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Creative Commons Lizenz creative commons licence
Titel (primär) Spatial patterns of water quality impairments from point source nutrient loads in Germany's largest national River Basin (Weser River)
Autor Yang, S.; Büttner, O.; Kumar, R.; Jäger, C.G.; Jawitz, J.W.; Rao, P.S.C.; Borchardt, D.
Journal / Serie Science of the Total Environment
Erscheinungsjahr 2019
Department ASAM; CHS
Band/Volume 697
Seite von art. 134145
Sprache englisch
Keywords Point source nutrient loads; Dilution; In-stream nutrient uptake; Eutrophication; Hydrological alteration
Abstract We employed the well-established Horton-Strahler, hierarchical, stream-order (ω) scheme to investigate scaling of nutrient loads (P and N) from ~845 wastewater treatment plants (WWTPs) distributed along the river network in urbanized Weser River, the largest national basin in Germany (~46K km2; ~8.4 million population). We estimated hydrologic and water quality impacts at the reach- and basin-scales, at two steady river discharge conditions (median flow, QR50; low-flow, QR90). Of the five WWTPs class-sizes (1 ≤ k ≤ 5), ~68% discharge to small low-order streams (ω < 3). We found large variations in capacity to dilute WWTP nutrient loads because of variability in (1) treated wastewater discharge (QU) within and among different class-sizes, and (2) river discharge (QR) within low-order streams (ω < 3) resulting from differences in drainage areas. For QR50, reach-scale water quality impairment assessed by nutrient concentration was likely at 136 (~16%) locations for P and 15 locations (~2%) for N. About 90% of these locations were lower-order streams (ω < 3). At QR50 and only with dilution, basin-scale cumulative nutrient loads from multiple upstream WWTPs increase impaired locations to 266 (~32% of total) for P. Considering in-stream uptake decreased P-impaired streams to 225 (~27%), suggesting the dominant role of dilution in the Weser River basin. Role of in-stream uptake diminished along the flow paths, while dilution in larger streams (4 ≤ ω ≤ 7) minimizes the impact of WWTP loads. Under QR90 conditions [(QR50/QR90) ~ 2.5], water quality impaired locations will likely double for the basin-scale analyses. Long-term water quality data suggested that diffuse sources are the primary contributors for water quality impairments in large streams. Our data-modeling synthesis approach is transferable to other urbanized river basins and extends understanding of point source impacts on water quality across spatial scales.
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Yang, S., Büttner, O., Kumar, R., Jäger, C.G., Jawitz, J.W., Rao, P.S.C., Borchardt, D. (2019):
Spatial patterns of water quality impairments from point source nutrient loads in Germany's largest national River Basin (Weser River)
Sci. Total Environ. 697 , art. 134145