India's Riverine Nitrogen Runoff Strongly Impacted by Monsoon Variability

Area of Science:

• Environmental Science
• Hydrology
• Water Quality

Background:

• Agricultural intensification in India has led to increased nitrogen pollution, impacting water quality.
• The pathways of reactive nitrogen and long-term riverine flux data are poorly understood, hindering effective management.

Purpose of the Study:

• To analyze the seasonal, annual, and regional variability of dissolved inorganic nitrogen (DIN) fluxes in seven major Indian river basins from 1981 to 2014.
• To identify the key drivers of this variability, particularly in relation to precipitation and agricultural practices.

Main Methods:

• Utilized dissolved inorganic nitrogen (DIN) and river discharge data spanning 34 years (1981-2014).
• Employed statistical analysis to characterize seasonal, interannual, and regional patterns of DIN fluxes.
• Correlated nitrogen fluxes with precipitation data and fertilizer application rates.

Main Results:

• Significant seasonal and interannual variability in nitrogen runoff was observed, with 68-94% of DIN fluxes occurring between June and October.
• Annual precipitation was the primary driver, explaining 52% of the variability in regional and interannual DIN fluxes.
• Little correlation was found between rising fertilizer rates and riverine nitrogen runoff in most basins, suggesting other nitrogen pathways.

Conclusions:

• Riverine nitrogen runoff in India is highly sensitive to precipitation variability and monsoon intensification.
• Projected climate change impacts on rainfall pose a significant risk to water quality through increased nitrogen runoff.
• The influence of ongoing agricultural intensification on riverine nitrogen loads remains uncertain, highlighting the need for further research.