Improving water quality Drentsche Aa is urgent: Groningen drinking water supply depends on it

In recent years, the province, municipalities, and water authority – together with nature organisations and also (on a voluntary basis) farmers and businesses – have tried to reduce the leaching of crop protection agents in the Drentsche Aa, but it appears to be insufficient. An advisory committee including Prof. Jasper Griffioen (water quality management) and Prof. Frank Groothuijse (European and national environmental law), both attached to Utrecht University, has studied which follow-up steps are needed to secure the drinking water supply. 

The aim of the Implementation Programme Surface Water Extraction Drentsche Aa (UPDA) was to reduce the number of norm violations of crop protection agents at the intake point for drinking water preparation of Waterbedrijf Groningen by 95 per cent by 2023. This concerns agricultural protection agents used in, among others, flower bulb growing, beet growing and outdoor vegetables cropping. Bulb and lily production in particular is known for its negative impact on the environment and water quality. But agricultural toxins and manure can also leach into the watercourses of the Drentsche Aa from agricultural fields, especially if arable farming takes place right up to the stream edges (which is still too often the case).

In the report of the UPDA advisory committee, Griffioen and Groothuijse map out how the pollution comes about and what (legal and administrative) instruments are available to reduce pollution with crop protection agents (CPAs). For instance, there is compelling evidence that CPAs wash out and run off into surface water during heavy rainfall in the summer period. Furthermore, monitoring data show that (for some CPAs) water quality will not meet European Water Framework Directive (WFD) requirements by 2027. Therefore, measures to reduce CPAs cannot be delayed, the researchers conclude.

The two researchers also analysed which instruments for regulating CPA emissions on surface waters (used for drinking water intake) are available to state, province, water authority and municipalities. They conclude that the existing instruments are only partly used and partly inadequate. On page 37, they note: “The duty of care that applies to all administrative bodies under the Drinking Water Act (Drinkwaterwet), to identify the sustainable safeguarding of the public drinking water supply as an imperative reason of major public interest, is not – or insufficiently – applied by administrative bodies as a guiding principle.”

While drastically restricting existing (legal) land use will be difficult, it is quite possible to place restrictions on future use in current zoning and environmental plans, in order to prohibit further expansion of lily farming, for example. They also consider a legal restriction of existing and legal (but undesirable) land use to be feasible if this is included in the Provincial Rural Area Programme (PPLG), because the PPLG integrally addresses several aspects at once – overall water quality, climate as well as nitrogen: “The importance of protecting the Drentsche Aa from CPA pollution can be included in the PPLG. The committee also explicitly advocates this.”