The above figure shows the wave measurement locations at lake IJssel and lake Sloten. At several locations wind and wave observations are taken. The photo concerns location FL2, which is located on the east of lake IJssel. The wave measurements were executed using capacitance wires. This system proves to be sensitive for marine growth. The effect of cleaning of the instrument on the reference level is indicated on the lower right site. Prior to data processing all measurement records have been corrected for the influence of marine growth and other disturbing factors. The result is a detailed database of recorded wind and wave conditions in enclosed lakes that can be further used for calibration of wave models (SWAN).