WEISS Methodology

WEISS enables to map all relevant pollutants in a geographically detailed manner. This covers all substances caused by all major emission sources and their pathways to the water bodies. The WEISS system has a generic design and software implementation, making it into a unique tool for the purpose.

WEISS can be applied to areas of different sizes: from industrial or rural complexes to entire EU Member States or from small sub-catchments to large transnational river basins. The study area is represented as a regular grid made up of cells, in resolutions ranging from a few square meters to several square kilometers. The resolution can be chosen according to the quality of the available data, the specific requirements and, of course, the processing speed expected during use of the system. WEISS also allows the user to decide on the sources and substances to be included in the system. These lists can be expanded as new information becomes available with time. Sources are represented in a hierarchical structure of maximum five levels, enabling a clear overview and fast access to the required information.

WEISS handles both point and diffuse sources and the aggregation of both. The system is available as a software application that can be fully configured by the user and is perfectly able to grow with the user's needs and the availability of data.

WEISS can be used to create and maintain an emission inventory of annual loads per substance and per source. Loads can be aggregated by sector, by sub-area, by substance, etc., both at the source and in each node of the material flow scheme.

The material flow scheme represents all possible transport routes, from the source to the surface water. This enables to track the substance on its path and to determine the contribution of different pollutants at a geographically detailed level at all times.  WEISS thus provides insight into the origin of pollutants which concentrations are measured in rivers.

WEISS is technical in nature, yet very user-friendly. Input screens are available to define the entire application, involving characteristics of each substance and source as well as the geographical information required to represent the sources.

The user interface hides the technicalities of the underlying software framework for the user. This software framework consists of coupled algorithms to be selected from a built-in library, specified, chained, and sequentially executed according to the characteristics of each source. The algorithms implement alternative methods for the spatial allocation of point, line and surface sources and the integration of different transport routes, via direct discharge, run-off, or sewage. In addition, algorithms are available to visualize results in graphs and perform analyses. These analyses range in complexity. Simple analyses involve summing substances over sources, across hierarchical levels and over various geographical administrative or hydrological sub-divisions.

Sophisticated analyses involve scenario and trend analyses. The algorithms deployed to the effect vary too from general to highly specific. Specific algorithms usually require more input data of higher quality and can therefore only be used if the necessary input data is available.WEISS is continually expanded with new algorithms, allowing the system to grow in terms of functionality, capability and accuracy. If necessary, or if efficiency gains can be achieved, specific algorithms can be developed and added to optimize the processing of available data, to improve the representation of specific sources, or to facilitate applications in specific areas.

Bottop-up approach

The representation of the sources in WEISS is based on a basic formula stating that the gross emission (GE) of a substance is the product of an emission explanatory variable (EEV) and an emission factor (EF).

The emission explanatory variable (EVV) is the physical activity or the physical element that causes the emission. Examples are the number of square metres of zinc gutter in terraced houses, or, the fields where maize is grown, for which farmers use Terbuthylazine, an active crop protection product. The emission explanatory variables in WEISS are generally represented in a spatially explicit manner. They are spatial patterns showing the occurrences of the sources. To the effect, WEISS is supporting the user to generate a map featuring the pattern. In the above examples, these are maps with the location of terraced houses specifying the associated square metres of zinc gutter, or, the map with the parcels where maize is grown.

The emission factors (EF) represent the quantity of substance that is annually released per unit of the emission explanatory variable. Thus, there is an emission factor that represents the amount of zinc released per square meter of gutter and another one specifying the quantity of active substance of Terbuthylazine per hectare of maize. In WEISS, emission factors may also have a spatial dimension. The corrosion of building materials, for example, is known to be a function of volumes of precipitation, of acid rain in industrial areas, and, of concentrations of salt in the air in coastal areas.  Scientific research is required to define both the EEV and the EF per source-substance combination. WEISS supports the factual use of this scientific knowledge in policy-making by automating the necessary calculations.