Control of Nitrogen Exports From River Basins to the Coastal Ocean: Evaluation of Basin Management Strategies for Reducing Coastal Hypoxia

M. Lee, C. Jung, E. Shevliakova, S. Malyshev, H. Han, S. Kim, K. Kim, Peter R. Jaffe

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

The spread of coastal hypoxia is a pressing global problem, largely caused by substantial nitrogen (N) exports from river basins to the coastal ocean. Most previous process-based modeling studies for investigating basin management strategies to reduce river N exports focused on the impacts of different farming practices or land use, used watershed models that simplified many mechanisms that critically affect the state of N storage in land, were limited mainly to fairly small basins, and did not span multiple climate regimes. Here we use a process-based land-river model to simulate historical (1999–2010) river flows and nitrate-N exports throughout the entire drainage network of South Korea (100,210 km2), which encompasses varying climate, land use, and hydrogeological characteristics. Based on projections by using multiple scenarios of N input reductions and climates, we explore the impacts of various ecosystem factors (i.e., N storage in basins, climate and its variability, anthropogenic N inputs, and basin location) on river nitrate-N exports. Our findings have fundamental implications for reducing coastal hypoxia: (1) a small reduction of N inputs in basins, including intensively utilized human land use, can have a greater improvement on water quality; (2) heightening climate variability may not increase long-term mean river N exports yet can significantly mask N input reduction effects by producing N export extremes associated with recurring coastal hypoxia; and (3) N exports to the coastal ocean can be most efficiently reduced by decreasing N inputs in subbasins, which are receiving high anthropogenic N inputs and are close to the coast.

Original languageEnglish (US)
Pages (from-to)3111-3123
Number of pages13
JournalJournal of Geophysical Research: Biogeosciences
Volume123
Issue number10
DOIs
StatePublished - Oct 2018

All Science Journal Classification (ASJC) codes

  • Soil Science
  • Forestry
  • Water Science and Technology
  • Palaeontology
  • Atmospheric Science
  • Aquatic Science
  • Ecology

Keywords

  • basin management strategies
  • coastal hypoxia
  • land-river models
  • nitrogen cycle modeling
  • nitrogen-input reductions
  • river nitrogen exports

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