Experiences in the Assessment of Groundwater Chemical Status in the NetherlandsTon de Nijs, Michiel Zijp & Wilko Verweij
Contents • A short introduction to the Assessment of Groundwater Chemical Status • Experiences in Implementation • Conclusions
Status Compliance • Dutch Guidance on Chemical Status Compliance
BlaEuAtlas 1645 Anthropogenic influences on hydrology
Ir. D.F. Woudagemaal steam-driven pumping station
Waterboards • Water boards are among the oldest forms of local government in the Netherlands, some of them having been founded in the 13th century. • Water boards are charged with managing the water barriers, the waterways, the surface water levels, and the surface water quality in its region. Currently, the Water boards are not responsible for groundwater but the Provinces
Collaboration Water Boardssurface water Provincesgroundwater In general, Netherlands is on schedule concerning the implementation of the WFD/GWD, concept River Basin Management Plans are ready. However, collaboration was limited due to: • the time constraints imposed on water managers, • the historically limited body of knowledge acquired by both sides on the interaction between groundwater and surface water. With the new Water Law in the Netherlands the Water Boards will become responsible for the shallow groundwater River Basin Management Plan
Impacts on threshold values • Interaction between ground- & surface water is not well known, especially in the polder areas. A new hydrological model is currently developed including groundwater, surface water and their connections. • Assumption in derivation of threshold values: All surface waters are groundwater-dependent Threshold values of nutrients are defined by the most “sensitive” surface waters within the GWB
3. Different starting principles I don’t wanna use that “BRIDGE” method!
Derivation of Background Levels Since the early 90s Natural Background Levelsin the Netherlands are based on: 50 percentile with No Pre-selection EU-Bridge methodology 90 percentile with Pre-selection of stations that are not influenced by human activities In the Netherlands:EU Bridge method: 95% lower limitNBL = Highest Value of Two Methods More conservative Natural Background Levels
Arsenic in Dutch sediments • Locally high levels of Pyrite and Bog Iron • As is released when redox conditions change because of changes in groundwater flow due to: • Natural: Tidal movements or • Anthropogenic: Lowering of groundwater level or infiltration of NO3-
5. Absence of supporting environmental criteria for terrestrial ecosystems
Terrestrial ecosystems are solely defined by the abundance and composition of the biological elements and habitat types • Aquatic ecosystems are defined by composition and abundance of biological elements but also by their supporting hydro-morphological characteristics, nutrient levels, transparency, acidity and river flow; Additional supporting criteria for terrestrial ecosystems should be defined to secure the presence of specific species or habitat types including: nutrient conditions, acidity, salinity, groundwater level and other relevant physical/chemical parameters
Conclusions First, the Netherlands is on schedule concerning the implementation of the WFD/GWD: concept River Basin Management Plans are ready. • Integrated management of ground- and surface water will improve once the Water Law has been passed; • Lack of knowledge on the interaction between surface and groundwater. A new hydrological model is being developed; • Relative conservative background levels and threshold values; • Sometimes it is hard to distinguish natural and anthropogenic processes; • Supporting environmental criteria are needed for the terrestrial ecosystems.
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