When a lake turns green with algae, or nitrate shows up in drinking water, the most obvious question would be: Why can’t we fix this quickly?

In this episode of the Water Data Podcast, Veena Srinivasan speaks with Professor Nandita Basu from the University of Waterloo about nitrogen and phosphorus legacies – the hidden nutrient stores in soils, groundwater, and sediments that keep polluting waterways for decades.

They unpack how the Haber-Bosch process transformed agriculture, why nitrogen use efficiency stays low, and how drained agricultural landscapes can rapidly transport nitrates from fields to major river systems and even the Gulf of Mexico. They also explore why phosphorus behaves differently - sticking to soils and sediments, fuelling algal blooms, and creating stubborn feedback loops when lakes turn low-oxygen.

Finally, they discuss what can still be done: turning the ‘easy knobs’ like phosphate in detergents, targeting livestock manure hotspots, using small ponds and wetlands as high-impact interventions, and why India urgently needs far more empirical measurement to diagnose problems and track solutions.

The Water Data Podcast is a talk show on the science, systems, and stories of water hosted by Veena Srinivasan.

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Recording by Vraj Acharya, Nabina Chakraborty. Video editing by Vraj Acharya. Graphics and artwork by Aparna Nambiar. Audio mixing and mastering by Vijay Doiphode. Podcast production and management by Nabina Chakraborty and Pavan Srinath.