Introduction
The model makes use of several types of external data. Data is used either to set the boundary conditions for the model or to validate the model results. The data are updated regularly.
Nutrients
Data on nutrients are derived from Rijkswaterstaat. From the category nutrients and eutrophication: all parameters are selected and from the category veldparameters-OW the parameters concentration of Chl-a and extinction are selected. For the locations, all stations in Oosterschelde are selected and the stations WALCHRN2 in North Sea and STEENBGN and OESTDM in Volkerak Zoommeer. For the water temperature, the measurements from Rijkswaterstaat for the location Marollegat is used.
Overview of the locations where water quality data is available. The locations LODSGT, ZIJPE, WISSKKE, HAMMOT, STEENBGN and OESTDM are measured by Rijkswaterstaat.The locations NIOZ_1 to NIOZ_8 are measured by NIOZ
Data are downloaded (all nutrient and eutrophication parameters and chlorophyll-a) for all locations within the Oosterschelde, the location Walcheren 2 km, Steenbergen and Oesterdam and stored as *.csv file in the directory “./rawdata/WQData/Waterinfo/”. Parameters included in the files are included in the file:
- Chla: chlorofyll-a concentration [µg l-1];
- NH4: ammonium concentration in the water [mg-N l-1];
- NO2: nitrite concentration in the water [mg-N l-1];
- NO3: nitrate concentration in the water [mg-N l-1];
- NO2NO3: sum of nitrate and nitrite concentration in the water [mg-N l-1];
- Ntot: total nitrogen in the water, dissolved, particulate or total [mg-N l-1];
- KjN: sum of organic N and NH3 in the water [mg-N l-1];
- Ptot: total nitrogen in the water, dissolved, particulate or total [mg-P l-1];
- PO4: total ortho-phosphate concentration in the water [mg-P l-1];
- SO4: total sulphate concentration in the water [mg-S l-1].
The data are read and processed with the R-script “WQData_RWS.R” that is located in the subdirectory “./Preprocessing/”. Not all components are measured at all stations over the whole period. The nitrogen components and chlorophyll-a concentration are used to calculate dissolved inorganic nitrogen (DIN), particulate organic nitrogen (PON) and Chla.
- Missing data in NO2NO3 are supplemented from the sum of NO2 and NO3;
- Missing are supplemented by calculation from based on location-specific linear regression functions;
- Missing values particulate organic nitrogen (PON) are supplemented by the difference between Kjeldahl N (KjN) and NH4;
- Dissolved inorganic nitrogen (DIN) is calculated from the sum of NO2NO3 and NH4.
Dissolved inorganic nitrogen (DIN) and particulate organic nitrogen (PON) are expressed in mmol-N m-3 by dividing by the molecular weight of nitrogen (14 g mole-1) and multiplying by 1000 (l m-3). Additionally, NIOZ measured nutrients (NO3 and particulate organic nitrogen) and chlorophyll-a at 8 locations ((NIOZ_1 to NIOZ_8)) in the Oosterschelde from 1995 to 2013. The data are combined with the data from Rijkswaterstaat. Finally, negative values for PON are set to 0 and for the stations in the Oosterschelde, the concentration of particulate organic nitrogen is set to a maximum of 30 mmol-N m-3. The data are stored as R data file (WQData_*.rds) in the subdrirectory “./DataOS/WQData/”. The concentrations of WALCRN2, STEENBGN and OESTDM are used for the boundary concentrations at the North Sea, Krammersluizen and Bergse Diepsluis, respectively (function “Boundary_NPZ()”). The data in the Oosterschelde is used to compare the model results with the observation with the visualization app.
Overview of the data (Chla, DIN and PON) for the location WALCRN2.
Suspended solids
Data on total suspended matter (TPM) are derived from Rijkswaterstaat (see above). Data is selected from the locations WISSKKE, LODSGT and ZIJPE from 1-jan-2000 to 31-dec-2023. On average the total suspended matter concentrations in the Oosterschelde over the period 2000 - 2023 was 8.8 mg l-1 but is highly variable, depending on environmental conditions such as storms. On average the TPM values were highest at the location WISSKKE (14.1 mg l-1), and lowest at the locations ZIJPE (5.0 mg l-1) and LODSGT (7.4 mg l-1).
Total Suspended Matter (TPM) concentrations in the Oosterschelde at the locations WISSKKE, LODSGT and ZIJPE from 2000 until 2023 (Top). In the lower figure boxplots per month are presented. The red line represents the average values.
The monthly-averaged values show that the TPM concentrations are higher in the winterperiod than in the summerperiod. A cosine function is fitted through the monthly average values to derive a generic function of the TPM values throughout the year in the Oosterschelde.
TPM = 8.8 + 2.7 \cdot cos \left( \frac{2 \pi}{365.25} + 31.1 \right)
Monthly-averaged TPM concentrations in the Oosterschelde over the period 2000 - 2023. The indicates the fitted cosine function.
Water Temperature
Data on water temperature in the Oosterschelde is derived from Rijkswaterstaat. The location "Marollegat", situated in the eastern part of the Oosterschelde (slightly east from location NIOZ_8) is selected since a relative complete timeserie is available for this location from January 1st 2000. From the data, daily averaged water temperature is calculated. For the days with missing data, the averaged data from NIOZ is used. The data are stored as R data file (WaterTemp_*.rds) in the subdrirectory “./DataOS/WQData/”.
Daily averaged water temperature in the Oosterschelde from January 2000 to December 2023.
Irradiation
Data on irradiation are derived from the KNMI. Since the location Wilhelminadorp (323) has a gap in the data (January 6th 2014 to December 15th 2017 is missing), data from the location Westdorpe (319) is used. The variable Q in the raw datafile from KNMI contains data on Global radiation [J cm-2]. The irradiation is converted into units of W d-1. The data are stored as an R-data file (LightWestdorpe_*.rds) in the directory "/DataOS/KNMI/"
Irradiation (W d-1) at the location Westdorpe. In the upper panel all data are plotted from January 1996 to February 2024. In the lower panel a detail is presented for the period January 2021 to February 2024.
Bathymetry
A bathymetric map of the Oosterschelde is used to calculate the volumes and depths of the different compartments. The data are based on the ecotope map of the Oosterschelde for the year 2016 and is downloaded from the Data Management Center of Rijkswaterstaat (DMC-share). Gaps in the map are filled with available data from 2013. The map is converted to a raster with a resolution of 20m x 20m, with depths in meter relative to NAP, i.e. Dutch Ordnance Level which is approximately Mean Sea Level, and is stored as an R-data file in the directory "/DataOS/Bathymetry/"
Bathymetric map of the Oosterschelde in the year 2016. Depth is in meters relative to NAP.
Shellfish
The three types of shellfish species (Cockles, Mussels and Oysters) have different distribution within the Oosterschelde. The cockles are restricted to the intertidal areas. Mussels are cultured at the mussel culture plots. Oysters are cultured at the culture plots and at the wild oyster beds.
Distribution of shellfish populations in the Oosterschelde. Cockles are restricted to the intertidal areas (khaki). Mussels are cultured at the mussel culture plots (blue) and oysters are present at the culture plots (orange) and the wild oyster beds (green).
The total biomass of mussels at the culture plots in the Oosterschelde is estimated from the auction data. The cockle biomass is based on the results of the WOT survey. The estimation of the wild oyster biomass is based on Craeymeersch et al. (2024) at the stock of oysters at the culture plots is calculated from the landings.
Raw data are processed by the file "Shellfish.R". Data is stored as R data file (Shellfish_*.rds) in the subdirectory “./DataOS/Shellfish/”.
Yearly variation of the total stock (million kg fresh weight) of mussels at culture plots (blue), cockles (khaki), wild oysters (orange) and cultured oysters (green) in the Oosterschelde. top