title: Characterisation of diffuse pollutions from forested watersheds in Japan during storm events - its association with rainfall and watershed features.
abstract: Forest areas have been identified as important sources of nonpoint pollution in Japan. The managers must estimate stormwater quality and quantities from forested watersheds to develop effective management strategies. Therefore, stormwater runoff loads and concentrations of 10 constituents (total suspended solids, dissolved organic carbon, PO(4)-P, dissolved total phosphorus, total phosphorus, NH(4)-N, NO(2)-N, NO(3)-N, dissolved total nitrogen, and total nitrogen) for 72 events across five regions (Aichi, Kochi, Mie, Nagano, and Tokyo) were characterised. Most loads were significantly and positively correlated with stormwater variables (total event rainfall, event duration, and rainfall intensity), but most discharge-weighted event concentrations (DWECs) showed negative correlations with rainfall intensity. Mean water quality concentration during baseflow was correlated significantly with storm concentrations (r=0.41-0.77). Although all pollutant load equations showed high coefficients of determination (R(2)=0.55-0.80), no models predicted well pollutant concentrations, except those for the three N constituents (R(2)=0.59-0.67). Linear regressions to estimate stormwater concentrations and loads were greatly improved by regional grouping. The lower prediction capability of the concentration models for Mie, compared with the other four regions, indicated that other watershed or storm characteristics should be included in the prediction models. Significant differences among regions were found more frequently in concentrations than in loads for all constituents. Since baseflow conditions implied available pollutant sources for stormwater, the similar spatial characteristics of pollutant concentrations between baseflow and stormflow conditions were an important control for stormwater quality.
authors.affiliation: Graduate School of Life and Environmental Science, University of Tsukuba, Tsukuba, 305-8572, Japan. zhzhao22@yahoo.com
authors.forename: Zhao
authors.initials: Z
authors.lastname: Zhang
authors.forename: Takehiko
authors.initials: T
authors.lastname: Fukushima
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Onda
authors.forename: Shigeru
authors.initials: S
authors.lastname: Mizugaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Gomi
authors.forename: Ken'ichirou
authors.initials: K
authors.lastname: Kosugi
authors.forename: Shinya
authors.initials: S
authors.lastname: Hiramatsu
authors.forename: Hikaru
authors.initials: H
authors.lastname: Kitahara
authors.forename: Koichiro
authors.initials: K
authors.lastname: Kuraji
authors.forename: Tomomi
authors.initials: T
authors.lastname: Terajima
authors.forename: Kazuo
authors.initials: K
authors.lastname: Matsushige
authors.forename: Fulu
authors.initials: F
authors.lastname: Tao
mesh_terms: D004784:Environmental Monitoring / Q000706:statistics & numerical data*; D005544:Forecasting; D007564:Japan; D016014:Linear Models; D009566:Nitrates / Q000032:analysis; D009573:Nitrites / Q000032:analysis; D009584:Nitrogen / Q000032:analysis; D010710:Phosphates / Q000032:analysis; D010758:Phosphorus / Q000032:analysis; D000644:Quaternary Ammonium Compounds / Q000032:analysis; D011891:Rain; D014197:Trees; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014876:Water Pollution / Q000032:analysis; D014881:Water Supply
chemical_list: D009566:Nitrates; D009573:Nitrites; D010710:Phosphates; D000644:Quaternary Ammonium Compounds; D014874:Water Pollutants, Chemical; D010758:Phosphorus; D009584:Nitrogen