Monitoring water quality of the Southeastern Mediterranean sea using remote sensing Tamir Caras The Remote Sensing Laboratory Jacob Blaustein Institutes for Desert Research Ben-Gurion University of the Negev 1
Overview Water quality basics and overview Remote sensing of water quality Temporal and spatial dimension Problem solving: chlorophyll and TSS separation VENµS 2
Water quality basics and overview Water quality and detecting Pollution Physical Chemical Biological Thermal Sediments (TSS) Dissolved organic matter Algae Sea Surface Temperature (SST) 3 3
Sewage ponds - oxidation process 4
And anthropogenic pollution 5
Remote sensing of water quality Reflectance = Detected energy / Available energy 6
Spectral signature of ground features Signatures the foundation of detection Visible Reflected Infrared 7
Chlorophyll and TSS separation Suspended Matter [mgl -1 ] Problem : Suspended matter present in water affects Chl-a* detection erroneously high Chl-a detected * Chl-a represents algae that is an indicator of pollution Suspended Matter June 2001 Chlorophyll June 2001 Egypt Israel Egypt Israel Chlorophyll [mgm -3 ] 8
Solution: Careful masking high levels of sedimentation Chlorophyll June 2001 After masking sediments: Chlorophyll June 2001 Israel Egypt Chlorophyll [mgm -3 ] Chlorophyll [mgm -3 ] 9
Coastal pollution near Tel Aviv Chlorophyll (mg/m 3 ) 2 February 2003 A sewage pipe breaks and raw sewage pores into the sea 10
Monitoring an algal event: June 2001 13.06.2001 14.06.2001 15.06.2001 18.06.2001 20.06.2001 22.06.2001 24.06.2001 25.06.2001 11.06.2001 11
Monitoring sedimentation in Haifa port August 2016 12
VENµS - Scientific Applications Land Vegetation Agriculture Digital Elevation Model Atmosphere Water Water quality Inland and coastal water Precision farming Water vapor Aerosol optical thickness Cloud and height 13
VENµS Mission Characteristics Orbit: near polar, sun-synchronic (constant view angle) Altitude: 720 km Inclination: 98.27 Revisit time: two days Swath: 27.56 km Spatial resolution: 5.3 m Number of spectral bands: 12 (VIS-NIR) Tilting capability: +/-30 across and along track Radiometric resolution: 10 bits Equator crossing time: 10:30 AM, descending mode Mission start/duration: June, 2017, 4.25 years June 2017 14
Spectra of Water Constituents Volume Reflectance 1 0.1 Clear Water Null Null Point Point Chl, 0.0-20.0 ug/l SM, 0.0-20.0 mg/l 0.01 0.001 0.0001 CDOM, 0.0-20.0 mgc/l B1 B3 B2 B4 Clear Water B5 B6 B7 B8 B9 0.00001 400 450 500 550 600 650 700 750 Wavelength (nm) 15
Conclusion Venus may not be the best at any one category but it is the best all-rounder spaceborne sensor to date 16
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Remote Sensing of river chlorophyll ote Sensing dissolved carbon in lakes and coast 19
Red Sea seasonal climatologies of MODIS Chl-a (mg/m3) and SST ( C). Raitsos DE, Pradhan Y, Brewin RJW, Stenchikov G, Hoteit I (2013) Remote Sensing the Phytoplankton Seasonal Succession of the Red Sea. PLOS ONE 8(6): e64909. 20
Series of images showing how the digitised plume of a MODIS image relates to a clearer high resolution image and the range of TSS thresholds analysed in this study. Evans RD, Murray KL, Field SN, Moore JAY, Shedrawi G, et al. (2012) Digitise This! A Quick and Easy Remote Sensing Method to Monitor the Daily Extent of Dredge Plumes. PLOS ONE 7(12): e51668. 21
Absorption and Scattering Attenuation in Pure Water Maximum Transparency at 470 nm Effective Wavelength = 400 700 nm 22 22
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R 510 > 0.0055 Rule 1 A RS ( xi, yi) 26
Rule 1 A R 765 > 0.0001 RS ( xi, yi) 27
Rule 2 R R RS RS 670 765 ( xi, yi) ( xi, yi) > 2.0 28
Radiometer vs. Spectrometer Radiometer Point spectrometer Image spectrometer 29
Multispectral Camera 6 band 30
MS Camera on a Drone 31
Other Systems 32
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Water Constituents Chlorophyll Sediments Dissolved organic carbon 34
Scientific Applications 35 Band Center Land/Vegetation Water quality Atmosphere (nm) 1 420 Desert lower plants Dissolved organic matter; Turbidity 2 443 Atmospheric resistance Maximum chlorophyll-a vegetation indices absorption 3 490 Chlorophyll, other pigments; attenuation 4 555 Green peak; Vegetation Chlorophyll reference; indices Suspended sediments 5 638 Chlorophyll absorption; Suspended sediments Detect clouds and cloud edges Atmospheric correction Cloud properties Vegetation indices. 6 638 Digital Elevation Model Suspended sediments Top cloud detection 7 672 Red edge Chlorophyll absorption Cloud properties 8 702 Red edge 9 742 Red edge 10 782 Red edge 11 865 Maximum reflectance; Vegetation indices Water vapor reference 12 910 Water vapor April 27, 2006