{"id":1985,"date":"2020-03-09T12:17:01","date_gmt":"2020-03-09T12:17:01","guid":{"rendered":"http:\/\/www.icterra.pt\/?p=1985"},"modified":"2020-04-12T15:45:05","modified_gmt":"2020-04-12T15:45:05","slug":"temporal-and-spatial-variations-of-secchi-depth-and-diffuse-attenuation-coefficient-from-sentinel-2-msi-over-a-large-reservoir","status":"publish","type":"post","link":"https:\/\/www.icterra.pt\/legacy\/index.php\/2020\/03\/09\/temporal-and-spatial-variations-of-secchi-depth-and-diffuse-attenuation-coefficient-from-sentinel-2-msi-over-a-large-reservoir\/","title":{"rendered":"Temporal and Spatial Variations of Secchi Depth and Diffuse Attenuation Coefficient from Sentinel-2 MSI over a Large Reservoir"},"content":{"rendered":"<p style=\"text-align: justify;\"><span style=\"font-family: arial,helvetica,sans-serif; font-size: 12pt;\"><span class=\"inlineblock\">Gon\u00e7alo Rodrigues, <\/span><span class=\"inlineblock\">Miguel Potes, <\/span><span class=\"inlineblock\">Maria Jo\u00e3o Costa, <\/span><span class=\"inlineblock\">Maria Helena Novais, <\/span><span class=\"inlineblock\">Alexandra March\u00e3 Penha, <\/span><span class=\"inlineblock\">Rui Salgado, <\/span><span class=\"inlineblock\">Maria Manuela Morais <\/span><\/span><\/p>\n<p>&nbsp;<\/p>\n<p><span style=\"font-size: 12pt;\"><strong><span style=\"font-family: arial,helvetica,sans-serif;\">Temporal and Spatial Variations of Secchi Depth and Diffuse Attenuation Coefficient from Sentinel-2 MSI over a Large Reservoir<\/span><\/strong><\/span><\/p>\n<p style=\"text-align: justify;\"><span style=\"font-family: arial,helvetica,sans-serif; font-size: 12pt;\">The Alqueva reservoir (South of Portugal) in the Guadiana river basin constitutes the most important water resource in southern Portugal for domestic and agricultural consumption. We present a methodology developed to characterize spatial and temporal variations of Secchi depth and diffuse attenuation coefficient (both related to dissolved\/suspended particles and to water transparency), using high spatial resolution satellite images from Sentinel-2 Multi-Spectral Instrument (MSI). Empirical relations between satellite retrievals of surface reflectances and in situ measurements of water parameters were defined and applied to the entire reservoir for spatial and temporal analysis in the period July 2017\u2013June 2019, useful in the identification of microalgae blooms and rapid variations in water characteristics, which allowed us to differentiate five zones. Water estimates with lower transparency and higher attenuation of radiation were found in the northern area of Alqueva reservoir during the months characterized by higher water temperatures, with Secchi depth monthly averages near 1.0 m and diffuse attenuation coefficient near or above 1.5 m<sup>-1<\/sup>. Satellite retrievals of water with greater transparency in the reservoir were obtained in the southern area in months with low water temperature and atmospheric stability, presenting some monthly Secchi depth averages above 3 m, and diffuse attenuation coefficient below 0.8 m<sup>-1<\/sup>. January 2018 presented great transparency of water with a Secchi depth of 7.5 m for pixels representing the 95th percentile and diffuse attenuation coefficient of 0.36 m for pixels representing the 5th percentile in the Southern region. Read the full article <a href=\"https:\/\/doi.org\/10.3390\/rs12050768\">here<\/a>. <\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Gon\u00e7alo Rodrigues, Miguel Potes, Maria Jo\u00e3o Costa, Maria Helena Novais, Alexandra March\u00e3 Penha, Rui Salgado, Maria Manuela Morais &nbsp; Temporal and Spatial Variations of Secchi Depth and Diffuse Attenuation Coefficient from Sentinel-2 MSI over a Large Reservoir The Alqueva reservoir (South of Portugal) in the Guadiana river basin constitutes the most important water resource in [&hellip;]<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[252,253,254,255,256,183],"_links":{"self":[{"href":"https:\/\/www.icterra.pt\/legacy\/index.php\/wp-json\/wp\/v2\/posts\/1985"}],"collection":[{"href":"https:\/\/www.icterra.pt\/legacy\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.icterra.pt\/legacy\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.icterra.pt\/legacy\/index.php\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.icterra.pt\/legacy\/index.php\/wp-json\/wp\/v2\/comments?post=1985"}],"version-history":[{"count":2,"href":"https:\/\/www.icterra.pt\/legacy\/index.php\/wp-json\/wp\/v2\/posts\/1985\/revisions"}],"predecessor-version":[{"id":2093,"href":"https:\/\/www.icterra.pt\/legacy\/index.php\/wp-json\/wp\/v2\/posts\/1985\/revisions\/2093"}],"wp:attachment":[{"href":"https:\/\/www.icterra.pt\/legacy\/index.php\/wp-json\/wp\/v2\/media?parent=1985"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.icterra.pt\/legacy\/index.php\/wp-json\/wp\/v2\/categories?post=1985"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.icterra.pt\/legacy\/index.php\/wp-json\/wp\/v2\/tags?post=1985"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}