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Profile photo of Ronny Berndtsson

Ronny Berndtsson

Professor, Dep Director, MECW Dep Scientific Coordinator

Profile photo of Ronny Berndtsson

Groundwater nitrogen response to regional land-use management in South Japan


  • Zhi Qiang Yu
  • Kei Nakagawa
  • Ronny Berndtsson
  • Toru Hiraoka
  • Yoshihiro Suzuki

Summary, in English

For a better understanding of the effects of regional groundwater management for different land-use types on nitrogen content in groundwater, we investigated the Miyakonojo River Basin in south of Japan where the Nitrate Directive Plan has been in practice since 2004. For this purpose, we used nitrogen concentrations from 420 wells between 2000 and 2017 together with 8 different land-use categorizations. The data were analyzed using self-organizing maps (SOM) and results showed that forest recharge areas have lowest mean nitrogen concentrations of about 2.9 mg/L. Urban areas displayed a mean nitrogen concentration of about 4.4 mg/L. Agricultural land such as paddy fields had a mean nitrogen concentration of about 5.1 mg/L. Groundwater discharge and residential areas had mean groundwater nitrogen concentrations of 8.2 and 7.1 mg/L, respectively. Intensive agricultural land-use and wastewater discharge from urban areas caused the main groundwater nitrogen contamination in these areas. About 70% of the wells had a decreasing trend of groundwater nitrogen concentration (p < 0.05, p ≥ 0.05) during the period 2009–2017. About 20% of the wells displayed a trend reversal from 2000–2008 (increasing) to 2009–2017 (decreasing). In general, the Nitrate Directive Plan appears to have had positive effects for mitigating groundwater nitrogen problems. However, 30% of the wells still do not display a decreasing trend and some wells exceed maximum permissive level for drinking water. Thus, management needs to continue to improve groundwater conditions regarding nitrogen content.


  • Centre for Advanced Middle Eastern Studies (CMES)
  • MECW: The Middle East in the Contemporary World
  • Division of Water Resources Engineering
  • LTH Profile Area: Water

Publishing year





Environmental Earth Sciences





Document type

Journal article




  • Water Engineering


  • Groundwater nitrogen contamination
  • Mann–Kendall test
  • Self-organizing maps
  • Spearman’s Rho test




  • ISSN: 1866-6280