PhD Graduation

Last summer, the Wadden Sea was added to the UNESCO World Heritage List. Tourists, mussel growers, biologists, everyone wants to maintain this beautiful area. Therefore, regularly the water quality is monitored by sampling: quite an effort for the largest mudflat area in the world! Annelies Hommersom studied the possibilities to monitor water quality via its colour, by using optical remote sensing (satellite) data.

Although not all water quality parameters can be derived from optical satellite data, this data provides much information about the underwater climate. For example, the green colour of algae, and turbidity, can relatively easy be detected with optical satellites. Algae, in turn, can be used as indicators for eutrophication, while a low turbidity is important for plants and fish. Additionally, satellite data have a large spatial resolution, which simplifies monitoring.

To use optical satellite data for monitoring water quality, first the (specific) optical properties of the substances in the water had to be known. These properties, as well as the Wadden Sea water colour, were measured during field campaigns and appeared to be highly variable, due to tidal, seasonal, and weather related changes and a large spatial heterogeneity.

Next, two optical models types were tested. A locally calibrated model produced the concentrations of all parameters of interest, but could use more validation. The other model was qualitative, but valid for a large range of water contents and could visualise well-known changes in time and space. It can be concluded that monitoring water quality in the Wadden Sea and other extremely turbid areas by optical remote sensing is promising.

Promotor: Prof. Dr. J. de Boer
Co-promotor: Dr. S.W.M. Peters