More fertilizer and heavier monsoons spell future trouble for rivers in India

Washington, DC— India could be facing a water quality crisis as climate change affects the monsoon season, according to a new study from Carnegie’s Anna Michalak and Eva Sinha published in Environmental Science & Technology.

Rainfall and other precipitation wash nutrients like nitrogen from fertilizers into waterways. When rivers, lakes, and coastal areas get overloaded with this runoff, a dangerous phenomenon called eutrophication can occur, which sometimes leads to toxin-producing algal blooms or low-oxygen dead zones called hypoxia.

For several years, Sinha and Michalak have been studying the effects of nitrogen runoff and the ways that anticipated changes in rainfall patterns due to climate change could lead to severe water quality impairments. In this most-recent paper, they focused on the impact of agricultural nitrogen runoff from Indian river basins.

Between 1970 and 2015, the rate of fertilizer used by Indian farmers increased tenfold due to improvements in agricultural productivity needed to feed a growing population. However, the fate of the nitrogen from these applications remains largely unknown.

“Around the world, more than a fifth of nitrogen released by human activity ends up in aquatic ecosystems, where it increases the risk of severe water quality impairments,” Sinha explained.

She, Michalak, and Princeton University colleagues Venkatramani Balaji and Laure Resplandy set out to characterize seasonal, annual, and regional fluctuation in the amount of nitrogen dissolved in seven major Indian river basins over a 33-year period ending in 2014.

They revealed that the basins’ nitrogen content varied by season and year, which correlated with changes in precipitation. However, there was little evidence that the increased fertilizer deployed by Indian farmers over the last three decades ended up in these waterways.

“For now, the nitrogen from this agricultural boom has ended up in groundwater or the atmosphere,” Michalak said.

However, as climate change alters global precipitation patterns, and monsoons are expected to get more intense, this excess is increasingly likely to end up polluting these rivers and endangering water quality.  “Management strategies must account for the sensitivity to rainfall variation that our study revealed,” Sinha concluded. “They are a signpost that indicates potential risk for water quality issues as weather patterns become more extreme in a warming world.”

This work was supported by the U.S. National Science Foundation, the Cooperative Institute for Climate Science, Princeton University, the National Oceanic and Atmospheric Administration, the U.S. Department of Commerce, and the French Agence Nationale de la Recherche

The Carnegie Institution for Science ( is a private, nonprofit organization headquartered in Washington, D.C., with three research divisions on both coasts. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in the life and environmental sciences, Earth and planetary science, and astronomy and astrophysics.