The national wastewater-based epidemiological surveillance of psychoactive substances monitors the presence of various psychoactive substances in several wastewater treatment plants across Belgium. This dataset contains the results per treatment plant since the beginning of the surveillance in 2025. The results consist of the psychoactive substances concentrations over time as well as other data needed for the interpretations such as the flow rates of the treatment plants and the population covered.

Annual temperature extremes given in number of days: 1/ Total number of heatwaves occurring once in 20 years; 2/ Maximum length of the heatwaves occurring once in 20 years; 3/ Hot days: Mean annual number of days with maximum temperature > 25°C; 4/ Tropical days: Mean annual number of days with maximum temperature > 30°C; 5/ Frost days: Mean annual number of days with minimum temperature < 0°C. Heatwaves are defined according to the Royal Meteorological Institute of Belgium when the maximum temperature in Uccle is >= 25°C during at least 5 consecutive days, during which at least 3 days the maximum temperature is >= 30°C. The temperature extremes are available for the present target year 1975, which corresponds to the middle of the 30-year period 1961-1990.

Annual, summer and winter mean potential evapotranspiration given in respectively mm/year and mm/3 months and based on the Penman-Monteith definition. The potential evapotranspiration fields are available for the present target year 1975, which corresponds to the middle of the 30-year period 1961-1990.

Annual, seasonal and monthly precipitation amounts given in respectively mm/year, mm/3 months and mm/month. The precipitation amounts are available for the future target year 2085, which corresponds to the middle of the 30-year period 2071-2100, and for mean and high impact scenarios corresponding to respectively the 50th, and 5th or 95th percentiles of the change factors.

The number of inhabitants on January 1 according to the official definition of the population, by administrative entity (region, province, district and municipality) for Wallonia.

The localised unemployment rate calibrated on the labour force survey (LFS), by administrative unit (region, province, district and municipality) for Belgium.

Characteristics of the cadastral parcels - Exemption from withholding tax on immovable property corresponds to the dataset describing the parcels exempted from withholding tax on immovable property. The first class shows, at the national level, the number of parcels per exemption category, the total amount of cadastral income of these parcels, their surface area as well as the median cadastral income of each category. The second class includes this information at the level of the three regions. The following classes do the same at the level of provinces, arrondissements, municipalities, cadastral divisions and statistical sectors. The dataset can be freely downloaded as a zipped CSV.

Summer and winter mean relative humidity given in %. The relative humidity fields are available for the present target year 1975, which corresponds to the middle of the 30-year period 1961-1990.

The INSPIRE contour lines used for a cartographic representation of the relief at scale 1:50000, a product of the National Geographic Institute in Belgium. The dataset features are in accordance with the INSPIRE specifications.