Use of MODIS data for monitoring turbidity in Finnish lakes

The state of surface waters is affected by the quantity and quality of various suspended and dissolved substances. Loading from sources such as agriculture, fish farming, industry and municipalities can cause eutrophication and have other adverse effects on water quality. In Finland the quality of lake water is traditionally determined by collecting water samples and analyzing the samples in a laboratory and by making on-site measurements (e.g. Secchi depth, temperature). However, sampling is slow and expensive and does not include all lakes. Remote sensing instruments can cover large areas quickly and repeatedly and they are also relatively cheap to use once the retrieval methods have been developed into operational level. However, the revisit time for Landsat is 16 days so it is not suitable for operational monitoring especially in areas where cloud cover is frequent. Another interesting instrument is SeaWiFS. It produces daily data but only with 1000-m pixels. One of the latest spaceborne remote sensing instruments, the MODIS spectrometer, produces daily data with two 250-m channels. The objective of this paper is to assess the capabilities of MODIS for monitoring turbidity in Finnish lakes.