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Landsat imagery reveals declining clarity of Maine's lakes during 1995-2010.

Authors :
McCullough, Ian M.
Loftin, Cynthia S.
Sader, Steven A.
Source :
Freshwater Science; 2013, Vol. 32 Issue 3, p741-752, 12p
Publication Year :
2013

Abstract

Water clarity is a strong indicator of regional water quality. Unlike other common waterquality metrics, such as chlorophyll a, total P, or trophic status, clarity can be accurately and efficiently estimated remotely on a regional scale. Satellite-based remote sensing is useful in regions with many lakes where traditional field-sampling techniques may be prohibitively expensive. Repeated sampling of easily accessed lakes can lead to spatially irregular, nonrandom samples of a region. Remote sensing remedies this problem. We applied a remote monitoring protocol we had previously developed for Maine lakes .8 ha based on Landsat satellite data recorded during 1995-2010 to identify spatial and temporal patterns in Maine lake clarity. We focused on the overlapping region of Landsat paths 11 and 12 to increase availability of cloud-free images in August and early September, a period of relative lake stability and seasonal poor-clarity conditions well suited for annual monitoring. We divided Maine into 3 regions (northeastern, south-central, western) based on morphometric and chemical lake features. We found a general decrease in average statewide lake clarity from 4.94 to 4.38 m during 1995-2010. Water clarity ranged from 4 to 6 m during 1995-2010, but it decreased consistently during 2005-2010. Clarity in both the northeastern and western lake regions has decreased from 5.22 m in 1995 to 4.36 and 4.21 m, respectively, in 2010, whereas lake clarity in the south-central lake region (4.50 m) has not changed since 1995. Climate change, timber harvesting, or watershed morphometry may be responsible for regional water-clarity decline. Remote sensing of regional water clarity provides a more complete spatial perspective of lake water quality than existing, interest-based sampling. However, field sampling done under existing monitoring programs can be used to calibrate accurate models designed to estimate water clarity remotely. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
21619549
Volume :
32
Issue :
3
Database :
Complementary Index
Journal :
Freshwater Science
Publication Type :
Academic Journal
Accession number :
121641327
Full Text :
https://doi.org/10.1899/12-070.1