Abstract
Many water resources are threatened with nutrient pollution worldwide. This holds for rivers exporting increasing amounts of nutrients from the intensification of food production systems and further urbanization. This riverine nutrient transport causes coastal eutrophication. This study aims to identify cost-effective management options to simultaneously reach environmental targets for river export of nitrogen and phosphorus by the Yangtze River (China) in 2050. A newly developed modelling approach is used that integrates the Model to Assess River Inputs of Nutrients to seAs (MARINA) with a cost-optimization procedure, and accounts for socio-economic developments, land use and climate changes in a spatially explicit way. The environmental targets for river export of nutrients aim to reduce the gap between baseline and desirable nutrient export. Our baseline is based on MARINA projections for future river export of nutrients, while the desirable nutrient export reflects a low eutrophication potential. Results show the possibilities to close the gap in river export of both nutrients by 80–90% at a cost of 1–3 billion $ per year in 2050. Recycling of animal waste on cropland is an important cost-effective option; reducing synthetic fertilizer inputs provides an opportunity to compensate for the additional costs of the recycling and treatment of manure and wastewater. Our study provides new insights on the combination of cost-effective management options for sub-basins of the Yangtze. This can support the design of cost-effective and sub-basin specific management options for reducing future water pollution.
Highlights
Water resources are often threatened with pollution
The main aim of this study is to identify cost-effective management options to simultaneously reach environmental targets for river export of total dissolved N (TDN) and P (TDP) by the Yangtze in 2050
The Yangtze is projected to export around 1916 kton of TDN and 211 kton of total dissolved P (TDP) to coastal waters in 2050 under Scenario 1 (Figs. 1,3)
Summary
Water resources are often threatened with pollution. This includes nutrient pollution in rivers from intensive food production systems (e.g., Bluemling and Wang, 2018) and urban environments (e.g., Zhang et al, 2017) in many world regions (Yu et al, 2019). Rivers often export large amounts of the main nutrients nitrogen (N) and phosphorus (P). Many coastal waters are eutrophic (Breitburg et al, 2018). The Yangtze River (Chang Jiang), the third longest river of the world, is an example of this issue. Increasing exports of N and P by the Yangtze are a result of intensive human activities in sub-basins
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