System description
Catchment and water body
A thorough understanding of the system – from the catchment to the point of exposure – is the basis for analysing hazards and assessing risks. A description of your water system with special regards to cyanotoxins should include :
Geographic and hydrological information about the catchment
- Area, slope, soil types, other
- Drainage system
- Map and discharge of the tributaries
- Land use in the catchment e.g: area covered with forest, settlements, agriculture, industry, other
- Record of all activities in the catchment which may contribute to the nutrient input and estimation of possible nutrient loads (especially from agriculture and sewage, possibly also from other sources)
Information about the water body
- Water quality data, particularly nutrient concentrations and secchi depth readings
- For reservoirs and lakes: morphometry, retention time, thermal mixing regime
- For rivers: flow and discharge
- Phytoplankton population data; potentially also data on populations of zooplankton and fish as these may impact on phytoplankton population.
- Past data on cyanobacterial and cyanotoxin occurrence.
Additional information if the water body is a drinking water source
- Site(s) and depth(s) of drinking-water off-take(s)
- Methods of drinking water abstraction and treatment, e.g. pre-oxidation, flocculation, sedimentation, filtration, ozonation, GAC filtration, slow sand or riverbank filtration, disinfection, and information on operating parameters important for the removal of cyanobacteria and cyanotoxins (see also drinking water abstraction and drinking water treatment)
- Amount of treated water produced
- Distribution of treated water (especially for a complete WSP): map of mains, reservoirs in the system including their condition and retention times.
Additional information if the water body is used for recreation
- Location of bathing sites in relation to main wind directions; indications of bays in which cyanobacteria are often washed in
- Estimation of the intensity and time patterns of bathing activities (e.g. in holidays, on weekends, school swimming, approximate numbers of bathers, special facilities like diving towers or swimming platforms)
- Type and intensities of other activities, e.g. sailing and surf clubs, fishing clubs, water ski-ing
The validity of these data should be verified by periodic on-site inspections!