High resolution remote sensing of surface water GEOBIA for multi-temporal & multi-spectral data sets Eric Masson University Lille 1 Sciences and Technologies [email protected]

Presentation overview This presentation focusses on two cases of water remote sensing for SUstainable WAter(shed) Management The methodology used is based on GEOBIA (GEographical Object Based Image Analysis) using eCognition software •First case: Tahaddart watershed (Morocco) 1 unsustainable touristic water uses 2 surface water monitoring with a Spot5 data set •Second case: Mataiva lagoon (French Polynesia) 3 a reticulated lagoon full of phosphates 4 Atoll water monitoring with a Worldview2 data set •Conclusion 5 remote sensing of surface water and SUWAMA Tahaddart watershed

Mataiva lagoon

Conclusion

Fisrt case: Tahaddart watershed (Morocco)

©CNES 2009 Distribution Spot Image S.A.

Tahaddart watershed

Mataiva lagoon

Conclusion

1 Unsustainable touristic water uses (1/2) Touristic seasonnal pressure in Tangier region

Landscape features in advertising for Tangier region from 1023 touristic images Swimming pool Lagoons and cascades Beach Recreative grass Sea Luxurious bushes Funtains Trees Palm trees

Data: Délégation de Tanger, Ministère du tourisme, Maroc

Tahaddart watershed

Data: national and international touristic flyers, websites and leisure projects images

Mataiva lagoon

Conclusion

1 Unsustainable touristic water uses (2/2) Perception of Tangier environment: - touristic advertising is exhibited in luxurious wet and green environment - there is no reference to water scarcity or water access problems in resorts projects Consequences: - tourists are looking for landscapes and facilities without any idea of water balance consequences (over consuption, pollution…) - potential recreational water uses promote a huge tourisitic resort development on the Tahaddart shoreline to cope the growing touristic demand - major local impacts on hydro-ecosystems during the construction phase (many years) - long term impacts on water quality and quantity by supplying touristic sector water needs - future water conflicts in a semi-arid are under climate change Tahaddart watershed

Mataiva lagoon

Conclusion

Tahaddart shoreline and touristic developement upon coastal aquifers Backside view of june 2009

Photo credits: Masson E. 2009

Tahaddart shoreline and touristic developement upon coastal aquifers Same project (frontside view) after 2 years (june 2011)

Photo credits: Masson E. 2011

2. Surface water monitoring with a Spot5 data set (2/4) • Surface water monitoring is a solution to provide a good indicator of water scarcity for a «SUWAMA» in the tahaddart. The 9 april dam has been chosen for its strategic influence in Tangier region water supply • SPOT 5 sensor properties – Multispectral: XS, 4 bands (G, R, Nir, Swir), 10 m native to 2.5m (Pansharpening) – Panchromatic: PAN, 2 bands (backward & foreward view) 5m native to 2.5m (backward/foreward combination)

• SPOT 5 multitemporal dataset used – 1 archive dataset (June 2008) in dry year conditions (below average rainfall) – 2 acquisitions programing dataset (April & September 2009) in wet year conditions (above average rainfall) – 12 bands multitemporal dataset for surface water monitoring – Native 10m XS sensor data – No Pan data regarding to research project objectives

Tahaddart watershed

Mataiva lagoon

Conclusion

2. Surface water monitoring with a Spot5 data set (2/4) The 5 april Dam reservoir in april 2009 (wet year condition) - total surface of 1,451 ha - water supply for Tangier city - a “sustainable” solution to Tangier aquifer’s over consuption

©CNES 2009 - Distribution Spot Image S.A.

Tahaddart watershed

Mataiva lagoon

Conclusion

2. Surface water monitoring with a Spot5 data set (3/4)

Key map: - April 2009 (imagery) - September 2009 (red line) - June 2008 (white line)

Surface water evolution from june 2008 to september 2009

©CNES 2009 - Distribution Spot Image S.A.

Tahaddart watershed

Mataiva lagoon

Conclusion

2. Surface water monitoring with a Spot5 data set (4/4) GEOBIA classification ruleset used for water surface extraction

Results Date Surface (ha) Surface water variation 19 JUNE 2008 1167 -20 9 APRIL 2009 1451 0 24 SEPTEMBER 2009 1384 -5 Tahaddart watershed

Mataiva lagoon

Water availability period Dry year (early summer) Reference wet year (spring) Wet year (late summer) Conclusion

Second case: Mataiva lagoon (French Polynesia) Mataiva Atoll is the most western island of the Tuamotu archipelago (French Polynesia) N

Area of interest

Tahaddart watershed

2 km

Mataiva lagoon

Conclusion

3 a reticulated lagoon full of phosphates Description of Mataiva Lagoon - Maximum depth of 35meters (mean 8m) with a tide range of +/- 55cm - The lagoon is poorly connected to the sea despite its 9 hoas - 250 people living on the atoll including 4 tourist pensions - Main economic activity is coprah culture - Alga production of phosphates at high rate - One of the last native forest of the touamotus Impacts : - Low human impact except coconut plantation - High water turbidity due to phosphate and shallow water environnement - Low biodiversity compare to other Tuamotu atolls (lot of dead coral) - But high economical value regarding to phosphate potential exploitation - Phosphate extraction would lead to a higher turbidity with strong impact on lagoon habitats and biodiversity…

Tahaddart watershed

Mataiva lagoon

Conclusion

4 Atoll water monitoring with a Worldview2 data set (1/4)

Worldview2 data and sensors parameters

MS data wavelength Coastal: 400-450nm Blue: 450-510nm Green: 510-580nm Yellow: 585-625nm Red: 630-690nm Red edge: 705-745nm Nir 1: 770-895nm Nir 2: 860-1040nm Tahaddart watershed

Mataiva lagoon

Conclusion

4 Atoll water monitoring with a Worldview2 data set (2/4)

NDWI

R: Nir 1; G : Red; B: Green Tahaddart watershed

NDVI

Panchromatic band

R: Nir2; G: Red edge; B: Yellow

R: Red; G: Green; B: Blue

Mataiva lagoon

Conclusion

4 surface water monitoring with a Worldview2 data set (3/4) Classification ruleset building using: image segmentation, object information and GEOBIA algorithms

Tahaddart watershed

Mataiva lagoon

Conclusion

4 surface water monitoring with a Worldview2 data set (4/4) Results: • Each water classe (i.e. ocean, reef pond, lagoon pools and lagoon shallow waters) is exported to ArcGIS (shapefiles) including all object attributes • A fisrt step in Mataiva water monitoring has been done but many water quality indicators can be calculated using GEOBIA and Worldview2 imagery • The next steps are coral mapping and bathymetry classification combining field survey (64 depth points) and GEOBIA methodology • All the ruleset can be applied to other atoll by simple paste and copy pending minor ajustement and field validation

Tahaddart watershed

Mataiva lagoon

Conclusion

Conclusion 5 remote sensing of surface water and SUWAMA (1/2) • GEOBIA algorithms and eCognition 8 are very efficient tools for surface water monitoring • Multitemporal, multispectral, multirelosution and multisensor (i.e. optical, radar, lidar) dataset can be combined to build robust image classification rulesets • VHR data (i.e. Worldview 2) improves water surface monitoring of very small water body ressources • Satellite image archives (i.e. SPOT5) allows retrospective monitoring (30 years) of water bodies at high to very high spatial resolution • New satellite constellation (i.e. Rapide Eye) providing daily dataset will helps water ressource managers to monitore hydro-ecosystem flash disruptions Tahaddart watershed

Mataiva lagoon

Conclusion

5 remote sensing of surface water and SUWAMA (2/2) • SUWAMA strongly requires a monitoring of: – hydro-ecosystem functions, goods and services – landcover and landuses coupled with socio-economic data

• BUT SUWAMA also requires: – a broader knowledge intregation of the very complex sociohydro-ecosystems called watersheds

• SUWAMA will surely benefit from VHR remote sensing and geobia methodology to: – update GIS data to perform a spatially distributed monitoring of watersheds or watermass units – initiate a better collaboration between classical remote sensing analysts and field scientists comming from a wide range of scientific backgrounds Tahaddart watershed

Mataiva lagoon

Conclusion

Thank you for your attention