Hydrology from Space: a decade of development A potential for future services

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1 Hydrology from Space: a decade of development A potential for future services Jean-François Crétaux CNES, Legos, Toulouse, France Geneva, WMO, Nov 2012

2 Water is a global issue Availability of fresh water is inhomogenous World demography is increasing, the needs too

3 Regarding: - The complexity and heterogeneity of hydrological situations worldwide - The current issues of transboundaries water sharing - The scarcity of water in many parts of the world - The impact of global climate change on water resources - The needs of an efficient water management at basin scale Need to: - Setup and maintain hydrological gauging networks - Enhance international cooperation between laboratories, national agencies, and private sector - Develop international framework program for dissemination of data, expertise, training, advanced research - develop applications of new technologies, in particular Satellite Remote Sensing - Setup operational global data basis and operational services

1985-1990 1990-1994 1995-2000 2000-2004 <2004

4 In situ network for Rivers (Global Runoff Data Center) Date of last data < <2004 Evolution of in situ network Global Runoff Data Center

Space technics applied to Hydrology Radar altimetry

the presentation 1) highlight on each technics and

for the next 10 years 3) Is it possible to build

5 Space technics applied to Hydrology Radar altimetry Satellite Gravimetry Satellite imagery Objectives of the presentation 1) highlight on each technics and main results over the last 10 years 2) Perspectives for the next 10 years 3) Is it possible to build operationnal regional and global database and why do we need them?

6 Space observations allow to measure the Total Water Storage (TWS) Surface water Altimetry + imagery Soil moisture SMOS (ESA), SMAP (NASA) Underground water Aquifers Aquifers TWS Gravimetry: GRACE

7 Principle of altimetry

8 Altimetry over lakes: comparison with In Situ data (1/2) level (m ) level (m) 1135,3 1135,2 1135, ,9 1134,8 1134,7 1134,6 1134,5 1134,4 1134,3 1134,2 1134, ,9 1133, ,8 183,6 183,4 183, ,8 182,6 Lake Victoria, In Situ / Altimetry , , , Date (year) Lake Superior In Situ / altimetry date (year) Altimetry In Situ level (m ) Altimetry (m) Lake Victoria, scatter of In Situ / Jason ,7 1134,6 1134,5 1134,4 1134,3 1134,2 1134, ,9 Standart Deviation: 2.7 cm Coefficient of correlation: , ,1 1134,2 1134,3 1134,4 1134,5 1134,6 1134,7 Jasn-1 level (m) Lake Superior, Scatter In Situ / Altimetry ,8 183,6 183,4 183,2 Standart Deviation = 4.4 cm Coefficient of correlation = ,8 182,6 182,6 182, ,2 183,4 183,6 183,8 184 In Situ (m)

9 Comparison of data base products over lakes with in situ gauges data. (2/2) Hydroweb (Legos) River & Lakes (De Montfort) GRLM (USDA, Maryland Univ.) 3-4 cm <Accuracy < 1m Ricko et al., 2012

10 Altimetry on rivers Virtual stations: Intersection of satellite track with the river Possibility to compute water height time series Link Water level / discharge through rating curves Time sampling from 10 to 35 days

11 Comparison with in situ gauges Correlation: 0.97 RMS: 16 cm Courtesy of N. Bercher & S. Calmant

12 Virtual stations over the Amazon Basin (red) / In Situ network (yellow) High potential of synergy between «traditional» network with Satellite products

Mutual use of Radar Altimetry and In Situ

derived water levels are used to calculate the

Seasonnal range of variations: 7m, RMS: 26 cm

Impact on surface to deep water circulation from the

13 Mutual use of Radar Altimetry and In Situ measurements: Example of the Ganga Basin Space derived water levels are used to calculate the discharge of river from rating curve method. Seasonnal range of variations: 7m, RMS: 26 cm Hydroweb has been used by authors for this study Impact on surface to deep water circulation from the Gulf of Bengal to the SE Arabian Sea has been estimated (Papa et al., 2010, 2012, Durand et al., 2011)

14 Physic of measurement SATELLITE IMAGERY Modis, Meris, Landsat, Spot, Pleiades, Cbers, Sentinel-2 MAPING OF INUNDATED SURFACE (lakes, reservoirs, floodplains, swamps)

Example: Flood monitoring over the Inner Niger Delta (IND) From Modis Inter annual Monitoring of inundated areas, aquatic vegetation and vegetation 7000 open water over the IND 6000 The

lakes surface (km2) 5000 4000 3000 2000 1000 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Longitudinal patterns of precipitation with marked gradient from South (1200/1500

15 Example: Flood monitoring over the Inner Niger Delta (IND) From Modis Inter annual Monitoring of inundated areas, aquatic vegetation and vegetation 7000 open water over the IND 6000 The IND is a shallow area of 40,000 km2 Niger and Bani rivers supply to the IND with annual inundation which occur between August and October It is lowland constituded by channels swamps and lakes surface (km2) Longitudinal patterns of precipitation with marked gradient from South (1200/1500 mm/yr) to North (300 mm/yr) Over the IND, the main contributor of flood will be the surface water flow from upstream rivers with time shift which should be detected from Modis images analysis

16 Map of Modis classification over the Inner Niger Delta from Modis/Terra intruments at the maximum of inundation of 4 different years with pronounced inter-annual variability

17 Modis classification / rainfall (TRMM) open water Rainfall on Bani normalized data Time shift of 1.5 months Inter-annual variability date (year) Modis Classification / rainfall (TRMM) 1,2 1 open water rainfall on IND normalized value 0,8 0,6 0,4 0,2 First apparition of water on the IND correlated to direct rainfalls date (year) Modis Classification / Rainfall (TRMM) 1,2 Vegetation normalized data 1 0,8 0,6 0,4 rainfall on IND Vegetation cover correlated to rainfalls over the IND 0, date (year) Linkage with African Moonsoon

Why monitoring the IND water surface and level from RS is important?

strongly dependant on water resources in the IND (agriculture, fishing, pastoralism) The interaction among pre-flood, flood and post-flood conditions

IND flooding, the river systems, and the Western African moonsoon The IND can serve as a good natural laboratory to study climate change impact on surface

18 Why monitoring the IND water surface and level from RS is important? The Sahel is one of the most endangered zones worldwide The IND serves as crucial source of economic activity in Mali, with more than one million inhabitants strongly dependant on water resources in the IND (agriculture, fishing, pastoralism) The interaction among pre-flood, flood and post-flood conditions strongly affect land use patterns in and around the delta Need to examine how vulnerable is the IND to climate change Need to investigate the linkage between IND flooding, the river systems, and the Western African moonsoon The IND can serve as a good natural laboratory to study climate change impact on surface water resources in semi-arid region Development of a modern system of survey/alert/prediction for inundation in the IND is an ongoing challenge. A condition sine qua non is the availability of homogenised and standardised time series of remotely sensed data.

19 SATELLITE GRAVIMETRY What do we learned from GRACE? GRACE Land Surface Model / observations => Undergound water Indus km 3 /yr Ganga km 3 /yr Water pumping for irrigation Underground Water Storage: Map of trends (cm/yr) ( ) Rodell et al., 2009; Tiwari et al., 2009, Becker et al., 2010

TWS variations over river watershed from GRACE Yenisey Niger Stored water variations [ mm ] 150 100 50 0-50 -100-150 GRGS CSR GLDAS MSW GLDAS + SW 2002 2003 2004 2005 2006 2007

20 TWS variations over river watershed from GRACE Yenisey Niger Stored water variations [ mm ] GRGS CSR GLDAS MSW GLDAS + SW Congo Example of use of GRACE+altimetry on reservoirs to correct land surface model (Longuevergne et al. 2012): case study on Tigris Euphrate based on Hydroweb data

21 Space technics applied to transboundary water monitoring - 40 % of world s population lives in river or lake basins shared by at least 2 countries transboundary lakes and river basins, covering 50% of the Earth surface Hydrological, social and economical interdependencies between countries Additionnal threats arise from climate changes Potential of conflicts / opportunity for cooperation creation of international comitee of water management development of adaptation strategy need of sharing the information and of agreement on decision for water uses Need of accurate / real time monitoring of water quantity and quality One case study: Central Asia Before 1991 After 1991 USSR, one country, water management was centralised 6 countries are sharing the watershed of Amu Darya and Syr Darya

22 An example of transboundary water management and sharing issues: Central Asia after the collapse of the USSR

23 What kind of information could we get from satellite in such context? Continuous, Reliables, complementaries and independant measurements Lac Sarykamish Niveau (m) Altimétrie In Situ Issykkul Rms of difference: 4 cm after 2002 T/P + Envisat+GFO Jason2 In Sit u Only T/ P and GFO Envisat and Jason

24 Useful information for survey of reservoirs water height variations, especially when water management have incidence on downstream countries, but could be also conflictual 910 Toktogul (Kyrgyzstan) level (m) High water release of the reservoir in winter 2008 and 2009 for hydropower reasons

8000 Arnasay Floodplain 7000 Surface inondées (km2) 6000 5000 4000 3000 2000

25 8000 Arnasay Floodplain 7000 Surface inondées (km2) Linked to the Toktogul water level variations Uzbekistan complained from winter inundations during the years 2009, 2010 due to excessive water release from the reservoir.

Satellite data allow the surveying of floodplains and reservoirs in the Syr Darya

Discussion with Central Asian water agencies for development of cooperation in the

5 246 Envisat 256 254 T/P Envisat Jason2 245.5 252 level (m) 245 244.5 244 243.

26 Satellite data allow the surveying of floodplains and reservoirs in the Syr Darya Basin. Discussion with Central Asian water agencies for development of cooperation in the frame of the water management of rivers. Aydarkul Chardarya Envisat T/P Envisat Jason level (m) date Level (m) March April May June August December

27 Existing data base on lakes and rivers Inferred from Remote Sensing data Hydroweb (global lakes/reservoirs/rivers: level, surface, volume, TWS) GRLM (global lakes/reservoirs: level) Rivers & Lakes (global lakes,reservoirs/rivers: level) Dartmouth Observatory (global rivers/floodplains, water extent, discharge) Arc-Lake (global lakes, surface water temperature) Inferred from In Situ data GRDC (global, rivers: discharge) Hydrolare (global, lakes, levels, surface, volume, water temperature) Hybam (regional, rivers, level, discharge, sediments) Cawater (regional, lakes/reservoirs/rivers, discharge, level, volume) NOAA Great Lakes (regional, lakes/rivers, multi-parameters) Canadian water office (regional, lakes/reservoirs/rivers, levels, discharge) USGS (regional lakes/reservoirs/rivers, multi-parameters) Others????? Enhancement of satellite data use is needed Time for operationnal services?

28 Hydroweb (altimetry, imagery, and gravimetry for lakes and rivers) 160 lakes & Reservoirs 1300 VSover rivers TWS on 30 basins Hydroweb is part of the «Hydrolare» lake data centre hosted by State Institute of Hydrology of St Petersburg, under a GCOS/WMO framework program: Products of ECVs: Level, surface and volume variations of lakes from combination of satellite altimetry and imagery

29 GRLM: Global Reservoirs and Lakes Monitor (USDA, Univ. Of Maryland) NRT products: water level from satellite altimetry on ~100 reservoirs and lakes

30 An example of regional database for river monitoring: Hybam. Access to river levels, rating curves and discharges at VS and ground gauges (Amazon, Orenoque and Congo basins)

31 The Dartmouth Flood Observatory (Univ. of Colorado) In situ+remote Sensing data: Daily update Archive of large floods since 1985 River discharge worldwide

32 Cawater Portal of Knowledge for Water and Environmental Issues in Central Asia Very dense NRT data base with access to: Water level, volume, discharge, lnflow to reservoirs, reports, maps, bibliography etc

33 What is required for operational services? - Continuity of satellite missions - Updating products in NRT - Accuracy and integrity - Development of expert system for data processing and analysis - Free access of data and basic products Some limitations - Time sampling and spatial resolution of radar altimetry and gravimetry - Algorithm of data processing well adapted for ocean or big lakes, not rivers - Not all missions have free access of data - Program are not designed for hydrology (Sentinel) and «lobbying» still strongly needed - only small number of laboratories do deep investigation on the use of satellite technique for Hydrology

34 Remote Sensing future missions for surface waters What are the perspective? Satellite imagery Modis/Terra Sentinel-2 (ESA mission For GMES: 2014) High resolution imagery (10, 20 and 60 m) with full Earth coverage every 5 days Satellite radar altimetry Jason-2 (2008-) Jason-3 (mid 2013), Jason-CS (ESA: 2017) Altika (Dec 2012, CNES/ISRO, altimeter in Ka band) Sentinel-3 (ESA : 2014: ATSR, SAR Altimeter, Meris) HY2 (China, data not available now) Satellite Gravimetry Grace-2 (NASA/DLR mission: ) Satellite Interferometry SWOT Ka-Band SAR interferometric system with 2 swaths, each 60 km wide, will measure water height and water mask contour worldwide

2019-2020: SWOT Ka-Band SAR interferometric system with 2 swaths, each 60 km wide, and 22 days of

lakes of 250*250m at 10 cm of accuracy and slope of 1cm/km over 10 km along rivers Wide range of

35 : SWOT Ka-Band SAR interferometric system with 2 swaths, each 60 km wide, and 22 days of cycle Produces heights and co-registered all weather imagery Worldwide water surface estimation for lakes of 250*250m at 10 cm of accuracy and slope of 1cm/km over 10 km along rivers Wide range of applications in Hydrology: Inventory of all lakes worldwide Discharge on rivers Floodplains 3D mapping

Issues for the future Inventory od water ressources at global scale Impact of global change on global water cycle Contribution of continental water to the global Sea level rise Linkage between drough

36 Issues for the future Inventory od water ressources at global scale Impact of global change on global water cycle Contribution of continental water to the global Sea level rise Linkage between drough / flood and Climate => societal impacts Transboundary water management in a context of water scarcity and economical development Understanding of Deltas interaction with the ocean and coastal areas Assimilation of satellite data in models Build and maintain in situ networks Build and maintain regional and global data base Development of operational services

Issues include coverage gaps, delays, measurement continuity and consistency, data format and QC, political restrictions

Issues include coverage gaps, delays, measurement continuity and consistency, data format and QC, political restrictions Satellite-based Estimates of Groundwater Depletion, Ph.D. Chief, Hydrological Sciences Laboratory NASA Goddard Space Flight Center Greenbelt, MD Groundwater Monitoring Inadequacy of Surface Observations