Monitoring network for Nutrients in Agriculture-Specific Surface Water (MNLSO)
Intensive farming in the Netherlands produces manure that is spread on fields and pastures. This manure, in combination with other fertilisers, results in excessive concentrations of nitrogen and phosphate in soil, groundwater and surface water. The Dutch water authorities, the Ministry of Infrastructure and Water Management, and Deltares set up the Monitoring network for Nutrients in Agriculture-Specific Surface Water (MNLSO) in 2010 to monitor water quality in the area of nutrients (fertilisers) in agriculture-specific surface water. Existing monitoring locations of all the water authorities, which have agriculture as their only anthropogenic source of nutrients, were selected for the monitoring network.
Water quality problemin agriculture-specific surface water
The aim of the MNLSO was to determine whether there is a water quality problem in agriculture-specific surface water. On the basis of data from the monitoring network, a status and trend analysis was conducted to determine at the national level, and for the sand, clay and peat areas, whether, in agriculture-specific surface water:
1. The water-quality objectives for nutrients are being met;
2. There are upward or downward trends in nutrient concentrations.
In collaboration with the water authorities, the monitoring locations in question have been extensively studied over the last two years in order to rule out the influence of other anthropogenic sources, seepage or inlet water. This makes the monitoring network a valuable addition to the information from the status and trend analysis of the WFD waters and provides us with an understanding of the effectiveness of all the measures taken by agriculture and horticulture.
Nitrogen and phosphorus concentrations in Dutch surface waters have fallen since the early 1990s as a result of measures taken in agriculture and by industry and WWTPs. Although this trend is continuing, a large proportion of surface waters in the Netherlands are still eutrophic or potentially eutrophic. In the period 2015 through 2018, the water authority standards for N-total and P-total were not met at approximately 45-64% of the monitoring locations. The declining trends for N-total and P-total suggest that the manure policy is making an effective contribution to improvements in water quality in agricultural areas. However, compliance with water authority standards in many areas will require an additional effort.