Mechanisms of Basin-Scale Nitrogen Load Reductions under Intensified Irrigated Agriculture

摘要: Irrigated agriculture can modify the cycling and transport of nitrogen (N), due to associated water diversions, losses, changes in flow-paths. We investigate dominant processes behind observed long-term dissolved inorganic (DIN) concentrations loads extensive (465,000 km2) semi-arid Amu Darya River basin (ADRB) Central Asia. specifically considered a 40-year period (1960–2000) large irrigation expansion, reduced river flows, increased fertilizer application net increase N input into soil-water system. Results showed that decreases riverine DIN concentration near Aral Sea outlet ADRB primarily were recirculation water, which extends flow-path lengths enhances attenuation. The matched developed analytical relation between attenuation ratio, showing fourfold basin-scale from 85 99%. Such effects have previously only been at small scales, laboratory experiments individual agricultural plots. These results imply contributed increases agriculturally dominated drainage basins different parts world. Additionally, it be important for scale other pollutants, including phosphorous, metals organic matter. A six-fold lower export during 1981–2000, compared 1960–1980, was combined result drastic flow reduction almost 70%, decreased outlet. Several arid regions around world are projected undergo similar reductions discharge as climate change intensification, may therefore comparable shifts shown here ADRB. For example, future withdrawals 2005 2050 decrease by 40%.