Nitrogen Source Apportionment for the Catchment, Estuary, and Adjacent Coastal Waters of the River Scheldt

Abstract

ABSTRACT. Using the systems approach framework (SAF), a coupled model suite was developed for simulating land-use decision making in response to nutrient abatement costs and water and nutrient fluxes in the hydrological network of the Scheldt River, and nutrient fluxes in the estuary and adjacent coastal sea. The purpose was to assess the efficiency of different longterm water quality improvement measures in current and future climate and societal settings, targeting nitrogen (N) load reduction. The spatial-dynamic model suite consists of two dynamically linked modules: PCRaster is used for the drainage network and is combined with ExtendSim modules for farming decision making and estuarine N dispersal. Model predictions of annual mean flow and total N concentrations compared well with data available for river and estuary (r² ≥ 0.83). Source apportionment was carried out to societal sectors and administrative regions; both households and agriculture are the major sources of N, with the regions of Flanders and Wallonia contributing most. Load reductions by different measures implemented in the model were comparable (~75% remaining after 30 yr), but costs differed greatly. Increasing domestic sewage connectivity was more effective, at comparatively low cost (47% remaining). The two climate scenarios did not lead to major differences in load compared with the business-as-usual scenario (~88% remaining). Thus, this spatially explicit model of water flow and N fluxes in the Scheldt catchment can be used to compare different long-term policy options for N load reduction to river, estuary, and receiving sea in terms of their effectiveness, cost, and optimal location of implementation.

Development and Use of a Bioeconomic Model for Management of Mussel Fisheries under Different Nutrient Regimes in the Temperate Estuary of the Limfjord, Denmark

“…The SAF approach is generic and has been tested in various coastal areas around Europe (Hopkins et al 2012). For example, Vermaat et al (2012) developed a spatial dynamic model that allowed farming decisions to be improved by taking into account present and future societal settings. Melaku Canu et al (2011) and Schernewski et al (2012) both demonstrated how SAF could be used to address sustainable bivalve farming and to reduce illegal harvesting.…”

Consequence of altered nitrogen cycles in the coupled human and ecological system under changing climate: The need for long-term and site-based research

“…Substantial denitrification rates have even been found in N-rich downstream riverine systems, whereas no comparable P-removal process occurs (Billen et al 2009;Vermaat et al 2012). Consequently, this may lead to N-limitation that enhances the dominance of diazotrophic cyanobacteria in periods when the high-energy demand for N-fixation can be satisfied (Stal and Zehr 2008).…”

A Systems Approach Framework for the Transition to Sustainable Development: Potential Value Based on Coastal Experiments

“…Scheldt Delta. By coupling the computer softwares ExtendSim and PCRaster, the research team greatly improved the capacity of the SAF to evaluate spatially explicit problems, such as where different policy measures would be most efficiently and cost-effectively implemented and how diverse farm practices affect non-point nitrogen discharges in a complex agricultural-urban watershed (Vermaat et al 2012).…”

“…The relationship between nitrogen loading and eutrophication in the estuary is well studied, but the mixing of nitrogen from different sources in the river makes it difficult to quantify them individually and hence to formulate fair and efficient policies. The SAF application quantified the nonpoint and point sources of nitrogen in sufficient detail to resolve its apportionment and indicates that successful load reduction would require also reducing domestic urban sources (Vermaat et al 2012). …”