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.

What does it actually take to provide safe and affordable drinking water for everyone? And if households must store, filter, boil or buy water before they can safely drink it, can we really say the water system is providing a service?

In this episode of The Water Data Podcast, host Veena Srinivasan speaks with Professor Isha Ray, formerly of the Energy and Resources Group at the University of California, Berkeley, about drinking water access, affordability, inequality and the hidden labour involved in making water safe.

Drawing on research from India and California, Isha explains why drinking water deprivation is not simply a problem of poor countries. From nitrate-contaminated farmworker communities in California to intermittent urban water systems in India, the conversation shows how marginalisation, infrastructure and political power shape who receives safe water.

They explore the idea of “source-to-sip” water safety, why household filters can be technically effective yet fail in everyday life, and why asking women to continually store, treat and monitor their water creates an overlooked burden of time, money and anxiety.

The episode also examines India’s intermittent water systems and the Hubballi-Dharwad experiment with continuous 24/7 supply. Isha discusses what researchers learned about water quality, child health, household expenditure and the time people spend coping with unreliable supply.

Finally, Veena and Isha tackle one of the hardest questions in urban water management: how should water be priced? They discuss metering, cross-subsidies, lifeline water, affordability and why safe drinking water must ultimately be treated as a public service rather than simply a household responsibility.

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://dev.welllabs.org/wdp-isha-ray/

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 and Kanishka Goyal. Audio mixing and mastering by Vijay Doiphode. Podcast production and management by Nabina Chakraborty and Pavan Srinath.

How does saving water create a financial crisis for the utilities that supply it? And why do cities continue building water systems based on laws, infrastructure, and climate assumptions that are no longer relevant?

In this episode of The Water Data Podcast, Newsha Ajami joins host Veena Srinivasan to unpack the hidden risks inside modern water systems- from outdated water rights and groundwater overuse to drought, demand management, decentralised reuse, and climate resilience.

Newsha Ajami is an Iranian-American hydrologist, civil engineer, and environmental policy expert. Her work spans sustainable urban water management, the water-energy-food nexus, data science for environmental governance, and climate resilience. She is the founding director of the Governance for Risk, Resilience, and Recovery (GR3) program at the Stanford Doerr School of Sustainability. She has also worked with the Lawrence Berkeley National Laboratory and served on utility and regulatory boards in California.

In this conversation, Newsha and Veena discuss why water law often fails to align with water science, how California’s experience with the Colorado River and Central Valley groundwater holds lessons for India, and why bringing in more surface water does not automatically solve groundwater depletion.

Newsha explains why she prefers the term “demand management” over “conservation,” how outdoor water use and lawns shape urban water demand, and why utilities often face financial stress when conservation efforts succeed.

The episode then explores decentralised wastewater reuse, comparing San Francisco’s on-site reuse model with Bengaluru’s apartment-level sewage treatment systems, emphasising how growing cities can avoid copying outdated centralised models and instead build flexible, modular, and resilient water systems.

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-newsha-ajami/

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 Vraj Acharya and Nabina Chakraborty. 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 does it mean to measure water for the entire planet? Who collects the data behind SDG 6? And how do numbers from hundreds of countries become a global picture of water security, sanitation, wastewater, ecosystems and governance?

In this episode of The Water Data Podcast, Dr Maggie Kossida , from the UN-Water Integrated Monitoring Initiative for SDG 6 joins host Veena Srinivasan.

Dr Kossida helps coordinate one of the world’s most ambitious water-data efforts: bringing together information from 190+ countries to understand how the world is progressing on Sustainable Development Goal 6- clean water and sanitation for all.

Maggie explains how SDG 6 expanded the global water agenda beyond drinking water and sanitation to include water quality, wastewater treatment, water use efficiency, water stress, integrated water resources management, freshwater ecosystems, financing and community participation.

She also explains how global monitoring actually works: countries collect and own their data, UN custodian agencies support validation and quality checks, and the Integrated Monitoring Initiative helps coordinate across agencies and indicators. The episode explores why some indicators are much harder to track than others, why national averages can hide local water crises, and how SDG 6 data is increasingly being used to shape standards, policies, investments and national targets.

Finally, Veena and Maggie discuss why missing the 2030 targets should not be seen simply as failure. Instead, monitoring has revealed the gaps, strengthened systems, and created a shared language for water action across the world.

For young researchers, students and water professionals, Maggie also shares how the SDG 6 Data Portal, citizen science and Earth observation can open up new ways to explore global water data.

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-maggie-kossida/

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 Vraj Acharya and Nabina Chakraborty. 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 if technology was designed not to manage communities, but to strengthen their voice and agency?

In this episode of the Water Data Podcast, Professor Aaditeshwar Seth of IIT Delhi joins host Veena Srinivasan. Aaditeshwar is the co-founder of Gram Vaani and one of the key people behind CoreStack, a digital public infrastructure for commons, resilience, and equity.

In this episode, Aaditeshwar traces his journey from computer science and rural communication networks to building participatory tools for communities, civil society organisations, researchers, and governments. The conversation begins with his journey with Gram Vaani, a voice-based platform that enables rural communities to share local information, raise grievances, and strengthen public accountability.

From there, the episode moves into CoreStack, a shared technology and data ecosystem that brings together geospatial datasets, landscape indicators, planning tools, and community-facing applications. Aaditeshwar explains how tools like Know Your Landscape and Commons Connect can help planners, local facilitators, and communities understand drought risk, groundwater stress, land use change, water bodies, and other landscape-level challenges.

At the heart of the episode is a larger question: who gains power when data and technology enter environmental decision-making? Veena and Aaditeshwar discuss why technology is not neutral, why data should support rather than replace community agency, and how digital tools can help people collectively govern shared resources such as water, forests, land, and biodiversity.

The conversation also explores micro-watersheds, landscape stewards, MGNREGA-linked planning, PRADAN’s work with Commons Connect and Yuktdhara, and the challenge of sustaining open digital public infrastructure over time.

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-aaditeshwar-seth/

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 Vraj Acharya, Nanditha Gogate and Nabina Chakraborty. 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.

Where did the idea of “water security” come from? How did countries around the world come to agree on shared goals for drinking water, sanitation, river basin management and sustainable development? And why does water still lack the kind of global institutional architecture that exists for climate change and biodiversity?

In this episode, Dr Roberto Lenton, one of the world’s leading voices on water security and international development joins host Veena Srinivasan for a conversation on the evolution of global water policy over the last eight decades.

Roberto has spent more than six decades working across engineering, research, philanthropy, global institutions and water policy. His career has taken him from the Ford Foundation in India to the founding of the International Irrigation Management Institute, now the International Water Management Institute (IWMI), and to being an early proponent of the Global Water Partnership.

Drawing on his book, Confronting Water Insecurity: Global Institutions and the Transformation of Water Science, Policy and Practice, Roberto traces the history of global water cooperation from the creation of the United Nations after World War II to the Sustainable Development Goals and the water challenges ahead.

Veena and Roberto discuss why global water institutions emerged after 1945, how UNESCO came to host the International Hydrological Programme, and how the Harvard Water Programme helped shape early ideas around integrated planning and managing water for multiple purposes.

The conversation also explores the first UN Water Conference at Mar del Plata in 1977, the International Drinking Water Supply and Sanitation Decade, the Dublin Principles, the Rio Earth Summit, the Millennium Development Goals and Sustainable Development Goal 6.

Roberto explains how the term “water security” became more than a question of water scarcity. It brought together drinking water, sanitation, irrigation, floods, droughts, pollution, ecosystems and resilience into one wider framework.

The episode also examines the more difficult side of global water governance: the accountability mechanisms that emerged around dams and development projects, the limits of privatisation-led reforms, and the reasons why global institutions have often struggled to translate new ideas into real improvements on the ground.

Finally, Veena and Roberto look ahead to the future of water governance in a changing world shaped by climate extremes, AI data centres, demographic shifts and growing scepticism about multilateral cooperation. They ask whether water needs a stronger global science-policy mechanism, perhaps something equivalent to the IPCC for climate change.

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-robert-lenton/

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

How can satellites measure crop water use from space? Can they help farmers irrigate more precisely, improve yields, and make water distribution fairer across canal systems?

In this episode of the Water Data Podcast, Veena Srinivasan speaks with Professor Wim Bastiaanssen, a pioneer in satellite-based evapotranspiration mapping and the original developer of SEBAL — the Surface Energy Balance Algorithm.

Professor Bastiaanssen explains how satellite imagery can estimate actual evapotranspiration, soil moisture, crop water stress, and irrigation performance by combining land-surface temperature, vegetation data, and the surface energy balance. The conversation traces the journey from early field validation of SEBAL to its application across farms, irrigation systems, and river basins around the world.

Wim and Veena discuss how farmers can use simple satellite-based advisories to identify dry patches in their fields, prevent crop stress, and use water more productively. They also explore how the same data can help irrigation agencies understand whether canal water is reaching head-end and tail-end farmers equitably.

The episode further examines water accounting, data-model integration, the commercialisation of scientific tools, and the growth of platforms such as IrriWatch and HydroSat. It is a wide-ranging conversation on evapotranspiration, precision irrigation, water productivity, and how satellite data can support water security at scale.

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/wim-bastiaanssen/

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