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Water Observations from Space: accurate maps of surface water through time for the continent of Africa
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  • Meghan Halabisky,
  • Kenneth Mubea,
  • Fatou Mar,
  • Fang Yuan,
  • Chad Burton,
  • Eloise Birchall,
  • Negin Fouladi Moghaddam,
  • Ghislain Adimou,
  • Bako Mamane,
  • David Ongo,
  • Edward Boamah,
  • Ee-Faye Chong,
  • Nikita Gandhi,
  • Alex Leith,
  • Lisa Hall,
  • Adam Lewis
Meghan Halabisky
Digital Earth Africa

Corresponding Author:[email protected]

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Kenneth Mubea
Digital Earth Africa
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Fatou Mar
L'Observatoire du Sahara et du Sahel
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Fang Yuan
Digital Earth Africa
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Chad Burton
Digital Earth Africa
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Eloise Birchall
Digital Earth Africa
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Negin Fouladi Moghaddam
Digital Earth Africa
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Ghislain Adimou
AFRIGIST
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Bako Mamane
AGRHYMET
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David Ongo
RCMRD
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Edward Boamah
Digital Earth Africa
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Ee-Faye Chong
Digital Earth Africa
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Nikita Gandhi
Digital Earth Africa
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Alex Leith
Digital Earth Africa
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Lisa Hall
Digital Earth Africa
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Adam Lewis
Digital Earth Africa
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Abstract

Earth observation of waterbodies through time is a powerful tool in understanding both the location of waterbodies and their temporal dynamics. Water Observations from Space (WOfS), developed and well-tested in Australia, is a service providing historical surface water observations derived from Landsat satellite imagery from 1987 to present day. WOfS provides better understanding of where water is usually present; where it is seldom observed; and where inundation of the surface has been occasionally observed by satellite. We applied the WOfS algorithm to Africa and validated its accuracy through image interpretation of satellite and aerial imagery using an online tool created by the NASA Servir program, Collect Earth Online. The Digital Earth Africa Product Development Task Team, composed of four regional geospatial organisations RCMRD, AfriGIST, AGRHYMET and OSS, conducted the validation campaign and provided both the regional expertise and experience required for a continental-scale validation effort. In order to understand the accuracy and bias of the WOfS algorithm in Africa at both the continental-scale and regional zones, we generated 2900 sample points covering the continent including the main islands and distributed them into 7 Agro-ecological zones. We assessed whether the point was flooded, dry, or cloud covered, for 12 months in 2018, resulting in 34,800 assessed observations. As water information is available through WOfS in near real-time, it can be used for environmental monitoring, flood mapping, monitoring planned water releases, and management of water resources in highly regulated systems. WOfS is expected to be used by ministries and state departments of agriculture and water management in countries, international organizations, academia and the private sector.