Global NEWS

The Global NEWS (Global Nutrient Export from WaterSheds) model simulates the river export of nutrients from land to coastal seas. The model quantifies the annual river export of nitrogen, phosphorus, carbon, and silica in dissolved inorganic, organic, and particulate forms. Furthermore, Global NEWS calculates the source attribution of these elements as well as the Indicator for Coastal Eutrophication Potential (ICEP). The model distinguishes between point and diffuse sources of nutrients in rivers. Point sources include sewage effluents from wastewater treatment plants, and diffuse sources include typically leaching/runoff of nutrients to rivers from fertilised and non-fertilised soils. Global NEWS takes into account the retention and losses of nutrients in the river network, including losses due to denitrification, water consumption, and damming.

Global NEWS performs simulations at a global scale for over six thousand river basins. Model outputs are quantified at the basin scale as a function of human activities on land (e.g. agriculture and urbanisation) and basin characteristics (e.g. hydrology). Global NEWS uses gridded scale inputs with a spatial resolution of 0.5° × 0.5° from the IMAGE (Integrated Assessment of Global Environmental Change) model for human activities and from the WBM (Water Balance Model) for hydrology and climate. Simulations have been performed for past (1970), present (2000), and future (2030 and 2050) years with an annual simulation time step. The Millennium Ecosystem Assessment (MEA) scenarios were used to simulate nutrient export for future years.

The Global NEWS approach has formed the basis for a diverse range of studies of river export of nutrients. The nutrient export of different continents and specific regions have been examined, and a seasonal analysis has been performed. Furthermore, the models developed at the Water Systems and Global Change (WSG) group to calculate river export of plastics and triclosan follow the Global NEWS approach. Finally, the MARINA model that assesses river export of nutrients on a sub-basin scale for China is also based on Global NEWS. Current developments concerning Global NEWS at the WSG group focus on improving the hydrological input of the model by implementing the VIC model.

Figure: Examples of the Global NEWS model inputs (A) and outputs (B) for 2050 according to the Global Orchestration scenario of the Millennium Ecosystem Assessment. N = nitrogen.
Figure: Examples of the Global NEWS model inputs (A) and outputs (B) for 2050 according to the Global Orchestration scenario of the Millennium Ecosystem Assessment. N = nitrogen.

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