WORLD METEOROLOGICAL ORGANIZATION OPERATIONAL HYDROLOGY REPORT No. 43 CURRENT OPERATIONAL APPLICATIONS OF REMOTE SENSING IN HYDROLOGY by A. Rango and A.I. Shalaby WMO-No.884 Secretariat of the World Meteorological Organization - Geneva - Switzerland 1999 Cover: NOAA-AVHRRfalse color composite image illustrating extent offload waters on the Red River ofthe North in Minnesota and North Dakota, USA during April 1997. Theflood waters are shown in white, remaining snow cover in red, clouds in yellow and orange, and open land in blue. The image was produced by the National Operational Hydrologic Remote Sensing Center, National Weather Service; National Oceanic and Atmospheric Administration (courtesy ofT. Carroll and D. Cline) © 1999, World Meteorological Organization ISBN: 92-63-10884-6 NOTE The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the World Meteorological Organization concerning the legal status of any country, territory, city or area, or ofits authorities, or concerning the delimitation ofits frontiers or boundaries. CONTENTS Page FOREWORD . v SUMMARY (English, French, Russian, Spanish) . vii CHAPTER 1. INTRODUCTION . 1 1.1 Literature on applications of remote sensing in hydrology , . 1 1.2 Citations ofoperational applications of remote sensing in hydrology ", .. 1 1.3 Remote sensing for hydrologists . 1 1.3.1 Background . 1 1.3.2 Definitions . 1 1.3.3 Theory . 1 1.4 Definition ofoperational applications of remote sensing in hydrology ,. 2 CHAPTER 2. APPLICATIONS OF REMOTE SENSING IN HYDROLOGY ••••.•••..•••..•...•............ 3 2.1 Technical and economic aspects . 3 2.1.2 Economic consideration . 3 2.2 Remote s.ensing measurements of hydrological variables . 3 2.2.1 Precipitation . 3 2.2.1.1 Visible and infrared rainfall monitoring techniques . 4 2.2.1.2 Passive microwave rainfall monitoring techniques . 4 2.2.1.3 Multispectral/microwave sounding unit rainfall monitoring techniques .. 5 2.2.1.4 Ground-based radar rainfall monitoring techniques . 5 2.2.1.5 Satellite radar rainfall monitoring ..................................... 8 2.2.1.6 Water vapor imagery rainfall monitoring techniques . 8 2.2.2 Soil moisture and groundwater ,. 8 2.2.2.1 Soil moisture ...................................... .... 8 2.2.2.2 Groundwater......................................... 10 2.2.3 Evapotranspiration. ...................... ........... 11 2.2.3.1 Semi-empirical methods .......... 12 2.2.3.2 Analytical methods .... .. .. .. .. .. .. 12 2.2.3.3 Numerical models ..... ................................... ,. 13 2.2.4 Snow................................................................... .. 13 2.2.4.1 Snow cover distribution ,. 14 2.2.4.2 Snow accumulation ............................... 16 2.2.4.3 Snow metamorphism. ............................. .. 17 2.2.4.4 Snowpack ablation and snowmelt runoff . 17 2.2.5 Ice on land .............................., . 18 2.2.6 Surface water ...................... 19 2.2.6.1 Surface water area .. ......... 20 2.2.6.2 Surface water stagellevel ...... ......... 22 2.2.6.3 Surface water depth. ......... .............. 22 2.2.6.4 Surface water temperature. .................................... ..,. 22 2.2.6.5 Surface water salinity and mineralization , ,. ............ 23 2.2.6.6 Surface water suspended sediments .. 23 2.2.6.7 Surface water chlorophyll . 23 2.2.6.8 Other pollutants in surface water . 23 2.2.6.9 Surface water vegetation biomass 24 2.2.7 Basin characteristics . 24 2.3 Remote sensing inputs for hydrological models 27 2.4 Current operational applications .. 28 2.4.1 Precipitation . 28 2.4.2 Soil moisture and groundwater . 29 2.4.3 Evapotranspiration . 29 2.4.4 Snow . 29 2.4.5 Icc on land . 29 2.4.6 Surface water . 29 2.4.7 Basin characteristics 30 2.5 Future trends ... 30 iv CONTENTS Page CHAPTER 3. NEW REMOTE SENSING ADVANCES.... .. .. .•.. ...••.•. .. .. .. .•..... .......•....... 31 3.1 Recent state-of-the-art remote sensing technology advances and ongoing research 31 3.1.1 Satellites .. .. .. .. .. 31 3.1.2 Aircraft.. .. .. .. .... .. .. .. .. .. .. .. .. .. .. .. .. .. .. 31 3.1.3 Ground-based methods and radars . .. .. .. .. .. .. .. .. .. .. 32 3.2 Potential new applications in operational hydrology _........................ 32 CHAPTER 4. PROBLEMS IN APPLICATIONS OF REMOTE SENSING IN OPERATIONAL HYDROLOGY ., 34 4.1 Current limitations ofoperational utilization ofremote sensing _....................... 34 4.1.1 Status in developed countries .. .. .. .. .. .. .. 34 4.1.2 Status in developing countries _.. _ _. 34 4.2 Problem areas preventing the operational utilization of remote sensing in hydrology 34 4.2.1 Hydrological variables .............................................. 34 4.2.2 Hydrological models 35 4.2.3 Remote sensing technology _. __ _. 35 4.2.3.1 Limitations of the state-of-the-art ,._ , , 35 4.2.3.2 Consistency of data and need for calibration ofnew sensors ,........................ 36 4.2.4 Availability ofdata . .. .. .. .. .. .. .. ..... .. ... .. .... .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. 36 4.2.4.1 Geographical or climatological regions where remote sensing data are most applicable 36 4.2.4.2 Data acquisition and distribution capabilities of countries _, _ _. _. 36 4.2.5 Cost of data.. .. .. .... .. .. .. .. ...... .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. 37 4.2.6 Computer data-processing capability .. _.. __ _...................... 37 4.2.7 Data presentation/publication/dissemination _ ,............ .. 37 4.2.8 Human resources and training capability , ,..................... 37 CHAPTER S. A STRATEGY FOR ACCEPTANCE OF REMOTE SENSING IN OPERATIONAL HYDROLOGY 39 5.1 Past studies ofoperational hydrological observational needs and existing and future satellites. .. .................. .. 39 5.2 Development or modification ofhydrological models based on remote sensing infonnation 39 5.3 Demonstration ofsignificant technical and economic benefits _ ,,.,.... 39 5.4 Targeting major hydrological services 40 CHAPTER 6. ELEMENTS OF SUCCESSFUL REMOTE SENSING IN OPERATIONAL HYDROLOGY •..••.•• 41 6.1 Financial resources .......................................................... 41 6.2 Regional remote sensing centers , "............. 41 6.2.1 Expert advice _...... ,...... .. 41 6.2.2 Training of personnel . __ . ...... ... _.................. 42 6.3 Ground receiving stations .................... .. ............................ 43 6.4 Groundtruth networks . , _................. 43 6.5 Key ancillary support systems ,,.... .._... ..................... 43 CHAPTER 7. RECOMMENDATIONS 4S 7.1 Key approaches to include in developed countries , , ,,,_ 45 7.2 Key approaches to include in developing countries ,............................................ 45 REFERENCES 46 APPENDIX 1. Cited literature on applications of remote sensing in hydrology •...•..•••••••......•••••.•..••• 58 APPENDIX 2. Hydrological observational requirements and existing and planned satellites and sensors for hydrological applications. •.........•.......•...•..••••.....•.•...•.....•.•....•.•.•.•.... 60 APPENDIX 3. Specific sensors which might be carried by EOS 6S APPENDIX 4. StateMofatheaart of satellite data requirements and required capabilities ofnear-polar orbiting and geostationary satellites .....••.•.•.•..........•.••.... •..•...........•••.•••......... 66 ACRONYMS 71 FOREWORD Over the years, WMO has taken a particular interest in the potential of remote sensing for operational use in hydrology. Accordingly, WMO has issued a number of reports on the subject with the aim of advising national Hydrological Services of the current state of the art. In the past, the emphasis was mainly on the use of remote sensing for research, partly because the techniques had not been fully developed for routine application and partly because the satellites themselves were often designated as being for research with no guarantee of future continuity. This situation has now changed and remote sensing is being widely used in hydrology for a range of purposes. The fact that the opera­ tional community does not publish its results so frequently makes it even more valuable that WMO, through its Commission for Hydrology, maintains its role of monitoring and reporting on developments. At its ninth session in 1993, the Commission appointed Mr A. Rango (United States of America) as its Rapporteur on Applications of Remote Sensing and entrustred him with the task of preparing a report on "current applications of remote sensing in hydrology". To complete this task, Mr Rango invited Professor A.I. Shalaby of Howard University to assist him in putting together the report. It was then recommended for publication by the Commission for Hydrology at its tenth session. I should like to place on record the gratitude of th,e World Meteorological Organization to Drs Rango and Shalaby for the time and effort they have devoted to the preparation of this valuable report. (G.O.P. Obasi) Secretary-General SUMMARY This report provides information on the most recent advances in identifies applications of remote sensing in each subdiscipline, and operational use of remote sensing in hydrology and water identifies those applications that qualify as operational. New resources management. The application of remote sensing data advances in remote sensing are briefly surveyed in Chapter 3. The can be termed operational if at least one of two conditions is various problems that hinder operational applications are covered fulfilled: 1)