How does water that looks perfectly clean contain dangerous levels of arsenic? Even after decades of research and treatment technologies, why does arsenic exposure remain a drinking-water problem?

In this episode of The Water Data Podcast, hydrogeologist Prof. Abhijit Mukherjee joins host Veena Srinivasan to trace the arsenic story across the Bengal and Ganga-Brahmaputra aquifer systems.

In the conversation, Veena and Abhijit explore how arsenic naturally occurs in sediments, why the geology and geochemistry of the Bengal Delta allow it to enter groundwater, and how microbial activity, iron minerals, and changing chemical conditions underground influence its mobilization.

The conversation also examines how large-scale pumping can change groundwater flow and potentially mix water between aquifer layers, making apparently simple rules about "safe" and "unsafe" groundwater much harder to apply.

Abhijit argues that arsenic treatment itself is not necessarily the biggest challenge. Filters need to be maintained, contaminated filter media must be safely disposed of, drinking-water sources must be monitored, and solutions have to work after researchers and engineers leave.

Veena and Abhijit also discuss arsenic in irrigated agriculture and the unequal vulnerability to exposure. This episode asks a larger question: when the science of a water problem is reasonably well understood, what prevents that knowledge from becoming safe water for everyone?

The Water Data Podcast is hosted by Veena Srinivasan and produced by WELL Labs.

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

For all references and further readings related to the episode, visit https://welllabs.org/wdp-abhijit-mukherjee/

Subscribe to The Water Data Podcast on your favourite podcast app—and catch video episodes on the WELL Labs YouTube channel @welllabs.

Subscription links: Youtube, Apple Podcasts, Spotify, YouTube Music, Amazon Music, Audible, Castbox, and wherever you get your podcasts!

Recording by Nabina Chakraborty and Nanditha Gogate. Video editing by Srisabari Varaguna Pandian. Graphics and artwork by Aparna Nambiar. Audio mixing and mastering by Vijay Doiphode. Podcast production and management by Nabina Chakraborty and Pavan Srinath.

Can we measure evapotranspiration from space? And when a satellite produces a map of crop water use, how certain are those numbers?

Dr. Gilles Boulet joins host Veena Srinivasan for a deep dive into one of the most important and difficult-to-measure components of the hydrological cycle: evapotranspiration.

Evapotranspiration, or ET, combines evaporation from soil with transpiration through vegetation. In many semi-arid landscapes, it accounts for most of the water leaving the land surface. However, measuring ET across individual farms, irrigation commands, and entire watersheds is remarkably difficult.

In this episode, Gilles and Veena unpack what satellites actually observe, from vegetation and radar signals to land-surface temperature. They also discuss how scientists turn those observations into estimates of evapotranspiration.

They explore the role of flux towers and scintillometers, why satellite ET products contain uncertainty, and the differences between contextual and physics-based modeling approaches.

The conversation also looks ahead to TRISHNA, the Indo-French thermal-infrared satellite mission that aims to provide much more frequent land-surface-temperature observations at field-relevant spatial scales.

Additionally, the conversation answers questions regarding how better ET observations could help irrigation departments and groundwater agencies understand where water is actually being consumed, and whether we are close to producing reliable, near-daily maps of agricultural water use.

Dr. Gilles Boulet is a senior scientist at IRD and works with the Indo-French Cell for Water Science at the Indian Institute of Science, Bengaluru. His research focuses on land-surface processes, remote sensing, evapotranspiration, and field instrumentation.

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

For all references and further readings related to the episode, visit https://welllabs.org/wdp-gilles-boulet/

Subscribe to The Water Data Podcast on your favourite podcast app—and catch video episodes on the WELL Labs YouTube channel @welllabs.

Subscription links: Youtube, Apple Podcasts, Spotify, YouTube Music, Amazon Music, Audible, Castbox, and wherever you get your podcasts!

Recording by Nabina Chakraborty, Vraj Acharya and Nanditha Gogate. Video editing by Srisabari Varaguna Pandian. Graphics and artwork by Aparna Nambiar and Kanishka Goyal. Audio mixing and mastering by Vijay Doiphode. Podcast production and management by Nabina Chakraborty and Pavan Srinath.

What can 25 years of observing the same watershed teach us about groundwater? Can intensive pumping make groundwater deeper in valleys than on hills? Can decades of depletion be reversed by just a few exceptionally wet years? And how does fertilizer applied at the surface end up contaminating groundwater tens of metres below?

Professor Shekhar Muddu joins host Veena Srinivasan on the Water Data Podcast for a deep dive into the Kabini Critical Zone Observatory and what decades of field measurements have revealed about groundwater, agriculture, pollution and climate.

The conversation traces the evolution of the observatory from paired forested and agricultural catchments to a long-term interdisciplinary experiment studying groundwater levels, geochemistry, soil moisture, evapotranspiration and human water use.

Shekhar and Veena explore how intensive groundwater pumping altered natural groundwater gradients, how farmers responded to declining well yields, and how extreme rainfall events can produce large pulses of recharge. They also discuss research showing very high nitrate concentrations in parts of the aquifer, revealing how modern agricultural pollution can travel rapidly into deep groundwater through fractured hard-rock systems.

The episode also looks at the future of water observation in India, from satellite-based soil-moisture measurements to evapotranspiration monitoring, solar-induced fluorescence, carbon fluxes and the need for long-term environmental observatories.

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

For all references and further readings related to the episode, visit https://welllabs.org/wdp-sekhar-muddu/

Subscribe to The Water Data Podcast on your favourite podcast app—and catch video episodes on the WELL Labs YouTube channel @welllabs.

Subscription links: Youtube, Apple Podcasts, Spotify, YouTube Music, Amazon Music, Audible, Castbox, and wherever you get your podcasts!

Recording by Nabina Chakraborty, Vraj Acharya and Nanditha Gogate. Video editing by Srisabari Varaguna Pandian. Graphics and artwork by Aparna Nambiar and Kanishka Goyal. Audio mixing and mastering by Vijay Doiphode. Podcast production and management by Nabina Chakraborty and Pavan Srinath.