the estimation of seasonally varying parameters of hydrological models and for long-term changes (e.g. land-use changes) is demonstrated. Future perspectives are presented in the context of expected developments of new hydrological models adapted to the specific properties of remote sensing data and with respect to future sensors, particularly those to be flown on satellites in the near future. The potential of these sensors for hydrological modelling and water resources management purposes is highlighted. Key words hydrological modelling; hydrological parameters; new sensors in space; resolution in time and space; spectral bands

Mapping snow with repeat pass synthetic aperture radar

JIANCHENG SHI Institute For Computational Earth System Science (ICESS), University of California, Santa Barbara, California 93106, USA e-mail: [email protected]

SCOTT HENSLEY Radar Science & Engineering Section, NASA/Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109-8099, USA

JEFF DOZIER School of Environmental Science and Management, University of California, Santa Barbara, California 93106, USA

Abstract In hydrological investigations, modelling and forecasting of snow-melt runoff requires information about snowpack properties and their spatial variability. This study demonstrates a technique to map snow cover with both backscattering and coherence (with and without snow covered images) measurements. We found the coherence measurements provide a much easier way to map snow-covered area. For validation of this method, we compared the classification result with that derived from TM imagery. An accuracy of better than 86% can be achieved if we consider the classification result from TM imagery as ground truth. Key words backscattering; interferometric coherence; repeat-pass; SAR; snow mapping

Using earth observation for constraining uncertainty in sediment loss predictions

MARTYN SILGRAM, MIKE HUTCHINS ADAS Woodthorne, Wergs Road, Wolverhampton WV6 8TQ, UK e-mail: [email protected] STEVE ROBINSON, JEFF SETTLE, LESTER P. SIMMONDS University of Reading, Whiteknights, Reading RG6 6DW, UK

NICK VECK NRSC, Delta House, Southwood Crescent, Southwood, Hampshire GU14 ONL, UK

Abstract Current Earth Observation (EO) satellites have limited ability to discriminate variables necessary for predicting the impact of nutrient loss on water quality. This project investigates whether new hyperspectral EO sensors provide enhanced accuracy and more detailed spatial context to aid the characterization of crop type and fractional ground cover. These are key input parameters in models of field and catchment scale nitrogen, phosphorus and sediment loss to streams. Such contemporary information, when coupled with supporting (e.g. digital elevation model) data, will help identify vulnerable areas and provide a framework for developing pollution risk assessment tools based on the spatial co-location of risk factors (slope, erodable soils, crop type). Key words Earth observation; modelling; runoff; sediment

Application of complex process-based models of land surface processes in the interpretation of remote sensing

LESTER P. SIMMONDS Department of Soil Science, University of Reading, Reading RG6 6DW, UK e-mail: [email protected]

Abstract This paper provides examples of how a complex, process-based model of soil– vegetation–atmosphere transfers can contribute to the interpretation of remote sensing. The first is the derivation of a simple algorithm for estimating near-surface soil wetness from passive microwave remote sensing. The second is the use of vegetation cover information to estimate annual deep percolation through sandy soils in the Sahel. Key words deep percolation; infiltration; Sahel; soil water; SVAT model; SWEAT

Potential retrieval of tillage direction as a runoff indicator using Radarsat data

JILL SMYTH, FERDINAND BONN CARTEL, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada e-mail: [email protected]

STÉPHANE HARDY VIASAT Geotechnologies Inc., Montréal, Québec, Canada

AGNÈS REMOND BRGM, Orléans, France

PIERRE CLÉMENT Université Lumière Lyon II, Lyon, France

Abstract In agricultural regions, the assessment of surface conditions such as roughness is useful for the management and prevention of risks related to excessive runoff. This study evaluates the possibility of extracting tillage orientation as a preferred runoff direction from Radarsat data. Three standard mode images at high incidence angles and corresponding ground data were acquired over the Solnan watershed (France) in March 1998. Bivariate and multivariate regressions show that, on very rough fields, there is no correlation between backscatter and root mean square (rms) height. However, there is a significant relationship between tillage direction and backscatter, and this behaviour follows a sinusoidal form. Key words agriculture; bare soils; Radarsat; roughness; SAR imagery; tillage direction

Monitoring wetland hydrology in Atlantic Canada using multi-temporal and multi-beam Radarsat data

JENNIFER SOKOL Noetix Research Inc., 265 Carling Avenue, # 403, Ottawa, Ontario K1S 2E1, Canada e-mail: [email protected]

TERRY J. PULTZ Canada Centre for Remote Sensing, 588 Booth Street, Ottawa, Ontario K1A 0Y7, Canada

VICTOR BULZGIS Noetix Research Inc., 265 Carling Avenue, # 403, Ottawa, Ontario K1S 2E1, Canada

Abstract Wetland complexes comprise a large percentage of ground cover in central Labrador, Canada, and contain some of the largest peatlands in North America. The region experiences long cold winters and short cool summers, resulting in a limited growth period. Fens and bogs are the dominant wetland types. The level of moisture saturation, chemistry, topography and climate influence the development of wetland systems. Slight changes in these environmental factors can significantly alter vegetation species and health. As persistent cloud cover often limits the utility of optical remotely sensed data in Atlantic Canada, the value of using the all-weather capabilities of radar data become evident. Temporal sequences of Radarsat images were acquired in May, June and August 1999. During each time period, four Radarsat scenes with incidence angles spanning 20–49° (Standard 1, 4, 7 and Fine 1) were acquired. This paper describes changes in radar backscatter as a function of incidence angle, vegetation structure and moisture conditions. Key words incidence angle; beam mode; Labrador (Canada); Radarsat; wetland

Application of the SRM and SLURP models in eastern Turkey using remote sensing and geographic information systems

ÜNAL ŞORMAN Civil Engineering Department, Middle East Technical University, Ankara, Turkey e-mail: [email protected]

ENGİN UZUNOĞLU Natural Science Institute, Middle East Technical University, Ankara, Turkey

H. ILGAZ KAYA TÜBİTAK-Bilten, Ankara, Turkey

Abstract Today, global climatic issues and the water security problems resulting from the increasing water demand for hydropower and agricultural purposes from the rivers Tigris and Euphrates, in the Middle East, are quite important. The Snowmelt Runoff Model (SRM) was applied to the Karasu basin located in the upper Euphrates River drainage basin, in order to simulate and forecast the runoff from snow melting. A second study covered the application of the hydrological model SLURP-11 at a smaller scale. In combination these would enable early prediction of runoff from rainfall and snowmelt using snowmelt runoff estimation models coupled with Remote Sensing (RS) and Geographic Information System (GIS) technologies. The final aim of this study is to compare the results of the models SRM and SLURP, although applied on basins of different scales. Finally, conclusions are made about which kind of hydrological models are suitable for different basin characteristics and sizes. Key words GIS; Karasu basin (Turkey); SLURP; snowmelt runoff; SRM ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 409–411.

Remote sensing and estimation of root zone water content

PATRICK J. STARKS US Department of Agriculture, Agricultural Research Service, Grazinglands Research Laboratory, El Reno, Oklahoma 73036, USA e-mail: [email protected]

THOMAS J. JACKSON USDA-ARS Hydrology Laboratory, BARC-W, Beltsville, Maryland 20705, USA

Abstract A two-layer soil water budget model was evaluated for use in remote sensing studies of volumetric soil water content (v) in rangeland settings of central and south-central Oklahoma, USA. Field measurements and remotely sensed estimates of surface v were used separately to initialize the model. Model output of root zone v compared well to measured values for both model initialization scenarios. Modelled surface v diverged more from measured v when remotely sensed values were used to initialize the model than when field measurements were used. Overall, the model performed well, and its simplicity makes it suitable for implementation in remote sensing studies of spatial and temporal dynamics of soil water content over large regions. Key words Oklahoma, USA; passive microwave sensor; remote sensing; soil water budget; soil water content; two-layer model

Hydrological modelling study with digital image processing of multi- sensor satellite data over a small high mountainous catchment

ADDALA NARAYANA SWAMY Department of Geophysics, Andhra University, Visakhapatnam 530 003, India e-mail: [email protected]

PIETRO ALESSANDRO BRIVIO Remote Sensing Department, IRRS-CNR, Via Bassini 15, I-20133 Milan, Italy

Abstract The integration of visible and infrared satellite remote sensing information is made with ground meteorological and hydrological data to study the application of a semi- distributed temperature index model over a small high mountainous catchment in the Italian Alps. Nine sets of digital Landsat MSS and TM images covering a hydrological year were processed. Digital elevation model, slope, aspect and shaded relief maps coinciding with the satellite passes were generated using locally developed software known as Territorial Image Synthesis System (TISS). The areal extent of snow cover over the catchment for each scene has been estimated using parallele-piped, nearest neighbour and maximum likelihood methodologies of supervised classification. Daily snow depletion curves were developed and incorporated as input to the Snowmelt Runoff Model (SRM), along with pre-determined catchment morphological parameters. The model performance evaluation has indicated excellent results when compared to those obtained on other catchments of similar areal extent in different parts of the world. Key words Alps (Italy); digital elevation model; image processing; snow cover; snowmelt runoff model; supervised classification; Territorial Image Synthesis System (TISS); water resources management ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 139–141.

A prototype MODIS-SSM/I snow mapping method

ANDREW TAIT National Institute of Water and Atmospheric Research Ltd, PO Box 14-901, Kilbirnie, Wellington, New Zealand e-mail: [email protected]

JONATHAN BARTON General Sciences Corporation, 4600 Powder Mill Road, Suite 400, Beltsville, Maryland 20705-2675, USA

DOROTHY HALL NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.

Abstract A prototype MODIS snow-cover product, derived from AVHRR data, was compared with a prototype MODIS-SSM/I product for the same area in the mid-western United States. The combined MODIS-SSM/I product, which is less affected by persistent cloudiness, mapped 9% more snow cover than the MODIS-only product. Key words mid-west USA; MODIS; prototype algorithm; snow cover; SSM/I

A new heavy precipitation warning aid for Hungary

ÁGNES TAKÁCS 3268 Cripple Creek Trail, Boulder, Colorado 80305, USA e-mail: [email protected]

CECILIA M. I. R. GIRZ, EDWARD I. TOLLERUD NOAA Forecast Systems Laboratory, 325 Broadway, Boulder, Colorado 80305, USA SÁNDOR KERTÉSZ Hungarian Meteorological Service, Budapest, Hungary

Abstract The Griffith-Woodley satellite rain estimation technique and Takács’ new PMP method (Possible Maximum Precipitation, or PoMP) were tested over the Carpathian Basin during heavy rain events in 1998 and 1999. The satellite estimation technique and the PoMP methodology are outlined. A flood-producing, heavy rainfall event that occurred in Hungary in July 1999 is contrasted with a case from 1998. Key words extreme precipitation; flood forecasting; Probable Maximum Precipitation; satellite rain estimation ______Remote Sensing and Hydrology 2000 (Proceedings of a symposium held at Santa Fe, New Mexico, USA, April 2000). IAHS Publ. no. 267, 2001, pp. 586–588.

Flood modelling in a mountain basin using mesoscale meteorological models

STEFAN TASCHNER, RALF LUDWIG & WOLFRAM MAUSER Institute for Geography, Department of Geography and Geographical Remote Sensing, University of Munich, Luisenstrasse 37, D-80333 Munich, Germany e-mail: [email protected]

Abstract The results of a coupled meteorological and hydrological model are presented in order to demonstrate its capacity for real time flood forecasting. Model runs were conducted in the Ammer basin (Germany) for the 1999 Whitsun flood using different meteorological input data. Raingauge measurements from the German Weather Service (DWD) and SWISS MODEL (SM) precipitation fields are used for the hydrological simulation within the framework of the physically based GIS-structured hydrological model PROMET. The results of the SM forecast are used by applying different disaggregation schemes. The comparison of the results with measured discharges shows good agreement with distinctive variances depending on the chosen set of input. Key words flood forecasting; GIS; PROMET; RAPHAEL; scaling; TOPMODEL

Satellite derived actual evapotranspiration and groundwater modelling, Botswana

W. J. TIMMERMANS, A. M. J. MEIJERINK & M. W. LUBCZYNSKI International Institute for Aerospace Survey and Earth Sciences (ITC), PO Box 6, 7500 AA Enschede, The Netherlands e-mail: [email protected]

Abstract Evapotranspiration losses over an aquifer during a dry season in Botswana were determined with the multi-step Surface Energy Balance Algorithm for Land (SEBAL), using sequential Landsat TM and NOAA-AVHRR data, with concurrent meteorological field data for atmospheric correction and calibration. The SEBAL method yielded high actual -1 evapotranspiration (Ea) rates (<0.5 to 4 mm day ), if relatively dense savanna vegetation was present, even when groundwater was over 40 m deep. The association between vegetation pattern and Ea has been interpreted as due to significant uptake of water by deep roots. The mapping of the groundwater contribution to the evapotranspiration was provided through MODFLOW groundwater modelling using the evapotranspiration package with an extinction depth of 60 m. It is believed that a major part of the transpired water originates from the lower vadose zone. The validity of the satellite-derived Ea flux is discussed. Key words actual evapotranspiration; Botswana; deep roots; Landsat-TM; MODFLOW; sapflow; SEBAL

Summer flood mapping in a northern wetland using a combination of Radarsat and SPOT imagery

JESSIKA TÖYRÄ Department of Geography, University of Saskatchewan, 9 Campus Drive, Saskatoon, Saskatchewan S7N 5A5, Canada e-mail: [email protected]

ALAIN PIETRONIRO National Water Research Institute, 11 Innovation Boulevard, Saskatoon, Saskatchewan S7N 3H5, Canada

LAWRENCE W. MARTZ Department of Geography, University of Saskatchewan, 9 Campus Drive, Saskatoon, Saskatchewan S7N 5A5, Canada

Abstract This paper evaluates the use of Radarsat and SPOT imagery for mapping the extent of standing water in the Peace-Athabasca delta (Canada) wetland complex during the summer of 1998. It is hypothesized that since Radarsat and SPOT images contain complementary information, flood mapping would be more efficient when the two image types are used in combination. A Radarsat scene, a SPOT scene, and a combination of the two were classified using the Mahalanobis distance algorithm. The results indicate that wetland flood mapping in summer conditions is feasible with about 80% accuracy when a combination of Radarsat and SPOT imagery is used. Key words classification; flood mapping; multi-sensor; Peace-Athabasca delta (Canada); Radarsat; SPOT; wetland

Hydrological implications of remotely sensed thermal inertia

VALERIO TRAMUTOLI, PIERLUIGI CLAPS, MAURO MARELLA Dipartimento di Ingegneria e Fisica dell’Ambiente, Università della Basilicata, Contrada Macchia Romana, I-85100 Potenza, Italy e-mail: [email protected]

NICOLA PERGOLA, CARLA PIETRAPERTOSA Istituto di Metodologie Avanzate per l’Analisi Ambientale (IMAAA)–CNR, Tito (Pz), Italy

CANIO SILEO Dipartimento di Ingegneria Civile, Università degli Studi di Roma “Tor Vergata”, Via di Tor Vergata 110, I-00133 Roma, Italy

Abstract The potential of using the day/night temperature difference as an indicator of soil/canopy water content at short time-scales, based on AVHRR data, is considered. The goal of this approach is to evaluate the usefulness of introducing a soil thermal index in assessing the space–time variability of soil water content. Water balance model calibration, spatial models of precipitation, and flood forecasting (in the setting of initial conditions) may benefit from these results. Apparent Thermal Inertia (ATI), derived from AVHRR, was compared to daily precipitation and to an antecedent precipitation index to evaluate the evidence of time variability of ATI with regard to relative soil water content. Analysis of the spatial variability was also made to evaluate the robustness and the sensitivity of the ATI in the study area. Results from the computation of ATI over a 300 km2 river basin in southern Italy indicate that this index can provide useful information related to an indirect estimate of soil moisture. Key words ATI; AVHRR; Basilicata, Italy; soil moisture; remote sensing

Developments for snowpack water equivalent monitoring using Radarsat data as input to the Hydrotel hydrological model

RICHARD TURCOTTE, JEAN-PIERRE FORTIN, MONIQUE BERNIER & YVES GAUTHIER INRS-Eau, 2800 rue Einstein, CP 7500 Sainte-Foy, Québec G1V 4C7, Canada e-mail: [email protected]

Abstract A distributed hydrological model and an algorithm to extract snow water equivalent (SWE) from Radarsat data have been developed in parallel over the past years. Previous studies showed that the hydrological model can take advantage of updated SWE, as data from other sources become available, to improve accuracy of spring runoff simulation. However, Radarsat derived SWE, as promising as is it, showed a high sensitivity to the spatial distribution of the snow density which is required as input. This paper proposes a methodology for SWE monitoring that is based on integrating the two previous approaches with snow survey data. Key words hydrological model; Radarsat ScanSAR; snowpack water equivalent monitoring

Characterization of west African shallow flood plains with L- and C- band radar

NICK VAN DE GIESEN Center for Development Research, Bonn University, Walter-Flex St 3, D-53113 Bonn, Germany e-mail: [email protected]

Abstract The flood plains along the major rivers of West Africa are a potentially important agricultural resource. Satellite-based radar imagery can be used for characterization of flood patterns. Using dry and wet season Shuttle Imaging Radar (SIR-C) imagery, flood plain elements were classified as gallery-forests, open water, water with reeds, and non-flooded areas. The radar bands used are also available on other satellites (JERS and Radarsat). An error analysis based on histograms shows the results are good despite the lack of real time ground data. Key words flood plains; multi-frequency analysis; radar; SIR-C; West Africa; wetlands

Large scale soil moisture monitoring using C-band scatterometer data

WOLFGANG WAGNER German Remote Sensing Data Center (DFD), German Aerospace Center (DLR), PO Box 11 16, D-82230 Wessling, Germany e-mail: [email protected]

KLAUS SCIPAL Institute for Photogrammetry and Remote Sensing, Vienna University of Technology, Gusshausstrasse 27-29, A- 1040 Vienna, Austria

Abstract A method for monitoring soil moisture patterns using C-band scatterometers is described. The aim of this paper is not to go into the technical details of the retrieval algorithm, but rather to put the technique into context with previous efforts in active microwave remote sensing research and to point out a number of applications. Key words Africa; agronomy; change detection; climate change; meteorology; soil moisture

Aggregation rules for sensible heat flux estimates over agricultural fields in Mexico

C. J. WATTS, A. CHEHBOUNI, J. C. RODRIGUEZ, F. SANTIAGO IMADES/IRD, Reyes & Aguascalientes, Hermosillo, Sonora 83190, Mexico e-mail: [email protected]

J. GARATUZA-PAYAN ITSON, 5 de Febrero 818 sur, Ciudad Obregón, Sonora 85000, Mexico

J. SCHIELDGE Jet Propulsion Laboratory, Pasadena, California, USA

Abstract Three aggregation rules for estimating composite sensible heat flux are tested over fields of chickpeas and cotton in the Yaqui Valley irrigation district in Mexico. The results show that a simple average of the surface parameters for each field are adequate in this case. The implications of these results for the use of satellite data are discussed. Key words aggregation rules; irrigated crops; Mexico; sensible heat flux