- The Use Of MODIS Time Series Data To Map Chl_a and CDOM Variability in Lake Victoria
The Use Of MODIS Time Series Data To Map Chl_a and CDOM Variability in Lake Victoria
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Constance Banura, Uganda, firstname.lastname@example.org
Anthony Gidudu, Makerere University,Uganda, email@example.com
Kabiswa Edrisa, Member Institution Of Surveyors of Uganda,Uganda, firstname.lastname@example.org
Chlorophyll-a (Chl-a) and Colored Dissolved Organic Matter (CDOM) are key parameters in the assessment of water quality. Traditionally, these parameters are collected by carrying out in-situ measurements or taking of water samples for testing in the laboratory. This is time consuming, costly, cumbersome and irregularly carried out, but more importantly, does not give a synoptic perspective of the water quality variation on the lake. This becomes especially challenging when dealing with a lake the size of Lake Victoria.
This paper therefore explores the use of archived MODIS satellite imagery to study the distribution of Chl_a and CDOM on Lake Victoria. Standard Ocean Color Algorithms were used to extract Chl-_a and CDOM concentrations from MODIS imagery. Annual concentrations were then averaged to get an appreciation of the spatial variability of these parameters for the years 2003 – 2010. The Chl_a imagery was further reclassified according to Calrton’s index to determine the trophic level boundaries. The results show that in general Lake Victoria exhibits high concentrations of Chl_a implying that it is largely eutrophic.
The Chl_a and CDOM results around the shores are particularly high and may be attributed to increased surface run off from the lake’s catchment area. These are perspectives of water quality that are only possible with the use of satellite imagery. Given the advantages of high temporal resolution of MODIS imagery and the complete coverage of the lake, it is recommended that relevant stakeholders harness this technology to better improve on the management of their mandates.