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Title (Primary) Disentangling the impact of catchment heterogeneity on nitrate export dynamics from event to long-term time scales
Author Winter, C.; Lutz, S.R.; Musolff, A.; Kumar, R.; Weber, M.; Fleckenstein, J.H.;
Journal Water Resources Research
Year 2021
Department CHS; HDG;
Volume 57
Issue 1
Language englisch;
POF III (all) T31;
Data links
Keywords Water quality; Nitrate; Concentration‐discharge relationships; Nutrient export; Long‐term trends; Event dynamics
UFZ wide themes TERENO;
Abstract Defining effective measures to reduce nitrate pollution in heterogeneous mesoscale catchments remains challenging when based on concentration measurements at the outlet only. One reason for this is our limited understanding of the sub‐catchment contributions to nitrate export and their importance at different time scales. While upstream sub‐catchments often disproportionally contribute to runoff generation and in turn to nutrient export, agricultural areas (which are typically found in downstream lowlands) are known to be a major source of nitrate pollution. To examine the interplay of different sub‐catchments, we analyzed seasonal long‐term trends and event dynamics of nitrate concentrations, loads and the concentration‐discharge relationship in three nested catchments within the Selke catchment (456 km2), Germany. The upstream sub‐catchments (40.4 % of total catchment area, 34.5 % of N input) had short transit times and dynamic concentration‐discharge relationships with elevated nitrate concentrations during wet seasons and events. Consequently, the upstream sub‐catchments dominated nitrate export during high flow and disproportionally contributed to overall annual nitrate loads at the outlet (64.2 %). The downstream sub‐catchment was characterized by higher N input, longer transit times and relatively constant nitrate concentrations between seasons, dominating nitrate export during low flow periods. Neglecting the disproportional role of upstream sub‐catchments for temporally elevated nitrate concentrations and net annual loads can lead to an overestimation of the role of agricultural lowlands. Nonetheless, constantly high concentrations from nitrate legacies pose a long‐term threat to water quality in agricultural lowlands. This knowledge is crucial for an effective and site‐specific water quality management.
ID 23984
Persistent UFZ Identifier
Winter, C., Lutz, S.R., Musolff, A., Kumar, R., Weber, M., Fleckenstein, J.H. (2021):
Disentangling the impact of catchment heterogeneity on nitrate export dynamics from event to long-term time scales
Water Resour. Res. 57 (1), e2020WR027992