Satellite Observation of Regional-scale Lake Dynamics: A Progress Report

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Satellite Observation of Regional-scale Lake
Dynamics A Progress Report

• Yongwei Sheng, Junli Li, Laurence C. Smith
• Chintan A. Shah, and Evan A. Lyons
• UCLA Department of Geography

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Importance of Lake Dynamics
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Existing Lake Databases and Estimates

• GLWD
• Lake abundance 250k lakes (gt0.1 km2)
• Total lake area 2.4 million km2
• Lake area density 1.8 of density.
• Newly available SWBD datasets
• 56oS -- 60oN
• 580k lakes (compared with GLWD at 113k)
• A recent global lake estimate (Downing et al,
  2006)
• gt300 million lakes and ponds
• 4.6 million km2
• gt3.
• Problems
• Being complied from various sources
• Not being a systematic inventory
• Not addressing lake dynamics.

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Status on Lake Dynamics Studies

• Local-scale studies dominant.
• Regional-scale studies just a few.
• So far only lt2.5 of the high-latitude land
  surface has been studied for lake
  change-detection.
• 5,400 km2 lake change detection in western Arctic
  coast of Canada (Marsh et al, 2005)
• 34,570 km2 lake mapping in North Slope of Alaska
  (Frohn, Hinkel et al, 2005 Hinkel et al, 2007)
• 515,000 km2 lake change detection in West Siberia
  (Smith, Sheng et al., 2005).
• Middle and low-latitudes havent been intensively
  monitored either.
• Global-scale A systematic lake inventory is
  unavailable.
• A systematic assessment of regional- and
  global-scale lake changes in the past 30 years
  is crucial to understand the current changes and
  the likely future direction of terrestrial
  hydrology.

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On-going Progress
(Lehner and Doll, 2004)

• Pan-Arctic 1st peak
• Tibetan Plateau 2nd peak.

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Remote Sensing of Lake Dynamics

• Characteristics of lakes
• Abundant in small-size classes
• Various type of lakes
• Variant from season to season
• Stable season variant from region to region.
• Challenges to remote sensing
• Many high-resolution images!
• 8,000 scenes of cloud-free Landsat images.
• Images to be acquired in appropriate detection
  season, which varies from region to region
• Robust lake dynamics mapping techniques
• Replicability and Automation!

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Appropriate Image Acquisition Season Based on P
and T
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20.34 (2430 out of 11946) of freely available
scenes fall within one month of the ideal
monitoring time.
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Critical Lake Dynamics Mapping Techniques

• Image co-registration
• Lake identification.
• Replicability and Automation!
• Being tested in the Arctic and Tibetan Plateau.

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Automated PIF-based Image Co-registration
MSS June vs. August, 1973
PIF pseudo invariant features
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RMSE 0.27 pixel
Before
After
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Hierarchical Lake Mapping
SWOT mapping?
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1990s THP Product Version 0.0 500 TM
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2000s THP Product Version 0.0 600 ETM

• Arctic DEMs at low water from SWOT?

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Comparison with other products in North America

• GLWD 104k
• SWBD 222k
• New THP product gt4.7M      

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Landsat ETM Image (70W, 56N)
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GLWD
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SWBD
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THP ETM
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THP TM
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Landsat ETM Image (70W, 56N)
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Field Validation
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DGPS of lake shores
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Lake variation by repeated DGPS
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Topography Transects
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Water level fluctuations

• Water level in most lake varies between 5-10 cm.
• August is stable season for lake dynamics
  mapping.
• Some dynamic ones may vary 30 cm.

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Paleo Lake Recovery
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Recovered Paleo Lake Extent
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Waterlevel Drops
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Basin-based Analysis
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Paleo lake water loss vs. Paleo glacial shrinkage
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Recent lakes changes
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Tibet a possible SWOT validation site?

• Scientifically important
• Less populated
• Different types of lakes
• Various topography
• Leveloggers Landsat lake series.
• Oxygen!

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Expected Results from Lake Dynamics

• A systematic lake inventory
• Metrics of lake dynamics.
• Over-arching Science Questions and Hypotheses
• How have global lakes responded to global
  warming, and what does their future hold with
  respect to continued warming?
• What is the spatially explicit distribution of
  lake changes?
• Lake changes are significantly influenced by
  other factors besides climate, such as permafrost
  state, human impacts.

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Summary

• Such a high-resolution lake inventory useful to
  SWOT?
• Go global!
• Its time to do it!
• There is a lot of work!

• Acknowledgements
• Supported by NASA Terrestrial Hydrology Program
• NSF Arctic Science Program
• NASA NIP.

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Thank You!