Abstract

MONCAYO ERASO, Ricardo Javier  and  LOPEZ MARTINEZ, Mery Liliana. Optimization of Water Transparency Monitoring through MOD09GA: A Case Study in Lake Guamues, San Juan de Pasto, Colombia. Cienc. Ing. Neogranad. [online]. 2021, vol.31, n.1, pp.93-108.  Epub July 23, 2021. ISSN 0124-8170.  https://doi.org/10.18359/rcin.4930.

Lake Guamues (LG) has been considered a Ramsar Wetland since 2000. Due to its importance, lenttic ecosystems such as LG require monitoring programs that exceed their spatial and temporal scope. This study shows that using surface reflectance products, generated by the MODIS sensor, can be useful in verifying the spatial dynamics of the Secchi disk depth (ZSD), in the 2001-2020 period. To calibrate the model, an image matching the field work performed was used. The transparency data of the Secchi disk-measured water column was correlated with the image pixels captured in the band centered at 858.5 nm. To validate the model, the Leave Out One Cross Validation (loocv) method was used. Thus, it was determined that the quadratic model showed better results with an adjustment in its R2 = 0.74 and an error associated with observations less than 0.013 m. Spatial analysis revealed that LG has areas located at its banks, where the ZSD may be less than 0.5 m. Likewise, its ZSD average in the image taken on April 24 is 3.87 m. The temporal analysis of the lake indicates that between the 2006-2008 and 2017-2020 periods, greater variability has been reported for the observed points, with values of 3.3 and 2.8 m, respectively.

Keywords : Secchi's disk; MODIS; lentic; reflectance; remote sensing.

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