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Effects of Damming on River Nitrogen Fluxes: A Global Analysis
Author(s) -
Akbarzadeh Zahra,
Maavara Taylor,
Slowinski Stephanie,
Van Cappellen Philippe
Publication year - 2019
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2019gb006222
Subject(s) - denitrification , environmental science , biogeochemical cycle , hydrology (agriculture) , mineralization (soil science) , biogeochemistry , nitrogen cycle , nutrient , nitrogen , nitrogen fixation , sedimentary rock , phosphorus , soil science , geology , environmental chemistry , oceanography , ecology , chemistry , soil water , geochemistry , geotechnical engineering , organic chemistry , biology
Abstract Damming creates biogeochemical hotspots along rivers that modify the riverine flow of nutrients, including nitrogen (N). Here, we quantify the impact of dams on global riverine N fluxes using a reservoir N mass balance model. In‐reservoir processes represented in the model include primary production, mineralization of organic N, denitrification, and sedimentary burial. In addition, we explicitly account for N fixation as a source of N, assuming that the N to phosphorus (P) ratio of the inflow regulates the magnitude of N fixation in reservoirs. The model is scaled up via a Monte Carlo analysis that yields global relationships between N elimination in reservoirs, either by denitrification or burial, and the hydraulic residence time. These relationships are then combined with N loads to the world's dam reservoirs generated by the Global‐NEWS model and the estimated N fixation fluxes. According to the results, in year 2000, worldwide N fixation in reservoirs was on the order of 70 Gmol yr −1 , while denitrification and burial in reservoirs eliminated around 270 Gmol yr −1 , equal to 7% of N loading to the global river network. The latter is predicted to double to 14% by 2030, mainly as a result of the current boom in dam building. The results further imply that, largely due to N fixation in reservoirs, damming causes a global upward shift in riverine N:P ratios, thus lessening N limitation in receiving water bodies.